在加工过程中,若切削刀具、切削速度和进给量、加工表面都不变的情况下,所()完成的那一

题型:填空题

问题:

在加工过程中,若切削刀具、切削速度和进给量、加工表面都不变的情况下,所()完成的那一部分工序,称为工步。

考点:汽车制造工艺学汽车制造工艺学题库
题型:填空题

“不可知论”主张除感觉或现象外,什么也不能认识。下列对材料中“不可知论”的理解正确的是(   )

①不可知论认为物质是世界的本原 ②不可知论认为思维与存在没有同一性③不可知论否认意识的能动性和创造性 ④从世界观角度看,不可知论认为神创造了世界

A.①②

B.③④

C.②③

D.①④

题型:填空题

女性,44岁。心悸,心电图示房颤,胸片及PDE检查未见心脏结构异常。查体可见()

A.S1强弱不等

B.S1减弱

C.心前区震颤

D.收缩早期喷射音

E.抬举样心尖搏动

题型:填空题

Once upon a time, on an isolated island in the Java sea, lived short people who dominated(支配, 占优势) the food chain. Standing no more than three and a half feet tall, these human ancestors hunted giant rats, lumbering lizards(笨拙的蜥蜴), and miniature elephants.  

It sounds a bit like a fairy tale, but it's true. Unearthed relics on the island uncovered the remains of a race of tiny human ancestors. Homo floresiensis, as the newly discovered species has been named, apparently could date back to 13,000 years ago. This means they have a lot in common with modern humans.

So how and why did these people get so small? Scientists suspect that it's due to the fact that this race lived on an isolated island with limited resources. Take the miniature elephants for example. When elephants first came to the island either by swimming or by some kind of natural land raft, they were probably close to full size. But since there wasn't much to eat, over time smaller elephants lived longer and better. The smaller the elephant was, the less it had to eat to stay strong and healthy.

Scientists call this the "island role", and it can apply to humans as well as animals. Given the island's sparse(稀少) food supply, it makes sense that the early humans living there would have evolved (进化) a body size requiring less food to survive. So bigger isn't always better.

In the floresiensis, at least, getting smaller was the way to go.

小题1:According to the passage, the fact Homo floresiensis are very small is based on________.

A.the islanders in the Java Sea

B.the human ancestors

C.the unearthed relics

D.a newspaper report小题2: The underlined word "miniature" in the first paragraph most probably means______.

A.tiny

B.active

C.rare

D.wild小题3:People on the island got so small because____________.

A.they did not have enough food to eat.

B.they gradually developed for lack of food.

C.they shared less food with elephants.

D.they remained alive as the elephants.小题4: What might be the most suitable title of the passage?

A.The history of short people

B.Short people from a fairy tale

C.The proofs on short people

D.Short people on an isolated island小题5:According to the passage, getting smaller can make people and animals ____

A.run quickly

B.live longer

C.live weaker

D.run slowly

题型:填空题

肼(N2H4)是火箭发动机的一种燃料,反应时N2O4为氧化剂,生成N2和水蒸气。已知:

N2(g)+2O2(g)=N2O4(g)    ΔH="+8.7" kJ·mol-1

N2H4(g)+O2(g)=N2(g)+2H2O(g)  ΔH="-534.0" kJ·mol-1

下列表示肼跟N2O4反应的热化学方程式,正确的是

A.2N2H4(g)+N2O4(g)=3N2(g)+4H2O(g) ΔH="-542.7" kJ·mol-1

B.2N2H4(g)+N2O4(g)=3N2(g)+4H2O(g) ΔH="-1059.3" kJ·mol-1

C.N2H4(g)+N2O4(g)=N2(g)+2H2O(g) ΔH="-1076.7" kJ·mol-1

D.2N2H4(g)+N2O4(g)=3N2(g)+4H2O(g) ΔH="-1076.7" kJ·mol-1

题型:填空题

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