Yes, you'll need to get your bags and clear customs before checking right back in for the onward flight. When you get your bags do not go out the doors that lead to the arrivals hall of the airport. Instead, get your bags and walk towards the glass wall that, as you come down the escalator from immigration, is on your right. There's a customs lane there (go Green) you can pass through and then go immediately to the check in desk for onward domestic flights. Drop off your bags, check in, get boarding passes, and then you'll exit to your left. Go up two levels on a lift or escalator and you can go through security out to the gates to check in for the OVB flight. You'll never leave the building you arrive in. Very easy and straightforward.

PM if you care to what brings you to Novosibirsk. It's always nice to know what draws others out here.