How to search for articles from a specific journal in Google Scholar when the journal name is a subset of other journal names (e.g., Science)?

The site: qualifier can specify results from a particular URL.

In this case, searching "hierarchical model" site:sciencemag.org in either Google or Google Scholar seems to work.

Like Google, Google Scholar seems to support boolean operators. So one way to solve the problem would be to use "-source:[string]" (note the minus sign) to exclude by hand journals with names containing "[string]". This may take a few iterations of trial and error before you get only the results you want, and can of course also be used in conjunction with the "site:" qualifier to narrow things down further. E.g.

coffee source:"physical review" -source:"physical review letters"

Generally speaking, boolean searching is a powerful technique, and one that a lot of people seem to be unaware of.

You have to use source: followed by the name of the journal

For example, source:nature if you want to search in Nature