Meaning: system classification language-classification index; Topic language (title-title index. Unit word-unit word index, keyword-keyword index, descriptor-descriptor index); Code language (molecular formula index, structural index and other special indexes).
Objective: Search title, author's name, publisher, report number, patent number, etc.
2. External characteristics
Meaning: the main index questions (title), author's name, publisher, report number, patent number, etc. of the retrieval language of the external characteristics of the literature. Different documents are arranged according to the word order of article title and author's name, or according to the numerical order of report number and patent number, and the retrieval language that meets the needs of users is formed through the retrieval method of article title, author and number.
Objective: Search title, author's name, publisher, report number, patent number, etc.
Extended data
The literature retrieval approaches are as follows:
1, the way of the author
Many retrieval systems have author index and institution index (institution author or institution to which the author belongs), and patent literature retrieval systems have patentee index. The method of searching from the names of authors, editors, translators and patentees or the names of institutions and groups by using these indexes is collectively called author method.
2. Title mode
Some retrieval systems provide retrieval methods by title, such as title catalogue and periodical catalogue.
3. Classification method
Searching documents according to the subject classification system. This method is based on knowledge system. Therefore, it can better reflect the discipline system, reflect the affiliation, derivation and parallel relationship between disciplines and things, and facilitate us to find documents from the scope of disciplines and play the role of "analogy". Classified retrieval mainly uses classified catalogue and classified index.
Baidu encyclopedia-the external characteristics of literature