Citation impact of papers published from six prolific countries: A   national comparison based on InCites data
  Using the InCites tool of Thomson Reuters, this study compares normalized citation impact values calculated for China, Japan, France, Germany, United States, and the UK throughout the time period from 1981 to 2010. The citation impact values are normalized to four subject areas: natural sciences; engineering and technology; medical and health sciences; and agricultural sciences. The results show an increasing trend in citation impact values for France, the UK and especially for Germany across the last thirty years in all subject areas. The citation impact of papers from China is still at a relatively low level (mostly below the world average), but the country follows an increasing trend line. The USA exhibits a relatively stable pattern of high citation impact values across the years. With small impact differences between the publication years, the US trend is increasing in engineering and technology but decreasing in medical and health sciences as well as in agricultural sciences. Similar to the USA, Japan follows increasing as well as decreasing trends in different subject areas, but the variability across the years is small. In most of the years, papers from Japan perform below or approximately at the world average in each subject area. 
Lutz Bornmann and Loet Leydesdorff
cs.DL stat.AP