Digital collections containing open access (OA) publications, including reports, journal articles, conference papers, data and theses.

• AOASG list of Australian OA Repositories
• CORE - find and access full-text (typically PDF format) content from many OA journals, repositories and systems
• CSU Research Output (CRO)
• DOAB - academic peer-reviewed books and book chapters from 300+ publishers
• Knowledge Unlatched - monographs and journals in a wide variety of disciplines
• OAPEN - academic books in humanities and social sciences
• OpenDOAR - international directory of OA repositories and their policies
• Primo Search - limit search results to 'Open Access'
• SPARC (Scholarly Publishing & Academic Resources Coalition) repository resources
• Unpaywall - an open database of free scholarly articles

Other Library databases where search results can be easily limited to AO content, e.g. Scopus

The Public Access section of a Google Scholar profile contains the articles that are publicly available. 

An article can be publicly available from several sources including its publisher, an institutional repository, a research area specific repository and others. The Google Scholar indexing system tries to include all publicly accessible versions that follow their inclusion guidelines.

For more information see: https://scholar.google.com/intl/en/scholar/citations.html#publicaccess