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【判断题】
The main analytical techniques used for determination of trace elements in environmental samples include: Atomic absorption spectrometry (flame or electrothermal) (AAS, ET-AAS), atomic fluorescence spectrometry (AFS), inductively coupled plasma optical (or atomic) emission spectrometry (ICP-OES or ICP-AES), neutron activation analysis (NAA), X-ray fluorescence (XRF), proton-induced X-ray emission (PIXE), spark source or isotope dilution mass spectrometry (SSMS, IDMS), electrochemical (anodic stripping voltammetry and polarography) or inductively coupled plasma-mass spectrometry (ICP-MS).The main limitations for most of these analytical methods are sensitivity or precision problems due to interferences and sample matrix effects.In some cases these problems have been reduced or eliminated by the use of pre-analysis separation schemes, matrix-matchingof reagent blanks, calibration standards and samples; the inclusion of instrument background correction (AAS) or the coupling of hydride generation (HG), electro thermal vaporization (ETV), cold vapor (CV), flow injection (FI), ultrasonic nebulisation (USN) or laser ablation (LA) devices to the trace element detector.
A.
正确
B.
错误
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【简答题】设积分区域D:x^2+y^2≤4,则二重积分 化学极坐标下的二次积分为_________.
【简答题】设积分区域 ≤R^2,0≤z≤1,则三重积分 ( )
【判断题】In America, they like a firm handshake.
A.
正确
B.
错误
【简答题】What may a firm grip (handshake) show?
【单选题】以下不属于创建型模式是( )。
A.
代理(Proxy)
B.
生成器(Builder)
C.
原型(Protetype)
D.
单例(Singleton)
【简答题】设积分区域B:x^2+y^2≤2x,则二重积分 ( )
【单选题】Always use a firm handshake____________________________ .
A.
when you shake hands with an Italian
B.
when you shake hands with a British
C.
when you shake hands with a French
D.
when you shake hands with an American
【简答题】A firm handshake is key to interview success. As any serious job-hunter knows, it helps to dress smartly and smile at that all-important interview. But research has showed that a firm handshake is wha...
【简答题】A firm handshake is the key to interview success. As any serious job-hunter knows, it helps to dress smartly and smile at that all-important interview. But research has showed that a firm handshake is...
【单选题】以下不属于创建型模式是()。
A.
Adapter(适配器)
B.
BUILDER(生成器)
C.
PROTOTYPE(原型)
D.
SINGLETON(单例)
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