1. Choose words and phrases (prototypes rather than abbreviations) that are consistent with the theme of the paper and can summarize the theme, so that readers can judge the research object, materials, methods and conditions of the paper.

2. Keywords should be nouns or terms, and adjectives, verbs and adverbs cannot be selected as keywords.

3. Try to choose standard word included in the Chinese Thesaurus, because one word can only represent one theme concept. For example, in a paper with the theme of "engineering structure design", four key words "engineering structure", "structure", "design" and "structural design" can be found from China Thesaurus. Among them, "structure" and "design" are not specific and should be removed, so "engineering structure" and "structural design" are appropriate.

4, the choice of words should be refined. Synonyms and synonyms cannot be juxtaposed as keywords; Complex organic compounds usually use basic structural names as keywords, but chemical molecular formulas cannot be used as keywords; English articles, prepositions, conjunctions and some adverbs and nouns that lack retrieval meaning cannot be used as keywords.

5. The use of keywords should be unified and standardized, which can accurately reflect the names and terms of different disciplines. Abbreviations that are not commonly used or appear in papers, and abbreviations that are not recognized by professionals cannot be used as keywords.

6. The content is well known, and the conventional technical terms mentioned in the paper but not discussed and improved cannot be used as keywords.

7. Most keywords are selected from the title, but when there are not enough keywords in individual titles to reflect the theme, they should be selected from the abstract or text.

8, Chinese and English keywords should correspond, the number is exactly the same.