The center's digital archive implements a four-tier access classification, ensuring that materials are opened to the maximum extent while protecting privacy and ownership:
L0 Public Directory: public titles, summaries, sources, codes, and citation information are provided without full text. Applicable to materials whose ownership does not yet support full-text disclosure.
L1 Public Full Text: materials that have passed ownership, privacy, authorization, and ethics review can be downloaded as public copies.
L2 Researcher Access: public directory with the original address hidden. Researchers submit their identity, institution, and purpose for time-limited access after approval by the archive administrator.
L3 Internal Evidence: the public website does not store originals; only non-reversibly identifiable internal citations are retained, and public search, query, and caching are all excluded.
Combined search supports filtering by keyword, material type, region, access level, and date; L3 content does not appear in public search results. Researchers may submit a "Research Access Application" for L2 access.
(Source: This site's digital archive channel guidelines)