Abstract
Purpose: In order to enable to compare journal impact across subject fields, we proposed a source normalized indicator "SCJIF" considering the difference in citation practice (references per article) among citing journals, and examined the effect of normalization. Method: We calculated the SCJIFs of journals belonging to two subject fields, Clinical Neurology(CN) and Neurosciences(NS), which are near in subject but differ in the journal impact factors (JIFs) from each other, using the data of the Journal Citation Report Science Edition 2009. Results and Discussion: The JIFs of journals in NS were higher on average than those in CN, but the difference was reduced in the SCJIFs due to more references per article in NS than in CN. The difference in the JIF within each field (CN and NS) was also reduced in the SCJIF. This is supposed to be because some subdivided regions that have different citation practice exist in a field. Conclusion: The SCJIF gives a view different from one given by the JIF, by taking in consideration the different citation practice among and within subject fields.
