全文获取类型
收费全文 | 6475篇 |
免费 | 983篇 |
国内免费 | 589篇 |
专业分类
化学 | 1048篇 |
晶体学 | 68篇 |
力学 | 442篇 |
综合类 | 89篇 |
数学 | 2008篇 |
物理学 | 2907篇 |
无线电 | 1485篇 |
出版年
2024年 | 20篇 |
2023年 | 81篇 |
2022年 | 95篇 |
2021年 | 102篇 |
2020年 | 175篇 |
2019年 | 146篇 |
2018年 | 160篇 |
2017年 | 170篇 |
2016年 | 194篇 |
2015年 | 150篇 |
2014年 | 276篇 |
2013年 | 374篇 |
2012年 | 309篇 |
2011年 | 339篇 |
2010年 | 288篇 |
2009年 | 376篇 |
2008年 | 467篇 |
2007年 | 455篇 |
2006年 | 421篇 |
2005年 | 410篇 |
2004年 | 365篇 |
2003年 | 364篇 |
2002年 | 310篇 |
2001年 | 317篇 |
2000年 | 291篇 |
1999年 | 210篇 |
1998年 | 186篇 |
1997年 | 166篇 |
1996年 | 128篇 |
1995年 | 105篇 |
1994年 | 104篇 |
1993年 | 73篇 |
1992年 | 62篇 |
1991年 | 40篇 |
1990年 | 34篇 |
1989年 | 41篇 |
1988年 | 33篇 |
1987年 | 22篇 |
1986年 | 20篇 |
1985年 | 17篇 |
1984年 | 25篇 |
1983年 | 7篇 |
1982年 | 16篇 |
1981年 | 16篇 |
1980年 | 11篇 |
1979年 | 17篇 |
1978年 | 18篇 |
1977年 | 15篇 |
1976年 | 6篇 |
1973年 | 4篇 |
排序方式: 共有8047条查询结果,搜索用时 0 毫秒
1.
辐射型漏泄同轴电缆的设计 总被引:2,自引:1,他引:1
总结了漏泄同轴电缆的理论研究现状。围绕使用频带和耦合损耗这两个重要电气参数,讨论辐射型漏泄同轴电缆的设计方法。基于周期性槽孔结构的空间谐波的分析,讨论了抑制高次谐波以拓展使用频带的方法。利用时域有限差分方法和Matlab软件计算耦合损耗。 相似文献
2.
蓝牙与IEEE802.11g无线局域网(Wireless Local Area Network,WLAN)都工作在2.4GHz频段上,因此它们之间存在一定的干扰。分析了蓝牙与IEEE802.11g通信系统之间的干扰,并提出了解决这一问题的两种方法:自适应跳频和删除标记法,并对两种方法的性能做了比较。 相似文献
3.
电力系统谐波检测的现状与发展 总被引:7,自引:0,他引:7
准确、实时地对电力系统谐波进行检测有着重要的意义。本文根据电力系统谐波测量的基本方法,对近年来电力系统谐波检测的新方法进行了分析和评述。最后对电力系统的谐波测量进行了总结并提出了看法。 相似文献
4.
Robert S. Strichartz 《Proceedings of the American Mathematical Society》2002,130(3):805-817
Harmonic mappings from the Sierpinski gasket to the circle are described explicitly in terms of boundary values and topological data. In particular, all such mappings minimize energy within a given homotopy class. Explicit formulas are also given for the energy of the mapping and its normal derivatives at boundary points.
5.
K. Batra V. Prasad M. Mohan 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,20(2):191-198
The scattering of heavy ion with a multilevel Rydberg atom in the presence of an electromagnetic field is studied. The interaction
of Rydberg atom and the e.m field is explored using non-perturbative quasi-energy technique. Although the results are presented
for selected excitations but in actual calculations we have included many levels of the atom. The effect of various parameters
are shown on collisional excitation process. As an illustration detailed calculations are performed for the inelastic proton-Na
Rydberg atom collision accompanied by the transfer of photons and the effects of dressing due to the field are considered.
The emphasis of the present work is on collision induced transitions especially the case that involves change of orbital as
well as principal quantum number.
Received 26 December 2001 / Received in final form 8 April 2002 Published online 19 July 2002 相似文献
6.
We have investigated the effect of extended dislocations (0.5-3 μm) on charge distribution in GaN epilayer grown by metalorganic chemical vapor deposition on (0001) sapphire using atomic force microscopy (AFM) and scanning surface potential microscopy (SSPM). It has been observed for the surface at the extended dislocations present in undoped GaN film to be negatively charged showing 0.04-0.2 V higher potential relative to regions that contain no dislocations. In addition to the higher potential at the dislocation core, the surrounding surfaces, including the edge of the dislocations, are also negatively charged in a symmetric way around the dislocations revealing crater-shaped higher potential regions (∼0.04 V) relative to surrounding dislocation-free area. The experimental results show that the protrusion-type of dislocation is also negatively charged and its potential is dependent on the size of dislocation. 相似文献
7.
S. Mancini D. Vitali V. Giovannetti P. Tombesi 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,22(3):417-422
We show that the optomechanical coupling between an optical cavity mode and two movable cavity mirrors is able to entangle
two different macroscopic oscillation modes of the mirrors. This continuous variable entanglement is maintained by the light
bouncing between the mirrors and is robust against thermal noise. In fact, it could be experimentally demonstrated using present
technology.
Received 2 September 2002 / Received in final form 10 October 2002 Published online 7 January 2003 相似文献
8.
本文考虑广义C-R组^[1](H)的解f=u iv jw∈C^2的一些性质,提出与之相关的两个边值问题,用积分方程方法和调和函数性质证明了边值问题解的存在唯一性,并写出解的积分表达式. 相似文献
9.
Some new oscillation criteria are established for a second order neutral delay differential equations. These results improve oscillation results of Y.V. Rogo-vchenko for the retarded delay differential equations. The relevance of our theorems is illustrated with two carefully selected examples. 相似文献
10.
Harnack inequality for some classes of Markov processes 总被引:3,自引:0,他引:3
In this paper we establish a Harnack inequality for nonnegative harmonic functions of some classes of Markov processes with jumps.
Mathematics Subject Classification (2000): Primary 60J45, 60J75, Secondary 60J25.This work was completed while the authors were in the Research in Pairs program at the Mathematisches Forschungsinstitut Oberwolfach. We thank the Institute for the hospitality.The research of this author is supported in part by NSF Grant DMS-9803240.The research of this author is supported in part by MZT grant 0037107 of the Republic of Croatia. 相似文献