全文获取类型
收费全文 | 154篇 |
免费 | 4篇 |
国内免费 | 30篇 |
专业分类
化学 | 178篇 |
晶体学 | 2篇 |
数学 | 4篇 |
物理学 | 4篇 |
出版年
2023年 | 2篇 |
2022年 | 7篇 |
2021年 | 13篇 |
2020年 | 7篇 |
2019年 | 5篇 |
2018年 | 6篇 |
2017年 | 9篇 |
2016年 | 5篇 |
2015年 | 4篇 |
2014年 | 2篇 |
2013年 | 4篇 |
2012年 | 11篇 |
2011年 | 4篇 |
2010年 | 8篇 |
2009年 | 1篇 |
2008年 | 3篇 |
2007年 | 3篇 |
2006年 | 13篇 |
2005年 | 2篇 |
2004年 | 6篇 |
2003年 | 4篇 |
2002年 | 1篇 |
2001年 | 4篇 |
2000年 | 6篇 |
1999年 | 5篇 |
1998年 | 10篇 |
1997年 | 4篇 |
1996年 | 6篇 |
1995年 | 5篇 |
1994年 | 5篇 |
1993年 | 11篇 |
1992年 | 2篇 |
1991年 | 3篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1986年 | 1篇 |
1979年 | 1篇 |
排序方式: 共有188条查询结果,搜索用时 15 毫秒
1.
N. A. Gasviani M. Sh. Khutsishvili L. M. Abazadze 《Russian Journal of Electrochemistry》2006,42(9):931-937
Electrochemical reduction of sodium metavanadate in an equimolar KCl-NaCl melt and the effect of acid-base properties of environment on this process are studied by a voltammetry method on a stationary platinum electrode. It is established that the limiting current of the NaVO3 electroreduction process has a kinetic nature. The process proceeds via an autoinhibition scheme and its rate is limited by an acid-base reaction conjugated with an irreversible charge transfer reaction. A substantial role of cationic composition of the melt is revealed experimentally. Following acidification of the KCl-NaCl-NaVO3 melt by Mg2+ (from MgCl2), the process passes from an irreversible kinetic regime into a reversible diffusion (quasi-diffusion) process. Values of stability constants for vanadates produced with the aid of acid-base titration of vanadium pentoxide by oxygen ions in experimental conditions are presented. These values are taken into account when calculating kinetic parameters of the NaVO3 electroreduction. 相似文献
2.
用非水滴定法和Hammett系列指示剂测定了COS水解碱改性γ-Al_2O_3催化剂的表面碱强度分布.发现表面碱强度分布不均匀与表面能量分布不均匀相呼应.采用零点酸碱强度(H_(0,max))及碱中心区域分析法,Bronsted催化定律,进一步证实COS水解反应具有明显碱催化特征,较高活性催化剂的H_(0,max)一般为10左右,对COS水解反应起主要作用的碱性中心的碱强度(H_0)为4.8≤H_0≤9.8.对碱金属氧化物改性后的γ-Al_2O_3催化剂,Bronsted规律在每个碱强度分区域内是适用的. 相似文献
3.
过氧化氢氧化酸碱滴定法测定苯甲醛的含量 总被引:2,自引:1,他引:2
本文提出和建立了一种分析醛类化合物的方法,并用此方法测定了分析纯苯甲醛的含量为99.4%,相对标准偏差为0.21%,实验苯甲醛中所带的寻质苯甲醇以及乙醇,甲醇均不干扰测定,苯甲酸的干扰可以扣除,本法操作简单,终点易于掌握,推广应用方便。 相似文献
4.
测定了一系列氧化物的电子结合能,显示了铋系超导体与二元氧化物衬底材料的化学反应性可以用固态酸碱反应理论来描述,其反应性大小除了可以用衬底氧化物的酸碱参数估计以外,还可以用衬底氧化物氧离子的内层电子结合能估计. 相似文献
5.
