PubMed comprises more than 20 million citations for biomedical literature, life science journals, and online books. Citations may include links to full-text content
Provides a search of scholarly literature across many disciplines including theses, books, abstracts, patents and articles
A free digital archive of biomedical and life sciences journal literature
A comprehensive scientific research tool allows search journals, scientists' homepages, courseware, pre-print server material, patents etc.
A large abstract and citation database of research literature and web sources