Web of Science

An online subscription-based scientific citation indexing service that provides a comprehensive citation search. It gives access to multiple databases that reference cross-disciplinary research, which allows for in-depth exploration of specialized sub-fields within an academic or scientific discipline.

Scopus

Similar to Web of Science it is also a subscription-based bibliographic database containing abstracts and citations for academic journal articles.

Google Scholar 

A freely accessible web search engine that indexes the full text or metadata of scholarly literature. Google Scholar index includes most peer-reviewed online journals of Europe and America's largest scholarly publishers plus scholarly books and other non-peer reviewed journals.

JSTOR

A digital library containing predominantly digitalized back issues of academic journals like the Proceedings of the Royal Society of London, Science, Evolution, and many more.

The database provides full text searches of 1.900 journals but it also contains books, primary sources and current issues of journals.

Journal Citations Report

Offers a systematic, objective means to critically evaluate academic journals, with quantifiable, statistical information based on citation data. By compiling articles' cited references, JCR helps to measure research influence and impact at the journal and category levels, and shows the relationship between citing and cited journals.

Pubmed

A free search engine accessing primarily the MEDLINE database of references and abstracts on life sciences and biomedical topics. PubMed provides quality control in scientific publishing. Only journals that meet PubMed's scientific standards are indexed.

MathSciNet

A database from the American Mathematical Society (AMS) that contains information on about 2 million articles from 1,900 mathematical journals, many of them abstracted "cover-to-cover". In addition, reviews or bibliographical information on selected articles is included from many engineering, computer science and other applied journals abstracted by MathSciNet.

Tair

The Arabidopsis Information Resource (TAIR) maintains a database of genetic and molecular biology data for the model higher plant Arabidopsis thaliana . Data available from TAIR includes the complete genome sequence along with gene structure, gene product information, gene expression, DNA and seed stocks, genome maps, genetic and physical markers, publications, and information about the Arabidopsis research community.

Genevestigator

Genevestigator is an innovative online platform enabling researchers to globally explore public and proprietary expression data for research and clinical applications. It's a web-based application developed for biologists and medical researchers to rapidly find out how genes are expressed in different tissues, stimuli, drug treatments, diseases, or genetic modifications.