General
Queries can include the following Boolean operators:

     AND, OR, NOT

A query that contains several different operators needs round brackets to remove ambiguities, e.g. osteoporosis and (alcohol or tobacco)

Append field names between square brackets to restrict a search to a particular field. Abbreviations can be found in the [List of field names. Example: smith [au] and array [ti]

Use double quotes to identify phrases (e.g. "red blood cell").

The asterisk functions as a wildcard, replacing any number of characters (e.g. diabet* retrieves diabetes and diabetic). The question mark replaces one single character (e.g. j?nson retrieves Jonson, Jenson, Janson etc.)

Authors
Use the format smith_cp. Author names are automatically expanded to include all combinations of initials, e.g. smith_c retrieves Smith C, Smith CA etc. You can turn this off by using quotes, "smith_c" retrieves only Smith C

Journals
Use the full journal title or standard journal abbreviations (look up here), e.g. Journal of Biology or J Biol
Use the checkboxes under 'Include' to specify which major types of BioMed Central content you want to search, or alternatively, select individual journals by following the link to 'Full list of journals'.

Date
You can restrict to recent articles (published within a certain number of days), or you can restrict by year of publication.

Show results
You can use these options to order the results by relevance or date of publication and display more or fewer matches per page.