be动词后可以只加副词吗？比如It✀s everywhere.

be动词后面可以加副词作为表语。
不是所有的副词都能作表语（实际上只有小部分能）。quickly这样的直接由形容词派生来的副词通常都不能作表语。

这个就涉及哪些副词可以做表语

1、大部分副词小品词（即与介词同形的副词）都可以用作表语（以下大写表示）.
Mary was DOWN with a slight fever.
The light is still ON.
I'll be ALONG in a minute.
Are the Children BACK yet?
H'll be ROUND this afternoon.
Are you THROUGH (with your work)?
Is Staley ABOUT?
He hid the jewels when nobody was BY.
The storm was OVER before the morning.
He isn't UP yet?
Her office is just ABOVE.
His leave is UP tomorrow.
We're BEHIND in our plan.
I must be OFF now.

2、其他常作表语的副词
back,home,away,here,there,upstair,downstair,abroad,everywhere,anywhere,somewhere,nowhere等