ISSN is not a publication, but an international serial number. CN journals must have both CN and ISSN numbers. For example, if there is an international journal, then it only has an international serial number, and there is no CN serial number. This is not a CN periodical, but an international periodical. Journals without CN number do not belong to domestic journals. You'd better make it clear before you publish your paper. You can go to paper net, Tao Tao to learn about the knowledge of identifying the authenticity of periodicals, and then choose the periodicals to be published.