全文获取类型
收费全文 | 33457篇 |
免费 | 3722篇 |
国内免费 | 2191篇 |
专业分类
化学 | 2316篇 |
晶体学 | 23篇 |
力学 | 4021篇 |
综合类 | 443篇 |
数学 | 23260篇 |
物理学 | 9307篇 |
出版年
2024年 | 68篇 |
2023年 | 352篇 |
2022年 | 397篇 |
2021年 | 520篇 |
2020年 | 978篇 |
2019年 | 941篇 |
2018年 | 894篇 |
2017年 | 872篇 |
2016年 | 947篇 |
2015年 | 794篇 |
2014年 | 1537篇 |
2013年 | 2864篇 |
2012年 | 1544篇 |
2011年 | 2067篇 |
2010年 | 1897篇 |
2009年 | 2114篇 |
2008年 | 2247篇 |
2007年 | 2168篇 |
2006年 | 1876篇 |
2005年 | 1855篇 |
2004年 | 1544篇 |
2003年 | 1514篇 |
2002年 | 1316篇 |
2001年 | 1001篇 |
2000年 | 941篇 |
1999年 | 914篇 |
1998年 | 864篇 |
1997年 | 712篇 |
1996年 | 542篇 |
1995年 | 447篇 |
1994年 | 397篇 |
1993年 | 259篇 |
1992年 | 227篇 |
1991年 | 243篇 |
1990年 | 211篇 |
1989年 | 126篇 |
1988年 | 128篇 |
1987年 | 119篇 |
1986年 | 116篇 |
1985年 | 116篇 |
1984年 | 113篇 |
1983年 | 54篇 |
1982年 | 105篇 |
1981年 | 93篇 |
1980年 | 67篇 |
1979年 | 63篇 |
1978年 | 47篇 |
1977年 | 39篇 |
1976年 | 27篇 |
1973年 | 19篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
We derive and analyse four algorithms for computing the current induced on a thin straight wire by a transient electric field.
They all involve solving the thin wire electric field integral equations (EFIEs) and consist of a very accurate differential
equations solver together with various schemes to approximate the vector potential integral equation. We carry out a rigorous
numerical stability analysis of each of these methods. This has not previously been done for solution schemes for the thin
wire EFIEs. Each scheme is shown to be stable and convergent provided the radius of the wire is small enough for the thin
wire equations to be a valid model. 相似文献
82.
The Hawking radiation of Dirac particles in an arbitrarily rectilinearly accelerating Kinnersley black hole with electromagnetic charge and cosmological constant is investigated by using the generalized tortoise coordinate transformation. Both the location and the temperature of the event horizon depend on the time and the polar angle. The Hawking thermal radiation spectrum of Dirac particles is also derived. 相似文献
83.
Using the appropriate harmonic oscillator states and reasonable approximations, we construct coherent wavepackets corresponding
to the solutions of the Klein-Gordon equation for the attractive potentialV(r)=−k/r, k>0, in two and three space dimensions. We deduce the corresponding classical limit in two dimension by requiring that the
expectation value 〈r〉 of the radial variable is large. In the case of three dimensions, besides the condition of large 〈r〉, we make the uncertainty Δr=[〈r
2〉 − 〈r〉2]1/2 a minimum with respect to certain parameter of the wavepacket. We then investigate the trajectory traversed by the wavepacket
in the classical limit. We find that the classical limit of this relativistic quantal problem gives, in the leading order,
the same expression for the rate of motion of the perihelion as that given by the solution of the corresponding special relativistic
classical dynamical problem. We also briefly discuss some of the subtle aspects of the classical limit of the relativistic
quantal system, in general. 相似文献
84.
Bernard Bialecki 《Numerical Algorithms》1994,8(2):167-184
Cyclic reduction and Fourier analysis-cyclic reduction (FACR) methods are presented for the solution of the linear systems which arise when orthogonal spline collocation with piecewise Hermite bicubics is applied to boundary value problems for certain separable partial differential equations on a rectangle. On anN×N uniform partition, the cyclic reduction and Fourier analysis-cyclic reduction methods requireO(N
2log2
N) andO(N
2log2log2
N) arithmetic operations, respectively. 相似文献
85.
Zi‐Cai Li Tzon‐Tzer Lu Hung‐Tsai Huang Alexander H.‐D. Cheng 《Numerical Methods for Partial Differential Equations》2007,23(1):93-144
In this article we survey the Trefftz method (TM), the collocation method (CM), and the collocation Trefftz method (CTM). We also review the coupling techniques for the interzonal conditions, which include the indirect Trefftz method, the original Trefftz method, the penalty plus hybrid Trefftz method, and the direct Trefftz method. Other boundary methods are also briefly described. Key issues in these algorithms, including the error analysis, are addressed. New numerical results are reported. Comparisons among TMs and other numerical methods are made. It is concluded that the CTM is the simplest algorithm and provides the most accurate solution with the best numerical stability. © 2006 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2007 相似文献
86.
王军秀 《纯粹数学与应用数学》2007,23(3):406-408
利用欧拉公式研究了Gdk图的平面性,获得了一个重要定理,并由此得到了关于平面图色数的一个结论. 相似文献
87.
本针对P0函数互补问题,给出了一种微方程方法,并且证明了P0函数互补问题的解是微分方程系统的渐进稳定平衡点。在适当的假设条件下,证明了所给出的算法具有二次收敛速度。几个数值例子表明了该算法的有效性。 相似文献
88.
L.E. Payne 《Journal of Mathematical Analysis and Applications》2003,284(1):283-293
We consider some initial-boundary value problems for the linear and nonlinear heat equation where the gradient of the solution is prescribed on the boundary. Assuming that a solution exists, we obtain bounds for the solution and its gradient by maximum principle arguments or by means of differential and integral inequalities. 相似文献
89.
本文利用拟线性常微分方程解的非存在性定理得到了一类拟线性反应扩散方程(非牛顿渗流方程)爆破界的估计,从而推广了半线性反应扩散方程(牛顿渗流方程)相应结果. 相似文献
90.
A finite volume solver for the 2D depth‐integrated harmonic hyperbolic formulation of the mild‐slope equation for wave propagation is presented and discussed. The solver is implemented on unstructured triangular meshes and the solution methodology is based upon a Godunov‐type second‐order finite volume scheme, whereby the numerical fluxes are computed using Roe's flux function. The eigensystem of the mild‐slope equations is derived and used for the construction of Roe's matrix. A formulation that updates the unknown variables in time implicitly is presented, which produces a more accurate and reliable scheme than hitherto available. Boundary conditions for different types of boundaries are also derived. The agreement of the computed results with analytical results for a range of wave propagation/transformation problems is very good, and the model is found to be virtually paraxiality‐free. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献