Almost all antivirus companies offer Offline Installers and Offline Signature/VirusDatebase updates that can be downloaded elsewhere and then transferred to the offline system including Avira,Avast,Qihoo 360,BitDefender Internet Security
Qihoo 360 antivirus doesnt have BitDefender and Avira engines enabled by default, so u should enable them manually in settings menu.
http://www.360totalsecurity.com/en/features/360-total-security/ click "Download standalone virus database here" i.e.
http://free.360totalsecurity.com/vdb/360TS_VDB_BD_20150512.exe for BitDefender Engine and
http://free.360totalsecurity.com/vdb/360TS_VDB_Avira_20150512.exe for Avira engine (those links will become outdated one day and u should visit your self)
Original BitDefender internet security protection is better then Qihoo 360 with BitDefender Engine enabled, but Qihoo is free and doesnt req online registration. German Avira Antivirus also offers free version with offline installer