What kind of objects? Forms, reports and modules, you can convert your MDB
into an MDE, and it won't be possible to import those objects into other
databases.
For tables, queries and macros, you could apply Access User-Level Security
(ULS), but it's not bullet-proof: there are lots of hackers out there who
offer utilities or services to break ULS. (As well, it's been removed in
Access 2007)