Getting BibTeX from the bibliographic databases
Usually most of bibliographic databases (global ones, like Google Scholar, Scopus, WoS) or institutional repositories (e.g. the ones based on DSpace, Omega-PSIR, etc) keep a standard for presenting the the search results in the form of bibliographic lists so that you easily extract the items from the page result and load them to the bibliograpy menagers (Mendeley, Zotero, EndNote), and then you can download the positions in the bibteX form.
In order to be able to extract bibliographic positions from a search result page you can install in your web broser special browser extension. For example youcan find extensions for Chrome browser under:
https://chromewebstore.google.com/detail/mendeley-web-importer/dagcmkpagjlhakfdhnbomgmjdpkdklff - extension for Mendeley
https://chromewebstore.google.com/detail/endnote-click/fjgncogppolhfdpijihbpfmeohpaadpc