To understand the origin and development of something thoroughly, especially in academic study; to trace the source and flow.
研究任何一个复杂的课题，都要秉持“先河后海”的治学态度，从基础概念入手，逐步深入。
When researching any complex topic, one should adopt the 'first river, then sea' approach to learning, starting with fundamental concepts and gradually delving deeper.
Era:
Ancient
Frequency:
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