In addition, the citation frequency is determined by the citations in the Web of Science database rather than all conceivable citations.
More and more open access journals and journals with an open access option are endeavouring to become part of the Web of Science in order to obtain a JIF.
It is calculated by ranking a scientist's papers by the number of citations they have received.
The point at which the ranking and citation frequency are identical is the author's h-index.
However, the SJR indicator also incorporates an additional factor, namely the prestige of the journals which the citations come from (How frequently is this journal cited by others? The SNIP indicator controls for the differences in citation behaviour in different scientific disciplines by calculating the mean citation frequency of the articles in a journal and normalising this to the mean citation frequency of articles in the field.
This makes comparisons between journals more accurate.However, there is some controversy as to whether this is actually true.Journal Impact Factors are published on an annual basis in the Journal Citation Reports (JCR) which are marketed as a commercial product.That means it is not necessarily feasible to compare authors from different disciplines.In addition, two different authors may have entirely different publishing histories and yet still have the same h-index.When it comes to selecting a journal, the Journal Impact Factor (JIF) often plays a key role.Journals with a higher impact factor are often deemed to be of higher quality.It is important to remember that open access journals are often likely to have been launched relatively recently.However, the Journal Impact Factor cannot be calculated for a journal until it has been in the Web of Science for at least three years.This makes it particularly difficult to compare scientists who have been involved in research for significantly different lengths of time, as can be seen from the following example: A has published eight papers, B has published 12.Although the top-ranked papers published by A have been cited significantly more frequently than those published by B, both authors have an h-index of 7.