首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   11706篇
  免费   1543篇
  国内免费   908篇
化学   6723篇
晶体学   122篇
力学   405篇
综合类   50篇
数学   838篇
物理学   2931篇
无线电   3088篇
  2024年   24篇
  2023年   270篇
  2022年   270篇
  2021年   399篇
  2020年   416篇
  2019年   397篇
  2018年   320篇
  2017年   280篇
  2016年   507篇
  2015年   478篇
  2014年   585篇
  2013年   787篇
  2012年   986篇
  2011年   975篇
  2010年   622篇
  2009年   676篇
  2008年   767篇
  2007年   743篇
  2006年   647篇
  2005年   617篇
  2004年   393篇
  2003年   313篇
  2002年   337篇
  2001年   263篇
  2000年   248篇
  1999年   229篇
  1998年   201篇
  1997年   146篇
  1996年   146篇
  1995年   180篇
  1994年   153篇
  1993年   121篇
  1992年   107篇
  1991年   88篇
  1990年   80篇
  1989年   41篇
  1988年   52篇
  1987年   40篇
  1986年   40篇
  1985年   38篇
  1984年   26篇
  1983年   15篇
  1982年   29篇
  1981年   16篇
  1979年   9篇
  1978年   10篇
  1977年   8篇
  1976年   7篇
  1975年   7篇
  1971年   7篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
本文从应用角度简要介绍了《行波管质量与可靠性信息管理系统》的研制背景,数据库的数据来源,数据结构,系统构成及功能特点。  相似文献   
52.
53.
The objective of this paper is to present the subject of wavelets from a filter-theory perspective, which is quite familiar to electrical engineers. Such a presentation provides both physical and mathematical insights into the problem. It is shown that taking the discrete wavelet transform of a function is equivalent to filtering it by a bank of constant-Q filters, the non-overlapping bandwidths of which differ by an octave. The discrete wavelets are presented, and a recipe is provided for generating such entities. One of the goals of this tutorial is to illustrate how the wavelet decomposition is carried out, starting from the fundamentals, and how the scaling functions and wavelets are generated from the filter-theory perspective. Examples (including image compression) are presented to illustrate the class of problems for which the discrete wavelet techniques are ideally suited. It is interesting to note that it is not necessary to generate the wavelets or the scaling functions in order to implement the discrete wavelet transform. Finally, it is shown how wavelet techniques can be used to solve operator/matrix equations. It is shown that the “orthogonal-transform property” of the discrete wavelet techniques does not hold in numerical computations  相似文献   
54.
利用修正的非线性Schrodinger方程研究了单模光纤最小群速度色散波长附近的调制不稳定性,发现了一个新的由光纤四色散导致的调制不稳定性区域,该区域的调制范围与初始入射脉冲的功率和四阶色散有关。  相似文献   
55.
本文论述了帧中继交换的概念、标准,结构、特点网络式样及在互连网中的应用。  相似文献   
56.
The purpose of this paper is to study the relationship between the oxygen concentration and brightness degradation in ZnS:TbOF green thin-film electroluminescent (EL) devices. The characteristics including crystallinity, optical, and electrical properties were discussed. The brightness-voltage (B-V) measurement results shelved that with higher oxygen-content in ZnS:TbOF phosphor layer, lower brightness was measured. It was consistent with the poor crystallinity, worse photoluminescent intensity, and easier to get moisture in the oxygen-rich (O/Tb>1) phosphor film. Furthermore, deep level transient spectroscopy (DLTS) measurements identified that when the O/Tb ratio was greater than 1, the oxygen-related deep hole traps EH1 and/or EH2 could be detected in the ZnS:TbOF phosphor layer. These E H1 and/or EH2 traps were believed to be the main killers for the brightness of the device since they capture most of the holes from the generated electron-hole pairs. This evidence strongly supports that the modified energy transfer model is more dominant than direct impact excitation during the luminescent process  相似文献   
57.
谐振子薛定谔方程的简单解法   总被引:2,自引:0,他引:2  
物质的许多物理与化学性质都可以用线性谐振子模型解释,本文用简单的数学运算求解线性谐振子的薛定谔方程,避免了特殊函数等复杂的数学运算,得出了量子力学教材完全相同的结果。  相似文献   
58.
A series of Gd(1−x)Bx alloys have been prepared by arc melting method. After introducing small quantity of B atom in Gd, the Curie temperature of these alloys increase while the magnetic entropy changes are almost same as that of Gd. The refrigerant capacities of these alloys are also greater than that of Gd. These results suggest that Gd(1−x)Bx alloys may be utilized as refrigerant in household magnetic refrigeration.  相似文献   
59.
60.
We have reported a novel design of surface plasmon resonance (SPR) device, which uses alternating dielectric layers to enhance the SPR signal quality and modulate its resonant position. Admittance loci method of thin film design has been used in the design of such a device. The use of biomolecular thin film, such as DNAs or Porteins, in this design can result in resonant condition of wavelength changes as well. Bio-plasmonics is proposed for the research and development of novel devices, which use biomolecules as a part of the plasmon oscillation system to actively interact with nano/micro structure.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号