1, Thomson Reuters Branch, Thomson Reuters publishes a journalicationreports(JCR) every year. JCR has counted the influencing factors of more than 86,000 SCI journals. JCR divides journals into 176 different disciplines. According to the impact factors of journals, each subject classification is divided into four areas on average: Q 1, Q2, Q3 and Q4. In the classification of various disciplines, the top 25% (including 25%) journals with impact factors are divided into Q 1 region, the top 25% ~ 50% (including 50%) journals are in Q2 region, and the top 50% ~ 75% (including 75%) journals of Thomson Reuters are divided into four parts on average.
2. Department of China Academy of Sciences, which classifies mathematics, physics, chemistry, biology, geoscience, astronomy, engineering technology, medicine, environmental science, agriculture and forestry science, social science, management science and comprehensive periodicals as 13. Then, the journal 13 is divided into four grades, that is, four districts. According to the impact factors of various journals, the top 5% is 1, 6% ~ 20% is 2, 2 1% ~ 50% is 3, and the rest is 4. In the branch of Chinese Academy of Sciences, there are few magazines in 1 and 2 areas, and the quality of the magazines is relatively high, which are basically the top journals in this field.