Plasticsaresyntheticorman-madematerialswhichhaveuniqueandremarkableproperties.Manydifferentplasticsmaybeobtainedbymanipulatingthemoleculesandchangingthechemicalcombinations.Plasticshaveimportantrolesinagriculture,appliances,clothing,construction,electroni (共 7326 字) [阅读本文] >>