The Journal Impact Factor List for 2014, and the previous six years, is available at CiteFactor.org. Run by an international Advisory Board, CiteFactor is a resource that publishes the impact factors of scientific journals.
The Journal Impact Factor is based on four criteria, which include the quality of the publication and of the manuscript, as well as the presentational quality and the editorial quality. CiteFactor uses these criteria, along with analysis of citations, to generate a number for each journal. The lowest value is zero, and there is no upper limit, though the highest values are typically in the upper 50s. Journals can change value radically from one year to the next, depending on the current content of the publication.