全文获取类型
收费全文 | 31015篇 |
免费 | 3967篇 |
国内免费 | 2324篇 |
专业分类
化学 | 2479篇 |
晶体学 | 38篇 |
力学 | 3267篇 |
综合类 | 354篇 |
数学 | 21946篇 |
物理学 | 9222篇 |
出版年
2024年 | 42篇 |
2023年 | 428篇 |
2022年 | 476篇 |
2021年 | 555篇 |
2020年 | 1033篇 |
2019年 | 1004篇 |
2018年 | 907篇 |
2017年 | 887篇 |
2016年 | 928篇 |
2015年 | 748篇 |
2014年 | 1406篇 |
2013年 | 2644篇 |
2012年 | 1483篇 |
2011年 | 1807篇 |
2010年 | 1740篇 |
2009年 | 2003篇 |
2008年 | 2169篇 |
2007年 | 2039篇 |
2006年 | 1782篇 |
2005年 | 1744篇 |
2004年 | 1495篇 |
2003年 | 1394篇 |
2002年 | 1221篇 |
2001年 | 932篇 |
2000年 | 862篇 |
1999年 | 816篇 |
1998年 | 752篇 |
1997年 | 626篇 |
1996年 | 525篇 |
1995年 | 423篇 |
1994年 | 353篇 |
1993年 | 244篇 |
1992年 | 223篇 |
1991年 | 235篇 |
1990年 | 188篇 |
1989年 | 114篇 |
1988年 | 113篇 |
1987年 | 110篇 |
1986年 | 112篇 |
1985年 | 99篇 |
1984年 | 95篇 |
1983年 | 47篇 |
1982年 | 93篇 |
1981年 | 81篇 |
1980年 | 59篇 |
1979年 | 62篇 |
1978年 | 51篇 |
1977年 | 37篇 |
1976年 | 30篇 |
1973年 | 19篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
61.
Ruo Li Zhiyuan Sun Zhijian Yang 《Numerical Methods for Partial Differential Equations》2020,36(4):756-771
A discontinuous Galerkin method by patch reconstruction is proposed for Stokes flows. A locally divergence-free reconstruction space is employed as the approximation space, and the interior penalty method is adopted which imposes the normal component penalty terms to cancel out the pressure term. Consequently, the Stokes equation can be solved as an elliptic system instead of a saddle-point problem due to such weak form. The number of degree of freedoms of our method is the same as the number of elements in the mesh for different order of accuracy. The error estimations of the proposed method are given in a classical style, which are then verified by some numerical examples. 相似文献
62.
63.
板壳结构在航空航天、高速列车、能量采集等诸多工程领域已经得到了广泛应用. 将悬臂壁板倒置于轴向气流中并在壁板周围流场中设置刚性壁面可有效地调控壁板的失稳速度, 是俘能器优化设计的重要措施之一. 但针对刚性壁面作用下亚音速气流中倒置悬臂壁板的失稳机制仍需要开展深入研究. 本文以受限亚音速气流中倒置的二维悬臂壁板为对象, 以理论分析及风洞实验为手段, 研究了单侧刚性壁面效应对倒置悬臂壁板静态失稳特性的影响规律. 在理论分析中, 首先应用镜像函数法来处理壁面约束条件, 基于算子理论研究获得了以Possio积分方程为表征的壁板气动力, 壁面效应实际表征为一包含移位Tricomi算子的复合算子; 然后将壁板失稳方程的求解问题转化为定区间上的函数逼近问题; 最后, 依据Wererstrass定理并利用最小二乘法求解该最优函数, 以获得系统的失稳临界参数. 在试验研究中依据压杆稳定原理设计了壁板静态失稳的测试方法并完成了风洞实验. 理论分析结果表明, 壁板会发生发散(静气动弹性)失稳, 临界动压随壁板与壁面间距的增加而增大并最终趋于稳定(无壁面情况); 通过理论与风洞实验结果的对比分析, 验证了本文气动力及理论分析的适用性及准确性. 针对倒置悬臂壁板结构的气动弹性失稳问题, 本文提出的方法不涉及系统方程的离散及特征值求解问题, 而是将其转化为了定区间上的函数逼近问题进行求解, 这为弹性结构静气动弹性失稳问题的研究提供了一个可行的新思路. 相似文献
64.
