The full name of DOI is DigitalObject Unique Identifier, which refers to the digital object identifier. It can be understood as the unique "ID number" of digital resources, which can be used to identify digital resources such as documents, videos, reports or books.

At present, most academic documents (mainly after 2000) have their own DOI. As long as you know the DOI of a document, you can find out the author, title, periodical, official link and other information of the document. So as long as you enter the DOI of the document in the official WeChat account, the server can quickly find the document you need to download and return the download link.

Numbers and English after doi are the only identification symbols of journals and articles, which are generally compiled by journals when applying for articles to be included in the database. The article expects the volume number and page number to be important information. The information in doi number has no practical significance. DOI is a mathematical object identifier, usually called retrieval number. After the article is published, there will be several issues and editions for several years, and how many pages to how many pages are your article. Then it will be searched by SCI, EI, etc. The search number will be given to you.

After the periodical is the year, issue (edition): page number. Doi consists of two parts: prefix and suffix, separated by "/". The prefix consists of two parts, one is the directory code, and all doi directories are "10", that is, all Dior codes start with "10". The other is the registration agency code. Any organization or unit that wants to register doi can apply for registration agency code from IDF.

Classification of documents

According to the publishing type, there are books, periodicals, conference documents, scientific and technological reports, government publications, patent documents, technical standards, dissertations, product materials, technical files and so on. According to the types of carriers, there are writing, printing, miniature, listening and electronic documents.

According to the processing depth and content nature of literature content, there are countless useful facts, data, theories and methods recorded in first-class literature, second-class literature, third-class literature and zero-class literature.

The form of document classification is classification table, so it is customary to equate classification and classification table with one concept. But in fact, there is a difference between them, that is, literature classification is not only a classification table and its explanation, but also the practice of classification.

There are many kinds of classification, the common ones are: grade classification, title classification, group classification (or colon classification), binary classification, decimal classification, letter classification, natural classification, manual classification, subject classification and so on.