There are many basic ways to obtain information on the Internet:

1 If there is a website, visit it directly.

2 browse

3 browse the theme directory

4 Use the network search engine to search.

Searching for information in a database on the Web is called "Deep Web".

Join an e-mail discussion group or newsgroup.

Each of the above methods will be described in detail below.

1. If you have a website, visit it directly.

If you know the website address of the website you want to visit, you can use a web browser to visit the website. What is needed is to enter the URL in the address window. URL stands for Uniform Resource Locator. The URL indicates the Internet address of the corresponding electronic document. Every file on the Internet has a unique URL, regardless of its access protocol. Web browsers use URLs to access files in the host directory. The file is then displayed on the screen of the user's computer.

The format of URL is protocol://host/path/file name.

glance over

You can find useful information by browsing the homepage of the webpage, which is interesting but not common. Because the links are set by the creator of the home page, you don't know where these links will be connected in advance. A high-quality start page usually contains high-quality links. The website of university library contains good network links, which is a good place for you to start exploring.

3. Browse the subject directory

More and more universities, libraries, companies, institutions and even volunteers are creating subject directories to classify some information on the Internet. These directories are classified by topics and contain links to Internet resources related to these topics. Subject directories on the Internet are stored in duplicate but different databases. Most subject directories provide a search function, allowing users to query the database as needed.

When to use the subject directory? For general topics that need to be discussed and topics that users can browse, the subject catalogue is useful.

There are two basic types of subject catalogs: academic and professional catalogs are usually created and maintained by industry experts to serve research, while commercial portals usually contain catalogs to meet the needs of the general public and attract users' visits. You need to judge whether the relevant subject catalogue is suitable for your needs.

INFOMINE, located at the University of California, USA, is an example of an academic subject catalogue.

Yahoo is one of the most famous business portals.

Different subject directories have great differences in content selection. For example, the famous Yahoo does not carefully review the content submitted by users when adding web pages to its database. Therefore, it is not a reliable research resource and should not be used for research. INFOMINE only selects resources that are useful to academic and research groups. You need to consider the collection strategy of the directories you visit. One of the challenges of this problem is that not all directory service providers are willing to disclose their collection strategies and the identities and qualifications of people who comment on their websites. Many subject directories contain comment links that describe or evaluate the content of the website. High-quality comments from well-known commentators are better than those from Yahoo. This way, the notes written by the website creator are more valuable.

It is useful to know that some catalogues are the fruits of people's intellectual labor for many years. Therefore, it is very important to query the subject directory when doing research on the Web.

Suggestion:

If you are looking for a lot of resources, you can try the Internet index of the library. Supported by the federal government of the United States, the index collects a large number of resources of California libraries and comments on a large number of online resources on topics. After careful collection, objective and valuable annotation and hierarchical organization, the index has become the "Yahoo of the intellectual world".

WWW virtual library is the oldest and most exciting theme on the internet. Its catalogue contains a collection of individual topics, many of which are maintained by universities around the world.

INFOMINE is a large-scale academic website directory maintained by the University of California, USA, which can be browsed by subject, keyword or title. Each listed website has a description.

4. Use network search engine for research.

Internet search engines allow users to enter keywords related to topics and find websites containing relevant information. There are various search engines that support various Internet protocols. For example, Archie is used to search files stored in anonymous FTP sites.

At present, the Web itself has become the first choice in the Internet environment, and search engines located in the Web are becoming more and more popular. Web search engines can provide information of a large number of websites located on the Internet. Many search engines collect databases of various Internet protocols, including HTTP, FTP and newsgroups. They can also search multimedia or other types of files on the Web, and they can make a single search. Although online search engines are mainly developed by private companies, most of them are free.

The network search engine consists of three parts:

Crawler: A program that can link from one link to another, traverse the network, identify and read web pages. Index: Database search engine mechanism that contains copies of web pages collected by crawler: software that allows users to query the index, usually returning results according to relevance.

Note that the crawler traverses indiscriminately. Please note that some collected resources may be outdated, inaccurate or incomplete. Excluding these inaccurate resources, other found resources are of course well-founded and valuable. All search results need to be carefully evaluated.