It is shown that the Pauli equation and the concept of spin naturally emerge from logical inference applied to experiments on a charged particle under the conditions that (i) space is homogeneous (ii) the observed events are logically independent, and (iii) the observed frequency distributions are robust with respect to small changes in the conditions under which the experiment is carried out. The derivation does not take recourse to concepts of quantum theory and is based on the same principles which have already been shown to lead to e.g. the Schrödinger equation and the probability distributions of pairs of particles in the singlet or triplet state. Application to Stern–Gerlach experiments with chargeless, magnetic particles, provides additional support for the thesis that quantum theory follows from logical inference applied to a well-defined class of experiments. 相似文献
65.
阐明了引入溶剂渗透因子的必要性,较详细地介绍了两种渗透因子及它们间的关系。 相似文献
66.
The present paper is concerned with the asymptotic behaviors of radially symmetric solutions for the multi-dimensional Burgers equation on the exterior domain in , where the boundary and far field conditions are prescribed. We show that in some case where the corresponding 1-D Riemann problem for the non-viscous part admits a shock wave, the solution tends toward a linear superposition of stationary and rarefaction waves as time goes to infinity, and also show the decay rate estimates. Furthermore, we improve the results on the asymptotic stability of the stationary waves which are treated in the previous papers [2], [3]. Finally, for the case of , we give the complete classification of the asymptotic behaviors, which includes even a linear superposition of stationary and viscous shock waves. 相似文献
67.
This paper is concerned with the mixed initial–boundary value problem for semilinear wave equations with complementary frictional dampings and memory effects. We successfully establish uniform exponential and polynomial decay rates for the solutions to this initial–boundary value problem under much weak conditions concerning memory effects. More specifically, we obtain the exponential and polynomial decay rates after removing the fundamental condition that the memory-effect region includes a part of the system boundary, while the condition is a necessity in the previous literature; moreover, for the polynomial decay rates we only assume minimal conditions on the memory kernel function g, without the usual assumption of controlled by g. 相似文献
68.
Phase field models recently gained a lot of interest in the context of tumour growth models. Typically Darcy-type flow models are coupled to Cahn–Hilliard equations. However, often Stokes or Brinkman flows are more appropriate flow models. We introduce and mathematically analyse a new Cahn–Hilliard–Brinkman model for tumour growth allowing for chemotaxis. Outflow boundary conditions are considered in order not to influence tumour growth by artificial boundary conditions. Existence of global-in-time weak solutions is shown in a very general setting. 相似文献
69.
Florence Drui Emmanuel Franck Philippe Helluy Laurent Navoret 《Comptes Rendus Mecanique》2019,347(3):259-269
The over-relaxation approach is an alternative to the Jin–Xin relaxation method in order to apply the equilibrium source term in a more precise way. This is also a key ingredient of the lattice Boltzmann method for achieving second-order accuracy. In this work, we provide an analysis of the over-relaxation kinetic scheme. We compute its equivalent equation, which is particularly useful for devising stable boundary conditions for the hidden kinetic variables. 相似文献
70.
Barbara Niethammer Alessia Nota Sebastian Throm Juan J.L. Velázquez 《Journal of Differential Equations》2019,266(1):653-715
In this paper we consider the long-time asymptotics of a linear version of the Smoluchowski equation which describes the evolution of a tagged particle moving in a random distribution of fixed particles. The volumes v of these particles are independently distributed according to a probability distribution which decays asymptotically as a power law . The validity of the equation has been rigorously proved in [22] taking as a starting point a particle model and for values of the exponent , but the model can be expected to be valid, on heuristic grounds, for . The resulting equation is a non-local linear degenerate parabolic equation. The solutions of this equation display a rich structure of different asymptotic behaviors according to the different values of the exponent σ. Here we show that for the linear Smoluchowski equation is well-posed and that there exists a unique self-similar profile which is asymptotically stable. 相似文献