|Country||Papers||Citations||Citations per paper|
The data above were extracted from the Essential Science Indicators database of Thomson Reuters. This database, currently covering the period January 1999 through October 2009, 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 the 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 in physics is by citations per paper – among nations that collected 100,000 or more citations during the period – to reveal weighted impact. For articles with multiple authors from different nations, each nation receives full, not fractional, citation credit. Essential Science Indicators lists nations ranked in the top 50 per cent for a field over a given period, based on total citations. In physics, 88 nations are listed, meaning 176 were surveyed. Twenty-three nations collected at least 100,000 citations in this field during the period.
A comparison of this survey with a similar one from two years ago shows few meaningful changes in rank order by impact. However, England has moved up in the latest survey from eighth to sixth. Also, Russia has dropped out of the top 20 and India entered it, comparing 1997-2007 with 1999-2009.
For more information on Thomson Reuters Essential Science Indicators, see http://scientific.thomsonreuters.com/products/esi.