This is the basic measurement in bibliometrics. It is simply a count of the number of times an article has been cited.

Articles with more citations are likely to be more useful.

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Some journal databases will weight the raw citation count to account for differences between publishing practices in different disciplines.

An example is the Field Weighted Citation Index in Scopus.

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Citation benchmarking in Scopus.
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Highly cited papers in Web of Science
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Hot papers in Web of Science
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Production quality

Some articles receive a lot of citations when they are first published. Other articles are regularly cited over a longer period of time.

This measure can help you identify articles on topics which currently getting a lot of interest.

Some journal databases will allow you to see the citation pattern over a number of years.

Examples are:

• Web of Science – click on the citation count to see a list of articles citing the one you have found. Then click on Analyse Results. You can then rank the records by publication years.
• Scopus – click on View All Metrics to see a graph of citations over time.

If you are looking for articles which are relevant to a country or, if you know that a particular university has a strong research focus, you may want to see how many citations come from a country or university.

In Web of Science click on the citation count to see a list of articles citing the one you have found. Then click on Analyse Results. You can then rank the records by countries/territories or by organisations.

If you are looking for articles with an interdisciplinary focus you may want to see how many citations come from different disciplines.

In Web of Science click on the citation count to see a list of articles citing the one you have found. Then click on Analyse Results. You can then rank the records by research areas or Web of Science categories.

This is the oldest and simplest of the measures. It began in the 1960’s. It is calculated on journals and citations included in the Web of Science database.

The formula for each journal is:

Current year citations to articles published in the preceding two years
Articles published in the preceding two years

To find a journal’s JIF go to the Web of Science and click on Journal Citation Reports in the top menu. Enter the journal’s name in the search box and select it from the drop down list.

Web of Science does not include all items in a journal in the number of articles. Editorials and reviews may be excluded. Web of Science do not reveal what is included in or excluded from the denominator. This makes the accuracy of the calculation difficult to determine.

The formula does not weight the citation count to take account of variations in publishing rates between different disciplines. This makes it unwise to compare JIF’s for journals from different disciplines.

Introduced in 2007 this measure attempts to account for outlaying data. A single highly cited article in a year can cause a sudden jump in a journal’s JIF index. This will fall back in subsequent years.

It is calculated on the same basis as the JIF but uses the past five year’s data.

It has the same limitations as the JIF.

Introduced in 2007 this measure incorporates data from several databases:

• JSTOR
• Web of Science
• Microsoft Academic
• Socoal Science Research Network (SSRN)
• NASA
• DBLP
• arXiv
• PLOS

It uses a page rank algorithm, similar to Google where citations from higher ranked journals receive a higher weighting.

To find a journal’s Eigenfactor go to the Web of Science and click on Journal Citation Reports in the top menu. Enter the journal’s name in the search box and select it from the drop down list.

The SJR uses a page rank algorithm similar to the Eigen Factor. SJR scores are calculated using citation data from the Scopus database.

The SNIP weights citation counts based on the total number of citations for different disciplines. This makes it easier to compare journals across different disciplines.

The most widely accepted measure is the h index. This was defined by Jorge E Hirsch in 2005 as:

“A scientist has index h if h of his or her Np papers have at least h citations each and the other (Np – h) papers have ≤h citations each.”

Authors whose work has a greater impact will have a higher h index.

However, you should not compare h indexes for authors from different disciplines. See Warning above.

Early career researchers are at a disadvantage to older researchers whose papers have had time to accumulate more citations

A number of other indexes have been created in an attempt to overcome the limitations of the h index. The index is still the most quoted index.