【单选题】【消耗次数：1】
导热系数λ小于（ ）的材料称为绝热材料。
①
0.13
②
0.32
③
0.12
④
0.23
参考答案：
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【多选题】
绝热材料的导热系数与含水率的不正确关系是（）。
①
A含水率越大，导热系数越小
②
B导热系数与含水率无关
③
C含水率越小，导热系数越小
④
D含水率越小，导热系数越大
【简答题】
水的导热系数_____ 密封空气的导热系数，所以材料吸水后的绝热性能降低。
【简答题】
什么是材料的导热性？材料导热系数的大小与哪些因素有关？
随机题目
【单选题】
设<imgwidth="14"height="16"v:shapes="_x0000_i1089"src="http://wljy.whut.edu.cn/uploadfiles/word/xxds04.files/image004.png">元齐次线性方程组<imgwidth="54"height="20"v:shapes="_x0000_i1090"src="http://wljy.whut.edu.cn/uploadfiles/word/xxds04.files/image030.png">的通解为<imgwidth="108"height="32"v:shapes="_x0000_i1091"src="http://wljy.whut.edu.cn/uploadfiles/word/xxds04.files/image083.png">则矩阵<imgwidth="18"height="18"v:shapes="_x0000_i1092"src="http://wljy.whut.edu.cn/uploadfiles/word/xxds04.files/image008.png">的秩（）
①
<imgwidth="62"height="24"v:shapes="_x0000_i1093"src="http://wljy.whut.edu.cn/uploadfiles/word/xxds04.files/image086.png">
②
<imgwidth="90"height="24"v:shapes="_x0000_i1094"src="http://wljy.whut.edu.cn/uploadfiles/word/xxds04.files/image088.png">
③
<imgwidth="66"height="24"v:shapes="_x0000_i1095"src="http://wljy.whut.edu.cn/uploadfiles/word/xxds04.files/image079.png">
④
<imgwidth="18"height="18"v:shapes="_x0000_i1096"src="http://wljy.whut.edu.cn/uploadfiles/word/xxds04.files/image008.png">的每行元素之和都不等于零
【单选题】
以下结论中不正确的是（）
①
若存在可逆矩阵<imgwidth="18"height="20"v:shapes="_x0000_i1238"src="http://wljy.whut.edu.cn/uploadfiles/word/xxds05.files/image243.png">，使<imgwidth="70"height="24"v:shapes="_x0000_i1239"src="http://wljy.whut.edu.cn/uploadfiles/word/xxds05.files/image245.png">，则<imgwidth="18"height="18"v:shapes="_x0000_i1240"src="http://wljy.whut.edu.cn/uploadfiles/word/xxds05.files/image246.png">是正定矩阵
②
二次型<imgwidth="158"height="28"v:shapes="_x0000_i1241"src="http://wljy.whut.edu.cn/uploadfiles/word/xxds05.files/image248.png">是正定二次型
③
<imgwidth="14"height="16"v:shapes="_x0000_i1242"src="http://wljy.whut.edu.cn/uploadfiles/word/xxds05.files/image249.png">元实二次型正定的充分必要条件是<imgwidth="18"height="24"v:shapes="_x0000_i1243"src="http://wljy.whut.edu.cn/uploadfiles/word/xxds05.files/image233.png">的正惯性指数为<imgwidth="14"height="16"v:shapes="_x0000_i1244"src="http://wljy.whut.edu.cn/uploadfiles/word/xxds05.files/image249.png">
④
<imgwidth="14"height="16"v:shapes="_x0000_i1245"src="http://wljy.whut.edu.cn/uploadfiles/word/xxds05.files/image249.png">阶实对称矩阵<imgwidth="18"height="18"v:shapes="_x0000_i1246"src="http://wljy.whut.edu.cn/uploadfiles/word/xxds05.files/image246.png">正定的充分必要条件是<imgwidth="18"height="18"v:shapes="_x0000_i1247"src="http://wljy.whut.edu.cn/uploadfiles/word/xxds05.files/image246.png">的特征值全为正数
【单选题】
某人打靶的命中率为0.8，现独立地射击5次，那么5次中有2次命中的概率为（）
①
<imgwidth="75"height="25"v:shapes="_x0000_i1078"src="http://wljy.whut.edu.cn/uploadfiles/word/xxdsb08.files/image105.png">
②
