PubMed

PubMed is an interface for searching biomedical and life sciences journal articles and other related content:

• MEDLINE citations and links to some full-text articles.
• PubMed Central papers which are open access full-text articles.
• Articles that are "in process" prior to being indexed with MeSH terms.
• Articles submitted by publishers "ahead of print."
• National Center for Biotechnology Information (NCBI) Bookshelf.

Currently, PubMed contains over 30,000,000 citations.