Bielefeld Academic Search Engine BASE [Link]
BASE is one of the world's most voluminous search engines especially for academic web resources. BASE provides more than 240 million documents from more than 8,000 content providers. You can access the full texts of about 60% of the indexed documents for free (Open Access). BASE is operated by Bielefeld University Library.

Cosmos [Link]
Cosmos Foundation was founded by renowned scientists. A group of 100 scientist from various countries in different disciplines are started Cosmos (2010) with specific objective of providing quality information to the researcher. We offer academic database services to researcher.

Crossref [Link]
Crossref makes research outputs easy to find, cite, link, assess, and reuse. We’re a not-for-profit membership organization that exists to make scholarly communications better. We rally the community; tag and share metadata; run an open infrastructure; play with technology; and make tools and services—all to help put scholarly content in context.

Dimensions [Link]
Dimensions covers millions of research publications connected by more than 1.5 billion citations, supporting grants, datasets, clinical trials, patents and policy documents.

EuroPub [Link]
EuroPub is a comprehensive, multipurpose database covering scholarly literature, with indexed records from active, authoritative journals, and indexes articles from journals all over the world. The result is an exhaustive database that assists research in every field.

Google Scholar [Link]
Google Scholar is a freely accessible web search engine that indexes the full text or metadata of scholarly literature across an array of publishing formats and disciplines. Released in beta in November 2004, the Google Scholar index includes most peer-reviewed online academic journals and books, conference papers, theses and dissertations, preprints, abstracts, technical reports, and other scholarly literature, including court opinions and patents.

Index Copernicus World List [Link]
The growing interest in the ICI Journals Master List database, the number of applications and the number of journals which had not met the criteria required for the indexation, have inspired us to create a global database of scientific journals the ICI World of Journals. 

Lens  [Link]
The Lens Collective Action Project levels the playing field with universal and equitable access to open innovation knowledge. The Lens focuses on illuminating what innovation capabilities exist, who and which institutions have them, and how those capabilities fit into the complex jigsaw puzzle of problem solving.

LibsKey [Link]
Instant access to millions of articles provided by your library

OpenAIRE [Link]
OpenAIRE’s mission is closely linked to the mission of the European Commission: to provide unlimited, barrier free, open access to research outputs financed by public funding in Europe. OpenAIRE fulfils the EOSC vision substantially, as its operations already provide the glue for many of the user and research driven functionalities, whether these come from the long tail of science (repositories and local support) or domain disciplined research communities or Research Infrastructures.

Open Ukrainian Citation Index  [Link]
The OUCI is intended to simplify the search for scientific publications, to attract editorial attention to the problem of completeness and quality of the metadata of Ukrainian scholarly publications, and will allow bibliometrics to freely study the relations between authors and documents from various disciplines, in particular in the field of social sciences and humanities.

ROAD Directory of Open Access Scholarly Resources [Link]
The CIEPS, also known as the ISSN International Centre, is an intergovernmental organization which manages at the international level the identification and the description of serial publications and ongoing resources, print and online, in any subject.

Scilit [Link]
Scilit is a comprehensive, free database for scientists using a new method to collate data and indexing scientific material. Our crawlers extract the latest data from CrossRef and PubMed on a daily basis. This means that newly published articles are added to Scilit immediately.

Scite_  [Link]
scite is an award-winning platform for discovering and evaluating scientific articles via Smart Citations. Smart Citations allow users to see how a publication has been cited by providing the context of the citation and a classification describing whether it provides supporting or contrasting evidence for the cited claim.

Semantic Scholar [Link]
Semantic Scholar is and always will be open and free for all to use. In addition to the search and discovery tools available at semanticscholar.org, we provide the Semantic Scholar API and Open Research Corpus as free services to the research community.