全文获取类型
收费全文 | 585篇 |
免费 | 5篇 |
专业分类
化学 | 261篇 |
晶体学 | 4篇 |
力学 | 24篇 |
数学 | 45篇 |
物理学 | 256篇 |
出版年
2023年 | 3篇 |
2022年 | 3篇 |
2021年 | 15篇 |
2020年 | 24篇 |
2019年 | 13篇 |
2018年 | 24篇 |
2017年 | 23篇 |
2016年 | 27篇 |
2015年 | 7篇 |
2014年 | 9篇 |
2013年 | 21篇 |
2012年 | 28篇 |
2011年 | 35篇 |
2010年 | 27篇 |
2009年 | 24篇 |
2008年 | 34篇 |
2007年 | 23篇 |
2006年 | 20篇 |
2005年 | 11篇 |
2004年 | 14篇 |
2003年 | 17篇 |
2002年 | 8篇 |
2001年 | 11篇 |
2000年 | 10篇 |
1999年 | 5篇 |
1998年 | 6篇 |
1997年 | 8篇 |
1996年 | 12篇 |
1995年 | 5篇 |
1993年 | 4篇 |
1992年 | 4篇 |
1991年 | 5篇 |
1990年 | 9篇 |
1985年 | 4篇 |
1982年 | 8篇 |
1981年 | 9篇 |
1980年 | 6篇 |
1979年 | 9篇 |
1975年 | 3篇 |
1974年 | 4篇 |
1973年 | 3篇 |
1972年 | 3篇 |
1971年 | 3篇 |
1970年 | 3篇 |
1969年 | 3篇 |
1968年 | 7篇 |
1961年 | 2篇 |
1958年 | 5篇 |
1957年 | 4篇 |
1956年 | 4篇 |
排序方式: 共有590条查询结果,搜索用时 31 毫秒
531.
The photoinduced centers in the nominally pure, optically transparent ceramic PLZT 8/65/35 and samples doped with Cu, Mn,
Fe, and Co (0.1 and 0.01%) are investigated by ESR at 24 K. Photoinduced ESR signals are observed with g
eff=1.995 and 1.94, caused by Pb3+ and Ti3+ ions, respectively, and with g
eff=2.015, which can be assigned to an F center, i.e., an electron in an oxygen vacancy. The influence of heating and doping of the samples on the intensity of the
ESR signals is studied. An analysis of the results obtained corroborates models of the photoinduced centers and a scheme of
their local electronic levels.
Fiz. Tverd. Tela (St. Petersburg) 39, 1833–1837 (October 1997) 相似文献
532.
533.
A slow decay of the catalyst's activity may lead to qualitative changes in the phase pattern of the reaction, depending on the reversibility of steps involved in the reaction mechanism.
.相似文献
534.
V. I. Bykov A. N. Ivanova T. P. Pushkareva 《Reaction Kinetics and Catalysis Letters》1995,56(1):115-119
A mechanism of catalytic reaction suggested allows self-oscillations when a step of diffusion exchange is added: Z1X1, X1Y1, 2X1+Y13Z1, X1+Z2Z1 +X2. For the corresponding kinetic model parametric portraits are built and regions with unique unstable steady states (st. s.) are revealed. 相似文献
535.
S. G. Skuridin V. A. Dubinskaya L. B. Rebrov V. A. Bykov Yu. M. Yevdokimov 《Russian Chemical Bulletin》2007,56(12):2491-2498
Using the “structural conflict” method based on differences in the spatial organization of a liquid-crystalline dispersion
(LCD) of DNA-polycation complexes and the DNA cholesteric LCD, it was shown that in a solvent with specific properties, the
spatial structure of the LCD of DNA-polycation complexes can be controlled by biologically active compounds (BAC) that cause
either dissociation of the DNA-polycation complex or destruction of the polycation molecules. In both cases, the cholesteric
structure of LCD typical of the initial uncomplexed DNA molecules is recovered. The recovery of cholesteric LCD of DNA was
proved by circular dichroism spectroscopy and confirmed by X-ray diffraction and polarization microscopy. The fact that spatial
restructuring of LCD of the DNA-polycation complexes is induced by BAC in low concentrations opens up the possibility for
using particles of these dispersions as sensing elements (sandwich-type biosensing units) of biosensor devices. A new method
for determination of heparin based on the use of LCD of the DNA-polyconidine complexes was developed. The minimum heparin
concentration determined in the sample equals ∼ 0.4–0.5 μg mL−1.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2405–2412, December, 2007. 相似文献
536.
