1.PubMed: a free biomedical literature database provided by the National Institutes of Health, which contains a large number of medical journal articles and research reports.
2.MedlinePlus: Medical information resources provided by the National Library of Medicine, including information on diseases, drugs and health topics.
3. Science Network: contains a large number of literature indexes and citation databases in the fields of science, technology and medicine.
4. Google Academic: Google's academic search engine provides a wide range of academic literature search functions.
5. China HowNet: It provides a large number of China medical journals and dissertations, which is suitable for searching China medical literature.
These search engines and databases are commonly used retrieval tools in the medical field, which can help you find the medical knowledge and literature you need.