In physics there are INSPIRE (inspirehep.net) for high energy physics and NASA ADS ( http://adsabs.harvard.edu/abstract_service.html ) for pretty much all of physics, in the life sciences there is PubMed ( https://www.ncbi.nlm.nih.gov/pmc/citmatch/ ).

There is, of course, also Scopus (scopus.com) but it s not free.

Dilukshi - there are a range of resources - including Research Gate. Like you - I tend to rely on Google Scholar - but I can also track citation through other sources i.e. Mendeley (and as Artur highlights Scopus and you ISI). It also depends if you are only interested in direct citation or 'readings' as well? Let's assume that a percentage of readings will result in citation somewhere. In that case, I use sites such as Academic.edu and GrowKudos.

I prefer Mendeley as it is Free!

BASE

WorldCat

Cochrane reviews

Pubmed / Medline

ScienceDirect

Popline

Scopus

Google Scholar updates citation in prime time. Other sources take time. Sometimes never especially when there is a slight mistake in the author name or the reference. Google Scholar provides updated analytics with or without an error in references.

Thank you all. I appreciate your time.

Regards

Dilukshi