The retrieval types of papers are arranged by classification and can be retrieved by classification. There are mainly classification, subject method, author method, title method, organization method, code method and other methods.

A paper has only one retrieval number in the collection database, and the retrieval number will not be repeated, which is the ID number of the paper in the collection database. The uniqueness of the retrieval number is beneficial to the retrieval of papers. "Login number" is usually selected as the retrieval number.

Extended data

Compared with the literature retrieval platform, the paper retrieval number is generally considered as the "retrieval number". Being included is relative to the literature database, and they are not in the same dimension.

Specifically, SCI corresponds to SCIE (Science Citation Index Expand) abstract database, ISTP corresponds to CPCI-S abstract database, and EI corresponds to Ei Compendex abstract database. These abstract databases belong to a retrieval platform and must have corresponding retrieval numbers. Judging from the retrieval numbers of SCI and ISTP, the new version of * * * is recognized by WOS and cannot be distinguished.

Therefore, at present, these retrieval numbers do not have the function of representing specific databases. Then, the retrieval number cannot be a sufficient condition for articles to be included by SCI, ISTP and EI, but only a necessary condition.