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Eddy博士的指导手册-期刊影响因子和其他测量期刊影响力的标准 Dr. Eddy tutorial – The impact factor and other measures of journal prestige
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Eddy博士将为您解释英语期刊出版的基本知识,与您分享他作为一名研究员多年以来积累的经验。每周他将撰写有关期刊出版的重要内容。请阅读Eddy博士的关于如何成功发表论文的提示。


期刊出版过程
期刊影响因子和其他测量期刊影响力的标准

我们都知道,全球学者都面临着在知名英文期刊上发表论文的压力。期刊影响因子(IF)是公认的衡量期刊关注度和影响力的指标。因此,很多研究者主要根据影响因子选择发表论文的期刊。

影响因子的计算

影响因子一般是个比值。2010年影响因子计算公式如下:2
IFX = 2010年所引用的期刊X于2009年和2008年发表的所有论文
期刊X于2009年和2008年发表的所有论文

你可能已经看出,2010年的影响因子只能在2011年及以后使用。期刊影响因子每年计算一次,并公布在汤森路透发表的期刊引用报告(JCR)中。

影响因子的使用和误用

impact factor1. 作为衡量期刊关注度的客观指标。.可选择的期刊数量巨大,期刊的影响因子提供了衡量期刊发表论文整体质量的客观指标。一般来说,影响因子值越高,期刊的关注度越大。
journal prestige 2. 图书馆选择期刊。.目前全球有数以万计的期刊出版物。影响因子为图书馆管理员提供了一种判定保留哪些期刊并收录哪些新期刊的工具。
impact factor 3. 学术评估。.影响因子通常被用于研究者的学术评估过程,但是,这种使用方法是不正确的,因为影响因子仅表示期刊的整体质量,而不是期刊发表的某篇论文。
使用影响因子时的注意事项

使用影响因子比较或评估期刊时,应注意以下事项:4,5
  1. 期刊影响因子的绝对值没有意义。例如:影响因子为2的期刊在微生物学等领域关注度不很高,但在海洋学领域却有较高关注度。专业期刊 – 如疾病类期刊或关注灾害管理的期刊的影响因子值可能会较低,因为期刊论文主要为少数专业读者阅读或引用。6

  2. Impact Factor学科趋向不同。不同研究领域的引用习惯不同。因此,影响因子不能用于比较不同学科的期刊。例如:医学论文的引用频率远高于数学或工程类论文;因此,医学期刊的影响因子高于数学及工程期刊。7

  3. 影响因子在特定领域意义不大。例如:在计算机科学领域,会议论文被视为科技论文的主要形式。

  4. 无影响因子不能代表期刊不重要。汤森路透根据他们的引文数据库计算影响因子。数据库收入了约25,000家同行评审期刊的几乎一半。其数据库的覆盖范围分布也不均匀,某些学科领域期刊的收录率要高于其它领域。另外,虽然汤森路透数据库收录了来自60个国家的期刊,但来自欠发达国家的期刊并不多,而且只有少数非英语期刊。

小贴士

这是不常被引用的个案报告很难被发表的原因之一。事实上,某些期刊已完全停止发表个案报告,即使其对读者很有意义。
因影响因子导致的期刊惯例的改变

一般来说,影响因子对期刊编辑与对研究者同等重要。影响因子可用于衡量期刊的业绩,因此很多期刊编辑为提高期刊的影响因子而面临着压力。9另外,影响因子也可以操控。3,10-12例如:据发现,评论文章的引用数量最大,因此期刊可尽量多地发表评审文章提高期刊的影响因子。期刊编辑可以论文是否容易被引用为基础来选择论文。期刊也可要求作者引用期刊的其它论文(成为“自我引用”)。

影响因子的替代指标

影响因子占主导地位的局面已持续数十年。但是,近年来,人们开发出了衡量期刊关注度的替代指标。据发现,所有这些指标都互相密切相关。也就是说,根据这些指标进行的期刊排名几乎都是一致的,虽然期刊的绝对排名存在差异。因此,在选择关注或准备发表论文的期刊时,研究者可自由地使用以下任何一种指标,而无需局限于影响因子。13-15
Scimago期刊排名(DJR)
数据来源:Scopus
查询网址: http://www.scimagojr.com/ 免费
计算方法:来自知名期刊的引文分值高于来自较低等级期刊的引文(类似于谷歌网页排名的计算方法)。2010年的SJR根据2010年所引用的2007年、2008年和2009年(三年期)的论文数量计算。

