Once you have found the first experiment that supports your hypothesis, you can easily find other articles related to your topic using the process of citation chaining.
One way to do this is to review the article's reference list. These resources have been used by the author(s) of the original article and will likely contain evidence that may further support, contradict, or qualify your hypothesis. This is called backward citation chaining, because you are looking at resources that were published before the original article.
You can also search for articles that cite the article in which you found your first supporting experiment. This is called forward citation chaining, since you are now looking at articles that were published after the original article. Some databases, like PsycINFO, allow you to see if other articles in the database have cited the original article.