从八只牙齿说到SCI

  看过一篇关于08年奥运会的礼仪小姐的评选和培训的报道。报道指出这些千里挑一的幸运儿除了要符合年龄身高体重，身长比例等各种苛刻标准，他们还必须按照国际标准，笑起来只露八只牙齿。

 

  说实话我不知道这些标准和礼仪到底存在什么关系。年龄大点，体重重点，上身长点或笑起来嘴巴大点小点就会让人觉得礼仪不够吗？我也很孤陋寡闻，在此之前我还从来没听说过这个8个牙齿的国际标准。后来上谷歌找“8 tooth smile”，可惜啊谷哥也帮不上什么忙。我现在拭目以待明年在也是国际大都市的伦敦举行的奥运会，好奇他们的那些礼仪小姐们到底会露出几只牙齿。

 

  谷歌帮不上忙，照照镜子总可以吧，我真跑去对着镜子傻笑了一番，嘿嘿嘿。又是惭愧，看来如果这嘴巴不符合某种国际标准，这微笑的国际标准也挺坑人的。让我笑起来露六到七只牙齿还好，硬要露八只的话不仅基本上可以说礼仪尽失，而且。。

 

 

  嗯，知道，星爷，长得不好看不是俺的错，这盲目追求国际标准拿八只牙齿出来吓人就是我的不对了！

 

  我还见过不少拥有迷人笑容仪态万千的笑起来习惯上下牙一起露。我不敢想象要他们只露八只牙齿会是个什么模样，O型笑？

 

  普通人不符合标准，美国甜心之一的Julia Roberts应该能让人赏心悦目了吧？以拥有无敌海景超豪华魅力四射笑容而闻名的罗伯茨小姐。。哎呀不好，翻翻她的照片，罗小姐不笑则已，一笑起来就哗啦一排十只牙齿，有时候还达到18到20只！对不起罗小姐，您也被踢出局了！

 

 

 

  如果选礼仪小姐的目的是让她们带给运动员们和观众亲切热情得体的笑容，让大家视觉感觉都愉快的话，从上面的例子我可不可以这样说，露八只牙齿不一定能达到这个目的，或者除非把具有国际标准的嘴巴（如果有这个标准的话）也成为指标之一。这就是说八只牙齿不是充分条件。反过来，笑起来不符合八只牙齿标准的（比如罗伯茨，这里先不谈国籍问题:-) 可能其实恰恰可以是最合适的人选。换言之八只牙齿甚至也不是取得亲切热情得体笑容的必要条件。既不必要也不充分的条件，作为一个参考或者可以说得过去，但有必要成为评选的指标之一吗？

 

  其实如果你留意，这种拿既不必要也不充分的条件来作为硬性指标的例子可谓比比皆是，比如在国内看到很多招工广告似乎把年龄身高学历等限得很死。这些指标和要做的工作有什么必然的关系吗？招工的人真的清楚他想要的是什么还是只是想把大部分人以这种一刀切的简单的方式淘汰掉省心？但是话又说回来，我们又能不能因为这种种的不合理而得出结论说年龄身高体重甚至笑起来露的牙齿数就是邪恶的，都需要取缔打倒呢？

 

  写到这里，我想读者大概知道我真正想说什么了。我不是关心那八只牙齿。我想说的是，和八只牙齿，和身高体重年龄一样，目前在科学网争论不休的SCI（这里我仅用与之相关的影响因子来说明），都只是一些参考体系或数字，既不代表邪恶，也不代表天使。问题的关键是他们应不应该和需不需要作为指标或标准的一部分，比如用科研成果所发表在的杂志的影响因子作为评定这些成果和科研人员的贡献的标准。如果说某个指标在某种情况下是应该或需要，那理由又是什么，除了利有没有弊，是利大于弊还是弊大于利，需要硬性地一刀切吗，等等。只有用系统的，科学的，有客观数据支撑的方法去制定各种评定的标准并及时检讨可能造成的误差，我觉得才是长久可行之计。

 

  最后我还想补充的是，从影响因子的算法（看下面）大家可能一眼就可以看出来它只是一个在特定时间段内的平均值，一个snapshot，而且它只适用于期刊杂志，而不是里面具体的任何一篇文章。为了方便大家更全面地了解这个问题，我把维基百科对影响因子的解说贴在下面（不清楚有没有中文版）。注意文章里除了介绍其计算方法和历史等等，还讲到了领域的特殊性，讲到了关于影响因子在世界范围内引起的各种争论和批评，讲到了误用影响因子的一些例子以及一些国家和地区为此采取了的相应措施。

Impact factor (From Wikipedia, the free encyclopedia)

The impact factor, often abbreviated IF, is a measure reflecting the average number of citations to articles published in science and social science journals. It is frequently used as a proxy for the relative importance of a journal within its field, with journals with higher impact factors deemed to be more important than those with lower ones. The impact factor was devised by Eugene Garfield, the founder of the Institute for Scientific Information (ISI), now part of Thomson Reuters. Impact factors are calculated yearly for those journals that are indexed in Thomson Reuters Journal Citation Reports.