优点:SJR可指示哪些期刊被知名期刊引用论文的可能性更大,而不是仅仅指示哪些期刊被引用最多。
期刊影响因子(JIF)
数据来源:美国科学情报研究所
查询位置:期刊引证报告需订阅
计算方法:所有的引文分配的分值相等。影响因子以两年为周期进行计算。
优点:是使用最广泛的传统衡量期刊关注度的指标。学术界的大多数人都了解并使用期刊影响因子。
单篇文章源标准化影响 (SNIP)
数据来源: Scopus
查询网址: http://www.journalindicators.com/ 免费
计算方法:计算单篇文章源标准化影响的目的是实现某领域引文的标准化,因此消除了期刊影响因子在不同领域的高低变化。单篇文章源标准化影响也计算其它多种指标,如在某期刊学科领域内的引用潜力。
优点:在衡量各学科知名度方面,单篇文章源标准化影响的可靠性要明显高于期刊影响因子。16
特征因子分值(ES)和论文影响分值(AIS)
数据来源:美国科学情报研究所
查询网址: http://www.eigenfactor.org/ 免费
计算方法:特征因子分值类似于SIR,来自于知名期刊的引文所分配的分值较高。特征因子分值以5年为周期进行计算。最重要的是,特征因子分值还建立研究者针对各期刊所花费时间的数学模型。论文影响分值类似于影响因子,但论文影响分值利用特征因子分值进行计算,因此其计算结果比影响因子的可信度更高。
优点:有证据表明,相较影响因子,特征因子分值和论文影响分值是衡量期刊知名度的更可靠指标。14
结论
期刊影响因子用于评估期刊的非常有用的工具,但是,其使用方法必须合理。在决定投稿期刊时,不能只参考影响因子。必须牢记,关注较窄学科范围的期刊(如:诊断分子病理学)的影响因子可能低于关注学科范围广泛的期刊(如:病理学杂志)。最后,研究者应采取其它指标评估期刊质量,如单篇文章源标准化影响 和特征因子分值,以更好地了解期刊的关注度和影响力。

Contributors
The impact factor and other measures of journal prestige

It is a well known fact that academics worldwide face pressure to publish in prestigious English language journals. And the journal impact factor (IF) is the most widely recognized indicator of journal prestige and influence. Accordingly, many people choose which journals to publish in based largely on the IF. 1

Calculation of IF

The IF is basically a ratio. The 2010 IF is calculated as follows:2
IFX = All citations in 2010 to articles published in Journal X in 2009 and 2008
All citable articles published in Journal X in 2009 and 2008

As you might have guessed, IFs for 2010 become available only in 2011 and so on. Journal IFs are calculated yearly and disclosed in the Journal Citation Reports (JCR) published by Thomson Reuters.

Use and misuse of the IF

impact factor1. As an objective measure of journal prestige. There are a vast number of journals to choose from, and the journals’ IF provides an objective measure of the overall quality of work published in that journal. As a general rule, the higher the IF value of a journal, the more prestigious it is considered to be.
journal prestige 2. To select journals for libraries. There are tens of thousands of journal publications in existence. The IF provides library administrators with a tool to decide which journals to retain in their collections and which new ones to acquire for their libraries.
impact factor 3. Academic evaluation. The IF is often used in the process of academic evaluations of researchers for tenure, grants, funding, etc. However, this use is incorrect because the IF is only meant to indicate the quality of an entire journal, not the quality of individual articles published in the journal.3
Beware while using the IF

When using the IF to compare or assess journals, be on the lookout for the following:4,5
  1. The absolute value of a journal’s IF is meaningless. For example, a journal with an impact factor of 2 would not be very impressive in a subject like microbiology, but it would be in oceanography. Specialty journals - like disease-specific journals or journals focusing on disaster management - tend to have a low IF value because the journal articles are mostly read and cited by a small specialized audience.6

  2. Impact FactorDisciplinary trends are different. Citation habits vary across different research areas. Therefore, IFs should not be used to compare journals across disciplines. For example, citation frequency is much higher in medicine than in mathematics or engineering; therefore, medical journals have higher IFs than mathematical and engineering journals.7

  3. IFs are not very relevant in certain fields. For example, in computer science, conference proceedings are considered the principal form of scientific publication.

