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

• AOASG list of Australian OA Repositories
• AustLII - free online access to Australasian, and some international, legal materials
• Australian Bureau of Statistics - Australian statistics, most available free
• Cochrane Library - free (in Australia) access to international evidence-based healthcare resources, with much in full-text.
• CORE - find and access full-text (typically PDF format) content from many OA journals, repositories and systems
• CSU Research Output (CRO)
• Directory of Open Access Books (DOAJ - academic peer-reviewed books and book chapters from 300+ publishers
• Directory of Open Access Journals (DOAJ) - academic peer-reviewed journals 
• ERIC (Education Resource and Information Center) - the largest education database in the world, with much free content
• 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
• PLOS ONE - an online, international, peer-reviewed, open access science publication
• Primo Search - limit search results to 'Open Access'
• PubMed Central - a free online collection of life sciences and medical sciences journal literature
• SAGE Open - an open access, peer-reviewed journal in the humanities and social sciences
• SPARC (Scholarly Publishing & Academic Resources Coalition) repository resources
• Taylor & Francis Open - access to peer-reviewed journals across a range of subjects
• Unpaywall - an open database of free scholarly articles

Other Library databases where search results can be easily limited to OA 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