Golubic Rajna, Rudes Mihael, Kovacic Natasa, Marusic Matko, Marusic Ana
Department of Occupational Medicine, Andrija Stampar School of Public Health, Zagreb University School of Medicine, Zagreb, Croatia.
Sci Eng Ethics. 2008 Mar;14(1):41-9. doi: 10.1007/s11948-007-9044-3. Epub 2007 Nov 15.
As bibliographical classification of published journal items affects the denominator in this equation, we investigated how the numerator and denominator of the impact factor (IF) equation were generated for representative journals in two categories of the Journal Citation Reports (JCR). We performed a full text search of the 1st-ranked journal in 2004 JCR category "Medicine, General and Internal" (New England Journal of Medicine, NEJM, IF = 38.570) and 61st-ranked journal (Croatian Medical Journal, CMJ, IF = 0.690), 1st-ranked journal in category "Multidisciplinary Sciences" (Nature, IF = 32.182) and journal with a relative rank of CMJ (Anais da Academia Brasileira de Ciencias, AABC, IF = 0.435). Large journals published more items categorized by Web of Science (WoS) as non-research items (editorial material, letters, news, book reviews, bibliographical items, or corrections): 63% out of total 5,193 items in Nature and 81% out of 3,540 items in NEJM, compared with 31% out of 283 items in CMJ and only 2 (2%) out of 126 items in AABC. Some items classified by WoS as non-original contained original research data (9.5% in Nature, 7.2% in NEJM, 13.7% in CMJ and none in AABC). These items received a significant number of citations: 6.9% of total citations in Nature, 14.7% in NEJM and 18.5% in CMJ. IF decreased for all journals when only items presenting original research and citations to them were used for IF calculation. Regardless of the journal's size or discipline, publication of non-original research and its classification by the bibliographical database have an effect on both numerator and denominator of the IF equation.
由于已发表期刊文章的文献分类会影响该公式中的分母，我们调查了《期刊引证报告》（JCR）两类代表性期刊的影响因子（IF）公式的分子和分母是如何生成的。我们对2004年JCR类别“医学，综合与内科”中排名第一的期刊（《新英格兰医学杂志》，NEJM，IF = 38.570）和排名第61的期刊（《克罗地亚医学杂志》，CMJ，IF = 0.690）、“多学科科学”类别中排名第一的期刊（《自然》，IF = 32.182）以及与CMJ相对排名相同的期刊（《巴西科学院学报》，AABC，IF = 0.435）进行了全文搜索。大型期刊发表的被科学引文索引（WoS）归类为非研究项目的文章更多（编辑材料、信件、新闻、书评、文献条目或勘误）：《自然》杂志5193篇文章中有63%，《新英格兰医学杂志》3540篇文章中有81%，相比之下，《克罗地亚医学杂志》283篇文章中有31%，而《巴西科学院学报》126篇文章中只有2篇（2%）。一些被WoS归类为非原创的文章包含原创研究数据（《自然》中为9.5%，《新英格兰医学杂志》中为7.2%，《克罗地亚医学杂志》中为13.7%，《巴西科学院学报》中没有）。这些文章获得了大量引用：占《自然》杂志总引用量的6.9%，《新英格兰医学杂志》的14.7%，《克罗地亚医学杂志》的18.5%。当仅将呈现原创研究的文章及其引用用于IF计算时，所有期刊的IF均下降。无论期刊规模或学科如何，非原创研究的发表及其在文献数据库中的分类都会对IF公式的分子和分母产生影响。
