PubMed is a freely available database developed by the National Center for Biotechnology Information (NCBI). Subject coverage includes:
PubMed includes access to MEDLINE® and to citations for selected articles in life science journals not included in MEDLINE. PubMed also provides access to additional relevant Web sites and links to the other NCBI molecular biology resources.
The PubMed database contains more than 34 million citations and abstracts from the biomedical literature. PubMed facilitates searching across three National Library of Medicine resources: MEDLINE (includes Medical Subject Headings: MeSH), PubMed Central, and Bookshelf.
For your PubMed Article Assignment, remember to NOT use Review/Systematic Reviews as article types. Also, if you add the keyword United States to your search string, that will help find articles written by authors in the USA.
Sometimes (due to term mapping or truncation) PubMed searches for terms that you did not intend. The Search Details feature allows you to see what is actually being searched, which is sometimes different from what you entered.
To access the Search Details for one of the lines in your History, click the downward arrow under the "Details" column. This will expand the fields to show you all the different terms searched in that line.
In the search below, the only terms entered were lung cancer (no quotes):
Instead of only searching for the phrase lung cancer, PubMed also searched for "lung neoplasms"[MeSH] as well as other synonyms. These additional terms were searched because of PubMed's term mapping. If the phrase had been entered as "lung cancer" the term mapping would have been disabled.
The Search Details feature is one of the most powerful advanced search features in PubMed.