A more focused search engine

Here is a search engine that seem to significantly do better than google on very narrowly focused search (especially in science and especially for france): Reacteur.com. With this one I found this document (from here and here). Something I could not find easily with google. I understand the subject is very narrow, but sometimes this type of search is very much needed. Then again in order to further the initial search I had to go back to google to find this site.