全文获取类型
收费全文 | 179篇 |
免费 | 3篇 |
国内免费 | 2篇 |
专业分类
化学 | 130篇 |
力学 | 1篇 |
数学 | 9篇 |
物理学 | 44篇 |
出版年
2022年 | 5篇 |
2021年 | 6篇 |
2020年 | 2篇 |
2019年 | 6篇 |
2018年 | 6篇 |
2017年 | 4篇 |
2016年 | 10篇 |
2015年 | 6篇 |
2014年 | 8篇 |
2013年 | 13篇 |
2012年 | 10篇 |
2011年 | 7篇 |
2010年 | 12篇 |
2009年 | 4篇 |
2008年 | 7篇 |
2007年 | 12篇 |
2006年 | 4篇 |
2005年 | 4篇 |
2004年 | 4篇 |
2003年 | 6篇 |
2002年 | 7篇 |
2001年 | 7篇 |
2000年 | 7篇 |
1999年 | 4篇 |
1998年 | 3篇 |
1996年 | 3篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 3篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1976年 | 1篇 |
排序方式: 共有184条查询结果,搜索用时 15 毫秒
1.
D. A. Davydov S. Z. Nazarova A. A. Valeeva A. A. Rempel 《Bulletin of the Russian Academy of Sciences: Physics》2007,71(5):677-680
The order-disorder phase transition in vanadium monoxide of substoichiometric compositions VOy has been studied for the first time in situ by the Faraday method with a pendulum magnetic balance of the Domenically type. A minimum is found on the temperature dependence of the magnetic susceptibility of vanadium monoxide of different compositions at a temperature of about 700 K. X-ray diffraction analysis performed before and after measuring the magnetic susceptibility confirmed the change in the structure of vanadium monoxide and the possibility of atom-vacancy processes upon cooling and heating of the samples. 相似文献
2.
L. Ya. Zakharova F. G. Valeeva A. R. Ibragimova L. A. Kudryavtseva Yu. F. Zuev L. V. Avvakumova V. I. Kovalenko A. I. Konovalov 《Russian Chemical Bulletin》2007,56(1):62-69
The kinetics of alkaline hydrolysis of O-ethyl O-p-nitrophenyl chloromethylphosphonate in a sodium bis(2-ethylhexyl)sulfosuccinate—n-nonane—polyethylene glycol—water reverse micellar system was studied in a wide range of concentrations of the surfactant
and water. The sign of the catalytic effect of micelles is inverted in the presence of the polymer. A sharp change in the
apparent rate constant of hydrolysis of the phosphonate was found in a region of the temperature percolation threshold.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 60–67, January, 2007. 相似文献
3.
Feng Xian Liu-Cai Charlotte Pham Farida Bey Gilbert Hervé 《Reaction Kinetics and Catalysis Letters》2002,75(2):305-314
Effects of Cs+, H+ and Cu2+ counterions in the vanadium containing heteropoly compounds CsxH1-xVO[PMo12O40] and CsyH0.5-yCu0.25VO[PMo12O40] on the catalytic oxidation of isobutane and characterization by TGA, IR and ESR spectroscopies are reported. A high selectivity of 76% for methacrylic acid and methacrolein together has been obtained with Cs0.75H0.25VO[PMo12O40] catalysts at a reactivity of 5.3x10-1 mmol/h cm3. 相似文献
4.
Zakharova L Valeeva F Zakharov A Ibragimova A Kudryavtseva L Harlampidi H 《Journal of colloid and interface science》2003,263(2):597-605
Surface tension measurements and the kinetic study of the basic hydrolysis of ethyl p-nitrophenyl chloromethyl phosphonate were used to examine the structural behavior and catalytic activity of the cethyltrimethylammonium bromide (CTAB)-polyoxyethylene (10) oleyl ether, C(18)H(35)(OCH(2)CH(2))(10)OH (Brij 97)-water mixed micellar system. Application of the regular solution model to the experimental data yields the value of the interaction parameter beta as -4.6, which indicates an attractive interaction of the surfactants in the mixed micelle and reflects synergistic solution behavior of the mixture. The mixed micellar composition is found to be enriched in the surfactant with the lower critical micelle concentration (cmc). In the kinetic study a nonmonotonic change in the pseudo-first-order rate constant of basic hydrolysis of the substrate is observed with increasing mole fraction of nonionic surfactant. The pseudophase micellar model reveals that the concentration factor mainly contributes to the catalytic effect, while the microenvironmental factor plays a negative role. 相似文献
5.
