When science is no longer a personal choice and individual career, an objective measure to evaluate researchers comes into beings to decide funding allocation and job promotion. However, how to build an objective measure, or whether it really exists, is becoming one of most debated topics among academical world. No matter you like it or not, it is there and grows like a child.
It starts from the number of publications, move to citations you have, then changed to Journal impact factors and the combination of the number and citations together called h-index. Now a even newer version appeared in the latest issue of PNAS. You can read a really good discussion about all these measures and may inspire you to think more.
The website of Eigenfactor website: http://www.eigenfactor.org/
What Eigenfactor is? here is from the articel: " The Eigenfactor™ is now listed by Journal Citation Reports®. In practice, there is a strong correlation between Eigenfactors and the total number of citations received by a journal (2). A plot of the 2007 Eigenfactors for the top 200 cited journals against the total number of citations shows some startling results (Fig. 1). Three journals have by far and away the most overall influence on science: Nature, PNAS, and Science, closely followed by the Journal of Biological Chemistry. So, publish in PNAS with the full knowledge that you are contributing to one of the most influential drivers of scientific progress."
However, I like this comment best:
"The terrible legacy of IF is that it is being used to evaluate scientists, rather than journals, which has become of increasing concern to many of us. Judgment of individuals is, of course, best done by in-depth analysis by expert scholars in the subject area. But, some bureaucrats want a simple metric. My experience of being on international review committees is that more notice is taken of IF when they do not have the knowledge to evaluate the science independently."
Anyhow, evaluation of science is a human process. It needs some human evaluation more than just one number.