全文获取类型
收费全文 | 111篇 |
免费 | 4篇 |
专业分类
化学 | 65篇 |
晶体学 | 1篇 |
力学 | 4篇 |
数学 | 12篇 |
物理学 | 33篇 |
出版年
2022年 | 1篇 |
2020年 | 1篇 |
2019年 | 3篇 |
2018年 | 4篇 |
2016年 | 4篇 |
2015年 | 1篇 |
2014年 | 3篇 |
2013年 | 5篇 |
2012年 | 6篇 |
2011年 | 6篇 |
2010年 | 6篇 |
2009年 | 1篇 |
2008年 | 11篇 |
2007年 | 7篇 |
2006年 | 15篇 |
2005年 | 7篇 |
2004年 | 5篇 |
2003年 | 3篇 |
2002年 | 5篇 |
2001年 | 2篇 |
2000年 | 1篇 |
1999年 | 1篇 |
1998年 | 3篇 |
1997年 | 5篇 |
1996年 | 1篇 |
1981年 | 3篇 |
1979年 | 1篇 |
1975年 | 2篇 |
1974年 | 1篇 |
1972年 | 1篇 |
排序方式: 共有115条查询结果,搜索用时 15 毫秒
91.
Olanya G Iruthayaraj J Poptoshev E Makuska R Vareikis A Claesson PM 《Langmuir : the ACS journal of surfaces and colloids》2008,24(10):5341-5349
The adsorption behavior of bottle-brush polymers with different charge/PEO ratio on silica was studied using optical reflectometry and QCM-D. The results obtained under different solution conditions clearly demonstrate the existence of two distinct adsorption mechanisms depending on the ratio of charge/PEO. In the case of low-charge density brush polymers (0-10 mol %), the adsorption occurs predominantly through the PEO side chains. However, the presence of a small amount of charge along the backbone (as low as 2 mol %) increases the adsorption significantly above that of the uncharged bottle-brush polymer in pure water. As the charge density of the brush polymers is increased to 25 mol % or larger the adsorption occurs predominantly through electrostatic interactions. The adsorbed layer structure was studied by measuring the layer dissipation using QCM-D. The adsorbed layer formed by the uncharged brush polymer dissipates only a small amount of energy that indicates that the brush lie along the surface, the scenario in which the maximum number of PEO side chains interact with the surface. The adsorbed layers formed by the low-charge density brush polymers (2-10 mol %) in water are more extended, which results in large energy dissipation, whereas those formed by the high-charge density brush polymers (50-100 mol %) have their backbone relatively flat on the surface and the energy dissipation is again low. 相似文献
92.
Eskola AJ Timonen RS Marshall P Chesnokov EN Krasnoperov LN 《The journal of physical chemistry. A》2008,112(32):7391-7401
The kinetics of the CH3 + Cl2 (k2a) and CD3 + Cl2 (k2b) reactions were studied over the temperature range 188-500 K using laser photolysis-photoionization mass spectrometry. The rate constants of these reactions are independent of the bath gas pressure within the experimental range, 0.6-5.1 Torr (He). The rate constants were fitted by the modified Arrhenius expression, k2a = 1.7 x 10(-13)(T/300 K)(2.52)exp(5520 J mol(-1)/RT) and k2b = 2.9 x 10(-13)(T/300 K)(1.84)exp(4770 J mol(-1)/RT) cm(3) molecule(-1) s(-1). The results for reaction 2a are in good agreement with the previous determinations performed at and above ambient temperature. Rate constants of the CH3 + Cl2 and CD3 + Cl2 reactions obtained in this work exhibit minima at about 270-300 K. The rate constants have positive temperature dependences above the minima, and negative below. Deuterium substitution increases the rate constant, in particular at low temperatures, where the effect reaches ca. 45% at 188 K. These observations are quantitatively rationalized in terms of stationary points on a potential energy surface based on QCISD/6-311G(d,p) geometries and frequencies, combined with CCSD(T) energies extrapolated to the complete basis set limit. 1D tunneling as well as the possibility of the negative energies of the transition state are incorporated into a transition state theory analysis, an approach which also accounts for prior experiments on the CH3 + HCl system and its various deuterated isotopic substitutions [Eskola, A. J.; Seetula, J. A.; Timonen, R. S. Chem. Phys. 2006, 331, 26]. 相似文献
93.
