表示目的：
for this reason，， for this purpose， so that， in order to， so as to，
表示强调：
in deed， in fact， surely， certainly， no doubt， without any doubt， truly，
obviously， above all，
表示概括归纳：
in a word， in short， in brief， on the whole， to sum up， generally speaking， in my opinion， as far as I know， as we all know， as has been stated， as I have shown， finally， at last， in summary， in conclusion
