全文获取类型
收费全文 | 14508篇 |
免费 | 542篇 |
国内免费 | 187篇 |
专业分类
化学 | 5007篇 |
晶体学 | 26篇 |
力学 | 1791篇 |
综合类 | 24篇 |
数学 | 4701篇 |
物理学 | 3688篇 |
出版年
2024年 | 80篇 |
2023年 | 704篇 |
2022年 | 465篇 |
2021年 | 454篇 |
2020年 | 1525篇 |
2019年 | 1131篇 |
2018年 | 998篇 |
2017年 | 857篇 |
2016年 | 831篇 |
2015年 | 665篇 |
2014年 | 889篇 |
2013年 | 3010篇 |
2012年 | 657篇 |
2011年 | 271篇 |
2010年 | 191篇 |
2009年 | 213篇 |
2008年 | 236篇 |
2007年 | 232篇 |
2006年 | 217篇 |
2005年 | 222篇 |
2004年 | 230篇 |
2003年 | 159篇 |
2002年 | 136篇 |
2001年 | 91篇 |
2000年 | 107篇 |
1999年 | 58篇 |
1998年 | 92篇 |
1997年 | 61篇 |
1996年 | 54篇 |
1995年 | 33篇 |
1994年 | 35篇 |
1993年 | 48篇 |
1992年 | 22篇 |
1991年 | 28篇 |
1990年 | 27篇 |
1989年 | 22篇 |
1988年 | 17篇 |
1987年 | 17篇 |
1986年 | 11篇 |
1985年 | 17篇 |
1984年 | 17篇 |
1983年 | 10篇 |
1982年 | 14篇 |
1981年 | 26篇 |
1980年 | 8篇 |
1979年 | 11篇 |
1978年 | 10篇 |
1977年 | 10篇 |
1974年 | 5篇 |
1973年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
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
62.
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
63.
本文研究了混合范数空间H(p,q,a)中解析函数f的Taylor系数,对0<p≤2,0<q<∞,a>0和2≤p<∞,0<q<∞,a>0两种情形,分别给出了f属于H(p,q,a)的必要条件和充分条件。用上述结果我们还得到了几个关于混合范数空间的乘子定理,这些结果也推广了Hardy和Littlewood关于H^p空间的相应结论。 相似文献
64.
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
65.
纯生跳跃扩散型交换期权定价公式 总被引:1,自引:0,他引:1
在假定标的资产价格服从纯生跳跃过程的条件下,研究一类多资产期权——资产权重不同的交换期权,并在风险中性的条件下建立相应的定价方程,运用条件期望等相关知识得出交换期权的解析公式。文中最后列出一些特殊纯生跳跃扩散型交换期权的定价的例子. 相似文献
66.
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
67.
Starting from the vectorial Rayleigh diffraction integral formula and without using the far-field approximation, a solution of the wave equation beyond the paraxial approximation is found, which represents vectorial non-paraxial elliptical Gaussian beams in free space. The far-field expressions for non-paraxial Gaussian beams and elliptical Gaussian beams can be regarded as special cases treated in this paper. Some basic propagation properties of vectorial non-paraxial elliptical Gaussian beams, including the irradiance distribution, phase term, beam widths and divergence angles are studied. Numerical results are given and illustrated. 相似文献
68.
Higher-order implicit strong numerical schemes for stochastic differential equations 总被引:2,自引:0,他引:2
Higher-order implicit numerical methods which are suitable for stiff stochastic differential equations are proposed. These are based on a stochastic Taylor expansion and converge strongly to the corresponding solution of the stochastic differential equation as the time step size converges to zero. The regions of absolute stability of these implicit and related explicit methods are also examined. 相似文献
69.
第二类Fredholm积分方程的泰勒展开解法 总被引:3,自引:0,他引:3
本进一步发展了用Taylor公式求解第二类Fredholm积分方程的方法,并给出了近似解的误差精度分析. 相似文献
70.