When most search engines use it, they fill in a form in the search term and then request a search. The search engine queries its index, and then generates a page containing some or all of the linked resources of your search term. These resource lists are usually arranged in an orderly manner. This used to be a popular way to compare search content scores. If your search term appears in a document (including the title of the document, the beginning of the document, the end of the document, etc. ), the document will be at the beginning of the search results list. This kind of engine is considered as the first generation search engine.

A more complex technology in search engine technology is to rank search results according to concepts, keywords, websites, links or popularity. Search engines that support these functions are considered as the second generation search engines. These search engines have improved the ranking results. This is because human factors need to be added when determining the degree of correlation. For example, Google ranks search results according to the ranking scores of web pages linked to other pages. If other high-scoring pages link to this page, then this page has a high score. This strategy combines technology and human judgment.

All search engines have search rules. Before you start searching, you need to read the help files, and online tutorials can also help you learn these rules. At the end of this paper, some recommended tutorials are listed.

Suggestion:

Start with Google. This is a well-known second-generation search engine, and its page ranking is based on the number of links of popular web pages. The more popular the page containing these links, the higher the ranking position of the page. The arrangement position of these popular web pages is also determined in this way. The idea used here is that a high-quality webpage can be found through the link of another high-quality webpage. Google has achieved great success in the market, which is the witness of this ranking concept.

Another interesting link sorting engine is Teoma. The search tool divides the search results into three parts: a list of web pages sorted by scores, links to related websites given by experts, and concept classification based on topic keywords. These categories are dynamically generated and can optimize your search results. Sorting is somewhat different from Google. Teoma classifies web pages in the same category when searching for topics. They are called "popularity of specific topics".

Ixquick is a good place to go if your topic is unclear, or if you plan to get the results of multiple search engines with one search sentence at a time. The service uses multiple search tools at the same time, and returns search results excluding duplicate pages. This search process is called meta-search. It is worth mentioning that Ixquick only returns the first 10 related results in the source search service. This means that you can use multiple search engines to query at the same time. Other recommended meta-search engines are Vivisimo and ProFusion.

5. Explore the "deep network"

Recently, the concept of "deep" or "invisible" Web has appeared, which refers to the content stored in the Web database but inaccessible by search engines. In other words, it is "invisible" to search engines. Unlike retrieving static pages, crawler programs cannot access the database to retrieve content. In the past, these databases were few in number and were called professional databases and subject databases.

The best way to get information on the invisible network is to search these databases, which cover everything from academic resources to business information. Recently, dynamically generated information is likely to be stored in the database, including news, work information, flight information and so on. With more and more databases accessed through the Web, it will become the mainstream to find information on the Web through databases.

Other content that crawler does not collect includes non-text files, such as multimedia files, image files and non-standard format files such as PDF. Google is an exception. It can retrieve PDF, Word and other files.

Note: Many search engine websites and commercial portals regard being able to search deep Web as one of their services, and this kind of content aggregation is the general trend. For example, you can visit AltaVista to find news, maps, work information, auctions, shopping information and so on, which are not within the scope of crawler search. For another example, Google integrates the retrieval function of PDF and Microsoft Office files into its general search service.

Here are some websites that can search for deep Web:

Invisible network

/

More than 10000 databases, you can search the database you need.

Invisible-web.net

/

Dozens of subject-based databases from CNET

6. Join an e-mail discussion group or newsgroup.

Join thousands of email discussion groups or newsgroups. These discussion groups cover a large number of topics. You can ask professional questions and get answers from others. After joining these groups, you will receive news briefings on topics you are interested in every day. On the Internet, these discussion groups provide a good way to keep track of your professional topics. In addition, discussion groups can help you find the information you need, whether online or offline.

Some academic institutions have e-mail discussion groups, and many topics are about natural science. It is not surprising to find some experts among the participants. Newsgroups Newsgroups cover a wider range of topics, and there are many professionals among the participants. Carefully evaluate the opinions and information in any forum. Also note that a small number of e-mail discussion groups are also published to newsgroups. For example, the early music e-mail group EARLYM-L also existed in the newsgroup rec.music.early

E-mail discussion groups are managed by software programs, and there are three common programs: Listserv, Majordomo and Listproc. The commands to use these programs are similar.

