The phrase "research has shown" is correct and usable in written English. It is usually used to indicate that a study or scientific experiment has been conducted, and the results of this study or experiment inform the rest of the sentence. Example: Research has shown that children learn best when using hands-on activities.
Detailed research has shown otherwise.
And they also corroborate what prior research has shown.
But nonetheless, research has shown that uniform can be effective.
Recent research has shown that it is also biologically damaging.
Research has shown preschool to improve later performance in school.
Substantial research has shown that this is not the case.
Research has shown that patients expect a physical exam.
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