think up,think out,think over,think of.
think up,think out侧重于思考的结果,即是否想出了办法、计划等；
think up主要表示“设想、构思”之意；think out主要表示“仔细思考并研究出（计划等）,或者想透问题”等,两个短语均为动副结构；think over也为动副结构,侧重于思考,不涉及结果,表达“深思熟虑,仔细思考”之意；think of主要表示“考虑,关心,想起,对……有某种看法”之意,为动介（动词十介词）结构.表示看法、评价之时,常用一些副词来修饰,如think much／a lot／a great deal／highly／well／ill of…（对……评价高／好／不好）；若问评价如何,觉得怎样,常用what…think of…；若表示“以为,认为”时,则用think of…as.e．g．
①I can’t think of his name.我想不起他的名字.
②You mustn’t think of him as being irresponsible.你不要以为他是一个不负责任的人.
③She gained confidence in herself as she thought the matter over．她好好想了想这件事,对自己有了信心.
④He put his whole heart into thinking up ways to improve the quality of heir Products．他把全部心思都用来想办法提高产品质量.
⑤His theory is so complicated that nobody can think it out．他的理论是那样复杂,没有一个人能把它搞清楚