China has moved into second place, behind the United States, in the total number of top-cited scientific papers over the last decade and "hot papers" in the last two years. This means the nation's scientific literature has made considerable progress in quality and global influence, but the nation's impact gap with other scientific powerhouses remains substantial, according to a report published on Tuesday.

From 2009 to October, China had 30,755 scientific papers ranking in the top 1 percent by number of citations, accounting for about 20 percent of the world's total, according to results from the 2019 edition of Statistical Data of Chinese Science and Technology Papers.

"Hot papers" refer to a small group of papers published in the last two years that were quickly recognized and highly cited soon after publication. As of September, China published 1,056 such papers, about 32.6 percent of the world's total. The US tops the world with 1,562.

Academic paper citation is one of the key indications of a paper's quality and influence. The number of citations has long been treated as a reflection of a nation's strength in scientific research. The report, which examines scientific output from the Chinese mainland, has been released annually since 1987 by the Ministry of Science and Technology's Institute of Scientific and Technical Information of China, or ISTIC.

"Through the joint effort of China's scientific communities, we have made great progress in improving the overall quality and global influence of our science academic literature," said Dai Guoqiang, the director of the institute.

In terms of citations by subject, this year China became the world's most-cited country in materials science, chemistry and engineering, the report said.

Chinese scientists are also publishing more co-authored papers with international peers. In 2018, China co-wrote around 110,800 papers－13,400 more than in 2017－with more than 157 countries and regions. The US remains China's biggest partner in scientific literature, making up 55.7 percent of all Chinese co-written papers published last year.

However, the report also stressed the substantial gap between China and other scientific powerhouses, especially with the US, in the number of papers published in the world's top scientific journals, as well as in the number of articles included in the Science Citation Index, one of the world's most selective citation databases for scientific literature.

Last year, there were eight premier science journals that were cited over 100,000 times with an impact factor above 30. Of the 12,172 papers published in those journals last year, only 828, or 6.8 percent, were written by Chinese authors, ranking China fourth behind the US, the United Kingdom and Germany.

China's ranking has not changed since 2017 despite publishing 429 articles in Nature, Science and Cell last year, 120 more than the year before. The US enjoyed a sizable lead in the number of papers published in these top three journals at 2,588 last year.

Moreover, the average number of citations per paper by Chinese authors is around 10.9 for the last decade, still lower than the world's average of 12.68, said Guo Tiecheng, the deputy director of the ISTIC.

"While some of our best papers are getting thousands of citations each, there is still a substantial gap between the average impact of our scientific literature and that of developed countries," he said.