中文摘要：

该文借鉴期刊影响因子的概念，定义了一个可以反映一个国家所发表论文影响力的指标——国家论文被引强度（NCI），计算了1991—2014年间中国科研机构在Nature和Science上发表论文的NCI。研究结果表明，中国科研机构在Nature和Science上发表论文的影响力总体上不断升高，近5年在这两个刊物上发表（含参与发表）的全部论文和作为第一著作单位发表的论文的平均被引强度都已经超过期刊自身的影响因子，对期刊的学术影响力起到了正贡献，而且已经与美国、英国、德国、法国及日本等科技发达国家相当。

英文摘要：

In this paper, national papers＇ cited intensity （NC1）, as an index, is defined to reflect the impacts of papers of one country, by referencing the concept about impact factor （IF） of journal. The NCI is calculated on the papers published in Nature and Science between 1991-2014 by Chinese institutions. The findings show that the impacts of papers in Nature and Science by Chinese institutions are elevated continually as a whole. In recent 5 years, the mean NCIs of all papers and the papers that China＇s institutions as the first contribution institution, have exceeded the journal＇s IF, and have a positive contribution to the journal＇s IF. Furthermore, the China＇s NC1 has also matched to that of USA, UK, Germany, France, Japan, and other developed countries