期刊影响因子分析期刊影响因子分析

汤姆森科技信息集团 中国办事处汤姆森科技信息集团 中国办事处

Journal Citation Reports - Journal impact factor

Essential Science Indicators

Citation and citation analysis

Citation Analysis via Peer Assessment

50 years ago…

Garfield, E. “Citation indexes for science: A new dimension in documentation through association of ideas.” Science, 122 (3159), p.108-111, July 1955.

Cited Referencesassociation of ideas of its author

Cited Referencesassociation of ideas of its author

Citation Indexesnew approach to subject control of the literature of science

Citation Indexesnew approach to subject control of the literature of science

2004

Cited References

20001998

2001

1993

2003Times Cited

2003

2004

Cited References

Paper/Article Citing papers

How to define “citation”?

利用引文分析进行科研评估的理论基础 : Normative Perspective on citations

美国社会学家罗伯特 ·默顿 (Robert K. Merton): 《科学的规范结构》

文献引用的动机 Citation motivation: 原文献的科学价值

Citation – Impact, Influence, Importance, Performance• 科学期刊在同行科学家的交流中起着根本的作用。即科学文献能够代

表科学活动以及表现不同分支学科之间关系。在整个期刊系统中，可以区分出“重要”的国际性期刊

• 学术文献被重要的期刊文献引用的次数是这一文献的影响或国际显著性的一种度量

• Moed et al., The use of bibliometric data for the measurement of university research performance, Research Policy, 14, 131-149,1985;

• Oppenheim, C. Journal of Documentation, 1995

引文分析的前提

Web of Science® and its offspring

Web of Science Journal Citation Reports

Journal Impact Factor

Stats by journal

Stats by addressEssential Science

Indicators

Baselines

CustomizeResearch Services Group

National Science IndicatorsInstitutional Citation ReportsTopic Citation Reportsetc…

Web of Science® and its offspring

Article-level vs. Journal-level data

Science Citation IndexExpanded

Web of Science Journal Citation Reports

Journal Impact Factor

Stats by journal

Journal Citation Reports 独特的多学科期刊分析评价工具

自 1997 年以来的数据： 提供基于引文数据的期刊评价指标 显示出引用和被引期刊之间的相互关系

帮助用户以定量的方式了解全球的学术期刊

利用 JCR on Web深入了解学术期刊

Calculation of Journal Impact FactorExample: 2004 Impact Factor for New England Journal of Medicine

2002 2003 2004

366 papers published in 2003 14147 times cited in 2004

378 papers published in 2002 14549 times cited in 2004

378+366

14549+14147

＝744

28696

≒ 38.570

Journal Citation Reports 2004 Science Edition

Impact Factors only take the recent 3 years into consideration. What about the fields with a longer citation span?

Impact Factors only take the recent 3 years into consideration. What about the fields with a longer citation span?

2004 IF=38.570

The journal impact factor is a measure of the frequency with which the "average article" in a journal has been cited in a particular year.

The impact factor will help you evaluate a journal's relative importance, especially when you compare it to others in the same field.

Journal Impact Factor

• Average citation count in a particular year • Assigned at “journal level”• Assigned to journals indexed in Citation Indexes

– SCIE (Science Citation Index Expanded)– SSCI (Social Sciences Citation Index)

• Included in Journal Citation Reports® database• Updated annually• Helpful when evaluating a journal’s relative importance• Not intended to evaluate individual papers/researchers

Why Impact Factor?• Comparison of scholarly journals

– Journal collection development in a library– Decision-making support for

article submission by a researcher– Editorial policy development by

a journal publisher

• Problems in SIMPLE comparison of citation counts– Size (# of articles published in a year)– Frequency (# of issues published in a year)

Impact Factor:AVERAGE

citation count

Web of Science® record example

Cited References:

Items cited by this

article (29 items)

Times Cited:How many articles are citing this article (350

articles)

Records are counted at journal-level,

then included inJournal Citation Reports®

Look up journal infoin JCR

What you can tell in Journal Citation Reports®

• Which journals publish most number of articles? • Which journals are most cited in particular disciplines?• Which journals have “high impact” in particular

disciplines?• Which journals publish “hot” topics?• Journal’s self-citations• Review article rates• Cited-citing relationships of journals

×JCR is not for evaluating individuals/papers

Recognize skewed nature of citation data

• Citation distributions are not normal (the typical bell-shaped curve)

• Apparent at every level of analysis

• Citation distributions are extremely skewed: few papers or people are cited at high frequency, most cited little

67% papers are below the average

Web of Science, search conducted on Sept 28, 2005

Misuse of “Impact Factor”

I first mentioned the idea of an impact factor in 1955. At that time it did not occur to me that impact would one day become the subject of widespread controversy. …… It has been used constructively to select the best journals for Current Contents® and the Science Citation Index,® and for library collections. However, it has been misused in many situations, especially in the evaluation of individual researchers.

“The use of JCR and JPI in measuring short and long term journal impact”. Presented by Eugene Garfield at Council of Scientific Editors Annual Meeting held in May 9, 2000.

http://www.garfield.library.upenn.edu/papers/cseimpactfactor05092000.html

Essential Science IndicatorsSM

Essential Science Indicators

ESI lists the top 1% of scientists and institutions, and the top 50% of countries and journals;

also provides benchmarks for evaluating individual papers

Counted byscientist, country,institution, journal

Web of Science

Science Citation Index

ExpandedSocial Sciences Citation Index

Benchmarking data for papers

Benchmarking data for papers

Compare like with like

• THIS IS THE GOLDEN RULE OF CITATION ANALYSIS

• Always compare “apples with apples, not apples with oranges”

• Field averages are different, by 10:1

• Time affects citation counts

High Impact Papers Database, 1981-2004

ECR is only available in RSG customized data delivery.

ECR is only available in RSG customized data delivery.

ECR (Expected Citation Rates) is the average citation count of items that are published in the same journal, in the same year, and as the same document type.

ECR (Expected Citation Rates) is the average citation count of items that are published in the same journal, in the same year, and as the same document type.

Summary

• Citation Indexes– Web of Science®– Journal selection process

• Impact Factor– Included in JCR– Average citation count in a

particular year for a journal– Only account for recent years– Helpful in evaluating a

journal’s relative importance– Not intended to evaluate

individual papers/researchers• Characteristics of citation data

– Different citation patterns by disciplines

– Skewed distribution

• Benchmarks for research evaluation

– Included in ESI

– Average citation rates

– Percentiles

– Match against with the actual citation counts

– No simplistic ways for research evaluation by citation analysis

– Use citation data to COMPLEMENT peer review process

complement

Quantitative analysis and peer review complement one another!

Quantitative analysis and peer review complement one another!

Thank you!

谢谢！谢谢！

http://www.esi-topics.com/

http://in-cites.com/