"China Library Classification Number" refers to the classification code obtained by analyzing the subject of scientific and technological documents with "China Library Classification" and organizing the documents in different categories according to the subject attributes and characteristics of the documents.

China Library Classification is divided into 5 basic categories and 22 major categories. Chinese phonetic alphabet and Arabic numerals are mixed, one letter represents a big category, and the alphabetical order reflects the order of big categories, and the number after the letter is used as a mark. In order to adapt to the development of industrial technology and the classification of this kind of literature, the two-letter classification of industrial technology is adopted. The category names are as follows:

Marxism, Leninism, and Mao Zedong Thought ......................................................................................................................................................................

Philosophy b philosophy.

social science ...............................................................................................................................................................................

Politics, law

natural science ...............................................................................................................................................................................

O mathematical science and chemistry?

P astronomy, earth science

Q bioscience

Medicine and health

American agricultural science

technology

U transportation

V. Aviation and aerospace

X. Environmental Science and Labor Protection Science

Comprehensive books .............. ... Z comprehensive books.