Technical Notes - e1
Hands On - e6
The Docs Per Page pull-down menu lets you increase the number of citations displayed on a single page up to as many as 5,000, as shown in Figure 2.
The summary line in Figure 1 shows that only the first 20 citations (out of 355 found) are displayed on the current page. You can order citations, print, or save from only one page at a time. Before you consider ordering, printing, or saving, it is advisable to increase the number of citations displayed per page, so that one page displays your entire retrieval. To have all of the citations displayed on a single page, select a number higher than the total number of your search results. For example, to display 355 citations on one page select 1000 from the menu as shown in Figure 2. Next, click on the Search button again and PubMed will redisplay your citations according to your page length selection, as shown in Figure 3.
When all citations are displayed on one page, the summary line states only the total number of citations found, as shown in Figure 3. From this point, you can easily browse through the entire search results and click on the check boxes to mark citations for ordering, printing, or saving.
[Editor's Note: The Internet Grateful Med (IGM) Web interface to MEDLINE interacts with PubMed and also displays 20 citations per page as a default. Unlike PubMed, the IGM page length cannot be modified, but IGM remembers your selections across pages.]
MeSH terms are arranged hierarchically by subject categories into "trees" with more specific terms arranged beneath broader terms. You can view the hierarchy of MeSH terms in the PubMed MeSH Browser (see PubMed's home page sidebar). As shown in Figure 4 below, a display of the MeSH term Crohn Disease in the PubMed MeSH Browser shows that it is located in two trees and in the second tree, it is indented under Inflammatory Bowel Diseases.
In PubMed, MeSH terms are "exploded" automatically to retrieve citations that carry the specified MeSH heading and also retrieve citations that carry any of the more specific MeSH headings indented beneath it in the Tree structure. So, the search term, Inflammatory Bowel Diseases [mh] in the original search strategy was exploded and includes Crohn Disease. In addition, because the MeSH field tag is used, the search for the term is limited to only the MeSH Field. An unqualified search of a MeSH term (e.g., inflammatory bowel diseases without the [mh] tag) would search for Text Words as well as the exploded MeSH term.
Thus, the search term, crohn disease [mh] was accidentally included on both sides of the NOT expression by the explosion of the MeSH term, Inflammatory Bowel Diseases and that's what caused the zero retrieval. The search as typed in is shown below:
The search as it actually ran, with all the terms from the explosion included, is as follows:
Please note that Colitis, Ulcerative explodes to include the term Megacolon, Toxic and Inflammatory
Bowel Diseases explodes to include both Colitis, Ulcerative and Crohn Disease. Again, the appearance of Crohn Disease on both sides of the Boolean NOT is why there was no retrieval.
In PubMed, MeSH terms are always automatically "exploded" to include the more specific terms
underneath, unless you override this feature using the [mh:noexp] qualifier. The PubMed MeSH
Browser is a quick way to view the hierarchical placement of a MeSH term within the tree structure
(i.e., to check what other terms will be included in your search strategy if the MeSH term is
If you type in colitis, ulcerative/diagnosis [mh] in PubMed, both the MeSH heading and the
subheading will be exploded and the actual terms included in the search strategy will be as follows
(even though they are not displayed in the Details box):
To limit your search to only the specific MeSH heading/subheading combination, use the format: