定语分译 Semiconductors are a group of materials with their conductivity lying between that of conductors and that insulators. The flexibility and versatility of numerical control have led to the development ofa new type of machine tool called the machining center三、定语分译 Semiconductors are a group of materials with their conductivity lying between that of conductors and that of insulators. The flexibility and versatility of numerical control have led to the development of a new type of machine tool called the machining center