Journal Impact Factor is from Journal Citation Report (JCR), a product of Thomson ISI (Institute for Scientific Information). JCR provides quantitative tools for evaluating journals.

The impact factor is one of these; it is a measure of the frequency with which the “average article” in a journal has been cited in a given period of time.

The impact factor for a journal is calculated based on a three-year period, and can be considered to be the average number of times published papers are cited up to two years after publication. For example, the impact factor 2009 for a journal would be calculated as follows:
A = the number of times articles published in 2008-9 were cited in indexed journals during 2010

B = the number of articles, reviews, proceedings or notes published in 2008-9

Hence, Impact factor for 2010 = A/B

(note that the impact factor 2009 will be actually published in 2010, because it could not be calculated until all of the 2010 publications had been received. Impact factor 2010 will be published in 2011). For further reference, please visit http://www.sciencegateway.org/impact/.

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Other related link about journal impact factor are as follows:

> SCI 2009 Impact Factor Query

> Chemical, Chemistry and Catalysis related Journals

> How to Calculate Journal Impact Factor

> Journal Impact Factors

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