Aggregate Cited Half Life: An indicator of the turnover rate for a body of work on a subject.
Cited Half-Life: "The cited half-life is the number of publication years from the current year which account for 50% of current citations received. This figure helps you evaluate the age of the majority of cited articles published in a journal. Each journal's cited half-life is shown in the Journal Rankings Window. Only those journals cited 100 times or more times have a cited half life." (Ladwig & Sommese, 2005)
Eigenfactor: "Borrowing methods from network theory, eigenfactor.org ranks the influence of journals much as Google’s PageRank algorithm ranks the influence of web pages. By this approach, journals are considered to be influential if they are cited often by other influential journals."
g-index: Proposed by Egghe in 2006 to overcome a bias against highly cited papers inherent in the h-index. The g-index is the "highest number of papers of a scientist that received g or more citations, on average" (Schreiber, 2008a).
Google PageRank: "PageRank evaluates two things: how many links there are to a web page from other pages, and the quality of the linking sites.PageRank evaluates two things: how many links there are to a web page from other pages, and the quality of the linking sites." (Cutts, 2009)
h-index: NOTE: h-indexes vary depending on the source used to calculate them, for example, how deep the archive is, whether or not self citations are included, and what day you calculated the h-index as with each passing additional citations may occur. The most well known sources used to calculate researcher h-indexes are the following databases: Web of Science, Scopus and Google Scholar. Each of these databases may index different publications such as journals, books, conference papers, book chapters, and as such will influence the h-index. The Web of Science (W)S) and Scopus will list the articles they search to gather citations and they are selective. Google Scholar uses the articles and other items pulled into Google Scholar (GS), so selectivity is lower than WOS or Scopus. That said, as new types of scholarship (altmetrics) are adopted, GS will most likely catch a researcher's impact in some areas of study faster than the other two. Note that h-indexes vary with the various disciplines.
The h-index, or Hirsch index, measures the impact of a particular researcher (or team of researchers) rather than a journal. "It is defined as the highest number of publications of a researcher that received h or more citations each while the other publications have not more than h citations each (Schreiber, 2008a)." For example, a scholar with an h-index of 5 had published 5 papers, each of which has been cited by others at least 5 times. Note that an individual's h-index may be very different in different databases. This is because the databases index different journals and cover different years. For instance, Scopus only considers work from 1996 or later, while the ISI Web of Science calculates an h-index using all years that an institution has subscribed to. (So an ISI Web of Science h-index might look different when searched through different institutions.)
Immediacy Index: The average number of times a journal article is cited in the year it is published. Can be useful for comparing journals on cutting edge research. (Thomson Corporation, 2008)
Journal Impact Factor: The journal impact factor measures the importance of a journal and "is a measure of the frequency with which the 'average article' in a journal has been cited in a particular year or period" (Thomson Reuters, 2010).
How an Impact Factor is Calculated "The annual JCR impact factor is a ratio between citations and recent citable items published. Thus, the impact factor of a journal is calculated by dividing the number of current year citations to the source items published in that journal during the previous two years." (from an essay originally published in Current Contents June 20, 1994)
Journal Self-Citation: "A self-citation is a reference to an article from the same journal. Self-citations can make up a significant portion of the citations a journal gives and receives each year." (Thomson Reuters, 2010)
Related Journals: Calculated using the number of citations from the selected journal title, total number of articles in the related journal and total number of citations from the citing journal. Uses the number of citations from one journal to another to determine a relationship. (Thomson Reuters, 2010)
Self-Citation: "The practice of self-citation can be considered at many levels, including author self-citation, journal self-citation, and subject category self-citation..." (McVeigh, M. E., nd)
Unified Impact Factor: Useful when a journal title changes because the impact factor is generally affected for two years. You can view title changes by clicking on the Journal Title changes link on one of the following pages: Journal Search, Journal Summary List, or Marked Journal List (Thomson Reuters, 2010) & (Thomson Reuters, 2010a)