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1.
Paper 16 in this series1, 2, 3 was concerned with the equilibrium binding constants (K) of the shift reagent Europium tris (2, 2, 6, 6-tetramethylheptane-3, 5-dionate), Eu(thd)3, with primary, secondary and tertiary amines. One nitrogen heterocycle, pyridine, and two of its derivatives (see Table) were included. In the present paper we describe the binding constants for a further 9 nitrogen containing heterocycles and relate these to basicity and steric effects.  相似文献   
2.

A selective and sensitive method based on the ammonium derivatisation with o -phthaldialdehyde (OPA) and N -acetyl-cysteine (NAC) has been developed for ammonium determination in real water samples. The proposed procedure has been compared with ammonium reference methods such as Nessler reagent method and ammonium selective electrode. All procedures have been chemometrically tested and compared in terms of the main analytical properties. These procedures have been used to determine ammonium in unknown water samples. The OPA-NAC reagent method does not present any systematic error (proportional or constant), while Nessler reagent presents both of them for some samples assayed. The ammonium selective electrode is free of corrigible systematic errors, however presents amine interference. The OPA-NAC ammonium method is able to achieve a detection limit (LOD) of 0.07 mg/L in the sample, with a linear dynamic range up to 1.4 mg/L of ammonium.  相似文献   
3.
A convenient one-pot synthesis of fused phosphorus-heterocycles with biological activity via the cyclization reactions of Lawesson's reagent with bifunctional substrates is reported.  相似文献   
4.
This study examines the reagent gas pressure and ion source temperature dependence for dimethyl ether chemical ionization (DME CI) mass spectra recorded with an external source ion trap mass spectrometer (ITMS). Information for better controls of the reagent gas pressure in order to obtain fair CI spectra is provided. The origin of M+? ions observed in DME CIMS is discussed in detail. Furthermore, the ion source temperature effect on the DME CI is also investigated.  相似文献   
5.
原子吸收法间接测定泥炭水解物中的还原糖   总被引:1,自引:0,他引:1  
白燕 《光谱实验室》1994,11(5):53-55
本文研究是在常规分析基础上,提出的原子吸收法间接测定泥炭水解物中还原糖的方法。并探讨了方法中酸性介质、共存元素的影响等问题。本方法与常规方法比较,具有测定速度快,试剂用量少,准确性、重现性高等优点。  相似文献   
6.
卟啉及其配合物在分析化学中应用进展   总被引:7,自引:0,他引:7  
综述了卟啉及配合物在分析化学中的应用研究进展。重点介绍了其在光度分析、电化学、分子识别、探针等方面的应用。  相似文献   
7.
本文研究了PEG(聚乙二醇)-2000-钍试剂-(NH_4)_2SO_4体系对Fe(Ⅲ)、Al(Ⅲ)、Ni(Ⅱ)的非有机溶剂萃取行为。指出在pH为3.5-6.5(NaAc-HAc)的水溶液中,有(NH_4)_2SO_4存在下,Fe(Ⅲ)、Al(Ⅲ)可被PEG-2000相几乎完全萃取,而Ni(Ⅱ)则基本上不被萃取。从而获得了Ni(Ⅱ)与Fe(Ⅲ)、Al(Ⅲ)混合离子的定量分离。  相似文献   
8.
Summary A method for the determination of low relative molecular mass carboxylic acids (C1–C4) in water is reported. The acids are converted to p-bromophenacyl esters prior to a glass-capillary gas chromatographic separation. By utilizing electron-caputre detection the detectability is substantially improved compared to flame-ionization detection. A comparison of three different ways to treat the water samples and to produce the derivatives is made. It is shown that the , p-dibromoacetophenone reagent decomposes to a small extent which limits the utility of the reagent. Nevertheless a detection limit for formic acid of approximately 2.5 mgl–1 is obtained. The method is applied to the determination of formic and acetic acids in a paper kraft water sample.  相似文献   
9.
Positive and negative chemical ionization (CI) mass spectrometry is studied for hydrofluorocarbons (HFCs), hydrofluorocarbon ethers (HFEs), and perfluoroalkenes (PFCs) using various kinds of reagent gas. While no quasi-molecular ion was observed under electron impact ionization for saturated MFCs, [M-F]+ is detected under CI conditions using methane as a reagent gas. Mechanisms for the generation of [M-F]+ are discussed. Furthermore, nitrogen monoxide can be used as a reagent gas to observe [M + NO]+ for many HFCs and HFEs. In negative mode chloroform is also available to generate [M + Cl] for HFCs and HFEs containing -CHF- groups.  相似文献   
10.
The determination of inorganic phosphorus in human urine is very important, since it has diagnostic value in some clinical cases. Here we apply a simple, sensitive and direct method to determine inorganic phosphorus in urine. This new ensemble is prepared by adding ytterbium chloride and pyrocatechol violet in a 2:1 molar ratio in an aqueous solution of 10 mM 2-[4-(2-hydroxyethyl)-1-piperazinyl]ethanesulfonic acid buffer at pH 7.0. The addition of the urine sample turned the blue ensemble yellow and altered the UV–vis absorption spectra. The ensemble exhibits excellent selectivity for inorganic phosphorus over other constituents of urine. We validate the accuracy of our method by the standard procedure (molybdenum blue assay for phosphate). The detection results are basically consistent with normal excretion of phosphate. Furthermore, we fabricated a new kind of inorganic phosphorus reagent kit, which enables us to inspect phosphate concentrations of urine with the naked eye. Fit for all kinds of various clinic uses, our reagent kit is a hopeful substitute for the molybdenum reagent kit.   相似文献   
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