全文获取类型
收费全文 | 1717篇 |
免费 | 29篇 |
国内免费 | 9篇 |
专业分类
化学 | 1020篇 |
晶体学 | 6篇 |
力学 | 21篇 |
数学 | 247篇 |
物理学 | 461篇 |
出版年
2023年 | 8篇 |
2022年 | 18篇 |
2021年 | 15篇 |
2020年 | 28篇 |
2019年 | 34篇 |
2018年 | 22篇 |
2017年 | 30篇 |
2016年 | 53篇 |
2015年 | 43篇 |
2014年 | 48篇 |
2013年 | 76篇 |
2012年 | 96篇 |
2011年 | 105篇 |
2010年 | 89篇 |
2009年 | 62篇 |
2008年 | 105篇 |
2007年 | 136篇 |
2006年 | 115篇 |
2005年 | 117篇 |
2004年 | 91篇 |
2003年 | 66篇 |
2002年 | 73篇 |
2001年 | 35篇 |
2000年 | 32篇 |
1999年 | 19篇 |
1998年 | 21篇 |
1997年 | 21篇 |
1996年 | 30篇 |
1995年 | 12篇 |
1994年 | 14篇 |
1993年 | 16篇 |
1992年 | 10篇 |
1991年 | 18篇 |
1990年 | 6篇 |
1989年 | 10篇 |
1988年 | 6篇 |
1987年 | 10篇 |
1986年 | 5篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1983年 | 3篇 |
1982年 | 12篇 |
1981年 | 7篇 |
1980年 | 5篇 |
1979年 | 4篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1975年 | 2篇 |
1972年 | 2篇 |
1967年 | 2篇 |
排序方式: 共有1755条查询结果,搜索用时 31 毫秒
151.
152.
V. T. Varlamov S. Ya. Gadomsky 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2017,91(5):835-842
The kinetics of the reaction between N-phenyl-1,4-benzoquinone monoimine (quinone monoimine) and thiophenol is studied in chlorobenzene at 343 K. The reaction has the same mechanism proposed earlier for a similar reaction involving N,N'-diphenyl-1,4-benzoquinone diimine (quinone diimine). This mechanism has two paths: chain and nonchain. An important difference between the kinetics of the two reactions is the apparent reversible nature of the chain reaction in the quinone monoimine + thiophenol system. This nature reveals itself when the concentrations of thiophenol are comparable to or slightly higher than the concentrations of quinone imine. In light of this, kinetic research is conducted under conditions where the concentrations of thiophenol are significantly higher than those of quinone monoimine, allowing us to simplify the kinetic features and obtain interpretable data. The rate constants of the reaction’s elementary steps are estimated and found to be three to five times lower for the reaction involving quinone monoamine than for the one involving quinone diimine. Both reactions have relatively short chains whose lengths do not exceed several tens of units. 相似文献
153.
154.
It is reported that S-glycosyl O-methyl phenylcarbamothioates (SNea carbamothioates) have a fully orthogonal character in comparison to S-benzoxazolyl (SBox) glycosides. This complete orthogonality was revealed by performing competitive glycosylation experiments in the presence of various promoters. The results obtained indicate that SNea carbamothioates have a very similar reactivity profile to that of glycosyl thiocyanates, yet are significantly more stable and tolerate selected protecting group manipulations. These features make the SNea carbamothioates new promising building blocks for further utilization in oligosaccharide synthesis. 相似文献
155.
156.
Sergey V. Korkin Alexei I. Lyapustin 《Journal of Quantitative Spectroscopy & Radiative Transfer》2011,112(10):1595-1608
This paper considers a scalar radiative transfer problem with high scattering anisotropy. Two computational methods are presented based on decomposition of the diffuse light field into a regular and anisotropic part. The first algorithm (DOMAS) singles out the anisotropic radiance in the forward scattering peak using the Small-Angle Modification of RTE. The second algorithm (DOM2+) separates the single scattering radiance as an anisotropic part, which largely defines the fine detail of the total radiance in the backscattering directions. In both cases, the anisotropic part is represented analytically. With anisotropy subtraction, the regular part of the signal, which requires a numerical solution, is essentially smoothed as a function of angles. Further, the transport equation is obtained for the regular part that contains an additional source function from the anisotropic part of the signal. This equation is solved with the discrete ordinates method. A conducted numerical analysis of this work showed that algorithm DOMAS has a strong advantage as compared to the standard discrete ordinates method for simulation of the radiance transmission, and DOM2+ is the best of the three for the reflection computations. Both algorithms offer at least a factor of three acceleration of convergence of the azimuthal series for highly anisotropic phase functions. 相似文献
157.
Cyclic voltammetry, galvanostatic charge?Cdischarge technique, potentiostatic intermittent titration technique (PITT), and electrochemical impedance spectroscopy (EIS) were used to study the behavior of a LiMn1.95Cr0.05O4 (substituted lithium?Cmanganese spinel) electrode in nonaqueous electrolytes at 25 °C. Quantitative and qualitative changes of the electrode transport parameters as functions of lithium concentration were analyzed. Several equivalent circuits are discussed; the results obtained by different methods are compared. The PITT and EIS results are in good agreement; the chemical diffusion coefficient D varies within 10?14?C10?9 cm2 s?1 depending on the lithium content in the LixMn1.95Cr0.05O4 electrode. 相似文献
158.
We consider the 1D Dirac operator on the half-line with compactly supported potentials. We study resonances as the poles of scattering matrix or equivalently as the zeros of modified Fredholm determinant. We obtain the following properties of the resonances: (1) asymptotics of counting function, (2) estimates on the resonances and the forbidden domain. 相似文献
159.
Alexei Zhedanov 《The Ramanujan Journal》2014,33(2):157-195
We construct new elliptic solutions of the restricted Toda chain. These solutions give rise to a new explicit class of orthogonal polynomials, which can be considered as a generalization of the Stieltjes–Carlitz elliptic polynomials. Relations between characteristic (i.e., positive definite) functions, Toda chain, and orthogonal polynomials are developed in order to derive the main properties of these polynomials. Explicit expressions are found for the recurrence coefficients and the weight function for these polynomials. In the degenerate cases of the elliptic functions, the modified Meixner polynomials and the Krall–Laguerre polynomials appear. 相似文献
160.
Suslin’s local-global principle asserts that if a matrix over a polynomial ring vanishes modulo the independent variable and is locally elementary then it is elementary. In this article we prove Suslin’s local-global principle for principal congruence subgroups of Chevalley groups. This result is a common generalization of the result of Abe for the absolute case and Apte, Chattopadhyay and Rao for classical groups. For the absolute case the localglobal principle was recently obtained by Petrov and Stavrova in the more general settings of isotropic reductive groups. 相似文献