Newsgroup lists can be accessed through news readers, and web browsers such as Netscape Communicator also include news readers. This makes it easy to access newsgroups in a graphical environment.

There is a good web-based directory that can help you find email discussion groups and newsgroups. This is Tilen.et, and the website is:/.

Actual combat of network search engine

How to form a query statement

Database search has three steps:

1 Define your concept

When searching the database, you need to divide your topic into several parts. For example, if you are looking for information about the budget agreement between President Bush and the Democratic Party, here are three concepts: Bush, the Democratic Party and the budget.

For each concept, list the key words.

Once the concepts are defined, it is necessary to list the keywords that describe each concept. Some concepts may have only one keyword, while others may have several keywords.

Clear up the logical relationship in your keywords.

Once the keywords used for searching are defined, it is necessary to establish the logical relationship between these keywords. The official name here is Boolean logic. Boolean logic can clarify the relationship between search terms by using logical operatORs AND, or and NOT.

Search sentence search results

Conditions that were met in World War I and World War II.

World War I or World War II contains at least one of these conditions.

World War I, not World War II, included the conditions of World War I, but did not include the conditions of World War II.

Some search engines can perform Boolean searches, but they do not explicitly use logical operators. For example, you are asked to list all the search criteria and choose to search all these criteria. This means and logic. Means to use any one of these conditions or logic. Most search engines use implicit Boolean logic, in which symbols or spaces are used to express logical relationships. For example, +bears+hibernate stands for AND logic.

Some search engines can use proximity operators. This is an AND logic that specifies the distance between words in the source file. For example, AltaVista uses the NEAR operator. Consider the following search: Bush is close to budget. In AltaVista, these two words are separated by no more than 10 words in the source file. This can help you ensure the relevance of your search results.

Most web search engines can't handle all the conditions in step 2 above with one search sentence. You may need to use different combinations to modify your search until you find satisfactory results. For example, we can start with Bush, the Democratic Party AND the budget agreement and connect these conditions with AND logic. Look at your search results. If not, repeat the above process with the replacement keyword in the budget concept. According to the initial search results, let's see what new search terms need to be added.

To learn more about normalized search, see Boolean search on the Internet.

1 1 search skills.

1 Read the guide on every search website. The search skills depend on the search engine you use. Different search engines have many options.

If you search for more than one condition, please specify the Boolean logic type used. For example, the search about the relationship between latitude AND temperature can be combined into+latitude+temperature on many web search engines, using logical AND.

When logical OR is used, synonyms or substitutes are included in the search sentence.

4 Check spelling.

If the search engine is case-sensitive, use uppercase letters.

If you are not satisfied with the search results, please use alternative words to search again.

7. Try to search from different information sources to get a variety of results. Information sources include newsgroups, Internet FAQs, comment pages in the catalog, and so on.

Try different search engines. No two search engines search in the same index.

Try a search engine that can start multiple search engines at the same time. Please note that you will lose the advanced query option function because not all engines support the same query format.

10 If there are too many search results or get irrelevant results:

Search in related fields

Add concept words, and some engines support searching again in existing search results. You can try this function on Hotbot or Lycos.

Use words specific to your topic and avoid words with broad meanings unless you plan to do a domain search.

Use Boolean logical operators and (+) to connect the appropriate items so that each item appears in the search results.

If possible, use the proximity operator to find nearby items in the document. Lycos provides a variety of proximity options for search terms.

If the search term is a statement, please enclose it in quotation marks, such as "global warming"

Don't eliminate unnecessary conditions when using Boolean operators.

1 1 If too few results are obtained:

Discard less important concepts to broaden the theme.

Use more common vocabulary.

FOR a single concept, use alternative items or spellings and connect them with Boolean logic operator OR.

On some search engines, try to find similar or related document options. For example, both Google and ProFusion provide this feature.