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PubMed is a database of citations and abstracts for more than 27 million articles. PubMed Central® (PMC) is an electronic archive of full-text journal articles, offering free access to its contents. PMC contains more than 4 million articles, most of which have a corresponding entry in PubMed.
PubMed does not have citations for certain types of PMC material, such as book reviews, that are considered out of scope for PubMed. These items constitute a small portion of the total PMC collection and there are no current plans to include them in PubMed.

For more details on the differences between the two databases please see the Fact Sheet titled “MEDLINE, PubMed, and PMC (PubMed Central): How are they different?
Check also PMC FAQs on what is PMC and who operates and oversees the database.