To access the advanced search features, you must first open the Advanced Search Builder. Click the Advanced link below the search bar (shown above). Type a term (e.g., asthma) in the search bar and click ADD to add it to the query box. To add additional lines (e.g., pollution, children) to your query, follow the same steps and choose either AND (default), or OR or NOT from the dropdown menu.
After formulating your query, you can either click Search to run the search or select Add to history from the dropdown menu to add the query to your history without searching.
The full list of fields can be accessed from the All Fields drop-down menus in the builder. Below are explanations of when and how to use some of the most common fields:
Click Show index to see an alphabetical display of all terms in each PubMed search field, with a preview of the number of results for that term in parentheses. You can browse by All Fields or within a specific field such as MeSH Subheadings. If you begin typing a search term before showing the index list, you will be taken to that place in the alphabet. This will help you see spelling and other variations in terms (e.g., nonhodkin s, nonhodgin's, nonhodgkin, nonhodgkin lymphoma, etc.). NOTE Fields and index terms will automatically be added to the top search bar as soon as they are selected/typed.
Below the Advanced Search Builder's query box is your search history: a record of the searches you have run (or those you have added without running). You can combine searches by clicking the appropriate "Add with" option from the Actions menu. The Builder will connect the searches with AND unless you change it to OR or NOT.
You can also delete a search from your history by selecting Delete. To save a search to your My NCBI account (see the My NCBI page), click Create alert and say no to accepting update emails.
TIP If one of your searches produces 0 results, you may be tempted to delete it. However, sometimes it can be helpful to know you've already tried a search and been unsuccessful.