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Citation and publishing practices differs between subject fields and this is reflected in some bibliometric indicators. In order to do bibliometric analyses on publications belonging to different subject fields advanced bibliometric indicators are used. These are always normalised, i.e. the publications are compared to other publications in the same subject area (or journal), the same publication year and of the same document type.
For basic bibliometric indicators like the Journal Impact Factor (Thomson Reuters) there is no normalisation, which means that you can’t compare the values between subject fields. This can be illustrated by looking at the journal with the highest Impact Factor within the subject category 'Immunology' which is about 49 and within the subject category 'Agriculture, Dairy and Animal Science' which is about 2.5.
The journals covered by Web of Science are classified within one or more subject category. In Journal Citation Reports (JCR) you can find the Journal Impact Factor and several other metrics. If the journal is classified within more than one subject category you can see how it is ranked in each subject (example). Besides the ranking information there are also values for Median Impact Factor and Aggregate Impact Factor (values based on all publications/journals within the subject area, example)
In order to adequately evaluate a journal you should compare the metrics for the journal with the metrics for the subject category/ies that the journal belongs to.
The Journal Impact Factor gives a picture of the usage/popularity of the journal and it is best to choose a journal with an Impact Factor better than the average for the subject category.
Consider also the subject classification of the journal since it reflects the audience/reach out for the journal and the citation and publishing practice.
An example, if you publish in a journal classified within Genetics and Heredity, then if your article is to perform better than the average article in bibliometric analyses where field normalized indicators are used, then it has to gain more citations than if you publish in a journal classified within Veterinary Sciences or Dairy and Animal Science.
The different citation based indicators used for journals gives a picture of the usage, but it is important to have in mind that the measures are on journal level.
One example
Only few of these articles are highly cited.
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