Paul Glasziou escribió:
> Dear All,
> Can anyone explain PUBMED's behaviour to me?
> Using PubMed: Clinical Queries I get the following "hits"
> asthma AND child - 1475
> asthma AND child* - 1575
> but
> asthma child - 1475
> asthma child* - 2
>
> The first pair make sense but the second is strange - with the truncated
> version getting far fewer hits.
> Any explanations (other than saying "always use the BOOLEANS")
> Thanks
>
Paul
The answer is on "Details" see below.
Place an asterisk at the end of a term to search for all terms that
begin with that word; for instance child* will find all terms that begin
with the root child, but if you write asthma child* will treat asthma
child* as a phrase (without boolean Pubmed think is a unique term) and
will find all terms that begin with the root asthma-child , e.g asthma
childhood, asthma children. Truncating a word in a multi-word query may
result in an unexpected phrase search.
Furthermore* t*runcation turns off automatic term mapping
<#AutomaticTermMapping> and the automatic explosion of a MeSH term.
(PubMed translate terms entered in the query box are matched against the
MeSH <#MedicalSubjectHeadings>(Medical Subject Headings) Translation
Table, the Journals Translation Table, the Full Author Translation Table
and an Author Index).
Details <#Details>
asthma AND child
(("asthma"[MeSH Terms] OR asthma[Text Word]) AND ("child"[MeSH Terms] OR
child[Text Word]))
asthma AND child*
Too long
asthma child
(("asthma"[MeSH Terms] OR asthma[Text Word]) AND ("child"[MeSH Terms] OR
child[Text Word]))
asthma child*
(asthma childhood[All Fields] OR asthma children[All Fields])
Best regards
------------------------------
Rafael Bravo MD
Centro de Salud Sector III
Getafe. Madrid. Spain
[log in to unmask]
http://www.infodoctor.org/rafabravo/
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