Show:
sqlite3 ~/Library/Preferences/com.apple.LaunchServices.QuarantineEventsV* 'select LSQuarantineDataURLString from LSQuarantineEvent'
Delete:
sqlite3 ~/Library/Preferences/com.apple.LaunchServices.QuarantineEventsV* 'delete from LSQuarantineEvent'
Source:
http://lifehacker.com/5976042/display-your-entire-download-history-on-a-mac-with-a-terminal-command