If they're actually in your garden bed you have a problem. There aren't any selective herbacides to work on a veggie or flower garden.

There is a product called preen that will stop weed & grass seeds from germinating that you can use in such a garden, but only if you don't need veggie or flower seeds to germinate as they will be stopped too.

To get rid of existing ones, you really have to go full out in killing them.

Completely cover the garden with black plastic, cardboard, or newspaper, or a thick landscape fabric (that sunlight cannot get through), for 1 month to 6 weeks. It will kill everything in there. It is important that you do not leave any gaps for light to get through. You will have nice rich soil at the end of this as well. This is really the only way to repair a neglected garden, many of the grassy weeds will come back if you merely try to pull them out.

If you like, you can try just pulling out the weeds nearest to your plants, and then putting the plastic/etc up to the base of your plants. It is more work but you can keep your plants. If you do this route I recommend cardboard, 2 layers thick, and then putting bark mulch on top of the cardboard, the cardboard will decompose, improving the soil, so you do not need to take it off after a month.

The next step is prevention to make sure it doesn't happen again. Put some kind of border between your bed and your lawn or wherever it is. If you put something 4-6 inches into the ground grass cannot send runners under it. Then make sure your bed always has ample mulch on it, 2 inches or so, and weed regularly while the weeds are small and easy to get rid of.