2. These four ways are:
Obtain the original text through the website of the organizer or publishing agency.
Get the original text through the search engine.
Obtain the original text through the full-text database.
Get the original text through the website of free electronic journals. 1. Search method according to the external characteristics of documents: (1) Ways of document names: such as titles of books, periodicals, articles and special documents. (2) Author channels: author, editor, translator, etc. (3) Serial number method: the serial number compiled when the document is issued. Such as report number, patent number, standard number and abstract number. (4) Other channels: such as publication type, publication date, country, language, etc. 2. According to the characteristics of the document content, the retrieval approach: (1) Subject approach: the subject content of the required document. Such as subject index, keyword index, etc. (2) Classification: the method of searching documents according to the subject classification system. (3) Other ways: search according to the unique characteristics of the subject. Such as molecular formula index, ring index, substructure index, etc. 3. Sectional method: that is, circular method. Alternately use the comprehensive retrieval methods of "backtracking method" and "common method". Loop continuously until the retrieval requirements are met. Advantages: when the retrieval tool is short of time and volume, it can continuously obtain the literature clues in the required year.