A calorimetric study of alloy formation in Au-Cu and Au-In systems was carried out. The heats of mixing, ΔH
mix, were measured at 1380,1484 and 1604 K for Au-Cu and at 1387, 1449 and 1505 K for Au-In in the full concentration range.
The results of experiments were described by approximating equations. Observed values of ΔH
mix were discussed using the phase diagrams of the systems. It was shown that the systems become closer to the ideal state with
increasing temperature. From the experimental data, the dependencies of the enthalpies of the systems on the composition and
temperature were estimated. The simultaneous effects of composition and temperature on enthalpy are represented in 3D diagrams.
The specific heats of the alloys, in the temperature range of experiments, were derived from the slopes of enthalpy planes.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
537.
E. E. Bykov S. N. Lavrenov M. N. Preobrazhenskaya 《Chemistry of Heterocyclic Compounds》2006,42(1):42-44
The total energies of derivatives of N-hydroxyindole, indole, and phenol, and of their corresponding anions have been estimated
with the aid of ab initio calculations on the 3-21G basis. The energies of proton removal were calculated from the difference
in total energies of the appropriate anions and molecules. By comparing the calculated energies of proton removal with experimental
values of pKa (acidity characteristic) a practically linear dependence was shown for the acidity characteristic on the energy of proton
removal for the series of compounds investigated. An empirical formula has been proposed expressing the dependence of pKa on the energy of proton removal, which makes it possible to predict pKa in this series by carrying out calculations of the energy of proton removal (transfer).
__________
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 47–50, January, 2006. 相似文献
538.
P. M. Silenko A. N. Shlapak A. I. Bykov N. I. Danilenko L. A. Klochkov A. V. Ragulya 《Theoretical and Experimental Chemistry》2007,43(2):85-89
The synthesis of fibrous Si3N4 nanostructures by gas-phase chemical deposition during the pyrolysis of silicon tetrachloride in a hydrogen and nitrogen
atmosphere was investigated. It was shown that the products contained both amorphous Si3N4 nanofibers and their α and β phases both with and without a silicon coating. In addition to the Si3N4 nanofibers the products also contained nanoribbons.
__________
Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 43, No. 2, pp. 81–84, March–April, 2007. 相似文献
539.
Mikhonin AV Myshakina NS Bykov SV Asher SA 《Journal of the American Chemical Society》2005,127(21):7712-7720
UV resonance Raman (UVR) spectroscopy was used to examine the solution conformation of poly-l-lysine (PLL) and poly-l-glutamic acid (PGA) in their non-alpha-helical states. UVR measurements indicate that PLL (at pH = 2) and PGA (at pH = 9) exist mainly in a mixture of polyproline II (PPII) and a novel left-handed 2.5(1)-helical conformation, which is an extended beta-strand-like conformation with Psi approximately +170 degrees and Phi approximately -130 degrees . Both of these conformations are highly exposed to water. The energies of these conformations are very similar. We see no evidence of any disordered "random coil" states. In addition, we find that a PLL and PGA mixture at neutral pH is approximately 60% beta-sheet and contains PPII and extended 2.5(1)-helix conformations. The beta-sheet conformation shows little evidence of amide backbone hydrogen bonding to water. We also developed a method to estimate the distribution of Psi Ramachandran angles for these conformations, which we used to estimate a Psi Ramachandran angle energy landscape. We believe that these are the first experimental studies to give direct information on protein and peptide energy landscapes. 相似文献
540.
We consider the kinetics of the photolysis of a halide RX in the gas phase by a rectangular photolyzing flash, involving the 3-stage cyclic kinetic scheme
. For certain values of the rate constants k1, k2 and k3 oscillations in the concentrations [Xi] are observed. Particularly pronounced oscillations occur for the quantity = [X2] – [X3], which is used to interpret the oscillations observed previously in a study of the photodissociative iodine laser for the iodides CF3I, C3F7I and i-C3F7I.Translated from Teoreticheskaya i Eksperimental'naya Khimiya, Vol. 26, No. 2, pp. 157–162, March–April, 1990. 相似文献