Table of Contents Overview of PubMed | Constructing a Simple Subject Search in PubMed |  Modifying a Search |  Creating a More Involved Search |  Using the Cubby to Save and Reuse Searches |  Using PubMed Features |  Getting From PubMed to Full Text Articles |  Using the Books Link
Links in this web site: Return Home PubMed Tutorial Online Literature Sources for Evidence-Based Medicine Links Cited During Evidence-Based Medicine Portion of Workshop Pharmacotherapy Search Filters Open PubMed in another window   Links in this topic: Using Limits Using Related Articles Turning off Automatic Term Mapping Phrase Searching (Use of Double Quotation Marks) Use of Truncation Use of Field Tags   Email the instructors: Barbara Folb Patricia Friedman	Modifying a Search Even before you move to a more advanced type of search, you can narrow or expand your search results using the following simple techniques. Using Limits Principles: Applying one or more limits will reduce the number of documents retrieved and focus the results. Access Limits by clicking on the word Limits below the search entry box. The most used limits are available from the Limits screen. Other choices of language or publication type can be identified using the Index feature. The Index feature can be used to see a list of all terms available for any search field. Once chosen, Limits stay in effect for all searches you run until you remove the check in front of the word Limits. Limits can be applied to a search after it is run or chosen before it is first run. Using some limits, such as Publication Type, may eliminate PREMEDLINE records from the search results. Examples: Applying limits to a current search: Run the search antibiotics economics upper respiratory infections if it is not currently displayed on your screen. Click the Limits button. On the limits page choose Randomized Controlled Trial in the Publication Types drop down box. Click the Go button next to the search entry box. The results screen displays. Note the check mark next to the word Limits and the yellow highlighted text showing what the current limits are. Applying limits before running a search: Click on the word Limits. If there are words in the search entry box, click on the Clear button to remove them. Type the new search into the box. For this example, type antibiotics urinary tract infections. Choose the limits needed. In this example, in the Publication Types drop down box choose Practice Guideline and in the publication date enter 1995 for the beginning year and 2001 for the ending year. Month and date are not required. Click the Go button next to the Search Entry Box. The results screen displays. Note the check mark next to the word Limits and the yellow highlighted text showing what the current limits are. Finding and Applying Additional Limits using the Index Feature: Click on the word Preview/Index below the Search Entry Box. Near the bottom of the page, click on the drop-down box All Fields. Choose Publication Type. In the search box next to the field drop-down box, type a. Click on the Index button to the right of the search box. A list of all possible publication types appears. Find concensus development conference, nih and click on it to highlight it. Click on the AND button above the list to add the highlighted term to the PubMed search entry box. Add the term peptic ulcer to the search entry box so that the search now reads peptic ulcer AND"consensus development conference, nih"[Publication Type] 9. Click on Goto run the search. Return to Table of Contents for this page Using Related Articles Related articles finds articles similar to the current one using an algorithm. This can find potentially useful articles that were not located with your search strategy. For more information on that algorithm, see Computation of Related Articles. Principles: Related articles works best with an article that has an abstract and has been indexed with MeSH terms. For more information on MeSH, see Medical Subject Headings. Articles retrieved are in order of relevance, not date of publication. If the first page is not on target, it is less likely that the next pages will contain useful articles. No Details button appears for the results of a Related Articles search, and it cannot be saved as a bookmarked URL. It is possible to combine a Related Articles search with another search using the History feature, but it is not possible to save and reuse them later. Example: From a page of search results, change the Display to Citation format. (See Viewing Search Results and Changing the View if you need help doing this.) Choose an article that has an abstract and indexing, and click on the Related Article link to the right of the citation. Examine the results. Observe the subject relation to the original article, and the order in which they are displayed. Now choose an article without an abstract, and click on the Related Articles link. Compare the results to the previous Related Articles search. Go to the History page by clicking on the word Historyunder the search entry box. Note that new search statements have appeared for the Related Articles searches. For more on using the History feature, see PubMed Help : History, http://www.ncbi.nlm.nih.gov/entrez/query/static/help/pmhelp.html#History, or the section Combining Searches using History and Boolean Operators in this document. Return to Table of Contents for this page Turning off Automatic Term Mapping In some instances automatic term mapping will give unwanted results. There are three ways to disable it or alter its function. Each one has other intended primary uses, which will also be discussed. Phrase Searching (Use of Double Quotation Marks) Principles: Double quotation marks tell PubMed to first search the index of known phrases for your phrase. If not found there, it then processes your terms using Automatic Term Mapping. Examples: For an example of a search for a phrase that is in the phrase index, compare the results of two searches, and examine the search Details: rational pharmacotherapy "rational pharmacotherapy" For an example of a search for a phrase that is not in the phrase index, compare the results of two searches: "kick boxing" kick boxing Note that the results are the same for both searches. Since PubMed does not recognize the phrase, it breaks the words apart, and searches for them separately. Kick is found only as a text word, but boxing is a MeSH term, and so it looks for it as a MeSH term or a text word. If it had any narrower terms, they would not be included in the results. This is different than the normal Automatic Term Mapping, which explodes all MeSH terms found in the mapping process. Use of Truncation Principles: Truncation is indicated with an * at the end of a root word. Truncation looks for up to 150 variations on the root word entered, and turns off mapping. Do not enter searches like bio*. There are too many variations, and the root is not specific enough in meaning to give usefull results. A truncated term that appears as part of a MeSH term will retriev the MeSH term, but a truncated term will not be mapped to the MeSH term for that concept if different words are used for it in the MeSH. Example: Enter and compare the Details of the following two searches: hypertens* AND drug therapy hypertension AND drug therapy Use of Field Tags Principles: Asking PubMed to search for a term in a specific field of the record, such as the title, author, or substance name field, turns off the Automatic Term Mapping. See the section Searching Specific Fields in this document for more detail on how to do this. For a list of all available fields, see PubMed Help : Search Field Descriptions and Tags. Example: Enter the following searches and compare the Details and number of records retrieved by each search: hypertension drug therapy hypertension[ti] AND drug[ti] AND therapy[ti] Back to Top of the Page
	This page was updated on April 24, 2001. Pages maintained by Barbara Folb folb@pitt.edu