Find papers authored by a specific number of authors
PubMed has an interface which you can call from a script. The intend to develop it is exactly your class of problem, which cannot be solved from the provided user interface.

This is the main page of NCBI Entrez API:
https://www.ncbi.nlm.nih.gov/books/NBK25501/

What you need to do is to query PubMed by keyword(s), for example this is a search by "concrete":

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/esearch.fcgi?db=pubmed&amp;retmode=json&amp;retmax=100&amp;sort=relevance&amp;term=concrete

Do multiple queries, to cover your field, for example you can also consider "brick" or "cement".

It returns a list of publications. For each publication, you would have to check the number of authors and keep ones with a single author. For each publication, you shall call:

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/esummary.fcgi?db=pubmed&amp;id=29510510&amp;retmode=json

Determine the size of the vector "authors", and only keep the ones of size one.