Used to determine the impact a particular journal has in a given field of research, based on citations to articles in the journal.
The Eigenfactor score divided by the number of articles published in journal. "I know how impactful the journal as a whole is, but what about the average individual article in the journal?"
Similar to the 5-Year Journal Impact Factor, but weeds out journal self-citations. It also, unlike the Journal Citation Reports impact factor, cuts across both the hard sciences and the social sciences. The calculation is based on the number of times articles from the journal published in the past five years have been cited in the Journal Citations Report year, but it also considers which journals have contributed these citations so that highly cited journals will influence the network more than lesser cited journals.
This metric is based on the articles published by a journal over 5 calendar years. h is the largest number of articles that have each been cited h times. A journal with an h5-index of 43 has published, within a 5-year period, 43 articles that each have 43 or more citations.
Journal Immediacy Index
Citations to articles from the current year, divided by the total number of articles from the current year. "How much is this journal being cited during the current year?"
Journal Impact Factor
Citations to articles from the most recent two full years, divided by the total number of articles from the most recent two full years. "How much is this journal being cited during the most recent two full years?"
SNIP - Source-Normalized Impact per Paper
SNIP weights citations based on the number of citations in a field. If there are fewer total citations in a research field, then citations are worth more in that field.
SJR - SCImago Journal Rank
Similar to Eigenfactor, this metric doesn't consider all citations of equal weight; the prestige of the citing journal is taken into account. Because of the broader coverage provided by Scopus though, SCImago provides scholars with more information about more titles than is provided by either the JCR or the Eigenfactor score. It expresses the average number of weighted citations received in the selected year by the documents published in the selected journal in the three previous years, --i.e. weighted citations received in year X to documents published in the journal in years X-1, X-2 and X-3.
5-Year Journal Impact Factor
Citations to articles from the most recent five full years, divided by the total number of articles from the most recent five full years. "How much is this journal being cited during the most recent five full years?"
The purpose is to establish the impact of an article. The most common way of evaluating this is to count the number of times an article has been cited in other articles.
Used as a means to distinguish an author's impact in a field. This calculates the amount of citations an author has had.
The h-index was developed in 2005 by Jorge Hirsch, see Further Reading for the paper where he defines this. In that paper he states "A scientist has index h if h of his/her Np papers have at least h citations each, and the other (Np − h) papers have no more than h citations each." H-index attempts to calculate the amount of impact as opposed to just the amount of citations. An example of h-index is, a scholar with an h-index of 5 has published 5 papers, each of which has been cited by others at least 5 times. Note: an individual's h-index may be very different in different databases. This is because the databases index different journals and cover different years.
Number of times cited
This is the most simplistic way to calculate the amount of times an author has been cited. It simply asks the question, "How many citations has this author had?" Many databases will show you the amount of citations for a specific author that they have in the database.
Formed as a way to review the impact of an article through social media as well as scholarly publications. The field of altmetrics is relatively new and therefore standards on how to compile this information range. For more information see the Altmetrics Manifesto .