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NIH Library Writing Center: Impact Factor & h-index

Bibliometrics

What are Bibliometrics?
Measures of a scientific writer's influence are called bibliometrics. Techniques for discerning this influence, or impact, range from simple counts of publications to sophisticated mathematical equations. Two of the most well-known bibliometrics are the impact factor, typically applied to journals, and the h-index, typically applied to authors.

What is an Impact Factor?
The impact factor, proposed by Eugene Garfield, 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 by the number of published articles in that journal during the previous two years. Journal Citation Reports calculates and publishes the annual impact factors for journals. A higher impact factor generally indicates that this journal's articles have been cited more.

Journal impact factors are searchable with Journal Citation Reports® through ISI Web of Knowledge SM.

What is an h-index?
The h-index was proposed by Jorge Hirsch in 2005 as an alternative to the impact factor. The h-index quantifies scientific productivity and the impact of a scientist based on the set of his/her most quoted papers and the number of citations that he/she has received in other people's publications. For example, an author or journal with an h-index of 30 has written at least 30 papers that have each had at least 30 citations. Thus, a higher h-index indicates more publications that have been cited more often. This metric is useful because it takes into account the uneven weight of highly cited papers or papers that have not yet been cited.

How many times have you been cited? What's your h-index?

    • Scopus: Search for your name in the Author Search. In the list of authors that comes up in the search results, click on Details. The Details page provides both the times cited and the h-index, with links to graphs and tables.

    • Web of Science: Register for ResearcherID to get your bibliometric data.

  • Google Scholar: Use the Author name field in the Advanced Search form to search for yourself. Google Scholar only provides citation counts for individual articles, not an author's entire career.

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