Question 2: What are the common retrieval fields in the database? 5-field limited retrieval refers to a retrieval method that limits search terms to one or several fields in database records. In the retrieval system, there are usually two kinds of fields available for retrieval in the database: the basic fields that express the characteristics of literature subject content and the auxiliary fields that express the external characteristics of literature. The basic fields include article title, abstract, description and free indexing words. Auxiliary fields include all fields except the basic fields. Each field has a 2-letter field identifier. In the command retrieval mode of dialogue retrieval system, when the retrieval is restricted by fields, the basic fields are represented by suffixes and the auxiliary fields are represented by prefixes. For example, puter and network/TI, DE mean to limit the search formula to the title field (TI) and descriptor field (DE); To find the literature published by the author Smith D., the search formula can be expressed as au = Smith, D. In most retrieval systems, if the user does not limit the scope of the annotation fields of the retrieval type, the system will search in four basic fields by default.
Question 3: What is pubmed database? Search the field and determine the research institution and mailing address of the first author of AB Digest advertisement. All fields except transliteration nomination and publishing country. AU author CN collaborator DP article publication date EDAT article input date PUBMED 1AU First author FAU author full name GR funding number, contract number or LA article is funded by the National Institutes of Health. ...
Question 4: What are the types of information retrieval tools? The process or technology of organizing and storing documents in a certain way on a certain carrier, and using corresponding methods or means to find out the documents that meet the needs of users. Literature retrieval is an important part of scientific and technological information work and the preliminary work of scientific research. Literature retrieval includes two parts: literature processing and sorting and literature retrieval. According to different processing depth, it can be divided into title retrieval, abstract retrieval and full-text retrieval; According to the different retrieval equipment, it can be divided into manual document retrieval and computer document retrieval. In the library's document retrieval service, the retrieval of documents needed for complex topics generally goes through the following processes: ① the analysis of retrieval topics, including the analysis of the nature of retrieval topics, the literature situation and requirements that readers have mastered, the types, languages and time limits of retrieval documents, and the difficulty of retrieval. (2) Make a retrieval plan, mainly to determine the retrieval strategy, arrange suitable personnel, put forward quality requirements, and specify the completion period. ③ Select the retrieval tool. ④ Determine the retrieval approach. ⑤ Provide retrieval results, including the source, collection unit and request number of the original document, so that readers can directly obtain the original document or a copy of the document. [Document retrieval tool]: 1. The meaning of retrieval tool refers to the tool used to report, store and find literature clues. It is the object of a certain range of literature items with search marks, and it is a secondary literature. Generally speaking, a retrieval tool should meet the following five conditions: ① a clear collection scope; (2) Having complete and clear document characteristic marks; (3) Each document entry must contain multiple document characteristic marks with retrieval significance, and be marked with retrieval marks; ④ Each project is scientifically organized into an organic whole according to certain laws; ⑤ There is an index part, which provides various necessary retrieval ways. Second, the types of retrieval tools At present, there are many retrieval tools available to people. Different retrieval tools have their own characteristics and can meet different information retrieval needs. There are different classification methods of retrieval tools, which can be divided into manual retrieval tools and mechanical retrieval tools according to the different means of processing literature information. According to the different publishing forms, it can be divided into periodical retrieval tools, single volume retrieval tools, card retrieval tools and film retrieval tools; According to the different carrier forms, it can be divided into: book retrieval tools, tape retrieval tools, card retrieval tools, microfilm retrieval tools and film retrieval tools. According to the different description formats, retrieval tools can be divided into the following four types. 1. Directory Search Tool Directory Search Tool is a tool to record specific publishing units, collection units and other appearance features. It takes a complete publishing or collection unit as the recording unit, and generally records the name, author and source of the literature. There are many kinds of catalogues, among which national bibliography, joint catalogue and collection catalogue are particularly important for literature retrieval. 2. Title-based retrieval tool A title-based retrieval tool is a retrieval tool that describes the external characteristics of a document (such as document title, author name, document source, etc.). ) Take a single document as the basic description unit, and report the document information quickly without content summary. The main difference between it and a directory is that it describes different objects. The object of catalogue description is the unit publication, and the object of title description is a single document. 