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   13121篇
  免费   2210篇
  国内免费   2484篇
化学   7127篇
晶体学   161篇
力学   486篇
综合类   204篇
数学   1179篇
物理学   3223篇
无线电   5435篇
  2024年   51篇
  2023年   189篇
  2022年   321篇
  2021年   375篇
  2020年   379篇
  2019年   442篇
  2018年   370篇
  2017年   430篇
  2016年   456篇
  2015年   613篇
  2014年   775篇
  2013年   936篇
  2012年   1017篇
  2011年   975篇
  2010年   971篇
  2009年   897篇
  2008年   1024篇
  2007年   969篇
  2006年   944篇
  2005年   830篇
  2004年   722篇
  2003年   691篇
  2002年   898篇
  2001年   805篇
  2000年   570篇
  1999年   300篇
  1998年   175篇
  1997年   107篇
  1996年   86篇
  1995年   56篇
  1994年   55篇
  1993年   36篇
  1992年   62篇
  1991年   59篇
  1990年   43篇
  1989年   29篇
  1988年   39篇
  1987年   20篇
  1986年   17篇
  1985年   12篇
  1984年   16篇
  1983年   11篇
  1982年   6篇
  1981年   5篇
  1980年   4篇
  1979年   4篇
  1966年   4篇
  1964年   4篇
  1960年   2篇
  1936年   3篇
排序方式: 共有10000条查询结果,搜索用时 218 毫秒
911.
912.
通过对南京华日公司在2002年从日本引进一条STN-LCD生产线设备维护修理情况进行探讨,为进口LCD生产线设备维护修理管理提供参考。  相似文献   
913.
Characteristics of single- and multi-finger mesa InGaAs/InP double heterojunction bipolar transistors (DHBTs) are compared. The current gain decreases with the increasing number nf of the emitter fingers due to the mutual thermal interaction between the fingers. The Kirk current can be as high as 150mA for four-finger DHBT. No degradation of the peak of the current gain cutoff frequency ft is found for multi-finger DHBTs. The peak of the maximum oscillation frequency fmax decreases with an increase of nf due to the increasing parasitic resistance of the base. The results are very helpful for applications of the common-base DHBTs in power amplifiers operating at very high frequencies.  相似文献   
914.
Metal–organic frameworks (MOFs) are widely used as porous materials in the fields of adsorption and separation. However, their practical application is largely hindered by limitations to their processability. Herein, new UiO‐66‐Urea‐based flexible membranes with MOF loadings of 50 ( 1 ), 60 ( 2 ), and 70 wt % ( 3 ) were designed and prepared by post‐synthetic polymerization of UiO‐66‐NH2 nanoparticles and a polyurethane oligomer under mild conditions. The adsorption behavior of membrane 3 towards four hydrophilic dyes, namely, eosin Y (EY), rhodamine B (RB), malachite green (MG), and methylene blue (MB), in aqueous solution was studied in detail. It exhibits strong adsorption of EY and RB but weak adsorption of MG and MB in aqueous solution. Owing to the selective adsorption of these hydrophilic dyes, membrane 3 can remove EY and RB from aqueous solution and completely separate EY/MB, RB/MG, and RB/MB mixtures in aqueous solution. In addition, the membrane is uniformly textured, easily handled, and can be reused for dye adsorption and separation.  相似文献   
915.
916.
The electromagnetic fields of a horizontal electric dipole buried in a medium covering one-dimensionally anisotropic medium are studied. There are three media, one-dimensionally anisotropic medium covered with a dielectric under the air. The electromagnetic field components are complex because of the multiple reflections from the up and down boundaries. The electromagnetic field components between air and one-dimensionally anisotropic medium are given, the trapped surface waves and lateral waves along the dielectric-anisotropic medium boundary are computed. The results have some practical applications in the communication in sea or lake above one-dimensionally anisotropic earth or sediments.  相似文献   
917.
讨论Li-Yorke敏感的乘积性质以及它的迭代不变性.主要证明了Li-Yorke敏感在乘积运算下是保持的,以及在一致连续意义下,它的复合运算也是保持的.同时,举例说明该结论对于一般的连续自映射不成立.  相似文献   
918.
A rapid,sensitive,selective and reliable strip assay based on DNA-functionalized gold nanoparticles for Hg2+ detection has been developed,with a detection limit 5 nmol/L.The measurement principle was based on thymine-Hg2+-thymine(T-Hg2+-T) coordination chemistry and streptavidin-biotin interaction.The major advantages of this assay are that results can be read visually without any instrument in less than 10 min and that it does not require any sample pretreatment.  相似文献   
919.
Numerical pseudodifferential operator and Fourier regularization   总被引:1,自引:0,他引:1  
The concept of numerical pseudodifferential operator, which is an extension of numerical differentiation, is suggested. Numerical pseudodifferential operator just is calculating the value of the pseudodifferential operator with unbounded symbol. Many ill-posed problems can lead to numerical pseudodifferential operators. Fourier regularization is a very simple and effective method for recovering the stability of numerical pseudodifferential operators. A systematically theoretical analysis and some concrete examples are provided.  相似文献   
920.
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