List of corpora: http://lindat.mff.cuni.cz/services/kontext/run.cgi/corplist
KonText is a basic web application for querying corpora available within the LINDAT/CLARIN project. It allows evaluation of simple and complex queries, displaying their results as concordance lines, computing frequency distribution, calculating association measures for collocations and further work with language data. This instance is a fork of KonText application (developed by the Institute of the Czech National Corpus) that has been further extended by the Institute of Formal and Applied Linguistics to suit the needs of LINDAT/CLARIN project.
Further detailed information on KonText search in English can be found here: https://wiki.korpus.cz/doku.php/manualy:kontext:index . The description is given for another set of corpora not present in Lindat, so specific corpora information may be different.