3. Abstract retrieval tool Abstract retrieval tool is a retrieval tool that abstracts a large number of scattered documents, selects important parts and arranges them in a concise way. According to the author of the abstract, it can be divided into author abstract and non-author abstract. Author's abstract refers to the abstract written by the original author; A non-author's abstract refers to an abstract written by a professional abstract author who is familiar with his major. According to the degree of detail, it can be divided into indicative summary and reporting summary. The indicative abstract shows the title, content scope, research purpose and source of the document in the shortest language, which is actually a supplementary explanation to the title, generally about 100 words; The purpose of the reportable abstract is to reveal the theme essence of the original text, basically reflect the content of the original text, the scope and purpose of the discussion, the research means and methods adopted, the results and conclusions obtained, and also include relevant data and formulas. Generally about 500 words, important articles can reach as many as 1000 words. 4. Index retrieval tool An index retrieval tool is a retrieval tool that arranges related items or knowledge units in some important documents in a specific range, such as book titles, periodical titles, names of people, place names, words, etc. , according to a certain method, and indicate the source, to provide users with literature clues.
Question: What is google's limited symbol retrieval and retrieval formula? The retrieval functions supported by general database, such as keyword retrieval, Boolean logic retrieval, subject retrieval, field retrieval, etc. At the same time, among thousands of search engines on the Internet, the performance of retrieval function in each search engine is not completely consistent, and the performance of the same retrieval function in different search engines is not completely consistent, and these retrieval functions are supported in different degrees in each search engine. (1) search language 1. Keyword Search Almost all search engines support keyword search. A keyword is not a word, but a word or phrase that can express a theme, such as music video and music. The specific process of keyword retrieval is: when a search word is input, the search engine will find the same string as the word in its database and list the results containing the string. 2. Natural language retrieval inputs query conditions according to natural language habits, and can find the required information without considering the search grammar, which is convenient to use. For example, enter "How can I learn to play the blues guitar?" This kind of search questions, search engines will automatically remove meaningless words for retrieval, and the search engines that support this retrieval language are Webcrawler and AlataVista. 3. Subject language retrieval can classify and query information according to the subject. Such as Yahoo! It's a classified subject index. 4. Concept retrieval Concept retrieval mainly refers to the retrieval of synonyms and synonyms. It not only simply searches for results containing search terms, but also retrieves results related to the concept of search terms. When consulting the concept of "Internet", we can also use "WWW" and "Web" to achieve the purpose of retrieval. Conceptual retrieval can expand the scope of retrieval and improve the recall rate. For example, Hotbot supports concept retrieval. (2) Search option 1. Boolean logic options Most search engines support three common boolean logic operators AND, or AND NOT, among which AND and or are the most supported in search engines, and almost all search engines support these two operators at present. Search engines such as Infoseek, AlataVista, Exite and Hotbot fully support these three operations. Some search engines only support the first two operations, such as Yahoo! The search engine does NOT support the not operation. At the same time, search engines suppORt different ways, some can directly use AND, or, NOT to search, some search engines use corresponding+,*,-to operate, and some search engines use menus to realize operations. For example, Hotbot provides "all words" and "any words" for AND and or respectively, which is an "exact match" of domestic Skynet search engines. 2. Interception retrieval is also a common method in database retrieval. In search engines, at present, most of them provide right-hand truncation, and the corresponding symbols are different. The more common ones are "*" and "?" . The former represents multiple characters and is widely used. Most search engines support this feature. The latter represents a character, which is supported by a few search engines. 3. Specific field options The specific field options of the search engine are similar to the limited search in general database retrieval, which refers to specifying the fields of the query to narrow the search scope. When searching, users can limit the search scope to options such as titles and keywords. In addition, the search engine also provides its unique network field definition options: URL address, host name, hypertext link, newsgroup, email and web document. For example, enter to find commercial sites, and enter t:game to find the results with game in the title of web documents. Using this kind of retrieval can improve the accuracy of retrieval and increase the relevance. At present, AltaVista, Lycos and Hotbot can provide limited retrieval functions. 4. Case matching is used to determine whether to find the result that exactly matches the case of the keyword you entered. It is helpful to improve the query accuracy.
