Probe is integrated into Entrez. This means that many features of Entrez search engine apply for the Probe search engine as well including such advanced search options as Limits, Index/Preview and History. They are described in details on other NCBI's help pages: see PubMed or OMIM help documents for good examples.

To get started with querying the Probe use search tips below.

Query type	Explanation	Example
Default search or automatic "AND" queries	Search terms typed in the query box are automatically ANDed i. e. the search engine returns documents that include all of them. Note: Search is not case-sensitive: "Cell SiRNA" and "cell sirna" are treated as the same search.	cell siRNA
Including words or boolean "AND" queries	Type AND in front of words that you want to be included in returned documents. Note: All boolean operators (AND, OR and NOT) should be capitalized.	tnf AND sirna AND mus
Excluding words or boolean "NOT" queries.	Type NOT in front of words that you want to exlude from your query.	tnf NOT rattus
Either/Or or boolean "OR" queries	If you equally interested in two or more alternatives, use OR operator.	rattus OR drosophila
Phrase search	Words enclosed in double quotes appear together in all returned documents.	"cell cycle arrest"
Word variation (Stemming)	To look for entries that contain words with the same prefix append the word's part with trailing wildcard * character.	tnf* tnfrs*
Search by fields	To search for entries that contain your search term in a particular field you can enter the term followed by the field qualifier in square brackets [] in the query box. Hint: To find out existing fields look into dropdown menu on Index/Preview page under Add Term(s) to Query or View Index subtitle on the page.	tnf[text word] cdc25b[gene name] mobbs[author] 6731[geneid] drosophila[organism]
Complex queries	Combine all of the above tips to construct a complex query	tnf[text word] OR tnfrs[gene name] tnf[text word] NOT tnfrs[gene name] NOT rattus[orgn] mobbs[author] OR dhar* "dharmacon research" OR shrna[probe type] (6731[geneid] OR 14102[geneid]) NOT mus[orgn]

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