<imgwidth="41"height="25"v:shapes="_x0000_i1079"src="http://wljy.whut.edu.cn/uploadfiles/word/xxdsb08.files/image107.png">
③
<imgwidth="96"height="26"v:shapes="_x0000_i1080"src="http://wljy.whut.edu.cn/uploadfiles/word/xxdsb08.files/image109.png">
④
<imgwidth="96"height="26"v:shapes="_x0000_i1081"src="http://wljy.whut.edu.cn/uploadfiles/word/xxdsb08.files/image111.png">
【单选题】
下列各式中有（）等于<imgwidth="120"height="28"v:shapes="_x0000_i1263"src="http://wljy.whut.edu.cn/uploadfiles/word/xxds05.files/image281.png">
①
<imgwidth="146"height="58"v:shapes="_x0000_i1264"src="http://wljy.whut.edu.cn/uploadfiles/word/xxds05.files/image283.png">
②
<imgwidth="146"height="58"v:shapes="_x0000_i1265"src="http://wljy.whut.edu.cn/uploadfiles/word/xxds05.files/image285.png">
③
<imgwidth="166"height="58"v:shapes="_x0000_i1266"src="http://wljy.whut.edu.cn/uploadfiles/word/xxds05.files/image287.png">
④
<imgwidth="156"height="58"v:shapes="_x0000_i1267"src="http://wljy.whut.edu.cn/uploadfiles/word/xxds05.files/image289.png">
【单选题】
设随机变量<imgwidth="19"height="17"v:shapes="_x0000_i1111"src="http://wljy.whut.edu.cn/uploadfiles/word/xxdsb09.files/image123.png">的数学期望<imgwidth="68"height="21"v:shapes="_x0000_i1112"src="http://wljy.whut.edu.cn/uploadfiles/word/xxdsb09.files/image145.png">，方差<imgwidth="75"height="25"v:shapes="_x0000_i1113"src="http://wljy.whut.edu.cn/uploadfiles/word/xxdsb09.files/image147.png">，则由切比雪夫不等式有<imgwidth="118"height="21"v:shapes="_x0000_i1114"src="http://wljy.whut.edu.cn/uploadfiles/word/xxdsb09.files/image149.png">（）
①
<imgwidth="16"height="41"v:shapes="_x0000_i1115"src="http://wljy.whut.edu.cn/uploadfiles/word/xxdsb09.files/image151.png">
②
<imgwidth="16"height="41"v:shapes="_x0000_i1116"src="http://wljy.whut.edu.cn/uploadfiles/word/xxdsb09.files/image153.png">
③
<imgwidth="16"height="41"v:shapes="_x0000_i1117"src="http://wljy.whut.edu.cn/uploadfiles/word/xxdsb09.files/image130.png">
④
<imgwidth="15"height="41"v:shapes="_x0000_i1118"src="http://wljy.whut.edu.cn/uploadfiles/word/xxdsb09.files/image132.png">
【单选题】
设<imgwidth="70"height="26"v:shapes="_x0000_i1082"src="http://wljy.whut.edu.cn/uploadfiles/word/xxds03.files/image096.png">是方程组<imgwidth="60"height="20"v:shapes="_x0000_i1083"src="http://wljy.whut.edu.cn/uploadfiles/word/xxds03.files/image098.png">的基础解系，则下列向量组中也可作为<imgwidth="60"height="20"v:shapes="_x0000_i1084"src="http://wljy.whut.edu.cn/uploadfiles/word/xxds03.files/image098.png">的基础解系的是（）
①
<imgwidth="174"height="26"v:shapes="_x0000_i1085"src="http://wljy.whut.edu.cn/uploadfiles/word/xxds03.files/image100.png">
②
<imgwidth="222"height="26"v:shapes="_x0000_i1086"src="http://wljy.whut.edu.cn/uploadfiles/word/xxds03.files/image102.png">
③
<imgwidth="138"height="26"v:shapes="_x0000_i1087"src="http://wljy.whut.edu.cn/uploadfiles/word/xxds03.files/image104.png">
④