Calculation

In a given year, the impact factor of a journal is the average number of citations received per paper published in that journal during the two preceding years.^[1] For example, if a journal has an impact factor of 3 in 2008, then its papers published in 2006 and 2007 received 3 citations each on average in 2008. The 2008 impact factor of a journal would be calculated as follows:

A = the number of times articles published in 2006 and 2007 were cited by indexed journals during 2008.
B = the total number of "citable items" published by that journal in 2006 and 2007. ("Citable items" are usually articles, reviews, proceedings, or notes; not editorials or Letters-to-the-Editor.)

2008 impact factor = A/B.

(Note that 2008 impact factors are actually published in 2009; they cannot be calculated until all of the 2008 publications have been processed by the indexing agency.)

New journals, which are indexed from their first published issue, will receive an impact factor after two years of 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 get an impact factor until they have been indexed for three years. Annuals and other irregular publications sometimes publish no items in a particular year, affecting the count. The impact factor relates to a specific time period; it is possible to calculate it for any desired period, and the Journal Citation Reports (JCR) also includes a 5-year impact factor.^[2] The JCR shows rankings of journals by impact factor, if desired by discipline, such as organic chemistry or psychiatry.

Use

The IF is used to compare different journals within a certain field. The ISI Web of Knowledge indexes more than 11,000 science and social science journals.^[3]

Criticisms

Numerous criticisms have been made of the use of an impact factor, including the more general debate on the usefulness of citation metrics. Criticisms mainly concern the validity of the impact factor, policies that alter it, and its incorrect application.^[4]

Validity

• The impact factor is highly discipline-dependent. The percentage of total citations occurring in the first two years after publication varies highly among disciplines from 1-3 percent in the mathematical and physical sciences to 5-8 percent in the biological sciences.^[5]
• The impact factor could not be reproduced in an independent audit.^[6]
• The impact factor refers to the average number of citations per paper, but this is not a normal distribution. It is rather a Bradford distribution, as predicted by theory. Being an arithmetic mean, the impact factor therefore is not a valid representation of this distribution and unfit for citation evaluation.^[7]
• In the short term — especially in the case of low-impact-factor journals — many of the citations to a certain article are made in papers written by the author(s) of the original article.^[8] This means that counting citations may be independent of the real "impact" of the work among investigators. Garfield, however, maintains that this phenomenon hardly influences a journal's impact factor.^[9] Moreover, a study of author self-citations in diabetes literature found that the frequency of author self-citation was not associated with the quality of publications.^[10] Similarly, journal self-citation is common in journals dealing in specialized topics having high overlap in readership and authors, and is not necessarily a sign of low quality or manipulation.^[11]
• Journal ranking lists constructed based on the impact factor only moderately correlate with journal ranking lists based on the results of an expert survey.^[12]

Editorial policies which affect the impact factor

A journal can adopt editorial policies that increase its impact factor.^[13][14]

• Journals may publish a larger percentage of review articles which generally are cited more than research reports.^[15] Therefore review articles can raise the impact factor of the journal and review journals will therefore often have the highest impact factors in their respective fields. Conversely, journals may choose not to publish minor articles, such as case reports in medical journals, which are unlikely to be cited and would reduce the average citation per article.
• Journals may change the fraction of "citable items" compared to front-matter in the denominator of the IF equation. Which types of articles are considered "citable" is largely a matter of negotiation between journals and Thomson Scientific. As a result of such negotiations, impact factor variations of more than 300% have been observed.^[16] For instance, editorials in a journal are not considered to be citable items and therefore do not enter into the denominator of the impact factor. However, citations to such items will still enter into the numerator, thereby inflating the impact factor. In addition, if such items cite other articles (often even from the same journal), those citations will be counted and will increase the citation count for the cited journal. This effect is hard to evaluate, for the distinction between editorial comment and short original articles is not always obvious. "Letters to the editor" might refer to either class.
• Several methods, not necessarily with nefarious intent, exist for a journal to cite articles in the same journal which will increase the journal's impact factor.^[17][18]

Manipulations of the impact factor

• In 2007, a specialist journal with an impact factor of 0.66 published an editorial that cited all its articles from 2005 to 2006 in a protest against the absurd use of the impact factor.^[19] The large number of citations meant that the impact factor for that journal increased to 1.44. As a result of the increase, the journal was not included in the 2008 and 2009 Journal Citation Reports.^[20]
• In 2008, a single article "A short history of SHELX" included a sentence that essentially instructs readers to cite the paper: "This paper could serve as a general literature citation when one or more of the open-source SHELX programs (and the Bruker AXS version SHELXTL) are employed in the course of a crystal-structure determination". This article received more than 6,600 citations. As a consequence, the impact factor of the journal Acta Crystallographica Section A rose from 2.051 in 2008 to 49.926 in 2009, more than Nature (31.434) and Science (28.103).^[21] The second most cited article in Acta Crystallographica Section A in 2008 had only 28 citations.^[22]

