In the past, papers were divided into national journals and local journals, but as long as there were serial numbers (domestic serial number CN and international serial number ISSN), they were all official journals published in China, which was equivalent to the national level. Some excellent periodicals are core periodicals, generally referring to the catalogue of core periodicals of Peking University Press, and the titles are usually divided into general public publication and core periodicals; Check the natural science, with serial number, which belongs to the national level and meets the requirements of your professional title evaluation. As for the exchange of papers by provincial trade associations, it refers to the papers exchanged at provincial and ministerial meetings.