B. A. Korolev L. A. Osmolovskaya Yu. V. Kuznetsov L. G. Stolyarova L. D. Smirnov 《Russian Chemical Bulletin》1992,41(2):333-336
Examination of the acid-base properties of 5-hydroxybenzimidazoles has shown them to exist in nitromethane as the 5-hydroxy-tautomers. Substituents in the 2-position have a predominantly inductive effect on the basicity of the 3-nitrogen, rationalized as in other nitrogen heterocycles by the proximity of the substituents to the reaction center.N. N. Semenov Institute of Chemical Physics, Russian Academy of Sciences, 117977 Moscow. The Research Institute for Intermediates and Dyes, 103787 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 2, pp. 421–425, February, 1992. 相似文献
6.
Thermodynamic and kinetic parameters have been established for the reaction between the carbon acid, 4-nitrophenylnitromethane,
(4-NPNM), and the base N’-n-propyl-N,N-di-n-propylbenzimidamide, (N’PDPBA), in mesitylene and in chlorobenzene. In some cases deuteron transfer from 4-(D2)NPNM to the base has also been studied. In addition, some results for the proton transfer reaction in tetrahydrofuran have
been collected. Spectrophotometric methods have been employed to monitor the ion-pair product, which is solvatochromic. In
general the solvent dependence of the parameters is as expected, but there is some indication of specific solvation. The kinetic
isotope effects of 11 and 8 in mesitylene and chlorobenzene, respectively, are larger than those predicted classically. However,
as is discussed the n-propyl group on the secondary nitrogen of the base may serve to reduce the extent of tunneling compared
to that in an unsubstituted analogue by a steric effect. 相似文献
7.
The relationship among intrinsic surface reaction constant (K) in 1-pK model, point of zero net charge (PZNC) and structural charge density (σst) for amphoteric solid with structural charges was established in order to investigate the effect of σst on pK. The theoretical analysis based on 1-pK model indicates that the independent PZNC of electrolyte concentration (c) exists for amphoteric solid with structural charges. A common intersection point (CIP) should appear on the acid-base titration curves at different c, and the pH at the CIP is pHPZNC. The pK can be expressed as pK=-pHPZNC log[(1 2αPZNC)/(1-2αPZNC)], where αPZNC≡σst/eNANs, in which e is the elementary charge, NA the Avogadro‘s constant and Ns the total density of surface sites. For solids without structural charges, pK=-pHPZNC. The pK values of hydrotalcite-like compounds (HTlc) with general formula of [Mg1-xFex(OH)2](Cl,OH)x were evaluated. With increasing x, the pK increases, which can be explained based on the affinity of metal cations for H^- or OH^- and the electrostatic interaction between charging surface and H^- or OH^-. 相似文献
8.
The effect of 1,1,2,2-tetrachloroethane (TCE) on the IR spectra of HCl complexes withN,N-dimethylformamide (DMF) and 1-methyl-2-pyrrolidone (N-MP) with strong quasisymmetric hydrogen bonds was studied using Multiple Attenuated Total Reflection (MATR) IR spectroscopy.
The addition of TCE does not change the background absorption spectra, but results in a change in the extinction coefficients
of some bands of these complexes. The analysis of the spectra shows that the HCl−DMF complexes interact only with one molecule
of TCE, and the HCl−N-MP complexes interact with two molecules of TCE. It is shown that the neutral component of the system (TCE) has no effect
on the parameters of the strong quasi-symmetric H-bond in the complexes studied.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 956–960, May, 1997. 相似文献
9.
Neural growth inhibitory factor (GIF), a member of metallothionein family (metallothionein-3, MT3), was well known by its distinct neural growth inhibitory activity, which is not shown by other MT isoforms. However, till now, people still did not know clearly how GIF exerts its biological functions. Since it has been reported that GIF might serve as NO scavenger and was related to the release of zinc, our study was focused on the interaction of GIF and NO. By studying the reactions of human GIF and human MTlg with SNOC-a type of NO donor, it was found that GIF was more reactive than MT-lg toward SNOC. In order to further figure out if the high reactivity of GIF in this reaction resulted from the acid-base catalysis, several mutants were constructed: E23K, E41G/E43A, E23K/E41G/E43A. By studying their basic properties and the reactions toward SNOC, it was found that the S-nitrosylation of GIF was not only related to the acid-base catalysis, but also to the accessibility of metal-thiolate clusters. 相似文献
10.