There are several types of academic search engines that can help researchers find scholarly articles and publications. CORE indexes hundreds of thousands of research articles from institutions and open access journals. Google Scholar provides millions of articles, books, theses, and dissertations from its large database. Microsoft Academic searches millions of publications and presents search results with graphs and charts. The BASE search engine contains over 150 million documents from over 7000 sources, with 60% available in full text. Semantic Scholar uses artificial intelligence to provide optimized search results and was launched in 2015. CiteSeerX aims to improve dissemination of scientific information and provides freely accessible articles. Science.gov contains over 200 million pages across 60 databases and 2200 websites

1. WHAT ARE THE VARIOUS TYPES
OF ACADEMIC SEARCH
ENGINES?
CORE
CORE has hundreds and thousands of
research articles. It collects data from
institutions, open access journals, and
repositories. CORE has found its
importance in plagiarism detection,
literature-based discovery, finding
subject experts, and research impact
evaluation.
Google Scholar, a product from
Google, provides millions of relevant
articles, books, thesis, and
dissertations. Millions of documents
are available in the Google scholar
database.
GOOGLE SCHOLAR
Microsoft operates Microsoft academic
research. It has millions of publications in
its database. Apart from delivering
thousands of articles for a single search
query, this search engine also analyses
data and presents it in the form of
graphs and charts.
MICROSOFT
ACADEMIC SEARCH
The BASE is a powerful academic
search engine with more than 150
million documents obtained from more
than 7000 sources. Bielefeld University
Library operates BASE. Almost 60% of
the indexed articles can be accessed
in full texts.
BASE
Allen Institute for Artificial Intelligence
developed semantic scholar and
made it public in 2015. It incorporates
the use of Artificial Intelligence to
provide an optimum user experience.
SEMANTIC
SCHOLAR
CITESEERX
With a vision to improve the
dissemination of scientific information
among scholars and researchers, the
search engine mostly provides the
freely accessible article. CIteSeerX
provides data for non-commercial
purposes.
SCIENCE.GOV
Science.gov provides free results related to technical and scientific
information. It has over 200 million pages, with searching access to over
60 databases and 2200 websites. No registration is required to access
the information and is designed for scholars, researchers, students,
entrepreneurs, and teachers.
Source - https://www.cognibrain.com/top-academic-search-engines-for-research/