ince 1981, the People’s Republic of China has sharply increased its output of scientific papers, according to a new Science Watch survey of that nation’s research. Figures also indicate that the citation impact of research from China is trending upward in key fields, and that over the last decade China-based authors have been increasingly represented in an elite selection of each year’s most highly cited papers.

The graph below shows the number of papers listing at least one author address in China that were indexed in each year by Thomson Scientific since 1981. From 1,650 papers indexed in 1981, China increased its presence to more than 40,000 papers published in Thomson-indexed journals in 2003—an increase of more than 2,000%. In terms of overall share of Thomson-indexed literature, China progressed from 0.38% of the database in 1981 to 5.07% in 2003. China’s output obviously outpaces that of its Asian neighbors displayed in the graph—compared, for example, to the roughly 18,500 papers indexed from South Korea (although, in a point of comparison not shown in the graph, China has yet to rival the 75,000+ papers recorded by Thomson Scientific in 2003 that listed at least one author address in Japan). The table at the bottom of the page, presents a more-detailed breakdown of recent output from China, showing 20 main fields of science ranked by China’s percent share of Thomson-indexed papers in each field for the cumulative period 1999 to 2003. The table also shows the citation-impact average (that is, cites per paper) for China in each field, along with the world average.

China’s largest representation of papers over the last five years, as the table shows, was in the field of materials science, with nearly 15,000 papers indexed between 1999 and 2003, constituting 10.45% of the field as reflected in the Thomson database. The physical sciences clearly predominate at the top of the list, with materials science followed by mathematics (8.72% share), physics (8.19%), chemistry (7.17%), and engineering (6.24%) in the top five. In fact, pharmacology is the only life-sciences field to rank among the top ten in terms of China’s representation.

As to impact: China’s citation average in its most prolific field, materials science, was 1.64 cites per paper, 76% of the world average of 2.16 cites. In all the fields shown here, in fact, the impact of China’s research has yet to match the world average, although the nation was close in the field of agricultural sciences, where China’s mark of 2.10 cites per paper was just 7% below the world average of 2.26 cites.

Although China’s citation impact may currently lag the world average in these fields, the graph below suggests that the nation’s impact is on the upswing. The graph depicts citation impact compared to the world average in four of China’s most active fields, in overlapping five-year periods from 1981 to 2003.

One immediately noticeable feature of the graph is that materials science and mathematics—China’s two fields of greatest concentration in the database—display a pronounced dip in citation impact during the mid-1980s. This seems analogous to an observation made in these pages three years ago, in a survey of research in South Korea, a nation with a similar upturn in output over the past two decades (see Science Watch, 12[3]: 1-2, May/June 2001). During the 1980s, when China was producing a comparative handful of papers, it’s likely that one or two highly cited reports had the effect of artificially inflating the nation’s citation-impact figures in these fields. With a growing output of papers since the 1980s, this effect is negated, resulting in the dip shown in the graph. Since the late 1980s, citation impact has unmistakably trended upward, with mathematics currently highest (of the four fields shown) on the path toward the world average.

Another indication of China’s growing presence on the scientific stage is provided in the table to the right. Based on figures from Thomson Scientific’s ISI Essential Science Indicators, the table shows the number of "high-impact" papers—those that ranked among the top 1% most-cited papers of each year since 1993—featuring at least one China-based author. As the table shows, China’s store of such papers increased nearly tenfold in the course of the last decade, from 25 to 223.

According to ISI Essential Science Indicators, the most-cited paper of the last ten years featuring exclusively Chinese institutions is W.Z. Li, et al., "Large-scale synthesis of aligned carbon nanotubes," Science, 274(5293): 1701-3, 1996; this paper, from authors at the Institute of Physics, Chinese Academy of Sciences, Beijing, and the Central University for Nationalities, Beijing, has been cited nearly 600 times. Also highly cited is W.Q. Han, et al., "Synthesis of gallium nitride nanorods through a carbon nanotube-confined reaction," Science, 277(5330): 1287-9, 1997, from authors at Tsing Hua University, Beijing; this paper has now been cited more than 450 times.

Rank	Field	China world share, 1999-2003 (%)	China no. papers, 1999-2003	China citation impact	World citation impact
1	Materials Science	10.45	14,970	1.64	2.16
2	Mathematics	8.72	6,379	1.03	1.31
3	Physics	8.19	37,985	2.13	3.70
4	Chemistry	7.17	37,024	2.40	3.92
5	Engineering	6.24	18,457	1.13	1.55
6	Geosciences	4.88	5,332	1.97	3.60
7	Computer Science	4.76	2,213	0.99	1.26
8	Space Science	3.83	1,838	3.05	7.15
9	Pharmacology	3.27	2,652	2.35	4.67
10	Ecology/Environmental	3.20	3,158	1.96	3.35
11	Economics & Business	2.54	1,381	1.56	1.72
12	Plant & Animal Sciences	2.00	4,548	1.90	2.93
13	Biology & Biochemistry	1.87	5,348	3.22	7.74
14	Agricultural Sciences	1.78	1,544	2.10	2.26
15	Microbiology	1.70	1,431	3.90	6.95
16	Clinical Medicine	1.52	13,522	3.49	5.03
17	Molecular Biology	1.44	1,624	6.97	13.45
18	Neurosciences	1.13	1,664	4.47	8.18
19	Psychology/Psychiatry	0.98	983	2.28	3.37
20	Immunology	0.79	510	4.69	10.83
SOURCE: Thomson Scientific National Science Indicators