The data were extracted from the Essential Science Indicators database of Thomson Reuters. This database 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 a journal-to-category field-definition scheme. Papers in multidisciplinary journals, such as Nature and Science, are selectively assigned to a field based on paper-by-paper analysis. Both articles tabulated and citation counts are for the period indicated. Naturally, scientists publishing large numbers of papers have a greater likelihood of collecting more citations than those publishing fewer papers. This ranking is by citations per paper to reveal weighted impact.

A threshold of 100 papers was employed to identify particularly active scientists. For articles with multiple authors, each receives full, not fractional, citation credit. Essential Science Indicators lists authors ranked in the top 1 percent for a field over a given period, based on total citations. For these data, 7,200 authors are listed in the field of chemistry, so about 720,000 author records were reviewed to obtain the results. Of the 7,200 authors, 3,264 published 100 or more papers during the period surveyed. The list:

For more information, see http://scientific.thomsonreuters.com/products/esi