There are a handful of sample questions for 1Z0-051 here:
And for 1Z0-052 here:
Beyond that, the only valid means of getting sample questions is by purchasing practice tests from a reputable source such as SelfTest Software or Transcender. Books in the Oracle press series also have end-of-chapter questions to test your skills. I've not found most of the OPress questions to be much like the actual test questions, but they do help to verify your knowledge of the topics.
1) Oracle Certification have got more intimate with Kaplan (selftest):
... see https://blogs.oracle.com/certification/entry/0772
... and/or http://education.oracle.com/pls/web_prod-plq-dad/db_pages.getpage?page_id=208
2) Beware of using sample papers too early in your exam preparation ... they can be a good tool for confirming your knowledge, they are a very poor way of attempting primary learning. And from once you have seen a specific question once and seen its answer it has less value next time round, so treat good quality practice tests as a precious resource not to be gourged upon near the start of your preparation.