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【简答题】
根据句意从方框中选用合适的词语，并用其适当形式填空。 need; sleep; opportunity; learn from; proud of 1. He lost an ______ to study abroad. 2. He______to do his homework now, or he can't finish it on time. 3. Because of the coming exam, he didn't ______well, now he's very ______. 4. We should be ______ our great motherland. 5. Students should ______ each other.
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【简答题】纺织纤维如何分类?
【单选题】The purpose of the ashing step in graphite-furnace atomic-absorption spec-troscopy is to（）
A.
Vaporize metal atoms to be analyzed
B.
Cause the metal species to form carbides which are more volatile
C.
Convert the graphite furnace to ash to avoid carbide formation
D.
Burn off organic species that would interfere with the elemental analysis
【简答题】纺织纤维如何分类？各有哪些主要的性能特点？
【简答题】Atomic Emission Spectroscopy
【单选题】In ______, Erwin Müller, working at Siemens Research Laboratory, invented the field emission microscope, allowing near-atomic-resolution images of materials.
A.
1926
B.
1932
C.
1936
D.
1946
【单选题】Which of the following is the function of the atomizer in the emission system of Atomic Absorption Spectroscopy?
A.
To split the beam into two
B.
To break the steady light into pulsating light
C.
To break large mass of liquid into small drops
D.
To reduce the sample into atomic state
【简答题】纺织纤维按纤维的物理属性是如何分类的?
【单选题】Which electronic transition in atomic hydrogen corresponds to the emission of visible light?
A.
from n = 5 to n = 2
B.
from n = 1 to n = 2
C.
from n =3 to n = 4
D.
from n = 3 to n =1
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