For much of the 1990s, the Czech political landscape was dominated by the Civic Democratic Party.
The most of the 1990s the Czech political landscape was dominated by the Civic Democratic Party.
I would like to ask whether two above sentences are grammatically correct (in terms of the time determination) and express the same thing.
In your example
For much of the 1990s
means you are trying to emphasize a duration of time.
You could also express it as
For most of the 1990s...
During most of the 1990s...
As @michaeldorgan points out the most is a type of comparison, and you might use
In the 1990s, the Czech political landscape was dominated the most by the Civic Democratic Party.
which has more emphasis on domination rather than duration, but could be understood to have the same meaning as your original sentence.
