Most of them are negative results, though usually not overtly presented as such. In my experience, it's extremely rare for a researcher to throw away months of hard work because the result is null. They almost always find a way to augment it or spin it, write up the paper with the phrase "more research is needed" in the conclusion, and submit to a mediocre venue.

Can you give an example, because I have seen very few papers with negative or 'null' results. I'm not even sure what 'null' results means.

Null means "without value, effect, consequence, or significance; being or amounting to nothing".

Google "reproducibility crisis", "Why Most Published Research Findings Are False" by Ionnadis, "The Garden of Forking Paths" by Gelman.