  4. Not having an IF doesn’t make a journal unworthy. Thomson Reuters calculates IFs based on their citation database. The database indexes roughly half of the approximately 25,000 peer-reviewed journals8 believed to be published. The coverage of their database is unevenly distributed as well, with some subject areas better indexed than others. In addition, although it indexes journals from 60 countries, there are not many publications from under-developed countries and only a small number of journals that publish in languages other than English.

Not so fun fact

This is one of the reasons that case reports, which are not frequently cited, are difficult to publish. Indeed, some journals have ceased publishing case reports all together, even though they can be highly useful to readers.
Changes in journal practice because of the IF

The IF is as important, if not more, for journal editors as for researchers. The IF is used to measure journal performance, and many journal editors are under pressure to increase their journal’s IF.9 Further, IFs can be manipulated.3,10-12 For example, review articles have been found to attract the most number of citations, so journals may try to publish more review articles to increase their IF. Journal editors may select articles on the basis of how likely they are to be cited. Journals may also ask authors to cite other papers from the journal (called “self-citations”).

Alternatives to the IF

The IF ruled the roost for several decades. However, alternative indicators of journal prestige have been developed in recent years. It has been found that all of these indicators correlate closely with each other. In other words, journal rankings based on these indicators tend to be similar, though there may be differences in the absolute journal rankings. So researchers should feel free to use any one of the below indicators, and not limit themselves to the IF, when selecting journals to follow or publish in.13-15
Scimago Journal Rank (SJR)
Data source: Scopus
Can be found at: http://www.scimagojr.com/ free
How it’s calculated: Citations from prestigious journals are given more weight than citations from lower-tier journals (similar to Google’s PageRank algorithm). SJR for 2010 is calculated by counting 2010 citations to papers published in 2007, 2008, and 2009 (three-year period).
Why it’s useful: SJR indicates which journals are more likely to have articles cited by prestigious journals, not simply which journals are cited the most.
Journal Impact Factor (JIF)
Data source: ISI Web of Science
Can be found in: Journal Citation Reports subscription required
How it’s calculated: All citations are given equal weight. The IF is calculated over a two-year period.
Why it’s useful: It is the traditional and most widely accepted measure of journal prestige. Most people in the academic world know about and use the JIF.
Source Normalized Impact per Paper (SNIP)
Data source: Scopus
Can be found at: http://www.journalindicators.com/ free
How its calculated: SNIP is computed so that citations are normalized by field. Thus, it eliminates variations found in JIF wherein the IFs are high in certain fields and low in others. They calculate several other metrics as well, like citation potential in the journal’s subject field.
Why it’s useful: SNIP is a much more reliable indicator than the JIF for comparing journals among disciplines. It is also less open to manipulation by journals.16
Eigenfactor score (ES) and Article Influence Score (AIS)
Data source: ISI Web of Science
Can be found at: http://www.eigenfactor.org/ free
How its calculated: ES is similar to SJR; it also gives greater weight to citations from prestigious journals. ES is calculated over a 5-year period. Like SNIP, it also normalizes citations by field. Finally, it tries to mathematically model the time that a researcher spends with each journal. The AIS is similar to the IF, except the AIS is calculated using the ES, making it a more robust calculation than the IF.
Why it’s useful: The evidence indicates that ES and AIS are more robust indicators of journal prestige and influence than the IF. 14
Conclusion
The journal impact factor is a very useful tool for the evaluation of journals, but it must be used wisely. The decision on which journal to send your manuscript to should not rest solely on the IF. It is especially important to remember that a journal with a narrow focus (e.g., Diagnostic Molecular Pathology) may have a lower IF than a more broad-based journal (e.g., Journal of Pathology). Finally, researchers should look up other indicators for journal quality, like SNIP and Eigenfactor score, to get a better idea of journal prestige and influence.
Contributors