The data above were extracted from Thomson Scientific’s Essential Science Indicators database. This database, currently covering the period January 1997 to December 2007, surveys only journal articles (original research reports and review articles) indexed by Thomson Scientific. Articles are assigned to a category based on the journals in which they were published and Thomson Scientific’s 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 – to reveal weighted impact. For articles with multiple authors from different nations, each nation receives full, not fractional, citation credit. For more information on Thomson Scientific’s Essential Science Indicators, see http://scientific.thomson.com/products/esi.
Next week: hot papers in materials science