title: The evolution of academic performance in nine subspecialties of internal medicine: an analysis of journal citation reports from 1998 to 2010.
abstract: BACKGROUND
  Internal medicine includes several subspecialties. This study aimed to describe change trend of impact factors in different subspecialties of internal medicine during the past 12 years, as well as the developmental differences among each subspecialty, and the possible influencing factors behind these changes and differences.
  
  
  METHODS
  Nine subspecialties of internal medicine were chosen for comparison. All data were collected from the Science Citation Index Expanded and Journal Citation Reports database.
  
  
  RESULTS
  (1) Journal numbers in nine subspecialties increased significantly from 1998 to 2010, with an average increment of 80.23%, in which cardiac and cardiovascular system diseases increased 131.2% rank the first; hematology increased 45% rank the least. (2) Impact Factor in subspecialties of infectious disease, cardiac and cardiovascular system diseases, gastroenterology and hepatology, hematology, endocrinology and metabolism increased significantly (p<0.05), in which gastroenterology and hepatology had the largest increase of 65.4%. (3) Journal impact factor of 0-2 had the largest proportion in all subspecialties. Among the journals with high impact factor (IF>6), hematology had the maximum proportion of 10%, nephrology and respiratory system disease had the minimum of 4%. Among the journal with low impact factor (IF<2), journal in nephrology and allergy had the most (60%), while endocrinology and metabolism had the least (40%). There were differences in median number of IF among the different subspecialties (p<0.05), in which endocrinology and metabolism had the highest, nephrology had the lowest. (4) The highest IF had a correlation with journal numbers and total paper numbers in each field.
  
  
  CONCLUSIONS
  The IF of internal medicine journals showed an increasingly positive trend, in which gastroenterology and hepatology increase the most. Hematology had more high IF journals. Endocrinology and metabolism had higher average IF. Nephrology remained the lowest position. Numbers of journals and total papers were associated with the highest IF.
authors.affiliation: Department of Nephrology, State Key Laboratory of Kidney Diseases, Chinese PLA General Hospital, Beijing, People's Republic of China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhang
authors.forename: Jia
authors.initials: J
authors.lastname: Kou
authors.forename: Xue-Guang
authors.initials: XG
authors.lastname: Zhang
authors.forename: Li
authors.initials: L
authors.lastname: Zhang
authors.forename: Shu-Wen
authors.initials: SW
authors.lastname: Liu
authors.forename: Xue-Ying
authors.initials: XY
authors.lastname: Cao
authors.forename: Yuan-Da
authors.initials: YD
authors.lastname: Wang
authors.forename: Ri-Bao
authors.initials: RB
authors.lastname: Wei
authors.forename: Guang-Yan
authors.initials: GY
authors.lastname: Cai
authors.forename: Xiang-Mei
authors.initials: XM
authors.lastname: Chen
mesh_terms: D000047:Academies and Institutes / Q000706:statistics & numerical data*; D007388:Internal Medicine / Q000706:statistics & numerical data*; D055811:Journal Impact Factor; D013223:Statistics as Topic; D013997:Time Factors