Irrespective of the scan mode, any scan weather in the discovery or service scanning state can be paused. The intermediate results would be saved, and the user can resume the scan anytime in the future.
It must be noted that if the scan is paused while discovery (port scanning would have been going on), then the port scanning results for the ports that have already been scanned would be saved; the scan would start for unscanned ports once the user resumes. Likewise, if the scan is paused during service scanning, then whatever services would have been scanned, their results would be saved, and the user gets the flexibility to analyze the results of the services that would be scanned. When the scan resumes, the service scanning will start for unscanned services.
The following screen shots show how to pause an ongoing scan:
In order to resume the scan...