Nanjing, surrounded by green mountains and rivers, is the capital city of Jiangsu province. Though it has long been a popular destination for tourists, the 'ancient capital' is often overlooked by foreign investors who flock to nearby, and much larger, Shanghai.

Nanjing's 2012 budget for scientific research and development was US$1.5 billion, comprised of equal contributions from local government and industry. The city's eight pillar industries in the high-tech sector are supported by more than 100 universities and research institutions, including the premier institution for education — Nanjing University (NJU).

NJU is by far Nanjing's largest contributor to the Nature Index, and fourth overall in China by weighted fractional count (WFC). In 2013, the university published 391 articles (WFC = 194.6), accounting for 64% of the city's WFC. Despite this output, NJU contributed only one article (WFC = 0.05) to Science and none to Nature.

NJU derives most of its WFC from chemistry. Huangxian Ju, Jingjuan Xu and Hongyuan Chen from the school of chemistry and chemical engineering are NJU's largest contributors. Ju — also the director of the Ministry of Education Key Laboratory of Analytical Chemistry for Life Sciences — produced 13 articles (WFC = 11.8) on fluorescent sensors, which have applications in bioimaging. Xu and Chen co-authored nine articles (WFC = 8.4) on electrochemiluminescence, a biosensing technology for detecting cell surface proteins and DNA.

NJU is also productive in astrophysics, which makes up 15% of its fractional count (FC). However, owing to the down-weighting of astrophysics journals in the index, these publications contribute a WFC of only 6.9. Jilin Zhou and Zigao Dai from the school of astronomy and space science contribute the most to this field. Zhou co-authored four articles on planetary formation, while Dai contributed to three on gamma-ray bursts — extremely energetic explosions observed in distant galaxies.

Nanjing also has six smaller research universities and one institute of the Chinese Academy of Sciences (CAS) that each contribute 2–10% of the city's WFC. Southeast University (SEU) has the second largest output and is focused on the physical sciences, which make up two-thirds of its WFC. In 2013, the 112-year-old institution published 65 articles (WFC = 30.9), with Tiejun Cui, the vice president of the school of information science and engineering, being the most prolific contributor. Cui led 11 articles (WFC = 6.1) on transformation optics, a novel class of materials with potential use in stealth devices.

Nanjing Medical University (NJMU), founded in 1934, was one of the first institutions to offer postgraduate medical education in China. In 2013, the university published 28 articles (WFC = 7.3), with life sciences research representing 81% of its output. It also has the highest proportion of papers in Nature and Science in the city, which comprise 4.6% of its WFC. NJMU's president, Hongbing Shen, is the most active contributor to the index, having led five genome-wide association studies (WFC = 1.4), all published in Nature Genetics.

Nanjing is also the strongest city in China for astrophysics, which comprises 18% of its FC — ahead of Beijing (11%), Hefei (8%) and Hong Kong (5%). This knowledge base is largely due to the Purple Mountain Observatory (PMO), a CAS institute. Last year, PMO published 102 articles (WFC = 6.3), the majority from three contributors. Dejin Wu, the deputy director of the division of dark matter and space astronomy, published six articles on solar flares and coronal loops; Yizhong Fan published five articles on dark matter and gamma-ray bursts; and Xuefeng Wu contributed to seven articles on gamma-ray bursts.

PMO has a number of high-profile projects underway. “We are in the preparation stage of launching our own observation satellites into space, and a team of scientists will also be setting up an observatory in Antarctica,” says Xuefeng Wu. “China's research capabilities in astrophysics have come a long way since the 1980s.”