There are six elements in the paper format, including title, table of contents, abstract, keywords, text and references, among which keywords and abstract are indispensable. Keywords are usually located below the abstract of the article, and the font size is usually different from that of the text. There are usually 3-8 keywords separated by semicolons. The exact number depends on the requirements of the article. Keywords are selected from the text, which are phrases or words that can best reflect the core content of the article. This is one of the main functions of keywords, and another key function is to facilitate the retrieval and inclusion of articles, so accurate keywords are helpful for the retrieval of articles. The general principle of keyword selection is accurate, concise and eye-catching. It is a brief and comprehensive summary of the content of the paper, which enables readers to quickly summarize the content of the paper. Like topics, abstracts are also common retrieval objects in various databases. An accurate, concise, easy to understand and informative abstract can increase the number of readers and the extractability of future papers, and the length of the abstract must be carefully considered on this basis. For example, for some English databases, if the abstract length exceeds the limit of 960 characters, the abstract recruiter may cut the length of the abstract to meet the requirements of the database.