Find papers authored by a specific number of authors For some concrete study, I need to find for some keywords, papers that have just one author. I used PubMed, Scopus and ISI Web of Science, but in any case, I could not find a way to filter bibliographic search results by a specific number of authors, or a number less than some exact number of authors. Anybody knows how to do this with mentioned tools (PubMed, Scopus and ISI Web of Science) or others?
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.