Xiaokai Zhang Daria A. Barkova Pavel V. Koshlyakov Ilya E. Gerasimov Evgeni N. Chesnokov Lev N. Krasnoperov 《Molecules (Basel, Switzerland)》2022,27(7)
The kinetics of the reaction of hydroxyl radical (OH) with dimethyl methylphosphonate (DMMP, (CH3O)2CH3PO) (reaction 1) OH + DMMP → products (1) was studied at the bath gas (He) pressure of 1 bar over the 295–837 K temperature range. Hydroxyl radicals were produced in the fast reaction of electronically excited oxygen atoms O(1D) with H2O. The time-resolved kinetic profiles of hydroxyl radicals were recorded via UV absorption at around 308 nm using a DC discharge H2O/Ar lamp. The reaction rate constant exhibits a pronounced V-shaped temperature dependence, negative in the low temperature range, 295–530 K (the rate constant decreases with temperature), and positive in the elevated temperature range, 530–837 K (the rate constant increases with temperature), with a turning point at 530 ± 10 K. The rate constant could not be adequately fitted with a standard 3-parameter modified Arrhenius expression. The data were fitted with a 5-parameter expression as: k1 = 2.19 × 10−14(T/298)2.43exp(15.02 kJ mol−1/RT) + 1.71 × 10−10exp(−26.51 kJ mol−1/RT) cm3molecule−1s−1 (295–837 K). In addition, a theoretically predicted pressure dependence for such reactions was experimentally observed for the first time. 相似文献
94.
Cyrill L. Naydenov Evgeni P. Kirazov Valentin S. Lozanov Ludmil P. Kirazov Vanio I. Mitev 《Chromatographia》2009,69(9-10):887-895
The process occurring as the background to IEF is electrolysis of water. During IEF the yield of water ions decreases, following a non-linear relationship similar to that of the current. Different extents of acidification and basification of the electrode solutions, causing a drift of the pH gradient, were observed. We derived a relationship underlying this process which enables calculation of the electrode current. By using a novel approach we showed that the sum of the pH of distilled water electrode solutions at the end of the IEF process tends to the ionic product of water. 相似文献
95.
Aleksandr Lushchik Cheslav Lushchik Tiit K?rner Peeter Liblik Vitali Nagirnyi Evgeni Shablonin Anna Shugai Evgeni Vasil'chenko 《Radiation measurements》2010,45(3-6):268-272
A brief overview of previously obtained and novel data on the manifestations of an analogue of Franck–Hertz effect in photo- and cathodoluminescence of wide-gap inorganic materials is presented. On the example of NaCl:Tl+ and MgO:Cr3+ single crystals, the excitation processes of the luminescence of 6s2 Tl+ ions and 3d3 Cr3+ ions by 5–15 keV electrons or 5–20 eV photons at 6–420 K have been studied. The rapid processes of the direct energy transfer to Tl+ by hot conduction electrons or to Cr3+ centers by hot electrons and/or hot valence holes have been separated from rapid excitonic and more inertial electron–hole processes. 相似文献
96.
We obtain bounds for the spectrum and for the total width of the spectral gaps for Jacobi matrices on ℓ2(ℤ) of the form (Hψ)
n
=a
n−1
ψ
n−1
+b
nψ
n
+a
nψ
n+1
, where a
n=a
n+q
and b
n=b
n+q
are periodic sequences of real numbers. The results are based on a study of the quasimomentum k(z) corresponding to H. We consider k(z) as a conformal mapping in the complex plane. We obtain the trace identities which connect integrals of the Lyapunov exponent
over the gaps with the normalised traces of powers of H.
Received: 17 April 2002 / Accepted: 1 October 2002 Published online: 13 January 2003
Communicated by B. Simon 相似文献
97.
