From Thomson Scientific's ISI Web of Knowledge ... the latest impact factors for most of the journals I read, i.e. those that publish cell biology & molecular biology manuscripts. Note that the list does not contain neuroscience or review journals.
(Inspired by Coturnix' entry.)
How exactly does one find Thomson's Impact Factor calculations?
How exactly does one find Thomson's Impact Factor calculations?
The calculation is simple: if a journal has a 2004 IF of 5, then papers published in that journal in 2001-2002 were cited, on average, 5 times each in 2003.
As for the data from which Thomson calculates this meaningless metric, one does not find that -- it is proprietary.