全文获取类型
收费全文 | 4809篇 |
免费 | 354篇 |
国内免费 | 478篇 |
专业分类
化学 | 184篇 |
晶体学 | 5篇 |
力学 | 552篇 |
综合类 | 108篇 |
数学 | 4216篇 |
物理学 | 576篇 |
出版年
2023年 | 50篇 |
2022年 | 35篇 |
2021年 | 46篇 |
2020年 | 82篇 |
2019年 | 113篇 |
2018年 | 102篇 |
2017年 | 135篇 |
2016年 | 131篇 |
2015年 | 76篇 |
2014年 | 173篇 |
2013年 | 341篇 |
2012年 | 177篇 |
2011年 | 205篇 |
2010年 | 232篇 |
2009年 | 256篇 |
2008年 | 276篇 |
2007年 | 356篇 |
2006年 | 290篇 |
2005年 | 242篇 |
2004年 | 224篇 |
2003年 | 255篇 |
2002年 | 231篇 |
2001年 | 166篇 |
2000年 | 188篇 |
1999年 | 167篇 |
1998年 | 172篇 |
1997年 | 168篇 |
1996年 | 110篇 |
1995年 | 72篇 |
1994年 | 66篇 |
1993年 | 63篇 |
1992年 | 48篇 |
1991年 | 60篇 |
1990年 | 31篇 |
1989年 | 21篇 |
1988年 | 27篇 |
1987年 | 33篇 |
1986年 | 23篇 |
1985年 | 39篇 |
1984年 | 30篇 |
1983年 | 9篇 |
1982年 | 18篇 |
1981年 | 14篇 |
1980年 | 16篇 |
1979年 | 23篇 |
1978年 | 17篇 |
1977年 | 9篇 |
1976年 | 13篇 |
1975年 | 3篇 |
1974年 | 3篇 |
排序方式: 共有5641条查询结果,搜索用时 437 毫秒
51.
Experiments on polymers indicate that large tensile stress can induce cavitation, that is, the appearance of voids that were
not previously evident in the material. This phenomenon can be viewed as either the growth of pre-existing infinitesimal holes
in the material or, alternatively, as the spontaneous creation of new holes in an initially perfect body. In this paper our
approach is to adopt both views concurrently within the framework of the variational theory of nonlinear elasticity. We model
an elastomer on a macroscale as a void-free material and, on a microscale, as a material containing certain defects that are
the only points at which hole formation can occur. Mathematically, this is accomplished by the use of deformations whose point
singularities are constrained. One consequence of this viewpoint is that cavitation may then take place at a point that is
not energetically optimal. We show that this disparity will generate configurational forces, a type of force identified previously
in dislocations in crystals, in phase transitions in solids, in solidification, and in fracture mechanics.
As an application of this approach we study the energetically optimal point for a solitary hole to form in a homogeneous and
isotropic elastic ball subject to radial boundary displacements. We show, in particular, that the center of the ball is the
unique optimal point. Finally, we speculate that the configurational force generated by cavitation at a non-optimal material
point may be sufficient to result in the onset of fracture. The analysis utilizes the energy-momentum tensor, the asymptotics
of an equilibrium solution with an isolated singularity, and the linear theory of elasticity at the stressed configuration
that the body occupies immediately prior to cavitation.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
52.
A UNIFORMLY CONVERGENT DIFFERENCE SCHEME FOR THE SINGULAR PERTURBATION PROBLEM OF A HIGH ORDER ELLIPTIC DIFFERENTIAL EQUATION 总被引:1,自引:0,他引:1
AUNIFORMLYCONVERGENTDIFFERENCESCHEMEFORTHESINGULARPERTURBATIONPROBLEMOFAHIGHORDERELLIPTICDIFFERENTIALEQUATION(刘国庆)(苏煜城)AUNIFO... 相似文献
53.
54.
Reduction in stored free energy provides the thermodynamic driving force for grain and bubble growth in polycrystals and foams. Evolution of polycrystalline networks exhibit the additional complication that grain growth may be controlled by several kinetic mechanisms through which the decrease in network energy occurs. Polyhedral boundaries, triple junctions (TJs), and quadruple points (QPs) are the geometrically distinct elements of three dimensional networks that follow Plateau’s rules, provided that grain growth is limited by diffusion through, and motion of, cell boundaries. Shvindlerman and co-workers have long recognized the kinetic influences on polycrystalline grain growth of network TJs and QPs. Moreover, the emergence of interesting polycrystalline nanomaterials underscored that TJs can indeed influence grain growth kinetics. Currently there exist few detailed studies concerned either with network distributions of grain size, number of faces per grain, or with ‘grain trajectories’, when grain growth is limited by the motion of its TJs or QPs. By contrast there exist abundant studies of classical grain growth limited by boundary mobility. This study is focused on a topological/geometrical representation of polycrystals to obtain statistical predictions of the grain size and face number distributions, as well as growth ‘trajectories’ during steady-state grain growth. Three limits to grain growth are considered, with grain growth kinetics controlled by boundary, TJ, and QP mobilities. 相似文献
55.
The purpose of this note is to study initial sequences of 0–dimensional subschemes of Hirzebruch surfaces and classify subschemes whose initial sequence has the minimal possible growth. 相似文献
56.
We present here a fine singularity analysis of solutions to the Laplace equation in special polygonal domains in the plane. We assume piecewise constant Neumann data on one component of the boundary. Our motivation is to study the so‐called Berg effect, which is explained in the introduction. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
57.
A macroscopic model for an intermediate state between type‐I and type‐II superconductivity 下载免费PDF全文
Karel Van Bockstal Marián Slodička 《Numerical Methods for Partial Differential Equations》2015,31(5):1551-1567
A vectorial nonlocal and nonlinear parabolic problem on a bounded domain for an intermediate state between type‐I and type‐II superconductivity is proposed. The domain is for instance a multiband superconductor that combines the characteristics of both types. The nonlocal term is represented by a (space) convolution with a singular kernel arising in Eringen's model. The nonlinearity is coming from the power law relation by Rhyner. The well‐posedness of the problem is discussed under low regularity assumptions and the error estimate for a semi‐implicit time‐discrete scheme based on backward Euler approximation is established. In the proofs, the monotonicity methods and the Minty–Browder argument are used. © 2015 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 31: 1551–1567, 2015 相似文献
58.
研究了一个三阶半线性微分方程的奇摄动非线性混合边值问题.利用边界层函数法构造了该问题的形式渐近解,并采用微分不等式理论证明了解的存在性,给出了渐近解的误差估计,最后得出了边界层函数指数型衰减的结论. 相似文献
59.
Brodskii and Milman proved that there is a point in C(K), the set of all Chebyshev centers of K, which is fixed by every surjective isometry from K into K whenever K is a nonempty weakly compact convex subset having normal structure in a Banach space. Motivated by this result, Lim et al. raised the following question namely “does there exist a point in C(K) which is fixed by every isometry from K into K?”. In fact, Lim et al. proved that “if K is a nonempty weakly compact convex subset of a uniformly convex Banach space, then the Chebyshev center of K is fixed by every isometry T from K into K”. In this paper, we prove that if K is a nonempty weakly compact convex set having normal structure in a strictly convex Banach space and F is a commuting family of isometry mappings on K then there exists a point in C(K) which is fixed by every mapping in F. 相似文献
60.