In the query box you can specify keywords (e.g. "radial", "hippocampus", "schizophrenia"), boolean operators ("and", "or", "not") and parenthesis ("(" and ")"). Keywords separated by spaces are equivalent to keywords separated by "and". The database searches for files containing words that match your pattern (as opposed to files containing lines which match your pattern). For example,
hippocampus and norepinephrinewill find files containing "hippocampus" and "norepinephrine". All searches are case-insensitive.
hippocampus and not norepinephrinewill find files which contain "hippocampus" but not "norepinephrine".
selection or regulalarisation and validationfinds files which contain both (1) either "selection" or "regulalarisation", and (2) "validation".
selection or (regulalarisation and validation)finds files which contain either (1) "selection", or (2) both "regulalarisation" and "validation".
Now try it for yourself!