2. Click the "Professional Search" option in the menu bar above.
3. The interface of professional retrieval is shown in the figure below. Just enter the required retrieval expression in the input box above. The following is a simple tutorial.
For example, it says searchable fields: SU= subject, TI= title, KY= keyword, AB= abstract, FT= full text, AU= author, FI= first responsible person, AF= institution, JN= document source, RF= reference, YE= year, FU= fund, CLC= Chinese library classification number.
And three retrieval examples are provided, and you can write the retrieval expression you need according to the format of the examples.
It is worth mentioning that sometimes when you enter the search content, you will be prompted that the user does not exist in the server and the parameters are wrong. This basically means that your search format is incorrect.
If you feel no problem after comparing the examples, then check whether you have mixed Chinese symbols in it, and the search requirements are all English symbols. Especially brackets, commas, quotation marks and other symbols, if they are used in Chinese, they will be reported incorrectly.
Extended data:
ingredient
1, a free word
Free words are also called arbitrary words, which can be randomly selected words or a natural sentence. Some databases can use natural sentences (that is, ask questions), but the system background will automatically extract keywords for the sentences.
2. Keywords
Keywords, also known as professional words and uncontrolled words, refer to those words that have practical significance in subject retrieval.
Keywords are ambiguous, that is, a keyword will have multiple synonyms or words with different spellings, such as a chemical substance, which has a scientific name and a common name and can be expressed by molecular formula, registration number or structural formula.
Therefore, when using keywords as search words, we must consider its synonyms and different writing methods, otherwise it will be missed. Keywords are called uncontrolled words to show their differences from subject words.
References:
Baidu encyclopedia-retrieval type