1, Google Academic, a search engine that can search academic articles for free, covers a very comprehensive research field, and there will be some books, patents and other types of materials for reference besides papers. Support advanced search functions such as keywords, classification and filtering.
2.iData, free to use, but the quantity is limited. You can directly search for keywords and select Online/Download. Web of Science is a comprehensive academic information resource website covering the largest number of disciplines, which contains a variety of authoritative and influential academic materials in the world and has great influence and authority on a global scale.
3, library Genesis, all English original e-books or papers. Sci-hup, an omni-directional document download tool, suggests using DOI to search and download, which directly ensures that the searched articles are what you are looking for. Download PDF format for free.
4. Eric, including periodical articles, books, comprehensive research reports, technical reports and papers ... Many resources can be obtained for free. Open access library provides comprehensive and high-quality papers free of charge, mainly covering physics, mathematics, humanities, engineering, chemistry, biology and medicine. No need to download, it is convenient to preview the main paper information directly, saving time.
5. The American free Science website Science is a comprehensive and multidisciplinary core periodical literature database. Elsevier, according to the key words you want to search, you can find relevant literature and recommended journals in this field.
6. China HowNet. It is also the most commonly used way to input topics or keywords for query, and China HowNet is also the most authoritative and commonly used database in China.
7. Baidu Academic. Baidu has many Chinese documents academically. Baidu Academic Search can retrieve paid and free academic papers, and accurately search by time screening, title, keywords, abstract, author, publication, literature type, and cited times.
8. Wanfang Database. Wanfang database is also a large literature database in China, and you can enter corresponding keywords to search.