A search in Scopus on the journal abbreviation New Engl J Med in Scopus gives 3 hits.

By combining the full journal title New England journal of medicine with the title of the first article gives a satisfying hit:

By combining the full journal title with the title of the second hit gives this unsatisfying hit:

By combining the full journal title with the title of the third hit gives this strange hit:

Everything is satisfying besides the publication year which differs between this hit, with publication year 1975, and the other hit in the first search, with publication year 1974. According to Pubmed it should be 1974.
Searching the full title New England journal of medicine gives both New England Journal of Medicine and New England Journal of medicine with a lower case m in medicine. Trying to truncate New Engl* J* Med* gives all hits, even the three records with abbreviations.

Searching the Social Science & Medicine journal with the following 3 variants gives 9.322 records on all three variants: Social Science Medicine, Social Science and Medicine or Social Science & Medicine.

Searching the journal abbreviation Soc Sci Med gives 7 records. All seven records are not possible to retrieve searching the article titles combined with full source title: Social Science and Medicine. Trying to truncate soc* sci* med* returns 8,557 records on the spelling social science and medicine, and also unrelated titles because the journal subtitle is also indexed. Together 11,833 records. Here you also retrieve variants as Soc Sci Med and Part A-F.

Testing some other titles gives the following results. Searching British Medical Journal gives 78,067 hits, but searching the abbreviation BMJ gives 13,231 hits.

Searching Lancet Neurol gives 88 hits and searching Lancet neurology gives 730 hits. Truncating the abbreviated title Lancet Neurol* gives 818 hits and that includes both the abbreviated records and Lancet Neurology and Lancet. Neurology.

So what’s the conclusion with Scopus: search both the abbreviation and the full title. Truncating the journal abbreviation gives you all titles including the abbreviated journal title records and sometimes irrelevant journal titles.

But what happens if you go to Sources button in Scopus and browse journals? Searching New England Journal of Medicine returns a list of 48887 records.

Compared to 50181 records searching in source title with truncated abbreviation New Engl* J* Med*. The 48887 records are all records on New England Journal of Medicine without the variants New England Journal of medicine and New Engl J Med.

Browsing Social Science and Medicine via Sources gives the same problem. Just the 8557 records and not the variants. Lancet Neurology gives 730 records and British Medical Journal 71322 records.

The conclusion is: If you want to be sure to receive all articles for a journal don’t use the browsing option through Sources-button in Scopus.