Are dumbbells enough to perform full body workouts?
Yes dumbells are enough to do a full body workout, however they aren't the best.
I used to do almost my full routine with dumbells. The reasoning behind this was to prevent muscle imbalances e.g. my right side was over compensating for my weaker left side during the bench press. The problem with this is that you cannot lift as much weight using dumbells thus you will not grow as much as you would have done using barbells. Take pretty much any exercise and you will see you will be able to lift more weight with a barbell as opposed to using two dumbells. This is due to the increased stress on stabiliser muscles using dumbells.
Another problem is that you can't preform certain exercises with dumbells. Conventional deadlifts are a prime example of an exercise which can't be performed with dumbells (in an efficient state, I know you can do variations), which is a massive strength and muscle builder. Squats can be preformed with dumbells but you won't be able to squat the same amount of weight as you will be gripping them with your hands as opposed to resting it on your back.
However don't let this put you off. If you only have access to dumbells use them. You will have a much better physique using them than using nothing.
Exercises I would recommend for a full body dumbell routine are -
Squats (you may want to buy some lifting straps for when your grip starts to fail)
Bent over row
Over head press (standing for stronger core, sitting to use heavier weight for delts)
Pull ups (dumbell can be held in legs)
Dips (dumbell can be held in legs)
Shrugs (I used deadlifts for trap development, however Shrugs are great)
All exercises 2-4 sets and 5-10 reps. Dosen't really matter what combination of reps and sets as long as you are pushing yourself and are continually progressing in weight every one or two weeks. Preform this workout every other day. Make sure you use strict form and go through the full range of motion, don't just cheat yourself for the sake of ego lifting.