Journal rankings in clinical medicine 1998-2008, based on citations per paper

	Journal	Papers	Citations	Citations per paper
1	Science	601	157,492	262.05
2	Nature	733	184,784	252.09
3	New England Journal of Medicine	192	24,425	1.21
4	CA-A Cancer Journal for Clinicians	1,731	206,824	119.48
5	Nature Medicine	3,635	334,992	92.16
6	Journal of the American Medical Association	3,635	334,992	92.16
7	Journal of Experimental Medicine	3,498	247,578	70.78
8	Nature Reviews Cancer	417	29,493	70.73
9	Proceedings of the National Academy of Sciences of the USA	4,369	307,878	70.47
10	Journal of Clinical Investigation	4,053	262,687	64.81

The data above were extracted from Thomson Reuters’ Essential Science Indicators database. This database, currently covering the period January 1998 through June 2008, surveys only journal articles (original research reports and review articles) indexed by Thomson Reuters. Articles are assigned to a category based on the journals in which they were published and Thomson Reuters’ journal-to-category field definition scheme. Both articles tabulated and citation counts to those articles are for the period indicated. Here our ranking of journals in clinical medicine is by citations per paper to reveal weighted impact. Essential Science Indicators lists journals ranked in the top 50 per cent for a field over a given period, based on total citations. In clinical medicine, 973 journals are listed, meaning that 1,946 journals in this field were surveyed. This ranking should be recognised as distinctly different from Thomson Reuters’ impact factor rankings, which are presented in the Journal Citation Reports issued each year. The impact factor is calculated as citations in Year 3 to a journal’s contents in Years 1 and 2, divided by the number of so-called citable items (regular articles and reviews) in Years 1 and 2. Thus, the above ranking reveals longer-term impact (citations per paper). The data for the multidisciplinary journals listed – Science, Nature and the Proceedings of the National Academy of Sciences of the USA – take into account only those articles that have been classified by Thomson Reuters as clinical medicine papers. For more information on Thomson Reuters’ Essential Science Indicators, see http://scientific.thomsonreuters.com/products/esi.