您要查找的是不是：
- Endorphins, a known substances produced in brains is an opioid receptor agonist which the brain produce in the presence of pain stimulus. 如果你一连几天、一天几次进行实验：诱发某人身感疼痛，再用吗啡为他止疼，到最后一天，悄悄用盐水取代吗啡，你会发现，此时盐水也能止痛。
- Phenobarbital has little analgesic action at subanesthetic doses.Rather, in sub anesthetic doses, this drug may increase the reaction to painful stimuli. 苯巴比妥亚麻醉剂量时几无镇痛作用，反倒会增加对疼痛刺激的反应。
- It was painful to admit that I was wrong. 要我承认错了，是很费力的。
- I stubbed my toe on the stone: it was very painful. 我把脚踢到了石头上，疼极了。
- He kicked in after a long and painful illness. 经过长期痛苦的疾病之后，他死了。
- Poor girl, I feel for you, toothache is painful. 可怜的姑娘，我都替你难受，牙痛真够呛。
- He gained the medal through his painful travail. 他通过艰辛的努力获得了奖牌。
- Praise is a stimulus for better work. 赞扬激励人更努力地工作。
- It is my painful duty to tell him he is dying. 要我把他即将去世的事告诉他，这使我十分为难。
- He twisted up with a sudden stab of pain. 一阵突然的剧疼使他挺不起身来。
- A provocation to action; a stimulus. 激励，刺激某种行动的刺激; 激励
- Hyperalgesia (the lowering of pain threshold and an exaggerated response to a painful stimulus); 痛觉过敏(痛阈下降和对正常情况下的疼痛刺激的反应性增加);
- He gave the boy's ear a painful tweak. 他用力拧了一下那男孩的耳朵。
- Abnormally sensitive to a stimulus. 过敏的对刺激不正常地敏感的
- He have a painful cut on his thumb. 他拇指上的伤口疼。
- Extension of the injured arm was painful. 把受伤的胳膊伸展开是很疼的。
- His incompetence was painful to witness. 他很无能，让人看著难受。
- A full requital of his striving pain. 这是对他艰苦努力的圆满回报。
- Observe carefully how the bacteria respond to this stimulus. 仔细观察细菌对这一刺激有什么反应。
- I assure you that you will feel no pain at all. 我保证你根本不会觉得疼的。
