工具书 关键词 句对库 合计 primary chinese textbook 0 1 0 1 primary school language textbook 0 0 1 1 primary chinese textbooks 0 0 2 2 elementary school language textbook 0 0 2 2        初等教育  合计 primary chinese textbook  0   0  primary school language textbook  1   1  primary chinese textbooks  2   2  elementary school language textbook  2   2