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The impact of an individual article can be measured by the number of times it has been cited. Many databases, and a number of software applications, tally the number of times a specific article has been cited. Please note that some disciplines are more heavily cited than others, and also that citation counts will vary from one source to another, depending on the number of and type of sources indexed per database.
There are also a number of alternative metrics, called altmetrics, that can be used to measure an article's impact.
Where can I find citation counts ("times cited," "cited by," or "citations")?
Many databases provide citation counts. Look for "Times Cited" "Cited by" or "Citations." Some examples include:
Microsoft Academic Search
Each source listed in the search results includes a citation count. To view the actual in-text citations from the articles that cited the source, click on "Citations: ##" beside the citation, then "Citation Context" in the left-hand column.
In addition to providing citation counts, each source listed in the search results has number of views, number of bookmarks, and number of shares in social media. Learn more about PLOS article-level metrics.
Web of Science
A database of all of the Web of Science Citation indexes, including 8500 international journals in the sciences, social sciences, and arts and humanities. Click on "Times Cited" to see the articles that cited the source.
The Hirsch index, more widely known as the h-index, is a measure of an author's (or group of authors' or journal's) scholarly impact. The h-index reflects both the number of publications and the number of citations per publication. An author with an h-index=12 has at least 12 papers that have each been cited 12 times.
Curtin Library, 2013. http://www.youtube.com/watch?v=Qk3pN0qHa0k
Where can I find an author's h-index?
Note: Google Scholar only provides an author's h-index if he/she has created a user profile. To set up a user profile, click on the link at the top of the web page for "My citations." For the h-index of journals, see Google Scholar Metrics.
Publish or Perish
A software program that reports h-index based on citation counts from Google Scholar and from Microsoft Academic Search.
Web of Science
A database of all of the Web of Science Citation indexes, including 8500 international journals in the sciences, social sciences, and arts and humanities. Perform an Author Search; on the search results page, click on "Create Citation Report" to view the h-index.
What are some limitations to the h-index?
- As with JCR, the h-index is not a fair means of comparing authors across subject areas, as some disciplines naturally publish and cite more than others.
- Because the h-index is calculated using the number of a researcher's publications, and therefore reflects an author's "scholarly age," persons with shorter career spans are at a disadvantage, regardless of the importance of their discoveries.
- An author's h-index will be invalid if another researcher has the same name; for this reason, the only truly reliable means of deriving an author's h-index is to use a list of publications provided by the author him/herself.
- The h-index does not account for self-citations or negative citations, and may, therefore, misrepresent an author's importance .
- When calculating an author's h-index using Web of Science, bear in mind that the author's books, book chapters, etc., will not be included; furthermore, the social sciences and humanities are not well represented within Web of Science.
The journal impact factor (JIF) measures the frequency with which the 'average article' published in a journal has been cited in a particular year. It measures a journal's relative importance as it compares to other journals in the same field. The JIF is a well-known and well-established metric.
Where can I find a journal's impact factor?
Journal Citation Reports (JCR)
Covers 7000+ peer-reviewed journals in approximately 200 disciplines. Journals can be sorted by impact factor, immediacy index, total cites, total articles, cited half-life, or journal title. Learn more about using and interpreting the JIF.
What are some limitations to the journal impact factor?
- Journal Citation Reports has very few open access journals, books and conference proceedings, and a finite number of journals. Most of these are English-language only.
- Because the JIF is calculated using data from a two or five year period, new journals are excluded. As well, many small journals are not represented.
- Journal titles are assigned to one or more subject categories in JCR; therefore, the same journal may be ranked differently depending on the category being reviewed.
- Citation practices vary from one field to another, precluding comparisons across different subject areas.
- Having a large number of citations is not necessarily a marker of merit, as articles can sometimes be cited for negative reasons.
- Large and multidisciplinary journals will have higher Journal Impact Factors than those that are more focused.
- Journal impact factors can be manipulated by authors self-citing, by groups of authors citing each other's work, by an increase in multiple authorship of papers, and by certain editorial practices, such as publishing numerous review articles.
The Eigenfactor ranks journals based on the number of citations its articles receive, weighting citations that come from other influential journals more heavily. A benefit of the Eigenfactor over the JIF is that it excludes self-citations.
The Article Influence score is the Eigenfactor divided by the number of articles in the journal. This metric is most directly comparable to the JIF.
