全文获取类型
收费全文 | 2902篇 |
免费 | 371篇 |
国内免费 | 167篇 |
专业分类
化学 | 272篇 |
晶体学 | 35篇 |
力学 | 1574篇 |
综合类 | 51篇 |
数学 | 491篇 |
物理学 | 1017篇 |
出版年
2024年 | 11篇 |
2023年 | 21篇 |
2022年 | 30篇 |
2021年 | 47篇 |
2020年 | 75篇 |
2019年 | 46篇 |
2018年 | 67篇 |
2017年 | 81篇 |
2016年 | 102篇 |
2015年 | 53篇 |
2014年 | 121篇 |
2013年 | 247篇 |
2012年 | 149篇 |
2011年 | 124篇 |
2010年 | 108篇 |
2009年 | 138篇 |
2008年 | 164篇 |
2007年 | 180篇 |
2006年 | 196篇 |
2005年 | 170篇 |
2004年 | 139篇 |
2003年 | 145篇 |
2002年 | 96篇 |
2001年 | 94篇 |
2000年 | 92篇 |
1999年 | 108篇 |
1998年 | 82篇 |
1997年 | 86篇 |
1996年 | 70篇 |
1995年 | 65篇 |
1994年 | 44篇 |
1993年 | 30篇 |
1992年 | 51篇 |
1991年 | 48篇 |
1990年 | 22篇 |
1989年 | 12篇 |
1988年 | 27篇 |
1987年 | 20篇 |
1986年 | 20篇 |
1985年 | 15篇 |
1984年 | 7篇 |
1983年 | 3篇 |
1982年 | 10篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 5篇 |
1978年 | 5篇 |
1977年 | 4篇 |
1971年 | 2篇 |
1957年 | 2篇 |
排序方式: 共有3440条查询结果,搜索用时 265 毫秒
941.
A semi-infinite prismatic cylinder composed of a linear anisotropic classical elastic material is in equilibrium under zero body force and either zero displacement or zero traction on the lateral boundary. The elastic moduli become perturbed. Under suitable conditions on the base load decay estimates are derived for the difference between corresponding quantities in the unperturbed and perturbed bodies. The amplitude in each estimate involves a multiplicative factor that tends to zero as the perturbation tends to zero. The analysis, based upon a first-order differential inequality, introduces apparently new modifications of Korn's inequalities of the first and second kind. 相似文献
942.
The use of constant viscosity, highly elastic polymer solutions, so called Boger fluids, has been remarkably successful in elucidating the behavior of polymeric materials under flowing conditions. However, the behavior of these fluids is still complicated by many different physical processes occurring within a narrow window of observation time and applied shear rate. In this study, we investigate the long-time shear behavior of an ideal Boger fluid: a well characterized, athermal, dilute, binary solution of high molecular weight polystyrene in oligomeric polystyrene. Rheological measurements show that under an applied steady shear flow, this family of polymer solutions undergoes a transient decay of normal stresses on a timescale much longer than the polymer molecule's relaxation time. Rheological and flow visualization results demonstrate that the observed phenomenon is not caused by polymer degradation, phase separation, viscous heating, or secondary flows from elastic instabilities. Although the timescale is much shorter than that associated with polymer migration in the same solutions (MacDonald and Muller, 1996), the appearance of this phenomenon only at the rates where migration has been observed suggests that it may be a prerequisite for observing migration. In addition, we note that through sufficient preshearing of the sample, the normal stress decrease suppresses the elastic instability. These results show that there is considerable uncertainty in choosing the appropriate measure of the fluid relaxation time for consistently modeling the critical condition for the elastic instability, the decay of normal stresses, and the migration of polymer species. 相似文献
943.
This paper examines the problem of finding thermal stresses, caused by a symmetric indentation of a line crack by an inclusion in an infinite isotropic elastic heat conducting solid. The thermal and elastic problems are reduced to a system of triple integral equations. In each case the solution of the triple integral equations is obtained in a closed form. The expressions for the stress intensity factor at the edge of the line crack, the strain energy density function and the resultant pressure applied to the inclusion are obtained. The expression for the displacement component is also obtained. Finally the results for the physical quantities are displayed graphically. 相似文献
944.
945.
弹性力学中Fredholm积分方程组解法的表达通式及其讨论 总被引:2,自引:0,他引:2
本文采用覆盖域的概念,给出受外力作用的任意形状弹性体采用Fredhikm积分方程组解法的统一表达式,而且就含洞的无限大体且远场应力不为零,边界上有集中力作用等特殊情况进行讨论并给出相应的表达式,对边界上作用力和覆盖域边界上作用力之间在合力和合力矩上的关系也作了讨论,文中给出的算例表明,对于一些简单情况可以求得解析解。而对于需要采用数值解的问题,本文工作具有精度高、收敛快的优点。 相似文献
946.
947.
介绍目前水利水电工程设计中常遇到的软弱地基上拱形围堰的光弹性试验研究.其中包括异弹模组合模型浇制与粘结、水砂压荷载模拟及主要试验成果. 文中分析了在上述荷载作用下拱堰的受力特点和工作状态,探讨了低弹模基础和边界条件不对称性对堰体内力的作用和影响,提出了进一步改善应力和稳定条件的途径和措施. 相似文献
948.
Ayhan TUTAR Ayhan SARIOGELUGIL 《应用数学和力学(英文版)》2006,27(11):1481-1489
The relaxed elastic line of second kind on an oriented surface in the Minkowski space was defined and for the relaxed elastic line of second kind which is lying on an oriented surface the Euler-Lagrange equations were derived. Furthermore, whether these curves lie on a curvature line or not was investigated and some applications were given. 相似文献
949.
Summary The viscoelastic behavior of polymeric systems based upon the Leonov model has been examined for (i) stress growth and relaxation with intermittent shear flow, (ii) stress relaxation after a step in the shear strain and (iii) elastic recovery after shear flow. A large number of modes have been conveniently incorporated through the determination of the model parameters from conventional rheological data by using an effective least-square procedure. With a sufficient number of modes, the predictions are in very good agreement with corresponding experiments in literature, including the recent data for cases (i) and (ii) obtained by optical methods.The present theory agrees also with the Lodge-Meissner relation (
11 –
22)/
12 =
0 in a step-shear experiment. In general, the Leonov model leads to results which, in these test cases, are comparable to those from Wagner's theory. It is, however, considerably less difficult to apply, thus offering the possibility of analysing flow problems of practical interest.With 16 figures and 1 table 相似文献
950.
无限均质弹性体中圆片裂纹受均布载荷时的超奇异积分方程封闭解 总被引:2,自引:0,他引:2
本文运用一种特殊技巧将一个受均布压力作用的圆片裂纹超奇异积分方程化为Abel积分形式,从而可获得超奇异积分方程中未知位移间断的封闭解。再利用这个封闭解和应力强度因子的定义,得到了一个无限弹性体中受均布载荷分布时圆片裂纹前沿I型应力强度因子的精确表达式。所得到的结果与现有解完全相同。 相似文献