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你这里说的应该是部分倒装，部分倒装结构是， 助动词+ 主语+ 动词原形。
I knew little that she had already left. 改为倒装句为：Little did I know that she had already left.
(把 knew 拆成  did + know)
He rarely goes to the movies. 改为倒装句：Rarely does he go to the movies.
(把goes拆成does + go)
动词原形的助动词就是（do）.
另外，倒装句中基本没有否定句。