Oracle Export table with table statement stitching SQL

Some time ago there is a need to export the database of 500 table structure, using the Plsqldev tool can also export the build table statements, but need to manually a table one table, very laborious. I wrote a splice of SQL.

Select ' Select Dbms_metadata.get_ddl (' | | segment_type| | "", "" | | segment_name| | "", "" | | Owner | | From dual, ' from dba_segments where segment_name= ' Ale_criticaldegree '
or Segment_name=trim (' Ale_criticaldegree ')
or Segment_name=trim (' Ale_alertlevel ')
.................

or Segment_name=trim (' Pub_spellmodel ');

Oracle Export table with table statement stitching SQL