Secrets are generally papers related to classified projects, that is, conventional classified contents, such as classified national natural science foundation projects (hereinafter referred to as "national nature"), classified national major social science foundation projects, or other classified contents, such as classified national key laboratories and classified military academies.

Among them, confidential items generally have a confidentiality period, which is 3-5 years or longer in China. After the confidentiality period, it will be entered into HowNet together with the master's and doctoral dissertations of that year. If it is other confidential content, it may only be communicated on the intranet, and the disclosure time shall be stipulated separately (or restricted or even not).