NSDL:美國國家科學圖書館是美國的一個數字化線上圖書館，主要涉及科學、技術、工程和數學等理工方面的教育和研究。面向老師和圖書館人員，免費提供多媒體資源。

NSDL面向中小學教師、在讀大學生、圖書館人員，提供免費的、以國家數學課程標準為核心的數學課程和活動，專家部落格還擁有豐富的教師資源、教案和多媒體資源。

NSDL is an online science library with links to high quality science, technology,
engineering, and math resources for K-12 teachers, faculty, librarians, students and informal learners.

The National Science Digital Library provides high quality online educational resources for teaching and learning, with current emphasis on the sciences, technology, engineering, and mathematics (STEM) disciplines—both formal and informal, institutional and individual, in local, state, national, and international educational settings.

NSDL does not hold content directly—instead, we provide structured descriptive information (metadata) about web-based educational resources held on other sites by their providers, who contribute this metadata to NSDL for organized search and open access to educational resources via NSDL.org and its services.

Most resources in the library adhere to principles of Open Educational Resource (OER) access, although some resources are restricted to provider site membership, or may have a cost associated with them (indicated in the full record of the resource).