PubMed comprises over 30 million citations for biomedical literature from MEDLINE, life science journals, and online books. PubMed citations and abstracts include the fields of biomedicine and health, covering portions of the life sciences, behavioral sciences, chemical sciences, and bioengineering. PubMed also provides access to additional relevant web sites and links to the other NCBI molecular biology resources.
BIOSIS Citation Index provides access to BIOSIS content using citation-based searching and discovery. This database allows the user to search content from journals, meetings, books, and patents in the life sciences and biomedicine, with backfiles available to 1926.
Web of Science Core Collection is a multidisciplinary citation index that includes scholarly articles, conference proceedings, and books in the biomedical, psychosocial, and arts and humanities. The collections contain Science Citation, Social Sciences Citation Index, Arts and Humanities Citation Index , Conference Proceedings Citation Index, Book Citation Index, Emerging Sources Citation Index and Current Chemical Reactions index.