adjective
BAD : I'm studying for a scientific degree.
GOOD : I'm studying for a science degree.
BAD : He's good at scientific subjects.
GOOD : He's good at science subjects.
BAD : The Scientific Centre is next to the History Museum.
GOOD : The Science Centre is next to the History Museum.
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Scientific is mainly used to describe something that is done or produced by scientists: 'We still don't have a scientific explanation for these mysterious events.' 'Many scientific research projects are funded by the private sector.'
When you mean 'used for, devoted to, based on or specializing in science', use science + noun: 'a new science laboratory', 'a science lesson', 'science fiction'.