全文获取类型
收费全文 | 7873篇 |
免费 | 646篇 |
国内免费 | 323篇 |
专业分类
化学 | 1865篇 |
晶体学 | 38篇 |
力学 | 777篇 |
综合类 | 124篇 |
数学 | 3010篇 |
物理学 | 3028篇 |
出版年
2024年 | 20篇 |
2023年 | 82篇 |
2022年 | 169篇 |
2021年 | 172篇 |
2020年 | 201篇 |
2019年 | 190篇 |
2018年 | 168篇 |
2017年 | 237篇 |
2016年 | 277篇 |
2015年 | 259篇 |
2014年 | 376篇 |
2013年 | 701篇 |
2012年 | 354篇 |
2011年 | 373篇 |
2010年 | 323篇 |
2009年 | 456篇 |
2008年 | 472篇 |
2007年 | 483篇 |
2006年 | 385篇 |
2005年 | 348篇 |
2004年 | 322篇 |
2003年 | 287篇 |
2002年 | 252篇 |
2001年 | 188篇 |
2000年 | 221篇 |
1999年 | 182篇 |
1998年 | 180篇 |
1997年 | 167篇 |
1996年 | 126篇 |
1995年 | 119篇 |
1994年 | 111篇 |
1993年 | 86篇 |
1992年 | 85篇 |
1991年 | 44篇 |
1990年 | 53篇 |
1989年 | 46篇 |
1988年 | 40篇 |
1987年 | 40篇 |
1986年 | 37篇 |
1985年 | 22篇 |
1984年 | 31篇 |
1983年 | 17篇 |
1982年 | 19篇 |
1981年 | 18篇 |
1980年 | 22篇 |
1979年 | 21篇 |
1978年 | 15篇 |
1977年 | 13篇 |
1976年 | 16篇 |
1974年 | 5篇 |
排序方式: 共有8842条查询结果,搜索用时 15 毫秒
61.
Durand William A.Pham Ngoc Dinh 《Journal of Mathematical Analysis and Applications》2003,282(1):95-106
An electromagnetic diffraction problem in a wedge shaped region is reduced to a system of coupled functional difference equations by means of Sommerfeld integrals and Malyuzhinets theorem. By introducing an integral operator it is shown that the solutions of this system of functional equations can be defined in terms of integral representations whose kernels are solutions of a singular integral equation of Cauchy-Carleman type for which an explicit solution is given. 相似文献
62.
We investigate a new parallel all-optical clock recovery scheme based on heterodyne beats of an optical sideband-filtered signal. The oscillating clock signal is recovered when the filtered sideband is combined with a stable local oscillator. The filtering is performed with an optical resonator, which by nature provides possibility for multiwavelength operation. The local oscillator could be realized by a multiwavelength laser, whose emission wavelengths are injection seeded with carrier wavelengths of the input data. The output signal of such a configuration benefits from a reduced bit-pattern effect and a stable offset level. The sideband filtering is demonstrated for 23 simultaneous channels at 100 GHz DWDM grid, each hosting a data stream of 10 Gbit/s. 相似文献
63.
数码相机原理与系统设计研究 总被引:7,自引:0,他引:7
介绍了数码相机的工作原理 ,分析了数码相机的系统结构 ,提出了设计数码相机的处理流程。典型的数码相机系统有镜头、闪光灯、光学取景器、LCD显示屏、图像数据存储扩展设备接口、图像数据传输接口、供电系统以及核心处理器等八个主要模块。数码相机的数据流向从图像传感器开始 ,止于图像数据的存储和传输。数据流的处理主要包括模数转换、光学黑电平钳位、针对镜头的边缘畸变的运算修正、坏像素处理、白平衡处理、伽马校正、色彩合成处理、边缘检测 (锐度检测 )和伪彩色检测 (伪彩色抑制 )、JPEG压缩和图像存储器等模块 相似文献
64.
Eric Flauraud Frdric Nataf Isabelle Faille Roland Masson 《Comptes Rendus Mecanique》2003,331(12):849-855
We present in this paper a domain decomposition method to treat faults in geological basin modeling. The particularity of this model is that the faults whose widths are very small in comparison with the basin size, are not characterized as subdomains any more but as interfaces between sedimentary blocks. The originality of this work lies in the formulation of this new fault model and in the definition and the computation of the interface conditions between the subdomains. To cite this article: E. Flauraud et al., C. R. Mecanique 331 (2003). 相似文献
65.
Ansgar Jüngel 《Mathematische Nachrichten》1997,185(1):85-110
A multi-dimensional transient drift-diffusion model for (at most) three charged particles, consisting of the continuity equations for the concentrations of the species and the Poisson equation for the electric potential, is considered. The diffusion terms depend on the concentrations. Such a system arises in electrophoretic modeling of three species (neutrally, positively and negatively charged) and in semiconductor theory for two species (positively charged holes and negatively charged electrons). Diffusion terms of degenerate type are also possible in semiconductor modeling. For the initial boundary value problem with mixed Dirichlet - Neumann boundary conditions and general reaction rates, a global existence result is proved. Uniqueness of solutions follows in the Dirichlet boundary case if the diffusion terms are uniformly parabolic or if the initial and boundary densities are strictly positive. Finally, we prove that solutions exist which are positive uniformly in time and globally bounded if the reaction rates satisfy appropriate growth conditions. 相似文献
66.
The current status of the R & D activities is presented on electron beam processing of polymers being carried out at TRCRE. Topics included are sterilization of medical products, graft polymers for selective separation or absorbents and curing of liquid prepolymer-monomer systems. 相似文献
67.
具有非局部边界条件的奇摄动反应扩散问题 总被引:2,自引:0,他引:2
本文研究了一类具有非局部边界条件的奇摄动反应扩散初始边值问题.在适当的条件下,利用比较定理讨论了问题解的渐近性态. 相似文献
68.
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
69.
We deal with the differential conditions for local optimality. The conditions that we derive for inequality constrained problems
do not require constraint qualifications and are the broadest conditions based on only first-order and second-order derivatives.
A similar result is proved for equality constrained problems, although the necessary conditions require the regularity of
the equality constraints. 相似文献
70.