Progress was frustratingly slow.

进展慢得使人沮丧。

But the process is frustratingly slow.

但这过程慢得让人郁闷。

Some are finding, frustratingly, that they cannot.

但有些人沮丧地发现，无法办到。

This leads to frustratingly bad science, in my opinion.

这导致了很糟糕的研究。

Words are no longer frustratingly "irrational" to him anymore.

语言对他而言不再是令人沮丧和荒谬的。