全文获取类型
收费全文 | 1442篇 |
免费 | 110篇 |
国内免费 | 24篇 |
专业分类
化学 | 88篇 |
力学 | 54篇 |
综合类 | 4篇 |
数学 | 274篇 |
物理学 | 653篇 |
无线电 | 503篇 |
出版年
2024年 | 5篇 |
2023年 | 39篇 |
2022年 | 39篇 |
2021年 | 51篇 |
2020年 | 52篇 |
2019年 | 37篇 |
2018年 | 44篇 |
2017年 | 81篇 |
2016年 | 70篇 |
2015年 | 59篇 |
2014年 | 104篇 |
2013年 | 100篇 |
2012年 | 67篇 |
2011年 | 93篇 |
2010年 | 85篇 |
2009年 | 87篇 |
2008年 | 93篇 |
2007年 | 86篇 |
2006年 | 59篇 |
2005年 | 48篇 |
2004年 | 34篇 |
2003年 | 32篇 |
2002年 | 27篇 |
2001年 | 26篇 |
2000年 | 19篇 |
1999年 | 14篇 |
1998年 | 25篇 |
1997年 | 10篇 |
1996年 | 9篇 |
1995年 | 16篇 |
1994年 | 9篇 |
1993年 | 6篇 |
1992年 | 10篇 |
1991年 | 10篇 |
1990年 | 5篇 |
1989年 | 3篇 |
1988年 | 4篇 |
1987年 | 1篇 |
1986年 | 5篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有1576条查询结果,搜索用时 15 毫秒
1.
WKB近似下的Fourier衍射成象方法 总被引:1,自引:0,他引:1
对于介质目标微波衍射成象,本文引入了WKB近似来模拟目标内部总场。基于这种近似,我们导出了Fourier衍射公式,并采用了广义滤波逆传播方法由目标空间谱实现目标特性的重建。计算机模拟结果表明采用WKB近似重建目标特性较Born近似有明显改善。 相似文献
2.
Dimitrios Tzovaras Nikos Grammalidis Michael G. Strintzis 《Signal Processing: Image Communication》1998,11(3):205-230
In the present paper techniques are examined for the coding of the depth map and disparity fields for stereo or multiview image communication applications. It is assumed that both the left and right channels of the multiview image sequence are coded using block- or object-based methods. A dynamic programming algorithm is used to estimate a disparity field between each stereo image pair. Depth is then estimated and occlusions are optionally detected, based on the estimated disparity fields. Spatial interpolation techniques are examined based on the disparity/depth information and the detection of occluded regions using either stereoscopic or trinocular camera configurations. It is seen that the presence of a third camera at the transmitter site improves the estimation of disparities, the detection of occlusions and the accuracy of the resulting spatial interpolation at the receiver. Various disparity field and depth map coding techniques are then proposed and evaluated, with emphasis given to the quality of the resulting intermediate images at the receiver site. Block-based and wireframe modeling techniques are examined for the coding of isolated depth or disparity map information. Further, 2D and 3D motion compensation techniques are evaluated for the coding of sequences of depth or disparity maps. The motion fields needed may be available as a byproduct of block-based or object-based coding of the intensity images. Experimental results are given for the evaluation of the performance of the proposed coding and spatial interpolation methods. 相似文献
3.
Successive column correction algorithms for solving sparse nonlinear systems of equations 总被引:1,自引:0,他引:1
Guangye Li 《Mathematical Programming》1989,43(1-3):187-207
This paper presents two algorithms for solving sparse nonlinear systems of equations: the CM-successive column correction algorithm and a modified CM-successive column correction algorithm. Aq-superlinear convergence theorem and anr-convergence order estimate are given for both algorithms. Some numerical results and the detailed comparisons with some previously established algorithms show that the new algorithms have some promise of being very effective in practice.This research was partially supported by contracts and grants: DOE DE-AS05-82ER1-13016, AFOSR 85-0243 at Rice University, Houston, U.S.A. and Natural Sciences and Engineering Research Council of Canada grant A-8639. 相似文献
4.
SHIHongju SHIYongji 《半导体光子学与技术》1998,4(4):197-208,234
The liquid crystal televison spatia light modulator(LCTVSLM)characterized is usable in optical processing applications.e.g.,optical pattern recognition,associative memory,optical computing,correlation detection and optical data processing systems.The array performance and real-time optical correlation applications are reviewed. 相似文献
5.
P. G. J. van Dongen 《Journal of statistical physics》1989,54(1-2):221-271
A general method is used for describing reaction-diffusion systems, namely van Kampen's method of compounding moments, to study the spatial fluctuations in reaction-limited aggregation processes. The general formalism used here and in subsequent publications is developed. Then a particular model is considered that is of special interest, since it describes the occurrence of a phase transition (gelation). The corresponding rate constants for the reaction between two clusters of sizei and sizej areK
ij=ij (i, j=1, 2,). For thediffusion constants D
j of clusters of sizej the following class of models is considered:D
j=D if 1Js andD
j=0 ifj>s. The casess= ands< are studied separately. For the models= the equal-time and the two-time correlation functions are calculated; this modelbreaks down at the gel point. The breakdown is characterized by a divergence of the density fluctuations, and is caused by the large mobility of large clusters. For all models withs< the density fluctuations remain finite att
c, and the equal-time correlation functions in the pre- and in the post-gel stage are calculated. Many explicit and asymptotic results are given. From the exact solution the upper critical dimension in this gelling model isd
c=2. 相似文献
6.
该文提出了基于超像素级卷积神经网络(sp-CNN)的多聚焦图像融合算法。该方法首先对源图像进行多尺度超像素分割,将获取的超像素输入sp-CNN,并对输出的初始分类映射图进行连通域操作得到初始决策图;然后根据多幅初始决策图的异同获得不确定区域,并利用空间频率对其再分类,得到阶段决策图;最后利用形态学对阶段决策图进行后处理,并根据所得的最终决策图融合图像。该文算法直接利用超像素分割块进行图像融合,其相较以往利用重叠块的融合算法可达到降低时间复杂度的目的,同时可获得较好的融合效果。 相似文献
7.
The spatial distribution function and second moments of circular freely jointed chain are derived based on an analytical method. The circular Gauss chain, which is simple for long chains, is compared with the circular freely jointed chain, which is exact for short chains. It is shown that the Gauss chain model predicts a more compact configurational distribution than the exact freely jointed chain. The two chain models, however, become closer to each other when the chain length increases. It is found that the difference of the mean square radius of gyration calculated with these two chain models is a constant, independent of the chain length. 相似文献
8.
基于Labview的光学空间滤波远程虚拟实验 总被引:4,自引:0,他引:4
提出了一种利用Labview实现光学空间滤波模拟的新方法,并对经典的阿贝-波特实验设计了仿真程序.该程序可根据用户设置的参量生成二维网格光栅作为整个物理过程的输入物,允许用户选择多种不同的滤波方式,如低通、高通、方向滤波等,并可依次操纵成像的各个步骤.程序可脱离编程环境独立运行,具有跨平台、界面友好、易于操作等优点,并可架设基于浏览器的远程虚拟实验. 相似文献
9.
大学、企业研发与区域创新的空间统计与计量分析 总被引:18,自引:0,他引:18
利用空间统计的Moran指数和空间计量经济学的空间误差模型和空间滞后模型,对2000年中国大陆31个省域的创新产出与大学与企业的关系进行了空间计量经济分析。结果发现:31个省域创新能力贡献主要是由企业研究与开发投入实现,大学研发对区域创新能力没有明显的作用,大学与企业研发的结合也没有对区域创新产生明显贡献。 相似文献
10.