史学家陈寅恪在《陈垣敦煌劫余录序》中指出：“一时代之学术，必有其新材料与新问题。取用此材料，以研求问题，则为此时代学术之新潮流。治学之士，得预于此潮流者，谓之预流。其未得预者，谓之不入流。此古今学术史之通义，非彼闭门造车之徒，所能同喻者也。”①这里所谓“? The historian Chen Xi pointed out in the book “The Preface to Dunhuang’s Grave Rest”. “In an era of academics, there must be new materials and new problems. Using this material to study issues is the new trend of academics for this era. Scholars of scholarship must presume this trend, that is, pre-flow. Whoever has not attained the presupposition is said to be non-influential. This is a common understanding of the history of ancient and modern scholars. Here is the so-called "?