The default display for PubMed results is Recently Added. Change this setting to Relevance in order to see the articles that fit your search the best at the top of the list.
Many PubMed articles will be labeled with one of the following statuses. If they have not reached "PubMed - indexed for MEDLINE" stage then you may not be able to use MeSH terms to find those articles.
Epub Ahead of Print
-Some articles will be labeled with this tag. This means that the publisher has submitted the citation for the article before it has actually been published. These may be harder to access via ILL if we do not subscribe directly to the journal.