extra ply附加层extraadj.额外的n.额外之物；临时演员adv.特别地Extracurricular-sports课外体育活动Extracurricular research课外科研extracellular tachyzoite细胞外速殖子extra-curriculum books课外书Extracellular expression胞外表达extranuclear inheritance核外遗传extra large size bearing特大型轴承extratropical jet stream温带急流extra-deep water level超深水位Extracellu- lar matrix细胞外基质