directrixn.准线directadj.直接的；笔直的；坦白的v.对准；指挥；指示；命令direct-to-home直达户directed diffusion定向扩散directivity factor指向性因数direct drive motor直接驱动电动机direct index plate直接分度盘direct compression单纯受压direct flow burner直流燃烧器directivity signal方向性信号Direct in situ PCR直接原位PCRdirect cannulation直接插管