皮皮学，免费搜题
登录
搜题
【单选题】
金属的铸造性能主要有( )。
A.
流动性和收缩性
B.
流动性和导热性
C.
热膨胀性和收缩性
D.
导热性和热膨胀性
拍照语音搜题，微信中搜索"皮皮学"使用
参考答案：
参考解析：
知识点：
.
..
皮皮学刷刷变学霸
举一反三
【简答题】如图，在菱形ABCD中，∠BAD=2∠B，AB=6cm，则AC=（    ）cm。
查看完整题目与答案
【单选题】如图，在边长为6的菱形ABCD中，∠DAB=60°，以点D为圆心，菱形的高DF为半径画弧，交AD于点E，交CD于点G，则图形阴影部分的面积是（ ）
A.
18√3-9π
B.
18-3π
C.
9√3-9π/2
D.
18√3-3π
查看完整题目与答案
【简答题】如图，已知菱形ABCD的边长为6，∠BAD=60°，AC∩BD=O，将菱形ABCD沿对角线AC折起，得到三棱锥B-ACD，点M是棱BC的中点，DM=3 。 （1）求证：OM∥平面ABD； （2）求证：平面ABC⊥平面MDO； （3）求三棱锥M-ABD的体积。
查看完整题目与答案
【单选题】如图，菱形ABCD中，∠BAD=60°，M是AB的中点，P是对角线AC上的一个动点，若PM+PB的最小值是3，则AB长为 [     ]
A.
3
B.
C.
6
查看完整题目与答案
【单选题】如图，在菱形ABCD中，∠A=60°，E、F分别是AB、AD的中点．若EF=2，则菱形ABCD的边长为（　　）
A.
4
B.
5
C.
6
D.
7
查看完整题目与答案
【单选题】what is gene?
A.
DNA that encodes specific protein
B.
RNA
C.
codon
D.
allele
查看完整题目与答案
【单选题】如图，菱形ABCD中，∠BAD=60°，M是AB的中点，P是对角线AC上的一个动点，若PM+PB的最小值是3，则AB长为（　　）
A.
3
B.
3
C.
6
D.
2 3
查看完整题目与答案
【多选题】What are the major hurdles for the success of gene therapy?
A.
Short-lived nature – Before gene therapy can become a permanent cure for a condition, the therapeutic DNA introduced into target cells must remain functional & the cells containing the therapeutic DNA must be stable. Problems with integrating therapeutic DNA into the genome & the rapidly dividing nature of many cells prevent it from achieving long-term benefits. Patients require multiple treatments.
B.
Immune response – Any time a foreign object is introduced into human tissues, the immune system is stimulated to attack the invader. Stimulating the immune system in a way that reduces gene therapy effectiveness is possible.
C.
Multigene disorders – Some commonly occurring disorders, such as heart disease, high blood pressure, Alzheimer's disease, arthritis, & diabetes, are affected by variations in multiple genes, which complicate gene therapy.
D.
Some therapies may breach the Weismann barrier (between soma and germ-line) protecting the testes, potentially modifying the germline, falling afoul of regulations in countries that prohibit the latter practice.
查看完整题目与答案
【单选题】In wild-type flowering plants, carpel development is determined by what class of gene products?
A.
A gene products
B.
A + B gene products
C.
B + C gene products
D.
C gene products
E.
A + C gene products
查看完整题目与答案
【简答题】如图，菱形ABCD的边长为6，∠BAD=60°，AC∩BD=O．将菱形ABCD沿对角线AC折起，得到三棱锥B-ACD，点M是棱BC的中点， DM=3 2 ． （Ⅰ）求证：OM ∥ 平面ABD； （Ⅱ）求证：平面ABC⊥平面MDO； （Ⅲ）求三棱锥M-ABD的体积．
查看完整题目与答案
相关题目：
【简答题】如图，在菱形ABCD中，∠BAD=2∠B，AB=6cm，则AC=（    ）cm。
查看完整题目与答案
【单选题】如图，在边长为6的菱形ABCD中，∠DAB=60°，以点D为圆心，菱形的高DF为半径画弧，交AD于点E，交CD于点G，则图形阴影部分的面积是（ ）
A.
18√3-9π
B.
18-3π
C.
9√3-9π/2
D.
18√3-3π
查看完整题目与答案
【简答题】如图，已知菱形ABCD的边长为6，∠BAD=60°，AC∩BD=O，将菱形ABCD沿对角线AC折起，得到三棱锥B-ACD，点M是棱BC的中点，DM=3 。 （1）求证：OM∥平面ABD； （2）求证：平面ABC⊥平面MDO； （3）求三棱锥M-ABD的体积。
查看完整题目与答案
【单选题】如图，菱形ABCD中，∠BAD=60°，M是AB的中点，P是对角线AC上的一个动点，若PM+PB的最小值是3，则AB长为 [     ]
A.
3
B.
C.
6
查看完整题目与答案
【单选题】如图，在菱形ABCD中，∠A=60°，E、F分别是AB、AD的中点．若EF=2，则菱形ABCD的边长为（　　）
A.
4
B.
5
C.
6
D.
7
查看完整题目与答案
【单选题】what is gene?
A.
DNA that encodes specific protein
B.
RNA
C.
codon
D.
allele
查看完整题目与答案
【单选题】如图，菱形ABCD中，∠BAD=60°，M是AB的中点，P是对角线AC上的一个动点，若PM+PB的最小值是3，则AB长为（　　）
A.
3
B.
3
C.
6
D.
2 3
查看完整题目与答案
【多选题】What are the major hurdles for the success of gene therapy?
A.
Short-lived nature – Before gene therapy can become a permanent cure for a condition, the therapeutic DNA introduced into target cells must remain functional & the cells containing the therapeutic DNA must be stable. Problems with integrating therapeutic DNA into the genome & the rapidly dividing nature of many cells prevent it from achieving long-term benefits. Patients require multiple treatments.
B.
Immune response – Any time a foreign object is introduced into human tissues, the immune system is stimulated to attack the invader. Stimulating the immune system in a way that reduces gene therapy effectiveness is possible.
C.
Multigene disorders – Some commonly occurring disorders, such as heart disease, high blood pressure, Alzheimer's disease, arthritis, & diabetes, are affected by variations in multiple genes, which complicate gene therapy.
D.
Some therapies may breach the Weismann barrier (between soma and germ-line) protecting the testes, potentially modifying the germline, falling afoul of regulations in countries that prohibit the latter practice.
查看完整题目与答案
【单选题】In wild-type flowering plants, carpel development is determined by what class of gene products?
A.
A gene products
B.
A + B gene products
C.
B + C gene products
D.
C gene products
E.
A + C gene products
查看完整题目与答案
【简答题】如图，菱形ABCD的边长为6，∠BAD=60°，AC∩BD=O．将菱形ABCD沿对角线AC折起，得到三棱锥B-ACD，点M是棱BC的中点， DM=3 2 ． （Ⅰ）求证：OM ∥ 平面ABD； （Ⅱ）求证：平面ABC⊥平面MDO； （Ⅲ）求三棱锥M-ABD的体积．
查看完整题目与答案