全文获取类型
收费全文 | 1222篇 |
免费 | 27篇 |
国内免费 | 36篇 |
专业分类
化学 | 104篇 |
力学 | 48篇 |
数学 | 490篇 |
物理学 | 643篇 |
出版年
2024年 | 2篇 |
2023年 | 9篇 |
2022年 | 9篇 |
2021年 | 13篇 |
2020年 | 18篇 |
2019年 | 25篇 |
2018年 | 12篇 |
2017年 | 17篇 |
2016年 | 19篇 |
2015年 | 30篇 |
2014年 | 38篇 |
2013年 | 53篇 |
2012年 | 33篇 |
2011年 | 50篇 |
2010年 | 42篇 |
2009年 | 61篇 |
2008年 | 89篇 |
2007年 | 74篇 |
2006年 | 75篇 |
2005年 | 39篇 |
2004年 | 45篇 |
2003年 | 39篇 |
2002年 | 60篇 |
2001年 | 61篇 |
2000年 | 57篇 |
1999年 | 57篇 |
1998年 | 52篇 |
1997年 | 10篇 |
1996年 | 10篇 |
1995年 | 34篇 |
1994年 | 14篇 |
1993年 | 12篇 |
1992年 | 9篇 |
1991年 | 12篇 |
1990年 | 15篇 |
1989年 | 16篇 |
1988年 | 8篇 |
1987年 | 13篇 |
1986年 | 8篇 |
1985年 | 8篇 |
1984年 | 8篇 |
1983年 | 6篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1978年 | 4篇 |
1977年 | 4篇 |
1974年 | 2篇 |
1948年 | 1篇 |
排序方式: 共有1285条查询结果,搜索用时 0 毫秒
71.
H.-K. Zhao J. Wang 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,9(3):513-524
The time-dependent transport through an ultrasmall quantum dot coupling to two electron reservoirs is investigated. The quantum
dot is perturbed by a quantum microwave field (QMF) through gate. The tunneling current formulae are obtained by taking expectation
values over coherent state (CS), and SU(1,1) CS. We derive the transport formulae at low temperature by employing the nonequilibrium
Green function technique. The currents exhibit coherent behaviors which are strongly associated with the applied QMF. The
time-dependent currents appear compound effects of resonant tunneling and time-oscillating evolution. The time-averaged current
and differential conductance are calculated, which manifest photon-assisted behaviors. Numerical calculations reveal the similar
properties as those in classical microwave field (CMF) perturbed system for the situations concerning CS and squeezed vacuum
SU(1,1) CS. But for other squeezed SU(1,1) CS, the tunneling behavior is quite different from the system perturbed by a single
CMF through gate. Due to the quantum signal perturbation, the measurable quantities fluctuate fiercely.
Received 28 May 1998 相似文献
72.
D. Boilley A. Marchix B. Jurado K. -H. Schmidt 《The European Physical Journal A - Hadrons and Nuclei》2007,33(1):47-52
We propose a new formula for the saddle-to-scission time that is more general that the one based on Kramers' approach. Its
validity and applicability is then studied in detail. Such a formula is useful for the evaluation of the fission time of very
heavy nuclei. 相似文献
73.
Y.H. Yang Y.G. Wang M. Liu 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,22(4):455-459
Magnetic-impurity-scattering effects in a quasi-2D disordered electron system have been investigated theoretically with the
diagrammatic techniques in perturbation theory. The analytical expressions for magnetoconductivities due to weak-localization
effects have been obtained as functions of elastic, inelastic and magnetic scattering times. The relevant dimensional crossover
behavior from 3D to 2D with decreasing the interlayer coupling has been discussed, and the condition for the crossover has
been obtained.
Received 20 March 2001 and Received in final form 28 June 2001 相似文献
74.
75.
普通化学教学改革与探索 总被引:1,自引:0,他引:1
结合近几年的普通化学教学实践,我们分析了普通化学教学实践过程中存在的一些问题,并提出了培养学生的创新能力,不断更新教学内容,将理论教学与实验教学相结合等几方面建议。 相似文献
76.
77.
D. Dantchev J. Rudnick 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,21(2):251-268
We study the behavior of systems in which the interaction contains a long-range component that does not dominate the critical
behavior. Such a component is exemplified by the van der Waals force between molecules in a simple liquid-vapor system. In
the context of the mean spherical model with periodic boundary conditions we are able to identify, for temperatures close
above T
c, finite-size contributions due to the subleading term in the interaction that are dominant in this region decaying algebraically as a function of L. This mechanism goes beyond the standard formulation of the finite-size scaling but is to be expected in real physical systems.
We also discuss other ways in which critical point behavior is modified that are of relevance for analysis of Monte Carlo
simulations of such systems.
Received 21 November 2000 and Received in final form 28 February 2001 相似文献
78.
79.
Since the (original) ghost fluid method (OGFM) was proposed by Fedkiw et al. in 1999 [5], a series of other GFM-based methods such as the gas–water version GFM (GWGFM), the modified GFM (MGFM) and the real GFM (RGFM) have been developed subsequently. Systematic analysis, however, has yet to be carried out for the various GFMs on their accuracies and conservation errors. In this paper, we develop a technique to rigorously analyze the accuracies and conservation errors of these different GFMs when applied to the multi-medium Riemann problem with a general equation of state (EOS). By analyzing and comparing the interfacial state provided by each GFM to the exact one of the original multi-medium Riemann problem, we show that the accuracy of interfacial treatment can achieve “third-order accuracy” in the sense of comparing to the exact solution of the original mutli-medium Riemann problem for the MGFM and the RGFM, while it is of at most “first-order accuracy” for the OGFM and the GWGFM when the interface approach is actually near in balance. Similar conclusions are also obtained in association with the local conservation errors. A special test method is exploited to validate these theoretical conclusions from the numerical viewpoint. 相似文献
80.
In this paper we consider a collocation method for solving Fredholm integral equations of the first kind, which is known to be an ill-posed problem. An “unregularized” use of this method can give reliable results in the case when the rate at which smallest singular values of the collocation matrices decrease is known a priori. In this case the number of collocation points plays the role of a regularization parameter. If the a priori information mentioned above is not available, then a combination of collocation with Tikhonov regularization can be the method of choice. We analyze such regularized collocation in a rather general setting, when a solution smoothness is given as a source condition with an operator monotone index function. This setting covers all types of smoothness studied so far in the theory of Tikhonov regularization. One more issue discussed in this paper is an a posteriori choice of the regularization parameter, which allows us to reach an optimal order of accuracy for deterministic noise model without any knowledge of solution smoothness. 相似文献