1)表层次: 
first／firstly ／to begin with ／in the first place
second／secondly／furthermore
third／thirdly／what is more／besides
 in addtion ／finally 

2)表转折:
by contrast ／although ／though／ yet
at the same time ／but 
despite／the fact that
even so ／in contrast 
nevertheless ／even though
 for all that ／notwithstanding 
on the contrary／ however in spite of
on the other hand ／otherwise 
instead ／still ／regardless 

3)表因果: 
therfore ／consequently 
because of／ for the reason
thus／ hence ／due to 
owing to ／so ／accordingly 
thanks to ／on this account ／since ／as 
on that account ／in this way ／for ／as a result 
as a consequence 

4）表让步： 
still ／nevertheless／in spite of ／all the same 
of course ／despite ／even so ／after all