Question 6: What does the search number mean?
Question 7: What symbols can be added to the search words in the idiom search? Every search engine has its own query method, which can only be used freely if it is mastered skillfully. Different search engines provide different query methods. If you want to know more, you can go to various websites to query, but there are some general query methods, which are basically found in various search engines. Let me introduce it to you.
Because using directory query is relatively simple, you only need to determine the directory where the target is located, and then open it layer by layer and gradually refine it to find it. So below we mainly introduce the use of keywords for query. (Free contact with buyers)
1, simple query
Enter keywords in the search engine, and then click "Search", and the system will return the query results soon. This is the simplest query method, which is convenient to use, but the query result is inaccurate and may contain a lot of useless information. }
2. Use double quotation marks with ()
Adding double quotation marks (half-width, as well as other symbols to be added below) to the keyword to be queried can realize accurate query. This method requires accurate matching of query results and excludes evolutionary forms. For example, if you type "telex" in the text box of a search engine, it will return the website with the keyword "telex" in the webpage, instead of returning the webpage such as "telephone fax".
3. Use the plus sign (+)
Using a plus sign before a keyword is equivalent to telling the search engine that the word must appear on the web page of the search results. For example, entering "+computer+phone+fax" in a search engine means that the content to be searched must contain three keywords: "computer, phone and fax".
Step 4 Use the minus sign (-)
Using a minus sign in front of a keyword means that the keyword cannot appear in the query results. For example, if you enter "TV Station-CCTV" in the search engine, it means that "CCTV" must not be included in the final query results.
5. Use wildcards (* and? )
Wildcards include an asterisk (*) and a question mark (? ), the former means that the number of matches is not limited, and the latter means that the number of matched characters is limited, which is mainly used in English search engines. For example, if you enter "putter *", you can find words such as "putter, puters, puterised, puterized" and enter "P? Ter ",only words like" Pute, Pate, Peter "can be found.
6. Use Boolean retrieval
The so-called Boolean retrieval refers to a query method that expresses the logical relationship between keywords through standard Boolean logical relationship. This query method allows us to input multiple keywords, and the relationship between each keyword can be expressed by logical relational words.
And, called logical and, is connected by AND, which means that the two words it connects must appear in the query results at the same time. For example, if you enter "computer and book", the query result must include both computer and book.
Or, called logical OR, means that either of the two connected keywords can appear in the query results. For example, if you enter "computer or book", you can only ask for computer or book, or both computers and books in the query results.
Not, called "not" logically, means that among the two connected keywords, the second keyword should be excluded from the concept of the first keyword. For example, if you enter "cars instead of cars", you need to include cars in the query results, but not cars at the same time.
Near means that the word spacing between two keywords cannot exceed n words.
In the actual use process, we can use all kinds of logical relations comprehensively and flexibly to make more complicated queries.
7. Use parentheses
When two keywords are connected by another operator and you want to list them as a group, you can put parentheses around the two words.
8, using meta-word retrieval
Most search engines support the function of "meta-words". According to this function, users can put meta-words in front of keywords, so that they can tell search engines what specific features you want to retrieve. For example, you enter "Title: ... >; "In search engines. & gt
Question 8: Symbol in search ~ Symbol: For example, if you want to search for a word similar to "predecessor", enter "~ predecessor", and the page you get will contain not only the word "predecessor", but also words such as "predecessor" and "predecessor". Double quotation marks: montypython should be entered when entering a search request to ensure that this phrase is within quotation marks. In this way, if these two times do not match into an exact phrase in the prescribed order, the page will not be listed in the search results. Click here to learn more about williamlong.info/archives/728..