1. Standards of core journals: Class E journals usually refer to core journals, including the Overview of China Core Journals jointly edited and published by Peking University Library and Peking University Library Journal Work Research Association, and the publications listed in the Citation Report of China Sci-tech Journals published once a year by China Institute of Sci-tech Information (hereinafter referred to as SINOPEC).
2. The standard of publishing difficulty: In terms of publishing difficulty, E-class periodicals are usually considered as one-star periodicals, and the publishing difficulty is relatively low. Specifically, if the paper is published in restricted public publications, or in journals without postal codes, it is recognized as a class E journal. In addition, if you make a report at a provincial academic conference and include it in a collection of officially published papers (with a book number), it can also be regarded as an E-type periodical.
Please note that different institutions or evaluation systems may have different classifications and standards. The above information is for reference only. If more specific standards are needed, it is recommended to consult relevant institutions or consult relevant literature.