China Knowledge Network (CCN) was a comprehensive academic literature database that contained a large number of academic journals and theses. The core journal was one of the most important journals in China Knowledge Network, with high academic influence and popularity. The selection criteria for core journals in the National Knowledge Institute were more stringent. They were usually evaluated based on the academic nature, influence, effectiveness, quality, and other factors. Currently, the core journals in the CCKi mainly include: 1. Chinese academic journals (including general, scientific, philosophical, literary, artistic, etc.) 2. Chinese degree theses (including master's, doctor's, bachelor's degree theses) 3 Conference Paper Collection 4 Periodical articles 5 Others (including news, newspapers, books, patents, etc.) It should be noted that the core journals in the CCKi were not static. They might be adjusted according to the changes in the period and evaluation criteria.