全文获取类型
收费全文 | 1994篇 |
免费 | 355篇 |
国内免费 | 77篇 |
专业分类
化学 | 96篇 |
晶体学 | 8篇 |
力学 | 855篇 |
综合类 | 14篇 |
数学 | 259篇 |
物理学 | 1194篇 |
出版年
2024年 | 3篇 |
2023年 | 13篇 |
2022年 | 34篇 |
2021年 | 37篇 |
2020年 | 70篇 |
2019年 | 54篇 |
2018年 | 54篇 |
2017年 | 64篇 |
2016年 | 74篇 |
2015年 | 78篇 |
2014年 | 104篇 |
2013年 | 137篇 |
2012年 | 106篇 |
2011年 | 142篇 |
2010年 | 92篇 |
2009年 | 128篇 |
2008年 | 119篇 |
2007年 | 109篇 |
2006年 | 121篇 |
2005年 | 85篇 |
2004年 | 93篇 |
2003年 | 82篇 |
2002年 | 69篇 |
2001年 | 56篇 |
2000年 | 75篇 |
1999年 | 38篇 |
1998年 | 54篇 |
1997年 | 41篇 |
1996年 | 36篇 |
1995年 | 20篇 |
1994年 | 23篇 |
1993年 | 37篇 |
1992年 | 17篇 |
1991年 | 18篇 |
1990年 | 23篇 |
1989年 | 20篇 |
1988年 | 10篇 |
1987年 | 11篇 |
1986年 | 9篇 |
1985年 | 12篇 |
1984年 | 8篇 |
1983年 | 4篇 |
1982年 | 8篇 |
1981年 | 13篇 |
1980年 | 5篇 |
1979年 | 5篇 |
1978年 | 4篇 |
1977年 | 4篇 |
1974年 | 2篇 |
1971年 | 2篇 |
排序方式: 共有2426条查询结果,搜索用时 0 毫秒
1.
In this work, a continuum model is presented for size and orientation dependent thermal buckling and post-buckling of anisotropic nanoplates considering surface and bulk residual stresses. The model with von-Karman nonlinear strains and material cubic anisotropy of single crystals contains two parameters that reflect the orientation effects. Using Ritz method, closed form solutions are given for buckling temperature and post-buckling deflections. Regarding self-instability states of nanoplates and their recovering at higher temperatures, an experiment is discussed based on low pressurized membranes to verify the predictions. For simply supported nanoplates, the size effects are lowest when they are aligned in [100] direction. When the edges get clamped, the orientation dependence is ignorable and the behavior becomes symmetric about [510] axis. The surface residual stress makes drastic increase in buckling temperature of thinner nanoplates for which a minimum thickness is pointed to stay far from material softening at higher temperatures. Deflection of [100]-oriented buckled nanoplates is higher than [110] ones but this reverses at higher temperatures. The results for long nanoplates show that the buckling mode numbers are changed by orientation which is verified by FEM. 相似文献
2.
3.
4.
Capillary gas chromatography coupled to microwave-inducedplasma detection furnishes sensitivity adequate for trace analysis when the signal is monitored at a carbon emission line. Work performed with one of these systems at high electronic gain for the carbon signal has revealed solvent band widths in excess of four minutes; these impeded quantification of peaks eluting after the solvent. This report discusses two phenomena which could be related to the unexpected intensity of this solvent response: photomultiplier tube saturation and carbon deposits in the quartz plasma discharge tube. 相似文献
5.
抽吸和压力梯度在层流边界层转捩过程中的作用 总被引:1,自引:0,他引:1
用空间模式的二次稳定性理论研究了抽吸和压力梯度对边界层三维亚谐扰动流动稳定性的影响.数值结果表明,固体边界上的抽吸有明显的层流控制作用,逆压梯度则有较强的不稳定作用. 相似文献
6.
The results of the analysis of the stability of stationary solutions of wave equations discribing a behavior of the nonlinear Fabry-Perot interferometer with a saturated paramagnetic filling are presented in this paper. The cases when paramagnetic medium is characterized by a homogeneously and nonhomogeneously broadened line of the magnetic resonance have been considered. Areas of unstable behavior of these characteristics of the resonance structure have been found. 相似文献
7.
Relative permeability functions for immiscible displacements in porous media show a wide range of profiles. Although, this
behavior is well known, its impact on the stability of the displacement process is unexplored. Our analysis clearly demonstrates
for the first time that the viscous instability characteristics of two-phase flows are governed not only by their end point
values, but are strongly dependent on the actual profile of relative permeability functions. Linear stability analysis predicts
the capacity of the flow to develop large scale fingers which can result in substantial bypassing of the resident fluid. It
is observed that relative permeability functions attributed to drainage processes yield a more unstable displacement as compared
to functions related to imbibition processes. Moreover, instability is observed to increase for those relative permeability
functions which result from increased wettability of the wetting fluid. High accuracy numerical simulations show agreement
with these predictions and demonstrate how large amplitude viscous fingers result in significant bypassing for certain relative
permeability functions. In the nonlinear regime, the finger amplitude grows at a rate ∝ t1/2 initially, drops to t1/4 at a later time and finally grows ∝ t. The basic mechanisms of finger interaction, however, are not substantially influenced by relative permeability functions. 相似文献
8.
Roberto Bassani 《Meccanica》2006,41(4):375-389
S. Earnshaw, a mathematical physicist born in England two centuries ago, was the author of studies on the transmission of
sound and light. His theory on the transmission of light by “detached particles” has also influenced some studies on the stability
of bodies in potential fields, particularly studies on the levitation of permanent magnets, i.e. on passive magnetic levitation.
This theorem was so well known that even Maxwell mentioned it, and is today cited almost as an axiom in the ambit of passive
magnetization. However, what is less well known is that the theory actually only relates to magnetostatics. In this paper,
the mathematic model of the theory that refers to stability is outlined, along with some works that refer to it, in particular
those on passive magnetic levitation. It is then pointed out that spaces of low instability exist in magnetostatics, and that
stability may exist in the magneto-stationary and in magneto-dynamic ambit. 相似文献
9.
The development of perturbations of the parameters of a dense gaseous envelope traveling with an acceleration driven by a difference in the pressures on either side is investigated numerically. Plane and axisymmetric time-dependent flows of a compressible medium are considered. The effect of both the density of the envelope and the form of the initial perturbations of its shape and motion on the mass cumulation in the compactions formed is studied. The evolutions of the perturbations of a layer and the surface of a contact discontinuity accelerated by an impinging plane shock wave are compared. 相似文献
10.
调制不稳定性对级联放大光纤传输系统信噪比的影响 总被引:1,自引:0,他引:1
在考虑光纤损耗和级联放大器的情况下,推导了调制不稳定性的产生条件和增益的普适解析表达式,分析了调制不稳定性对信噪比的影响,给出了一个新的计算信噪比的表达式。 相似文献