NSDL:美国国家科学图书馆是美国的一个数字化在线图书馆，主要涉及科学、技术、工程和数学等理工方面的教育和研究。面向老师和图书馆人员，免费提供多媒体资源。

NSDL面向中小学教师、在读大学生、图书馆人员，提供免费的、以国家数学课程标准为核心的数学课程和活动，专家博客还拥有丰富的教师资源、教案和多媒体资源。

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).