Do you close your office door when you don't want to be disturbed, or do you have an open-door policy? It's nice to be 100 percent accessible, but what does your open-door policy say to your staff?
If it says “I’m really not doing anything so important that it can’t be interrupted by the least little thing,” you will be. It also tells everyone up and down the ladder you're not working on anything that will move the needle. If you were, your door would be closed now and then so you can focus.
If your open-door policy says, "you can come in, but it had better be too important for an email or phone call," you'll likely get things done.
If you don't have a door, but an open cubicle, you'll need to place some kind of indicator that tells passers-by whether or not you're open to interruptions. A table lamp that you turn on when you're "open", a creative sign, or some other indicator that you can identify to your team as a signal of your accessibility.
If you don't have an office or you manage from outside an assigned space, you're a moving target. That doesn't mean you can't have a door policy. To reduce the frequency of "stop-and-chat" interruptions, start using this phrase: "can you send me an email on that?" By deferring your attention to minor issues, you reclaim your productivity. It sends a signal that you are the one who gets to determine which interruptions are mission-critical.
It will feel awkward at first, but before long the non-urgent interruptions will dwindle and your emails will increase... along with your accomplishments.
Whether you have a door or not, everyone has a "door policy." Manage the policy and you move the needle.