to specialize in

专门研究；专营

to and fro, to begin, to begin with, to break in on, to date, to deal with, to degree, to disapprove of, to excess, to go to law against, to look...in the face, to no avail, to one's advantage, to one's delight, to pay the bill, to refer to...as, to rule out, to say nothing of, to some extent, to speak of, to the best of, to the contrary, to the effect that, to the end of time, to the fore, to the full, to the life, to the limit, to the minute, to the number of, to the point, to the question, to this day, to-do, to...degree, toad, toad-in-the-hole, toadstool, toady, toast,