The top 500 cities by scientific output in 2017. [Photo/natureindex.com]

Beijing ranks in first place in a list of cities that produced the most high-quality research in 2017, and nine other Chinese cities made the top 50, according to the Nature Index 2018 Science Cities, a supplement of the British scientific journal Nature, published on Thursday.

The list sorted out and ranked 200 cities worldwide by their 2017 fractional count, a metric for the share of contributions to the authorship of articles in 82 high-quality research journals.

To calculate the fractional count, all authors are considered to have contributed equally to the article. The maximum combined fractional count for any article is 1.0.

The 2017 fractional count for Beijing reached 2,143.53, topping the list.

The table accompanying the list also shows that authors in Beijing produced 4,396 articles in 82 high-quality research journals and accounted for 23.5 percent of the papers published by China on these journals.

However, other Chinese cities -- like Nanjing at 12th place, Wuhan at 19th and Guangzhou at 25th -- are rising rapidly in scientific research, resulting in the declining share of Beijing in China's output for six consecutive years.

Shanghai at seventh is the other Chinese city among the top 10. Hong Kong, Hefei, Hangzhou, Tianjin and Changchun were also ranked between the 21st to 50th places.