In science nowadays the quality of a researcher is assessed through its publication in journals with a high impact factors. The impact factors was created by Thomson Reuters (http://thomsonreuters.com/products_services/science/free/essays/impact_factor/) and is the number of time a journal gets its article cited divided by the number of article it publishs. So an impact factor of 5 means that every paper is cited in average 5 times.
This metric was developed to assess journal quality of publication yet it is now more and more widely used by grant commission or selection comity to select amongst the candidate. A recent editorial in Science (http://www.sciencemag.org/content/340/6134/787.full) call for a stop in this destructive habits since it is threatening the prime aim of science: advance of knowledge.
The rise in open access fully online journals and their newly developped Alternative Metrics (Altmetric) will hopefully shift the attention from where you publish to what you are actually doing (publishing crappy/ consensual articles in Science or Nature should not be the aim of scientists, rather the knowledge you are creating).
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