If any of your drawers have handles (instead of knobs, like a u-shape) you can put a yardstick through them from top to bottom. A little inconvenient, but it does work.
I agree with Sherri G; it might be time to rearrange some things. We use the loop locks (It looks like two zip ties with a plastic square and some 'buttons' to press to open it) on our cabinet under the sink as it has all those yucky cleansers, but I also put the more kid-friendly things lower and the forbidden items up high. And Lee Lee's suggestion of the push-down locks will work, up to a point. eventually kiddos do get smart to these, but by then they are hopefully more aware of what's for them and what isn't.
One thing I did was to remove the knobs on the front of our stove. They were just the right height for Kiddo to twiddle once he got comfortable on his feet and was a toddler. Up until he was about 4.5 years old, they just lived in a pretty bowl on the counter and I grabbed them out when I needed to cook. It also ensured that the burners were turned off.
Some people like a toilet lock. I didn't use one at our house, but some families do.
I also kept the knife block way back from the edge of counter and still set my knives in a mason jar after I've washed them. This way, when Kiddo is helping me in the kitchen and grabs something out of the dishrack, a knife isn't even a possibility. We have a stepstool which needed storing, so we bought two of those spring-clamps that people usually use for brooms... instead, we mounted them horizontally so we didn't have a stepstool which would be falling over or climbed up on unless we were intending it to be used.
Okay, I probably sound super-cautious...most of these modifications were purely for my convenience... a lot of things not to have to say 'no' to!