Jīngguò jǐ nián de yánjiū, tā duì zhège lǐngyù yǐjīng liǎorányúxiōng.
After several years of research, she has a thorough grasp of this field.
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Literary and elegant — common in writing and formal speech to praise someone's deep understanding. In casual speech, 心里有数 conveys a similar idea more colloquially.
grammar
Pattern: 对...了然于胸 — 'to understand X thoroughly.' The 于 here means 'in/at,' a classical use preserved in many chengyu.
