The Science Citation Index (SCI) is a citation index originally produced by the Institute for Scientific Information (ISI) and created by Eugene Garfield. It was officially launched in 1964. It is now owned by Clarivate Analytics (previously the Intellectual Property and Science business of Thomson Reuters [1].
However, if you need to find the SCI Index Journal, you can find in many ways:
I am writing here the easiest ways-
Just Click this link: http://ipscience-help.thomsonreuters.com/incitesLiveESI/ESIGroup/overviewESI/esiJournalsList.html
You will get the complete list of the SCI Index journals. Clarivate Analytics updates the complete list regularly.
However, you can search the list by using the following links too!
http://ip-science.thomsonreuters.com/cgi-bin/jrnlst/jloptions.cgi?PC=D
http://ip-science.thomsonreuters.com/cgi-bin/jrnlst/jloptions.cgi?PC=SS
http://ip-science.thomsonreuters.com/cgi-bin/jrnlst/jloptions.cgi?PC=H
The above links are useful for different fields of research.
Reference:
1. Wikipedia