20 millions of records in Medline
PubMed provides free access to MEDLINE, NLM’s database of citations and abstracts in the fields of medicine, nursing dentistry, veterinary medicine, health care systems and preclinical sciences.
In comparison, Scopus claims 40 millions of records (http://www.info.sciverse.com/scopus/scopus-in-detail/facts/ )
Web of Science announced 46 millions (incl. non-scientific data) in 2009 (http://en.wikipedia.org/wiki/Web_of_Science )