【目的】 全面揭示SCI收录期刊的影响因子(Impact Factor,IF)与2年自被引率(Self-Cited Rate,SCR2)20年来的变化趋势,从宏观上考察SCI收录期刊的自引情况。【方法】 以1997—2016年SCI收录期刊为研究对象,以IF与SCR2为评价指标,考察IF与SCR2之间的相关性,分别绘制IF、SCR2的平均值与中位数的年度折线图。【结果】 SCI收录期刊的IF与SCR2呈显著负相关,各年度的相关系数平均值为-0.276;1997—2016年IF的平均值与中位数整体呈逐年上升的趋势,20年间分别上升了90.4%和134.2%;1997—2016年SCR2的平均值与中位数整体呈逐年下降的趋势,20年间分别下降了33.0%和38.3%;1997—2016年SCR2≥0.2、SCR2≥0.3、SCR2≥0.4与SCR2≥0.5的期刊数量占比也均呈逐年下降的趋势,20年间分别下降了48.6%、59.1%、66.5%、70.4%。【结论】 从宏观上讲,SCI收录期刊中高IF期刊的IF并不依赖于期刊自引;随着时间的推移,期刊自引对SCI收录期刊IF的贡献越来越小;检测期刊自引程度的自被引率(Self-Cited Rate,SCR)与SCR2的标准值应随着时间的推移作适当的修正。
[Purposes] This paper aims to entirely reveal the changing trend of impact factors (IF) and two-year self-cited rates (SCR2) of SCI journals over 20 years, and examine the self-citation of SCI journals from a macro perspective. [Methods] Selecting SCI journals from 1997 to 2016 as the research objects, IF and SCR2 were used as the evaluation indexes to investigate the correlation between IF and SCR2, and to draw the annual line charts of the average and median of IF and SCR2, respectively. [Findings] The IF of SCI journals has significant negative correlation with SCR2, and the average value of correlation coefficient of each year is -0.276. The average value and median of IF from 1997 to 2016 show an increasing trend year by year in general, with an increase of 90.4% and 134.2% in 20 years, respectively. However, the average value and median of SCR2 show a decreasing trend year by year, with a decrease of 33.0% and 38.3% in 20 years, respectively. The proportion of journals, of which SCR2 from 1997 to 2016 is equal to or larger than 0.2, 0.3, 0.4 and 0.5, also shows a decreasing trend by years, with a decrease of 48.6%, 59.1%, 66.5%, and 70.4% in 20 years, respectively. [Conclusions] Macroscopically speaking, the IF of SCI journals with higher IF does not mainly depend on journal self-citation. As time goes by, the contribution of journal self-citation to IF of SCI journals becomes smaller and smaller. The standard values of SCR and SCR2 for measuring the degree of self-citation of journals should be corrected appropriately over time.
Two-year self-cited rate,