EI Compendex indexing abstract (core data), which includes the title and abstract of the paper, is indexed and further processed by subject words and classification numbers. Whether there are subject words and classification numbers is the only sign to judge whether a paper is officially included in EI.
EI first page bibliography (non-core data). It is mainly reported in the form of title records. Some also have abstracts, but they have not been further processed, and there are no subject words and classification numbers. Therefore, the abstract on the first page is not necessarily a formal entry into EI. Since June 65438+ 10, 2009, China periodical data collected in Ei Compendex database are no longer divided into core data and non-core data.