But if there are too many words, it will be recognized by logical AND, for example, protein ambiguous isomerase can be recognized as a word.
It may also be recognized as "protein and ambiguity and isomerase", especially when symbols such as numbers appear, it is not easy to recognize as a phrase.
2. Secondly, the unrecognized phrases need to be emphasized in quotation marks, such as "Insight II".
Search by author, and the input format of author name is: last name+first name.
For example, enter: Freesman DJ, where "last name" is the full name and "first name" is the acronym (the first name can be omitted).
The magazine name you type can be full name or MedLine abbreviation format.
Or ISSN magazine number (see journal browsing).
When searching, you can add "*" to the suffix to search all words with the same prefix.
If you type: biolog*, you can find the words biological or biological.
You can also query multiple words in the form of phrases, and phrases that cannot be recognized and retrieved need to be emphasized in quotation marks.
If you type:?
Insight II?
Will be recognized as the phrase "Insight II" to be queried, if you type:?
Insight 2?
Then it is possible to identify these two words as "insight" and "II" respectively, and search in a logical and "insight and II" way. ?
3. Finally, conjunctions can be searched by AND, OR or NOT logic between words. ?
After entering the search term, don't forget to select the search period (30 days, range 10 year) and the number of pages of the displayed literature.
In the mouse-click interface, press Enter or "Search" button to enter the document summary page.
Extended data
Retrieval expression is one of the concrete manifestations of retrieval strategy, which is called retrieval formula for short. Search formulas generally consist of search terms and various logical operators.
Specifically, it is a retrieval command that can be recognized and executed by the computer by linking the logical relationship and positional relationship between retrieval words with various operators specified by the retrieval system.
The quality of retrieval structure is related to the success or failure of retrieval strategy.
The retrieval expressions mainly include logical expressions, cut-off expressions and position retrieval expressions. Among them, the most commonly used logical expressions are:
W (NW): W is the abbreviation of with. (W) means that the search words on both sides must appear in the record in order, and no other words are allowed to be inserted between the two words, only spaces or a punctuation mark.
(nW) means that at most n words can be inserted between the search terms on both sides, and the positions of the search terms cannot be reversed.
F: the abbreviation of field, (f) means that the search words on both sides of it must appear in the same field, but the word order of the two search words is not limited, and the number of words between the two search words is not limited.
For example, two search terms must appear in the title field, summary field or description field at the same time.
Short for near, (n) means that the positions of search words on both sides can be interchanged, and no other words can be inserted between two words, but spaces or punctuation marks are allowed.
(nN) indicates that at most n words can be inserted between the search words of the operator, and the positions of the two search words can be reversed.
L: It is the abbreviation of link. (L) means that there is a master-slave relationship between the search terms on both sides, with the former being the main one and the latter being the vice one. L can be used to connect the subject and subtitle.
S: It is the abbreviation of subfield. (s) It means that the search words on both sides must appear in the same subfield, just like a sentence or phrase, but the word order is not limited, and there can be several other words between two search words.
In some retrieval systems, double quotation marks are also used to indicate inseparable phrases or phrases, such as "civil engineering". In the search results, civil engineering must be a connecting phrase.
References:
Baidu Encyclopedia-Search Expression