SQL & PL/SQL

I am a bit confused about horizontal fragmentation in oracle, for example:

I have two databases A and B
I create a employee table in A database that has name, dept attributes

Now I want to fragment this table, put all the rows where dept=science to table employee in B database,

so in B database I type:

create table employee
as select * from employee@A
where dept='science';

But the employee table in A database still has all the data , thats not what I want, I want employees in A that are not from science dept

So how should I do this? in one step?