百度上说的过于绝对。how many通常应接名词或of短语，但也和how much一样，在意义很清楚的情况下可以省略其后的名词，单独用作宾语或者主语。例如：

How many do you smoke a day? 你一天吸多少支烟？《柯林斯词典》

In terms of extra staff — how many will we need? 就额外的员工来说，我们需要多少人？《牛津词典》

▲COCA中也不乏这样的例句：

How many do you have?

How many did you eliminate? 

How many have they passed restricting freedom? 

How many have blown themselves up on a bus in Tel Aviv? One? Two?

How many are willing to act on its behalf?