基本解释贝蒂数词组短语短语Betti deficiency number Betti 亏数graded Betti number 分次Betti数The first Betti number 第一Betti数Betti de ciency number Betti 亏数betti number of riemannian manifold 黎曼流形的贝蒂数专业释义数学贝蒂数