1. Keyword retrieval: This is the most commonly used retrieval method. By entering keywords related to the research topic, the system will return relevant documents. The choice of keywords is very important, and it needs to cover all aspects of the research topic as much as possible.
2. Subject retrieval: This method is to retrieve literature by selecting a specific subject or classification. For example, if the research topic is "climate change", you can choose topics such as "environmental science" or "geography" to search.
3. Author search: If you know that an author's research is related to your own research topic, you can directly search the author's literature.
4. Citation retrieval: This method is to find the literature that may be related to one's research topic by looking up other papers that have cited a certain paper.
5. Combined retrieval: This method combines the above methods and improves the accuracy and comprehensiveness of retrieval.
6. Advanced retrieval: Many databases provide advanced retrieval functions, and documents can be accurately retrieved by setting various retrieval conditions such as time, language and publication type.
7. Use professional databases, such as WebofScience, Scopus, PubMed, etc. These databases contain a large number of academic journals and conference papers, and are important tools for literature retrieval.
8. Use Google Academic: Google Academic is a free academic search engine, which can search a large number of academic papers, books, conference papers and so on.
The above are some commonly used methods of paper literature retrieval. Different methods are suitable for different research needs, and researchers can choose according to their own needs.