PubMed comprises more than 22 million citations for biomedical literature from MEDLINE, life science journals, and online books.
PubMed Central is an electronic archive for over 130+ full text journals, offering unrestricted access to its contents. Every full text article in PubMed Central has a corresponding entry in PubMed. PubMed Central contains all the peer-reviewed primary research articles from every participating journal. Other journal content, such as essays, reviews, and letters, is made available at the discretion of the publisher.