3、材料,目的是为了屏蔽:X射线[23]在内照射情况下,哪种因素危害程度更大?α射线[24]以下非电离辐射中,频率最高的是()紫外线[25]以下属于非电离辐射的是:手机辐射[26]电离辐射作用方式包括:以上都是[27]屏蔽β射线,首选:铝箔[28]具有相同质子数,但中子数不同的元素互称为( )。同位素[29]根据辐射事故的性质、严重程度、可控性和影响范围等因素,从重到轻将核及放射性突发事件分为()个等级。七[30]防护非电离辐射最重要的是:以上都是用since和for填空 1. ______ two years 2._______ two years ago
4、3. _______ last month 4.______ 1999 5._______ yesterday 仅供学习与交流,如有侵权请联系网站删除谢谢2精品好文档,推荐学习交流1. _______ 4 o’clock 2. ______ 4 hours 3._______ an hour ago 4. _______ we were children 10.______ she left here 11) We have learned five lessons ( ) the beginning of this term. 12) Mr
5、s Liao has been in hospital ( )last week. 13) I have stayed at my aunt’s ( )two weeks. 14). He has lived in Nanjing ________ the year before last. 15). I’ve known him __________ we were children. 16). Our teacher has studied Japanese _________ three years.17). She has been away f
6、rom the city ___________ about ten years. 18). It’s about ten years __________ she left the city.仅供学习与交流,如有侵权请联系网站删除谢谢2