1, the document identification code is the code used to indicate the content type of the document body. According to China Academic Journals (CD-ROM Edition) Retrieval and Evaluation Data Standard, every article or material should be marked with a document identification code.

2. In order to facilitate the statistics and periodical evaluation of documents, determine the retrieval scope of documents and improve the applicability of retrieval results, the author of each paper should determine the classification items of his own papers according to the five content classification document identification codes set by the Specification when writing a publicly published paper or contribution, and mark the document identification code after the classification number in China Library Classification.