<imgwidth="140"height="26"v:shapes="_x0000_i1088"src="http://wljy.whut.edu.cn/uploadfiles/word/xxds03.files/image106.png">
【单选题】
设<imgwidth="69"height="22"v:shapes="_x0000_i1152"src="http://wljy.whut.edu.cn:80/uploadfiles/word/xxdsb11.files/image208.png">是来自正态总体<imgwidth="58"height="22"v:shapes="_x0000_i1153"src="http://wljy.whut.edu.cn:80/uploadfiles/word/xxdsb11.files/image210.png">的样本,已知统计量<imgwidth="118"height="22"v:shapes="_x0000_i1154"src="http://wljy.whut.edu.cn:80/uploadfiles/word/xxdsb11.files/image212.png">是方差<imgwidth="18"height="18"v:shapes="_x0000_i1155"src="http://wljy.whut.edu.cn:80/uploadfiles/word/xxdsb11.files/image214.png">的无偏估计量,则常数<imgwidth="12"height="18"v:shapes="_x0000_i1156"src="http://wljy.whut.edu.cn:80/uploadfiles/word/xxdsb11.files/image216.png">等于（）
①
<imgwidth="12"height="37"v:shapes="_x0000_i1157"src="http://wljy.whut.edu.cn:80/uploadfiles/word/xxdsb11.files/image218.png">
②
<imgwidth="12"height="37"v:shapes="_x0000_i1158"src="http://wljy.whut.edu.cn:80/uploadfiles/word/xxdsb11.files/image220.png">
③
2
④
4
【单选题】
设<imgwidth="77"height="21"v:shapes="_x0000_i1232"src="http://wljy.whut.edu.cn/uploadfiles/word/xxdsb09.files/image322.png">，<imgwidth="73"height="17"v:shapes="_x0000_i1233"src="http://wljy.whut.edu.cn/uploadfiles/word/xxdsb09.files/image324.png">，则<imgwidth="15"height="17"v:shapes="_x0000_i1234"src="http://wljy.whut.edu.cn/uploadfiles/word/xxdsb09.files/image280.png">服从于（）分布
①
<imgwidth="48"height="21"v:shapes="_x0000_i1235"src="http://wljy.whut.edu.cn/uploadfiles/word/xxdsb09.files/image327.png">
②
<imgwidth="48"height="21"v:shapes="_x0000_i1236"src="http://wljy.whut.edu.cn/uploadfiles/word/xxdsb09.files/image327.png">
③
<imgwidth="46"height="21"v:shapes="_x0000_i1237"src="http://wljy.whut.edu.cn/uploadfiles/word/xxdsb09.files/image329.png">
④
<imgwidth="48"height="21"v:shapes="_x0000_i1238"src="http://wljy.whut.edu.cn/uploadfiles/word/xxdsb09.files/image331.png">
【单选题】
设<imgwidth="73"height="21"v:shapes="_x0000_i1028"src="http://wljy.whut.edu.cn/uploadfiles/word/xxdsb06.files/image002.png">，则（）
①
A和B不相容
②
A和B相互独立
③
<imgwidth="61"height="21"v:shapes="_x0000_i1025"src="http://wljy.whut.edu.cn/uploadfiles/word/xxdsb06.files/image004.png">或<imgwidth="61"height="21"v:shapes="_x0000_i1026"src="http://wljy.whut.edu.cn/uploadfiles/word/xxdsb06.files/image006.png">
④
<imgwidth="111"height="21"v:shapes="_x0000_i1027"src="http://wljy.whut.edu.cn/uploadfiles/word/xxdsb06.files/image008.png">
【单选题】
<imgwidth="467"height="83"v:shapes="图片_x0020_126"src="http://wljy.whut.edu.cn/uploadfiles/word/xxds02.files/image133.png">
①
-1
②
1
③
<imgwidth="26"height="45"v:shapes="图片_x0020_127"src="http://wljy.whut.edu.cn/uploadfiles/word/xxds02.files/image134.png">
④
<imgwidth="28"height="44"v:shapes="图片_x0020_128"src="http://wljy.whut.edu.cn/uploadfiles/word/xxds02.files/image135.png">