Assessing the academic quality of a particular journal or article is important. It can:
The JCR "impact factor" historically has been the main factor used to judge the relative importance of a journal in its field. However, because the index is based on only publications indexed in Web of Science the validity of this measurement is being disputed particularly in non-scientific fields and we are now seeing the other "impact" factors being published.
Using works indexed in the Web of Science, the JCR Journal Impact Factor is the average number of times articles from a journal published in the past two years have been cited in the JCR year. For example:
(from the Thomas Reuters site http://admin-apps.webofknowledge.com/JCR/help/h_impfact.htm)
How do I find a journal's "impact" factor?
Search for the published "impact" factor(s).
Are there other ways to evaluate "impact?"
Since one of the main criteria for calulating "impact" is the number of times articles from a journal are cited.
For more informaion: http://www.harzing.com/pop.htm