Words are handled differently by different search tools. Many search tools such as Google & Summon assume AND -- so if you enter nursing ethics, you'll retrieve items that contain both words in any order, and perhaps separated by other words.
Do you want a phrase? Use "quotation marks" to indicate a phrase.
For example, in Summon:
Caution: Each interface works differently. Check in the Help to learn how that interface works. For example, phrase searching is NOT recommended in a basic PubMed search as it turns off the automatic mapping to MeSH.