Recently in the series of papers L. Barreira, Ya.B. Pesin, J. Schmeling and H. Weiss performed a complete multifractal analysis of local dimensions, entropies and Lyapunov exponents of conformal expanding maps and surface Axion A diffeomorphisms for Gibbs measures. The main goal of these papers was primarily the analysis of the local (pointwise) dimensions. This is an extremely difficult problem and, for example, similar results for hyperbolic systems in dimensions 3 and higher have not been yet obtained. In the present work we concentrate our attention on the multifractal analysis of the local (pointwise) entropies. We are able to obtain results, which are similar to those mentioned above, for Gibbs measures of the expansive homeomorphisms with specification property. Note that such homeomorphisms may not have Markov partitions, which is a crucial condition in the previous works. However, due to the fact that less is known about thermodynamical properties of these dynamical systems we were able to obtain only the continuous differentiability of the multifractal spectrum of local entropies (compare: the same spectra for the dynamical systems with Markov partitions are analytic). We believe that the smoothness of the multifractal spectrum in our case can be improved. We have related the multifractal spectrum of the local entropies to the the spectrum of correlation entropies. These correlation entropies serve as entopy-like analogs of the Hentshel-Procaccia and Rényi spectra of generalized dimensions. This allows us to complete the duality between the multifractal analyses of local dimensions and entropies. Complete proofs can be found in [TV98] and will appear elsewhere. 相似文献
98.
Evgeni I. Get'man Stanislav N. Loboda Alexey V. Ignatov Vadim V. Prisedsky Mohammed A. B. Abdul Jabar Lyudmyla I. Ardanova 《ChemInform》2016,47(20):no-no
Pb8‐xLnxNa2(PO4)6 (x = 0—2.0; Ln: Y, La, Pr—Ho, Tm—Yb) with void structural channels are prepared by solid state reaction of PbO, Na2CO3, (NH4)2HPO4, and Ln oxides (Al2O3 crucible, 800 °C, 2—10 d). 相似文献
99.
Nikola G. Todorov Evgeni N. Valkov Marina G. Stoyanova 《Journal of polymer science. Part A, Polymer chemistry》1996,34(5):863-868
The chemical modification of poly(acrylonitrile) was carried out using monoethanolamine and 1,2-ethylenediamine. The effect of the reaction conditions on the content of basic groups was studied. Polymer analogous reactions were carried out by varying the amount of the starting reagents and the temperature. The amino-containing polymers were characterized by elemental analysis. The obtained water-soluble polymers were used as carriers of low-molecular substances. © 1996 John Wiley & Sons, Inc. 相似文献
100.
Evgeni Korotyaev 《Communications in Mathematical Physics》2000,213(2):471-489
The spectral properties of the Schr?dinger operator T(t)=−d
2/dx
2+q(x,t) in L
2(ℝ) are studied, where the potential q is defined by q=p(x+t), x>0, and q=p(x), x<0; p is a 1-periodic potential and t∈ℝ is the dislocation parameter. For each t the absolutely continuous spectrum σ
ac
(T(t))=σ
ac
(T(0)) consists of intervals, which are separated by the gaps γ
n
(T(t))=γ
n
(T(0))=(α
n
−,α
n
+), n≥1. We prove: in each gap γ
n
≠?, n≥ 1 there exist two unique “states” (an eigenvalue and a resonance) λ
n
±(t) of the dislocation operator, such that λ
n
±(0)=α
n
± and the point λ
n
±(t) runs clockwise around the gap γ
n
changing the energy sheet whenever it hits α
n
±, making n/2 complete revolutions in unit time. On the first sheet λ
n
±(t) is an eigenvalue and on the second sheet λ
n
±(t) is a resonance. In general, these motions are not monotonic. There exists a unique state λ0(t) in the basic gap
γ0(T(t))=γ0(T(0))=(−∞ ,α0
+). The asymptotics of λ
n
±(t) as n→∞ is determined.
Received: 5 April 1999 / Accepted: 3 March 2000 相似文献