Dependence is marked first by an increased tolerance, with more and more of thesubstance required to produce the desired effect, and then by the appearance ofunpleasant withdrawal symptoms when the substance is discontinued.
【译文】依赖的最初表现是不断增长的耐药量,要产生预期的效果需要的药剂量越来越大,而一旦中断使用就会出现难受的停药症状。
【析句】句子的主干结构是Dependence is marked。句中状语较长,注意and连接的两个by开始的介词词组是并列关系。
【讲词】dependence在句中的意思是“对药物的依赖”,withdrawal意为“停止用药”。