That, like a few other of their search sites they have, is in beta.
Plus it searches articles.
Great if you are a scholar, a teacher, a student, looking for articles on a particular subject.
And from what I see, you had better have a damn good article to get this google beta engine to find you.
And it does not index sites, etc.
They do have others they have in beta, plus they pull some, add some, etc.
All tweaking to get it to where they can have a particular search engine for a particular niche, etc.
They had for a bit an image search engine in beta, but I can't find it.
Was neat because it eliminated so many useless images.