2. Chinese abstract: Chinese abstract, within about 300 words.

The content should include the purpose of work, research methods, achievements and conclusions, highlight the creative achievements of this paper, and strive to refine the language. In order to facilitate literature retrieval, the key words (3-5) of the paper should be indicated on another line at the bottom of this page.

Generalized retrieval includes two processes: information storage and retrieval. Information storage is to gather a large number of chaotic information, and make it systematic and orderly by sorting, classifying, concentrating and indexing according to the appearance and content characteristics of information sources.

Extended data:

According to the content of search results, it is divided into the following three types:

1. Data retrieval: retrieval based on data in literature. For example, find the resistance of a certain material and the melting point of a certain metal;

2. Fact retrieval: according to the facts in the literature, retrieve the time, place or process of an event; For example, find out that Lu Xun was born in a certain year;

3. Literature retrieval: retrieval with the original literature as the retrieval object.