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气凝胶是一种密度特别小的新型固体材料.下列制备气凝胶的物质属于氧化物的是（ ）

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如图所示为汽车尾气净化装置中反应的示意图.下列对该净化装置的分析正确的是（ ）

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已知点$A(x_{1}$,$y_{1})$和$B(x_{2}$,$y_{2})$是一次函数$y=kx+2\left(k \gt 0\right)$图象上的两点,且$x_{1} \lt x_{2}$,则$y_{1}$______$y_{2}$.(填"$ \gt $"或"$ \lt ")$

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如图,三个正比例函数的图象分别对应表达式:①$y=ax$,②$y=bx$,③$y=cx$,其中$a$,$b$,$c$均为常数,则将$a$,$b$,$c$按从小到大排列为______$.($用"$ \lt $"符号连接）

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将一次函数$y=2x+1$的图象向下平移$2$个单位长度后得到函数图象的解析式是______.

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如图,点E在△ABC的中线AD的延长线上,且DE=AD． （1）求证:BE=AC； （2）若AB=3,AC=7,求AD的取值范围．

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如图,$AB=CD$,$AE=CF$,$DE\bot AC$于$E$,$BF\bot AC$于$F$,求证:$AB$ ∥ $CD.$

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如图,在四边形$ABDE$中,$C$是$BD$边的中点.若$AC$平分$\angle BAE$,$\angle ACE=90^{\circ}$,猜想线段$AE$、$AB$、$DE$的长度满足的数量关系为并证明.

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Elijah was a smart boy.But he was self-centered and had a very bad temper（脾气）When he got angry,he usually did some hurtful things.So,nobody wanted to be friends with him. Elijah\’s parents were worried about that.Finally

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Hello,I\’m Liu Yang.I was born in October,1978 in Henan.I am an astronaut （宇航员） now.I am the（1）______Chinese woman to go to space （太空）.Now I am in the space station （太空站） （2）______Chen Dong and Cai Xuzhe.We need to live

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A.Sorry,I don\’t know. B.You can take a bus there. C.It\’s pretty far from here. D.Let me write it down in my notebook. E.Where can I take a taxi? F.Thank you very much A:Excuse me,could you tell me how to get to the air

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I\’m Karol,a 19-year-old student from Honduras.For me,volunteering has been like a school of life where I\’ve learned a lot about myself.When I was 13,I started my volunteer work by （1）______（修理）bikes.In the neighborhood

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As a teenager,I had a lot of anger （愤怒） and was not good at communicating with my parents． One day,when I was getting ready for school,my mother handed me a T-shirt．It was my father\’s,not mine．At that time,I was taller

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My father taught us in a very different way.On the first day of my junior high,my father gave me a map with street names and directions（方向） on it.He told me how to walk to the school. My school was a little far away.My f

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家庭电路两根电源线,一根叫中性线,在正常下,中性线和大地之间的电压是______；另一根叫相线,相线和中性线之间有______的电压,相线和地之间也有______的电压.

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如图所示,图甲测电笔的笔尖应该是______$(选填"导体"或"绝缘体")$.在图乙和图丙中,正确使用测电笔的是图______.当用它插入插座的左孔时氖管不发光,插入右孔时氖管发光,则说明火线在插座的______孔.

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入冬以来,各地因为不安全用电引起的火灾事故明显有上升趋势.在家庭电路中除了发生______和______会造成电流过大引发安全事故外,线路连接处因为接触不良,也容易造成该处电阻______$(选填"变大"或"变小")$,造成局部过热,从而加速导线老化,引起火灾.

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如图,某家庭电路的输电线甲、乙从右端进户.闭合开关$S$,$LED$灯发光、电风扇正常工作,用试电笔检测插座,只有检测右孔时氖管发光.由于出现故障,电风扇停止工作,$LED$灯仍发光,用试电笔检测插座两孔,氖管均发光.该故障是（ ）

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如图所示为一款新式无线插座转换器,带有插头、一转多位插座、可调光节能台灯等多种功能,下列说法正确的是（ ）

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数轴上与表示$-1$的点距离$2$个单位长度的点所表示的数是______.

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