Boolean Logic
Basic useful Boolean terms include AND, OR, NOT, and ( ). These terms are used to connect the words in a search. They can be used by themselves or in combination to specify your search terms. Although Boolean terms can be used in the "Author" field (with last names only), they are most commonly used in the "Word(s)" fields. Words within a field are assumed to be connected by OR unless otherwise specified. The OR connector is not often used since it is the default expression between terms. However, it can be helpful in organizing a complex query.
The AND connector limits the search results to articles that contain all of terms that are connected by AND. For example, a search for "human diseases" will return all articles that contain the term "human" or the term "diseases" (and depending on the journal, this could cause an error). In practice, this will retrieve articles as diverse as human evolution and avian diseases. Inserting an AND statement like so: "human" AND "diseases" ensures that only articles that mention both "human" and "diseases" will be returned.
The NOT term can be used to exclude articles containing certain terms. For example, if you wanted to search for articles about the gene called "sos" that did not deal with "Drosophila," the search would be constructed as such: "sos" NOT "drosophila."
For more complex searches, these operators may be combined with one another, optionally using parentheses to group terms to avoid ambiguity in a complex query. For example, ("signal transduction" AND ("phosphorylation" OR "kinase")) NOT "xenopus" finds only articles that use the phrase "signal transduction" and either the word "phosphorylation" or the word "kinase", but do not mention the word "Xenopus."
NOTE that when using boolean terms, it does not matter if you select Any, All or Phrase from the Words section. They will all produce the same result when combined with boolean operators.
Using "Phrases"
Words in a field are assumed to be connected by a Boolean OR statement unless otherwise specified. One way to connect two words is by enclosing them in quotation marks. For example, the search "signal transduction" will return articles which include either the term signal or the term transduction (or both). A phrase search enclosed in quotation marks: "signal transduction" will only return articles where the term "transduction" immediately follows the term "signal"; articles containing only signal, only "transduction", or even "transduction signal" are not returned.
Using "Wildcards"
The wildcard character (*) can be used to search the beginning fragments of words, forcing a match with any word containing a given root. Although this function is somewhat duplicated with the search engine's Stemming feature, proper use of a wildcard can return a range of potentially interesting documents. For example, a search for "child*" will return articles containing "child, childcare" and "children"; likewise, a search for "phospha*" will return articles containing "phosphatase" and "phosphate."
Wildcards can also be used to truncate words before non-English characters such as an umlaut (ü) or an accent (é). Since these characters cannot be searched, a word such as the author name "Grundström" should be searched as "Grundstr*". Note that wildcards can only be used after characters; any characters following a wildcard in a single word will be discarded, and may cause an error.
Capitalization and Punctuation
Searches are case-insensitive as long as lower-case letters are used; upper-case search terms will retrieve only articles where the upper-case term is used. For example, a search for "thrombin" will return all articles containing the term, but a search for "Thrombin" will generally return articles where Thrombin is the first word in a sentence. In general, you should use lower-case in all of your searches unless you have a specific reason to do otherwise.
Punctuation is not searched and is treated as a space. The only exceptions to this are parentheses "()" and asterisks "*", and the use of a hyphen "-" in author's names. Therefore, the parentheses and the wildcard character have special meaning in the search context and cannot be searched in the text. If a search term includes punctuation (such as a dash "-" or a plus "+"), enclose the whole word in quotation marks to ensure that proper spacing is maintained in the search.
Stemming
This search mechanism uses a "stemming" mechanism to find words which are similar to the words you enter. For example, a search on "transcription" may turn up articles containing similar words such as transcript and transcribed. These additional words may not always be highlighted in the text. If you wish to disable stemming, enclose each individual term in quotation marks. If you do so, and also use Boolean connectors to combine terms, be sure that AND, OR, or NOT are not included in the quotation marks.
Search Term Highlighting
Search terms are highlighted in bold text in the title display of the search result, as well as in articles and Abstracts viewed from a search result. All words longer than four letters specified are highlighted, whether or not they are combined by quotation marks. For example, a search on "motor cortex" will highlight instances of the phrase "motor cortex", as well as any uses of the words motor or cortex.