Library Foundation

H-Factor:

Cumulative impact and relevance of an individual researcher's scientific research output. 
     H-Factors available: Scopus database - Author Search

Further Reading:    

Hirsch, JE.  An Index to Quantify an Individual's Scientific Research Output. PNAS 2005  102(46): 16569-16572  doi:10.1073/pnas.0507655102

Eigenfactor:

Algorithms that use the structure of the entire network (instead of purely local citation information) to evaluate the importance of each journal; puts citations and data into context.

ISI Web of Science: Impact Factors

Impact Factors are sometimes supplied by individual publishers. See publisher's webpages.

Science Watch

Sci-Bytes - What's New in Research
Thomson Reuters

SJR

SCImago: Journal & Country Rank
Journal and country scientific indicators
from SCOPUS (Elsevier B.V.)
Freely available on the Internet

IMPACT FACTOR:  A method of ranking, evaluating, categorizing, comparing journals, journal articles, books and even authors or researchers. Measures the frequency of citation in a given period of time. Provides quantitative evidence for evaluation of relative importance.

Caution

• Review articles are heavily cited and therefore may inflate impact factoring
  
  
• Long articles collect many citations and therefore yield high impact factors. Short articles lag in impact factor scoring.
  
  
• Self-citation produces high Impact Factors
  
  
• Citations in the national language of a journal are preferred which can scew factoring
  
  
• Impact Factors depend on the dynamics of a research field which can expand and contract
  
  
• Small research fields tend to lack high impact
  
  
• The number of citations differ between basic biomedical research and clincial publications. Research related to molecular genetics tends to be highly cited while clinical publications are not. Clinical medicine draws heavily on basic science references but not vice versa

Impact Factors are not a perfect tool to measure the quality of journal, articles, or researchers. They should be used in concert with additional criteria.

Formula Example

Journal X's impact factor for 2004

Number of Cites in 2003 to articles published in:
2002 =  866 citations
2001 = 1191 citations
     divided by
Number of articles published in:
2002 = 203 articles
2001 = 214 articles

Calculation:

Cites to recent articles      2057
Number of recent articles    417

Impact Factor   =  4.933