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Help with searching
When searching for an article, the more specific your search, the faster it will run, and the more likely it will return the actual article(s) of interest to you.
For best results, enter the minimum amount of information necessary to uniquely identify the article or articles, such as volume/page number, authors and/or specific key words.
There are three types of searches:
- Specify citation - year, volume, page
- Specify DOI (if the content contains DOIs)
- Specify author, keywords - author (2), title, abstract+title, text+abstract+title
If a search uses multiple fields, they are joined by AND in the search. Example: Author: Darwin AND Title: Species. In other words, search results must match both criteria.
Within each field of a keywords search, multiple words are, by default, joined by AND (i.e., the "all" button to the right of the field). Example: Title: Applied Physics is treated as a search for articles with titles having both Applied AND Physics (not necessarily next to each other). Use the "any" button next to the search fields to change this to OR (Applied OR Physics), or use the "phrase" button to change this to an exact phrase ("Applied Physics").
Main search strategies
Enter the volume and starting page number in the "Search by citation" box. This will uniquely identify the article, making it unnecessary to enter data in the other search box.
If you know the starting page number, enter it in the "Search by citation" box. The starting page—even without a volume—is still a fairly unique identifying number. Other citation information can be entered in the "Search by authors" or "Keywords" box.
Full titles, or fragments thereof, should be entered in "quotation marks". This forces a phrase search rather than our search engine searching for each word separately.
Authors can be entered in the "Author" field. The last name is the main identifier; first (F) initial can be used to further specify your search. If you use initials, they should be entered in the form Lastname, F. (for example, Darwin, C. - note also that the initial is optional, though middle initials can be included as well). Lastname, F.
Keywords can either be searched in the Title/Abstract, or anywhere in the article (which includes the title/abstract). The search engine connects multiple words (where a word is text between spaces, or a combination of characters and spaces between quotation marks) with OR statements. Single letters and common words cannot be searched.
Date ranges (at the bottom of the Search by Authors or Keywords box) can narrow your search in two ways. You can limit the search to recent articles, or specifically to older articles if you know that (for example) an article by Smith was published in 1996. Date ranges can also be used to limit the search results to articles for which the full text is available on-line by noting the starting date for full text availability and setting the "from" date accordingly.
A digital object identifier (DOI) is a unique alphanumeric identifier applied to a specific piece of intellectual property, particularly one presented in an online environment—be that object a book, a scientific paper, a song, an image, or something else. DOIs are commonly used when an article is published online ahead of print. The BMJ is a fully online first publication, and has been since July 2008. Online first publication means that page numbers are not known when the article went live, so a DOI is used instead.
Articles from a particular institution
Since authors' addresses and affiliations are indexed, they can be searched. For example, a full text search for Purdue will return articles by an author claiming a Purdue affiliation (as well as any articles written by someone named "Purdue"). This technique can narrow down an author search, especially if the author's name is common.
Extra benefits of full text searching
Searching the full text of an article can reveal much more information than a simple abstract search. More information than just the results and discussion is indexed; this information can be used to identify articles that are related in ways separate from the subject of the research.
Articles from a particular institution
Since authors' addresses and affiliations are indexed, they can be searched. For example, a full-text search for Purdue will return articles by an author claiming a Purdue affiliation (as well as any articles written by someone named "Purdue").
This technique can also be used to help narrow down an author search, especially in cases where the author's name is fairly common. In this case, enter the author's name in the "Author" field, and the institution (or better yet, just a single word to identify it) in the "Any" field.
Articles that cite a paper written by a certain author
It is often desirable to find articles that have referenced an important author or paper. This can be achieved by searching for the author's last name in the "Any" field. Such a search will return all articles written by the author, as well as any articles that cite an article written by the author.
Articles using a special reagent or technique
Articles using a particular technique can be easily identified by entering a keyword for the technique. For example, to retrieve articles that used Adobe Photoshop in the preparation and analysis of data, a search for photoshop in the appropriate field will return articles with that in common.
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.
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.
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: "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.
Capitalisation 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 authors' 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.
The 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.
There are two reasons that you may not get any articles back from your search: an error occurred with the search engine program itself, or there may not be any articles matching the search criteria.
If your search was executed properly but did not return any articles, the message "Your search retrieved zero articles." will be displayed at the top of the screen, along with some suggestions for narrowing your search. In this case, the search can be broadened as described above to redefine the search. Appropriate use of wildcards with search terms, or author names for which you are not sure of the exact spelling, can also help. There is also the possibility that no articles matching your interests are in the journal's collection.
When a true search error occurs, the message "There was a problem with our search system." will appear at the top of the screen. This most commonly means that too many articles were returned. This will happen if a common word (for example, and or the) is used. Single letters not included in a phrase will return similar errors. Finally, note that parentheses and quotation marks come in sets: if only one is used, an error will result. Ensure that you are not using common words or single characters; if the error cannot be resolved, send us feedback describing the problem.