medicalclub

medical college information and medical books
 
HomeHome  GalleryGallery  FAQFAQ  SearchSearch  RegisterRegister  MemberlistMemberlist  UsergroupsUsergroups  Log inLog in  

Share | 
 

 Journal Impact factor

Go down 
AuthorMessage
obecalprx
moderator
avatar

Number of posts : 203
Location : nepal
Registration date : 2007-09-19

PostSubject: Journal Impact factor   Thu Sep 20, 2007 10:24 pm

Journal Impact factor




The Impact factor, often abbreviated IF, is a measure of
the citations to science and social science journals. It is frequently
used as a proxy for the importance of a journal to its field.



The Impact factor was devised by Eugene Garfield, the founder of the
Institute for Scientific Information, now part of Thomson, a large
worldwide US-based publisher. Impact factors are calculated each year
by Thomson Scientific for those journals which it indexes, and the
factors and indices are published in Journal Citation Reports. Some
related values, also calculated and published by the same organization,
are:



* the immediacy index: the average citation number of an article in that year.

* the journal cited half-life: the median age of the articles that were
cited in Journal Citation Reports each year. For example, if a
journal's half-life in 2005 is 5, that means the citations from
2001-2005 are 50% of all the citations from that journal in 2005.

* the aggregate impact factor for a subject category: it is calculated
taking into account the number of citations to all journals in the
subject category and the number of articles from all the journals in
the subject category.



Overview



These measures apply only to journals, not individual articles or
individual scientists (unlike, say, the H-index). The relative number
of citations an individual article receives is better viewed as
citation impact.



It is, however, possible to measure the Impact factor of the journals
in which a particular person has published articles. This use is
widespread, but controversial. Eugene Garfield warns about the "misuse
in evaluating individuals" because there is "a wide variation from
article to article within a single journal".[1] Impact factors have a
huge, but controversial, influence on the way published scientific
research is perceived and evaluated.





Calculation



The impact factor for a journal is calculated based on a three-year
period, and can be considered to be the average number of times
published papers are cited up to two years after publication. For
example, the 2003 impact factor for a journal would be calculated as
follows:



A = the number of times articles published in 2001-2 were cited in indexed journals during 2003

B = the number of articles, reviews, proceedings or notes published in 2001-2



2003 impact factor = A/B


(note that the 2003 impact factor was actually published in 2004,
because it could not be calculated until all of the 2003 publications
had been received.)



A convenient way of thinking about it is that a journal that is cited
once, on average, for each article published has an IF of 1 in the
equation above.



There are some nuances to this: ISI excludes certain article types
(such as news items, correspondence, and errata) from the denominator.
New journals, that are indexed from their first published issue, will
receive an Impact Factor after the completion of two years' indexing;
in this case, the citations to the year prior to Volume 1, and the
number of articles published in the year prior to Volume 1 are known
zero values. Journals that are indexed starting with a volume other
than the first volume will not have an Impact Factor published until
three complete data-years are known; annuals and other irregular
publications, will sometimes publish no items in a particular year,
affecting the count. The impact factor is for a specific time period;
while it is appropriate for some fields of science such as molecular
biology, it is not for such subjects with a slower publication pattern,
such as ecology. It is possible to calculate the impact factor for any
desired period, and the web site gives instructions. Journal Citation
Reports includes a table of the relative rank of journals by Impact
factor, in each specific science discipline, such as organic chemistry
or psychiatry.



Small list of top 30 Journals according to IF







Full list for 2005 available here:
Back to top Go down
View user profile
 
Journal Impact factor
Back to top 
Page 1 of 1
 Similar topics
-
» Personal Journal Entries...dare we?
» Vendredi 15 Juillet : Journal
» Effect of Jupiter on Earth impact rate
» Constraining the stellar tidal dissipation factor
» Broadcast Radio - what impact has it had on our lives?

Permissions in this forum:You cannot reply to topics in this forum
medicalclub :: E-books & Articles :: Articles-
Jump to: