A primary source in biology...
More info and other types of primary sources in the sciences: http://library.albany.edu/infolit/prisci
Ulrich's™ is the authoritative source of bibliographic and publisher information for 300,000+ periodicals (open access. peer reviewed, newsletters, etc). Includes active titles, suspended titles, ceased titles (from 1974), and forthcoming titles.
Anali Perry, a librarian from Arizona State University Libraries, gives a quick definition of a peer-reviewed article.