Tā gōngzuò rènzhēn.
(He has been conscientious about his work.)
The truth value or force of such a sentence can be enhanced or diminished
by adverbials. We can use adverbials to emphasize the positive or negative poles
of the statement, as:
Tā gōngzuò quèshí rènzhēn.
(He has certainly been conscientious about his work.)
Tā gōngzuò gēnběn bú rènzhēn.
(He has not been conscientious at all about his work.)
In sentences of (2), the adverbials ‘quèshí’ (indeed) and ‘gēnběn’ (fundamental, at all) increase the truth value of the two extreme cases ‘being conscientious’ and ‘being not conscientious’. So the adverbials play the role of qualifying the speaker’s statement with respect to the actuality and validity of the statement.
 Loar, J. K. (2011). Chinese syntactic grammar: functional and conceptual principles. New York: Peter Lang.