Generally, there is a core, a national level and a core. These levels are explained in general journals, and there is no big requirement.

The main purpose of periodical grading is to extract and highlight a few excellent key periodicals from all periodicals, so the grading level is generally not much, mostly 2-3, and a few are above 4.

The first level of paper publication: class T.

This type level generally refers to the papers in specialized journals, mainly those published in SCIENCE and NATURE. Its publication is the most difficult, and most authors can't reach this level.

The second level of paper publication: class a.

This type level generally refers to authoritative core journals, mainly in internationally accepted SCIE, EI, ISTP, SSCI and A &；; Papers included in retrieval systems such as HCI, or papers published in Chinese core journals with authoritative influence in China. The difficulty of publishing is second only to class T, and it requires high English.