The volume number of a periodical is also called the document identification code. The document identification code is a classification code compiled according to China Academic Journal Retrieval and Evaluation Data Standard (CD-ROM Edition). Its function is to classify articles according to their contents, so as to facilitate literature statistics and periodical evaluation, determine the scope of literature retrieval and improve the applicability of retrieval results. They have the same name every time they are published (unless they are renamed). In order to distinguish different versions, they are generally numbered according to certain rules. Publications include monthly, biweekly, monthly, bimonthly, quarterly, annual or others. Taking the bimonthly Journal of Henan University as an example, it was published from June, 5438 to October, 2009/kloc-0. Generally, the serial number is "Journal of Henan University: Natural Science Edition, 2009 (1)". Of course, sometimes you bring a roll. The volume is counted as one volume every year since its publication, such as Journal of Henan University: Natural Science Edition, 2009,39 (1), in which 2009 represents the year, 39 represents the volume, and 1 represents 2009, that is, 39 volumes of1. The specific contents of periodical volume number: a- academic papers on theoretical and applied research (including summary reports); B- practical technical achievement report (science and technology), theoretical study and social practice summary (social science); C- Business guidance and technical management articles (including leadership speeches and special comments, etc.). ); D- General dynamic information (newsletters, reports, meetings, interviews, etc.). ); Electronic documents and materials (including historical materials, statistical data, institutions, people, books and periodicals, knowledge introduction, etc.). ). Journal volume number description: 1) Articles, abstracts, information, padding, advertisements, notices, etc. that do not belong to the above categories. Not marked with document identification number; 2) The document identification code of Chinese articles is marked with "document identification code:" or "[document identification code]", such as: document identification code: a; 3) The document identification code of English articles is "Documentcode:" Many journals have the first volume mark above the first issue.