PubMed is comprised of "more than 28 million citations for biomedical literature from MEDLINE, life science journals, and online books. Citations may include links to full-text content from PubMed Central and publisher web sites" (PubMed homepage).
MEDLINE is a database of citations to articles published in biomedical and life sciences journals. Currently about 5200 journals are indexed for MEDLINE.
A free archive for full-text biomedical and life sciences journal articles.
Learn more about PubMed, MEDLINE, and PubMed Central and how they are different.