Is it true that the diaphyses are at the ends of the bones?

No, that is not true. The diaphysis refers to the main or central shaft of a long bone, while the ends of the bones are called epiphyses. The diaphysis is primarily composed of compact bone and contains the medullary cavity, whereas the epiphyses are typically spongy bone covered by a thin layer of compact bone and are involved in joint formation.