It appears that the expression “Citation Index” often referes to a couple of documents as the “Science Citation Index”. It seems that there is not any “official” translation for that word.
However, Linguee shows some articles where it is directly translated as “Index de citations”. There does not seem to be any dedicated word in French, but this one is understandable. I don’t think anybody would have problems to understand it 🙂
I’m absolutely not sure if that’s even used in the world of scientific publication in French, but such a term could be translated in
Taux de citation
Indice de citation
Fréquence de citation
These transaltions would carry the idea of ranking authors and articles according to the way they are cited by others.
If you mean the database as a whole, I guess you could use
Base de citations
Index de citations
Table de citations
Maybe you are talking about this: