through many years ❍ 这位史学家收集资料，～，终于写成了一部百万余字的史学专著。This historian collected material through many years,and at last wrote a treatise on the science of history of more than a million words.
多历年所duō lì nián suǒ
年所：年数。经历的年数很多。比喻经历的时间很长。undergo a long time, through many years