Please use the advanced retrieval of cnki database to find the literature on prevention of COVID-19, and write the retrieval formula and the number of retrieval results.
1. open the website of China hownet and click "advanced search" to enter the advanced search page.
2. In the advanced search page, you can select the subject, keywords, title, full text, author, unit, abstract, cited documents, China classification number and document source, etc., and enter the search words you want.
3. Select the database and literature type to search, and then click "Search" to get relevant literature.
The following steps and examples can be referred to for the document retrieval formula of preventing COVID-19:
1. Enter the subject: "Preventing COVID-19".
2. Select literature type: you can choose research reports, academic papers, news reports, etc.
3. Select database: you can select all databases of China HowNet or a specific database.
4. Click "Search" to get the relevant literature on COVID-19 prevention.
please note that the specific search formula and the number of results will vary with different databases and search conditions.
Related content
Three quick retrieval methods of HowNet
The CNKI database is the core of this project, and the CNKI resource master database includes many data sub-databases, mainly including the online publishing master database of Chinese academic journals, the full-text database of outstanding doctoral (doctoral) papers in China, the full-text database of important newspapers in China and the full-text database of important conference papers in China;
China book full-text database, China yearbook online publishing database, China economic and social development statistics database, China economic information literature database, China legal knowledge resource database, China standard database, China patent database, national scientific and technological achievements database, foreign standard database, etc.
first, quick retrieval
after clicking on the library homepage to enter the full-text database of CNKI journals, click "quick retrieval" at the top of the retrieval box to enter the quick retrieval page, as shown in Figure 1. There is only one search box for quick retrieval, and there is no limit to fields, word positions and word frequencies. The system will search and match the full text. Enter the search term in the quick search box and click "Quick Search".
second, standard retrieval
standard retrieval is what we often call advanced retrieval, which can limit all kinds of retrieval fields, specify word frequency, etc., carry out effective Boolean logic combination retrieval, reduce retrieval redundancy and improve retrieval efficiency. Therefore, we generally advocate the use of standard retrieval for literature search.
Third, professional retrieval
Professional retrieval can provide a retrieval method of combining logical expressions according to the actual needs of users, which can effectively improve the precision rate.