全文获取类型
收费全文 | 605篇 |
免费 | 21篇 |
专业分类
化学 | 351篇 |
晶体学 | 4篇 |
力学 | 12篇 |
数学 | 92篇 |
物理学 | 167篇 |
出版年
2024年 | 2篇 |
2023年 | 3篇 |
2022年 | 23篇 |
2021年 | 14篇 |
2020年 | 10篇 |
2019年 | 21篇 |
2018年 | 19篇 |
2017年 | 25篇 |
2016年 | 27篇 |
2015年 | 26篇 |
2014年 | 26篇 |
2013年 | 54篇 |
2012年 | 45篇 |
2011年 | 49篇 |
2010年 | 28篇 |
2009年 | 25篇 |
2008年 | 35篇 |
2007年 | 31篇 |
2006年 | 24篇 |
2005年 | 27篇 |
2004年 | 19篇 |
2003年 | 12篇 |
2002年 | 11篇 |
2001年 | 4篇 |
2000年 | 3篇 |
1999年 | 5篇 |
1998年 | 5篇 |
1997年 | 2篇 |
1996年 | 8篇 |
1994年 | 4篇 |
1992年 | 3篇 |
1991年 | 3篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1987年 | 1篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1975年 | 3篇 |
1974年 | 2篇 |
1973年 | 4篇 |
1972年 | 2篇 |
1970年 | 3篇 |
1969年 | 2篇 |
1968年 | 1篇 |
1967年 | 1篇 |
1965年 | 2篇 |
排序方式: 共有626条查询结果,搜索用时 15 毫秒
1.
L. K. Aminov I. N. Kurkin D. A. Lukoyanov K. P. Chernov 《Physics of the Solid State》1997,39(8):1184-1186
Results are reported for measurements of the spin-lattice relaxation times of E′1 centers in quartz glass, produced by neutron irradiation, with the measurements made at two frequencies 9.25 and 24.0 GHz
over a wide temperature interval 1.5–300 K. The experimental data are interpreted on the basis of interaction mechanisms of
the spins with two-level systems with excitation energies ∼6, ∼26, and ∼420 cm−1. A small modification of the existing theory allows us to explain a number of features of the observed temperature and frequency
dependence of the relaxation rate. The results are compared with the data available in the literature on spin-lattice relaxation
of irradiation centers in crystalline quartz and quartz glass.
Fiz. Tverd. Tela (St. Petersburg) 39, 1335–1337 (August 1997) 相似文献
2.
Yu. A. Aminov 《Journal of Mathematical Sciences》1990,48(1):1-5
In this article we prove that the principal direction fields are holonomic and use them to introduce curvilinear coordinates on an immersed region in terms of which the linear element of Lobachevskií space is written in the form
where
The fundamental system of equations is established for an immersion ofn-dimensional Lobachevskií space into 2n-dimensional Euclidean space withn principal direction fields for the functions
i and, and a way of constructing an arbitrary local analytic immersion is shown.Translated from Ukrainskií Geometricheskií Sbornik, No. 28, pp. 3–8, 1985. 相似文献
3.
4.
Andrzej Czopnik Nataly Shitsevalova Alexander Krivchikov Vasyl Pluzhnikov Yuriy Paderno 《Journal of solid state chemistry》2004,177(2):507-514
We have measured heat capacity and thermal expansion of rare earth dodecaborides REB12 (RE=Y, Tb-Tm, Lu). YB12 and LuB12 are diamagnetics whereas the other dodecaborides are ordered antiferromagnetically. The amplitude of the heat capacity discontinuity at the Néel temperature and the shape of the heat capacity variation in the critical region for all these antiferromagnetics are characteristics for amplitude-modulated magnetic structures. In the ordered state TbB12 reveals two first-order phase transitions, most likely due to magnetic structure changes. The heat capacity of ErB12 just below the Néel point shows an anomaly of unclear origin. From the Schottky contribution to the heat capacity we have determined crystal field parameters. They are completely different than that is estimated from Point Charge Model. 相似文献
5.