Google Scholar Metrics
In addition to measuring an author's impact, h-index can also measure the impact of journals. To get started, browse the top 100 publications (available in several languages), ordered by their five-year h-index and h-median metrics. To see which articles in a publication were cited the most and who cited them, click on its h-index number to view the articles as well as the citations underlying the metrics.
Search for SJR and SNIP metrics, or download them in an Excel file.
SCImago Journal Rank (SJR) accounts for the number of citations received by a journal and the importance of the journal it came from. This metric is based on the idea that "all citations are not created equal." You can also find SJR metrics at SCImago Journal & Country Rank.
Source Normalized Impact per Paper (SNIP) is the ratio of a journal's citation count/paper and the citation potential in its subject field. Citation potential takes into consideration the citation norms based on subject area and journal type.
Ulrich’s Periodicals Directory/ulrichsweb.com
The most comprehensive directory of periodicals or serials available worldwide. Provides bibliographic information on 240,000+ journals, magazines, and newspapers.
Harzing Journal Quality List
A collation of business and economics journal rankings from a variety of sources, sorted by title, subject area or ISSN. The July 2013 edition contains 23 different rankings of 940 journals.
American Psychological Association (APA) Journal Statistics
Statistics about manuscript rejection rates, circulation data, publication lag time, and more, from the APA.
Altmetrics are new metrics which use the social web (download counts, page views, mentions in news reports, social media, and blogs) to measure and represent the amount of attention that an article receives from society. Altmetrics are complementary to traditional metrics, not an alternative, as the name might suggest.
What are the benefits of altmetrics?
- Altmetrics attempt to measure impact outside the academy.
- Altmetrics can provide a more immediate measure of impact; citation counts and h-index can take years to accumulate.
- Altmetrics can measure the impact of non-traditional publications, like datasets and code.
- Altmetrics can provide the context and reasons for a citation.
Where can I find altmetrics?
Offers a free bookmarklet and other paid services that provide article-level metrics derived from social media sites, newspapers, government policy documents, and other sources.
An open-source tool that allows authors to create an impact profile using metrics derived from social media sites and traditional citations. These metrics can also be applied to non-traditional publications, such as blog posts, data sets, and software.
Plum Analytics is a wholly owned subsidiary of EBSCO Information Services, and the recipient of Library Journal's 2013 Most Ambitious Database Award. Plum Analytics tracks more than 20 different types of artifacts, including journal articles, books, videos, presentations, conference proceedings, datasets, source code, and cases to help researchers measure their scholarly impact.
Social Science Research Network (SSRN)
Provides metrics such as abstract views, downloads, download rank. Note: You need to create a free SSRN account to view the references and citations.
What are some limitations to altmetrics?
- Altmetrics measure how much attention a publication receives, not its quality.
- Altmetrics utilize data sources popular in North America and Europe and may, therefore, under-represent authors from other parts of the world.
- Some disciplines or subjects naturally receive more attention than others; altmetrics, like journal impact factor and H-index, do not support comparisons across disciplines.
- The behaviour of metrics varies with time; some accrue more slowly than others, and older publications are not well-represented by measures such as shares via social media.
Bailey, C.W. (2013). Altmetrics bibliography. Retrieved from http://digital-scholarship.org/alt/altmetrics.htm (altmetrics)
Bergstrom, C. (2007). Eigenfactor: Measuring the value and prestige of scholarly journals. College & Research Library News, 68(5), 314-316. http://crln.acrl.org/content/68/5/314.full.pdf+html (journal metrics)
Bornmann, L., & Daniel, H. (2007). What do we know about the h index? Journal of the American Society for Information Science & Technology, 58(9), 1381-1385. doi:10.1002/asi.20609 (h-index)
Costas, R., & Bordons, M. (2007). The h-index: Advantages, limitations and its relation with other bibliometric indicators at the micro lvel. Journal of Informetrics, 1(3), 193-203. doi:10.1016/j.joi.2007.02.001 (h-index)
Hirsch, J.E. (2010). An index to quantify an individual's scientific research output that takes into account the effect of multiple coauthorship. Scientometrics, 85(3), 741-754. doi: 10.1007/s11192-010-0193-9 (h-index)
Ravallion, M., & Wagstaff, A. (2011). On measuring scholarly influence by citations. Scientometrics, 88(1), 321-337. doi: 10.1007/s11192-011-0375-0 (h-index)