它是一个无单位的数。

That's a unitless number.

youdao

它们的价值(在电容)通常是印刷无单位。

Their value (in pF) is normally printed without units.

youdao

为无合法证照的用人单位提供职业中介服务；

offering job intermediary services to any employing unit that does not have a lawful license；

youdao

First there was the observation by Michelson who back in the late 1880s had done very precise interferal metric measurements of the hydrogen lines and had observed that the 656 nanometer line 3 associated with the transition of n equals 3 to n equals 2 was, in fact, a doublet.

首先是麦克逊,在1880年底的观察,他以公制单位对氢原子的光谱线,作了准确的，无其他因素干扰的，测量,发现当n值由3变为2时,会同时得到波长为656纳米的谱线3,实际上是有两条线。

麻省理工公开课 - 固态化学导论课程节选