V. A. Mamedov V. N. Valeeva L. A. Antokhina G. M. Doroshkina A. V. Chernova I. A. Nuretdinov 《Chemistry of Heterocyclic Compounds》1993,29(5):607-611
The methyl ester and N,N-diethylamide of 2-azido-5-phenyl-4-thiazolecarboxylic acid were obtained by the reaction of the corresponding 4-substituted 2-hydrazino-5-phenylthiazole with NaNO2 in acid media. IR and UV spectroscopy were used to show that the compounds synthesized retain azide form in both the crystalline state and in solution. The reaction of azides with dicarbonyl compounds gave derivatives of 2-[5-methyl-4-acetyl-or 2-[5-methyl-4-ethoxycarbonyl-1,2,3-triazol-1-yl]-5-phenylthiazole-4-carboxylic acid.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 710–714, May, 1993. 相似文献
6.
Farida Larit Khaled M. Elokely Manal A. Nael Samira Benyahia Francisco Len Stephen J. Cutler Mohammed M. Ghoneim 《Molecules (Basel, Switzerland)》2021,26(4)
The in vitro activity of L. donovani (promastigotes, axenic amastigotes and intracellular amastigotes in THP1 cells) and T. brucei, from the fractions obtained from the hydroalcoholic extract of the aerial part of Hypericum afrum and the isolated compounds, has been evaluated. The chloroform, ethyl acetate and n-butanol extracts showed significant antitrypanosomal activity towards T. brucei, with IC50 values of 12.35, 13.53 and 12.93 µg/mL and with IC90 values of 14.94, 19.31 and 18.67 µg/mL, respectively. The phytochemical investigation of the fractions led to the isolation and identification of quercetin (1), myricitrin (2), biapigenin (3), myricetin (4), hyperoside (5), myricetin-3-O-β-d-galactopyranoside (6) and myricetin-3’-O-β-d-glucopyranoside (7). Myricetin-3’-O-β-d-glucopyranoside (7) has been isolated for the first time from this genus. The chemical structures were elucidated by using comprehensive one- and two-dimensional nuclear magnetic resonance (1D and 2D NMR) spectroscopic data, as well as high-resolution electrospray ionization mass spectrometry (HR-ESI–MS). These compounds have also been evaluated for their antiprotozoal activity. Quercetin (1) and myricetin (4) showed noteworthy activity against T. brucei, with IC50 and IC90 values of 7.52 and 5.71 µM, and 9.76 and 7.97 µM, respectively. The T. brucei hexokinase (TbHK1) enzyme was further explored as a potential target of quercetin and myricetin, using molecular modeling studies. This proposed mechanism assists in the exploration of new candidates for novel antitrypanosomal drugs. 相似文献
7.
8.
9.
The spin coherent state path integral describing the dynamics of a two-level system interacting with electromagnetic wave of circular polarization is considered. The propagator is first written in the standard form by replacing the spin by a unit vector aligned along the polar and azimuthal directions. Then it is determined exactly using a simple transformations. Thus, the exact energy spectra with corresponding wave functions are deduced. 相似文献
10.
We present the comaprative study of semileptonic and leptonic decays of Ds, D±and D0meson(D →M l+-αl-β, D → l+αlβ, D → l+αvα;α,β=e,μ) within the framework of R-parity violating the( Rp) Minimal Supersymmetric Standard Model(MSSM). The comparison shows that combination and product couplings,(λβiα λ* ij qor λβqkλ*αj k)contribution to the branching fractions of the said processes(under consideration) is consistent with or comparable to the experimental measurements in most of the cases. However, some cases exist where these contributions are highly suppressed. We identify such cases in our analysis and single out the important ones suitable for exploring in the future and current experiments. 相似文献