No, generally speaking there is only the regular ticket which allows entry at any point during regular operating hours. However most people do not do the parks from open-to-close, plus hours vary, so it's hard to call it a "full day" pass though I guess that's what it is. Once in the park there is really no way for WDW to limit how long a person stays so a half-day morning pass couldn't logistically be enforced.
Some conferences have a late-entry ticket, but it doesn't sound like that would even be helpful.
The more days you visit the less expensive the ticket is per day when calculating a per-day price. With a 10-day ticket in August/September that could be as low as $60-$63 per day, which is less than half the cost of a 1-day ticket on most dates. So if you can manage a longer vacation, you can save on the ticket cost in that sense.