Can I refuse to let my landlord into my apartment or house?

You must provide your landlord with reasonable access to your apartment so the landlord can make repairs, inspections, improvements, etc.  However, your landlord must give you 24 hours notice before accessing your apartment.  If your landlord shows up unannounced, you have the right to refuse access and ask your landlord to come back at a more convenient time.

Can my landlord enter my place without any notice to me?

When can my landlord evict me?