Incorrect application of impact factor

• The IF may be incorrectly applied to evaluate the significance of an individual publication or to evaluate an individual researcher.^[23]

This does not work well since a small number of publications are cited much more than the majority — for example, about 90% of Nature's 2004 impact factor was based on only a quarter of its publications, and thus the importance of any one publication will be different from, and in most cases less than, the overall number.^[24] The impact factor, however, averages over all articles and thus underestimates the citations of the most cited articles while exaggerating the number of citations of the majority of articles. Consequently, the Higher Education Funding Council for England was urged by the House of Commons Science and Technology Select Committee to remind Research Assessment Exercise panels that they are obliged to assess the quality of the content of individual articles, not the reputation of the journal in which they are published.^[25]

Responses

• Because "the impact factor is not always a reliable instrument" in November 2007 the European Association of Science Editors (EASE) issued an official statement recommending "that journal impact factors are used only - and cautiously - for measuring and comparing the influence of entire journals, but not for the assessment of single papers, and certainly not for the assessment of researchers or research programmes".^[4]
• In July 2008, the International Council for Science (ICSU) Committee on Freedom and Responsibility in the conduct of Science (CFRS) issued a "Statement on publication practices and indices and the role of peer review in research assessment", suggesting some possible solutions, e.g. considering penalising scientists for an excessive number of publications per year.^[26]
• In February 2010, the Deutsche Forschungsgemeinschaft (German Foundation for Science) published new guidelines to evaluate only articles and no bibliometric information on candidates to be evaluated in all decisions concerning "...performance-based funding allocations, postdoctoral qualifications, appointments, or reviewing funding proposals, [where] increasing importance has been given to numerical indicators such as the h-index and the impact factor".^[27] This decision follows similar ones of the National Science Foundation (US) or the Research Assessment Exercise (UK).^{[citation needed]}

Other measures of impact Related indices

Some related values, also calculated and published by the same organization, are:

• the immediacy index: the number of citations the articles in a journal receive in a given year divided by the number of articles published.
• the 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 half of all the citations from that journal in 2005, and the other half of the citations precede 2001.^[28]
• 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.

These measures apply only to journals, not individual articles or individual scientists (unlike 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. Garfield warns about the "misuse in evaluating individuals" because there is "a wide variation from article to article within a single journal".^[9] Impact factors have a large, but controversial, influence on the way published scientific research is perceived and evaluated.

PageRank algorithm

In 1976 a recursive impact factor that gives citations from journals with high impact greater weight than citations from low-impact journals was proposed.^[29] Such a recursive impact factor resembles the PageRank algorithm of the Google search engine, though the original Pinski and Narin paper uses a "trade balance" approach in which journals score highest when they are often cited but rarely cite other journals. A number of subsequent authors have proposed related approaches to ranking scholarly journals.^[30][31][32] In 2006, Johan Bollen, Marko A. Rodriguez, and Herbert Van de Sompel also proposed using the PageRank algorithm.^[33] From their paper:

	ISI Impact Factor		PageRank		Combined
1	52.28	ANNU REV IMMUNOL	16.78	Nature	51.97	Nature
2	37.65	ANNU REV BIOCHEM	16.39	Journal of Biological Chemistry	48.78	Science
3	36.83	PHYSIOL REV	16.38	Science	19.84	New England Journal of Medicine
4	35.04	NAT REV MOL CELL BIO	14.49	PNAS	15.34	Cell
5	34.83	New England Journal of Medicine	8.41	PHYS REV LETT	14.88	PNAS
6	30.98	Nature	5.76	Cell	10.62	Journal of Biological Chemistry
7	30.55	Nature Medicine	5.70	New England Journal of Medicine	8.49	JAMA
8	29.78	Science	4.67	Journal of the American Chemical Society	7.78	The Lancet
9	28.18	NAT IMMUNOL	4.46	J IMMUNOL	7.56	NAT GENET
10	28.17	REV MOD PHYS	4.28	APPL PHYS LETT	6.53	Nature Medicine

The table shows the top 10 journals by ISI Impact Factor, PageRank, and a modified system that combines the two (based on 2003 data). Nature and Science are generally regarded as the most prestigious journals, and in the combined system they come out on top^{[citation needed]}.

The Eigenfactor is another PageRank-type measure of journal influence,^[34] with rankings freely available online.^[35]

Article level metrics

Starting in March 2009, the Public Library of Science introduced "article level metrics"^[36] on every article in all of their titles.

See also

• h-index, for the impact factor of individual scientists, rather than journals.
• PageRank, the algorithm used by Google, based on similar principles.
• Eigenfactor, another journal citation ranking method.
• SCImago Journal Rank, an open access journal metric which is based on Scopus data and uses an algorithm similar to PageRank.
• Lowry protein assay paper by Oliver Lowry - one of the most cited papers in the scientific literature (cited over 200,000 times).

References