The natural index of universities is a database that counts the number of papers published by universities and research institutions (countries) in the most influential research-oriented academic journals in the world, relying on 82 top journals in the world, such as Nature, Science and Cell. The natural index was first released on 20 14 and 1 1, which has become an important index to evaluate the output of high-level academic achievements of scientific research institutions. Eighty-two source periodicals are divided into four categories: chemistry, earth and environmental science, life science and physics.

There are three ways to measure the natural index to track the author's unit information:

Article Count /AC)- No matter whether an article has one or more authors, each author's country or institution gets an AC score of 1.

Score count /FC)- FC considers the relative contribution of each paper author. The total FC score of an article is 1, which is shared equally by all authors under the assumption that everyone's contribution is the same. For example, if there are ten authors in a paper, the FC value of each author is 0. 1. If the author has multiple work units, then his personal FC score will be evenly distributed among these work units.

Weighted fraction count/WFC)-that is, adding weight to FC to adjust too many astronomical and astrophysical papers. Four journals of these two disciplines have been selected into the natural index, and the published papers account for about 50% of the papers published by international journals in this field, which is roughly five times that of other disciplines. Therefore, although the data compilation method is the same as other disciplines, the paper weight of these four journals is 1/5 of other papers.