A new Kohn-Sham formalism is developed for studying the lowest molecular electronic states of given space and spin symmetry whose densities are represented by weighted sums of several reference configurations. Unlike standard spin-density functional theory, the new formalism uses total spin conserving spin-density operators and spin-invariant density matrices so that the method is fully spin-adapted and solves the so-called spin-symmetry dilemma. The formalism permits the use of an arbitrary set of reference (noninteracting) configurations with any number of open shells. It is shown that the requirement of degeneracy of the total noninteracting energies of the reference configurations (or configuration state functions) is equivalent to the stationary condition of the exact energy relative to the weights of the configurations (or configuration state functions). Consequently, at any molecular geometry, the weights can be determined by minimization of the energy, and, for given reference weights, the Kohn-Sham orbitals can be determined. From this viewpoint, the developed theory can be interpreted as an analog of the multiconfiguration self-consistent field approach within density functional theory. 相似文献
6.
Yu. A. Aminov 《Journal of Mathematical Sciences》1994,72(4):3155-3159
It is assumed that a domain of a three-dimensional Lobachevsky space with curvature equal to – 1 is immersed into E
5.It is known that four asymptotic lines pass through every point on the immersed domain. It is proved that the second curvature of the asymptotic line is k
2 =1/cos, where is the angle formed by vector 3
from the natural frame of the asymptotic line and the normal plane of the submanifold. The third curvature k
3
satisfies k
3 |(d/ds) (1/k
2
) |and if k
3
0, then the fourth curvature is expressed in terms of k
2
and k
3.Thus, any curve in E
5
may not be an asymptotic line on a domain of a Lobachevsky space immersed in E
5.Translated from Ukrainskii Geometricheskii Sbornik, No. 35, pp. 5–10, 1992. 相似文献
7.
Alfaya RV Fujiwara ST Gushikem Y Kholin YV 《Journal of colloid and interface science》2004,269(1):32-36
3-n-propylpyridiniumsilsesquioxane chloride polymer, abbreviated as SiPy+Cl-, was used to coat a porous silica gel, SiO2, surface to form the chemically modified solid SiO2/SiPy+Cl-. The resulting polymer film was well adhered to the surface and presented an ion exchange capacity of 0.74 mmol g(-1). Metal halides, MClz [M=Fe(III), Cu(II), and Zn(II)], were adsorbed by the modified solid from ethanol solutions as neutral species by forming the surface anionic complexes described by the equation: mSiO2/SiPy+Cl-+ MClz <=> (SiO2/SiPy+)m[MCl(z+m)]m-, where the [MCl(z+m)]m- species adsorbed on the surface are FeCl4-, ZnCl4(2-), and CuCl4(2-). Accurate estimates of the specific sorption capacities and the heterogeneous stability constants of the immobilized metal complexes were determined with the aid of computational procedures. 相似文献
8.
Conclusions 1. The polarographic behavior of galanthamine, lycorine, pancratine, hordenine, and dl-narwedine on a support of 0.01 N (C2H5)4NOH has been studied.2. A chromatopolarographic method for determining the amount of galanthamine in a chloroform extract from plant raw material has been developed.Khimiya Prirodnykh Soedinenii, Vol. 6, No. 4, pp. 450–453, 1970 相似文献
9.
Ivachtchenko AV Tkachenko SE Sandulenko YB Vvedensky VY Khvat AV 《Journal of combinatorial chemistry》2004,6(5):828-834
The parallel solution-phase synthesis of a series of building blocks and combinatorial libraries based on natural bispidine scaffold has been accomplished. Key reactions include catalytic hydrogenation of the (-)-cytisine heterocyclic system, followed by alkali-mediated ring cleavage. Using this approach, a series of new bispidine core building blocks for combinatorial synthesis with three points of diversity were effectively synthesized. The libraries from libraries were then obtained in good yields and purities using solution-phase acylation reactions. Obtained combinatorial libraries of 3,4,7-trisubstituted bispidines are potentially useful in the discovery of novel physiologically active compounds. 相似文献