Electronic resources can be divided into databases, electronic periodicals, electronic books, electronic newspapers, dynamic information, software and so on according to their publishing forms. Among them, the database is the oldest and most influential electronic literature information resource. It has become the main body of electronic resources with advanced data processing technology, deeply processed information and perfect combination with the network. The database covers a wide range of fields and can be divided into four types according to its contents:

(1) Bibliographic database, including secondary literature databases such as bibliographies, indexes and abstracts;

(2) Numerical database, which mainly contains digital data, such as statistical data, scientific experimental data and scientific measurement data. (3) fact database, which mainly includes facts such as the phenomenon, situation and process of people, institutions and affairs, such as the directory of institutions and memorabilia; (4) Full-text database, which provides complete original full-text data and integrates original search and browsing functions, is the most convenient and promising electronic resource at present.