PubMed allows you to save citations temporarily using the Clipboard. Items in the Clipboard expire after 8 hours of inactivity.
To save a citation, select it by checking the small box to the left of the article and select Clipboard from the Send to menu (see the first image below). If you wish to save all of your results (500 maximum), do not make any selections first. Once items have been added to the Clipboard, you'll see an alert, as shown in the second image below.
Retrieve your saved results by clicking on the Clipboard link that appears under the search bar.
You also have the option to email results to yourself by clicking the Email button shown above. You may email up to 200 citations to a single address (see first bullet below).