The results of your most recent search are displayed beneath the Search History / Alerts section.
If you would like to see the results of an earlier search, that is displayed in your search history, select View Results to the right of the relevant search.
Immediately above the list of search results, you will find two drop-down menus headed Relevance and Page Options. These can be used to change the way that your results are displayed.
A Digital Object Identifier (or DOI) is a permanent, stable link to a specific item online. It is more stable than a URL, as URLs can change, for example if an organisation re-structures its website. You might see the DOI in a reference list or bibliography, as it is a reliable way to locate articles online.