全文获取类型
收费全文 | 665篇 |
免费 | 7篇 |
国内免费 | 3篇 |
专业分类
化学 | 237篇 |
晶体学 | 4篇 |
力学 | 14篇 |
数学 | 235篇 |
物理学 | 185篇 |
出版年
2023年 | 2篇 |
2022年 | 7篇 |
2021年 | 15篇 |
2020年 | 7篇 |
2019年 | 12篇 |
2018年 | 20篇 |
2017年 | 23篇 |
2016年 | 31篇 |
2015年 | 16篇 |
2014年 | 31篇 |
2013年 | 44篇 |
2012年 | 43篇 |
2011年 | 38篇 |
2010年 | 40篇 |
2009年 | 33篇 |
2008年 | 43篇 |
2007年 | 31篇 |
2006年 | 35篇 |
2005年 | 25篇 |
2004年 | 19篇 |
2003年 | 15篇 |
2002年 | 19篇 |
2001年 | 10篇 |
2000年 | 13篇 |
1999年 | 8篇 |
1998年 | 16篇 |
1997年 | 5篇 |
1996年 | 9篇 |
1993年 | 3篇 |
1992年 | 2篇 |
1991年 | 4篇 |
1990年 | 5篇 |
1989年 | 6篇 |
1988年 | 4篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1981年 | 2篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1978年 | 4篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1973年 | 2篇 |
1970年 | 2篇 |
1969年 | 2篇 |
1968年 | 1篇 |
1937年 | 1篇 |
1936年 | 1篇 |
排序方式: 共有675条查询结果,搜索用时 31 毫秒
31.
T. K. Goncharov V. V. Dubikhin E. L. Ignat’eva G. M. Nazin Z. G. Aliev S. M. Aldoshin 《Russian Journal of General Chemistry》2013,83(4):717-721
Structure of isoxazoline compounds formed via the reaction of alkyl-substituted benzonitrile oxides with ethylene was determined by X-ray diffraction method. Isoxazoline ring is flattened, the bond lengths in it depend slightly on the nature of substituents (CH3, C2H5) and their position in the benzene ring and the angle of rotation relative to the isoxazoline ring. The connection N-O has a length 1.422 Å. Thermal decomposition of isoxazolines in a liquid phase (160–280°C) is accompanied by the release of acetaldehyde and aromatic nitrile. Both the structure of the cycle and its stability is practically independent of the structure of an aromatic substituent. The rate constant of the initial stage is characterized by the low significance of kinetic parameters, E = 104°8 kJ mol?1 and log a(A/c) = 7.2±0.8. The results obtained are rationalized in terms of biradical mechanism of isoxazoline ring-opening that includes an efficient recombination of the biradical and its disappearance as a result of synchronous multi-center rearrangement with the release of acetaldehyde. 相似文献
32.
Results in Mathematics - The link operator $${P_{\alpha}^\rho(f,x)=\sum_{k=1}^\infty s_{\alpha,k}(x)\int_0^\infty \theta_{\alpha,k}^\rho(t)f(t)dt+e^{-\alpha x}f(0)}$$ , $${\alpha, \rho >... 相似文献
33.
The B-factor index for the binding site (BFIbs) to prioritize crystal protein structures for docking
Structural Chemistry - In cheminformatics, protein-ligand docking is a powerful tool applied for virtual screening, pose prediction, and binding affinity estimation. However, docking results depend... 相似文献
34.
35.
N. F. Bunkin N. V. Suyazov A. V. Shkirin P. S. Ignat’ev K. V. Indukaev 《Journal of Experimental and Theoretical Physics》2009,108(5):800-816
Experiments using phase-modulation interference microscopy and Mueller-matrix polarimetry show that double-distilled water free of foreign solid matter contains macroscopic light scatterers. Numerical calculations suggest that these scatterers can be represented as micrometer-size clusters of polydisperse air bubbles with effective radii between 70 and 90 nm. The fractal dimension of the clusters varies from 2.4 to 2.8, and their concentration is on the order of 106 cm?3. 相似文献
36.
Sorin‐Claudiu Roşca Dr. Chiara Dinoi Dr. Elsa Caytan Dr. Vincent Dorcet Prof. Dr. Michel Etienne Prof. Dr. Jean‐François Carpentier Dr. Yann Sarazin 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(19):6505-6509
Strontium and calcium (alkaline earth: Ae) olefin complexes stabilised by secondary Ae???F?C and β‐agostic Ae???H?Si interactions are presented. Olefin coordination onto the alkaline earths is plain in the solid state, and it is thermodynamically favoured over the coordination of THF. The existence of the Ae???olefin interactions is corroborated by solution NMR data and DFT computations. The coordination mode of the olefin varies with steric effects and, if enforced, olefin dissociation can be compensated by the other non‐covalent interactions, as supported by DFT computations. 相似文献
37.
A self-consistent set of equations describing the evolution of linear spherically symmetrical perturbations in the Friedmann
world is derived for an arbitrary equation of state. A singular part of perturbations corresponding to a massive particle-like
source is separated, an evolution equation for calculating the source mass is obtained and solved exactly. An exact solution
to evolution equations for perturbations at an arbitrary equation of state is constructed.
__________
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 66–76, January, 2008. 相似文献
38.
N. F. Bunkin N. V. Suyazov A. V. Shkirin P. S. Ignat’ev K. V. Indukaev 《Physics of Wave Phenomena》2008,16(4):243-260
Experiments on modulation interference microscopy and measurement of light scattering matrix elements showed that double distilled
water purified from solid impurities contains macroscopic scatterers of optical radiation. It follows from numerical calculation
that these scatterers can be micrometer-scale clusters formed by polydisperse air bubbles with effective radii of 70 to 90
nm. The fractal dimension of such clusters is within 2.4–2.8 and their concentration is ∼ 106 cm−3. 相似文献
39.
Sorin G. Gal 《分析论及其应用》2002,18(1):26-33
In this paper we construct bivariate polynomials attached to a bivariate function, that approximate with Jackson-type rate involving a bivariate Ditzian-Totik ω2-modulus of smoothness and preserve some natural kinds of bivariate monotonicity and convexity of function.The result extends that in univariate case-of D. Leviatan in [5-6], improves that in bivariate case of the author in [3] and in some special cases, that in bivariate case of G. Anastassiou in [1]. 相似文献
40.
Starting with the Vlasov-Boltzmann equation for a binary fluid mixture, we derive an equation for the velocity field u when the system is segregated into two phases (at low temperatures) with a sharp interface between them. u satisfies the incompressible Navier-Stokes equations together with a jump boundary condition for the pressure across the interface which, in turn, moves with a velocity given by the normal component of u. Numerical simulations of the Vlasov-Boltzmann equations for shear flows parallel and perpendicular to the interface in a phase segregated mixture support this analysis. We expect similar behavior in real fluid mixtures. 相似文献