Additional Keywords allows you to refine your results by specifying keywords within selected fields. Available fields are displayed in the drop-down menu. [Note that results are ranked by relevancy when searching the Title, Abstract, Subject Terms, Full-Text, and All fields.]
Use quotes to search for exact phrases (e.g., "space shuttle") or use the Advanced Search and select "Exact Phrase" from the first drop-down menu.
Use an asterisk ( * ) as a wild card to expand term searching (e.g., comput* searches for computation, computational, computer, computers, computerization, etc.).
Retain hyphens in words that commonly use them (e.g., x-ray).
Search for author in several ways (e.g., "Armstrong, Neil" or "Armstrong, N.").
Find multiple authors in one search by using last names only (e.g., Armstrong Aldrin).
Collection, Author, Availability Type, Document Type, NASA Center, Subject Category, and Subject Terms allow progressive refinement by browsing and selecting content features
Click red triangles to browse and select available values.
Click the [X] next to any value to exclude that item from your search.
Search History contains a list of recent searches that were run during the current search session.
To maintain the search history, the browser's "Cookies" setting must be enabled.
The search history will maintain up to 50 searches for 4 hours during the same browser session.
Click on any search link to view or modify the search.
Click on [X] next to any search link to delete it from the search history.
Click on the Clear link at the top of the list to delete all searches from the search history.
Click on the search history section header to expand/collapse it.