Keywords should accurately reflect the theme of the paper: On the basis of carefully studying the title, abstract, text content and various charts in the paper, the author should refine the concept of the theme and choose standardized words that can accurately reflect the theme and characteristic content of the paper.

(1) You can use the Library's Classified Glossary of Subject Words in China to screen and extract keywords accurately. You can also refer to the subtitle selection of each paragraph. For example, the key words of the article "Mechanism Analysis of Ecological Water Demand on Groundwater Ecosystem" are ecological water demand, groundwater ecosystem and ecological environment.

If the word "system" is used as the key word, it can not only represent the operating system, but also serve the system, which shows the significance of management system. Therefore, it does not have the retrieval significance of this paper. Therefore, the word "system" should be changed to the word "ecosystem" with independent retrieval significance.

(2) In addition, with the development of science and technology, new technical terms appear constantly, and the keywords selected in many scientific papers are new disciplines or new technical terms that are not listed in the existing thesaurus. When using these new free words, it depends on whether the following conditions are met: they have independent retrieval significance; Promote the development of new disciplines or new technologies; Accepted and compatible by domestic and foreign scientific and technological literature retrieval work; It conforms to the selection of keywords in internationally famous scientific and technological publications, especially in famous retrieval publications.