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   1566421篇
  免费   32298篇
  国内免费   8236篇
化学   694772篇
晶体学   20125篇
力学   74960篇
综合类   108篇
数学   243504篇
物理学   376392篇
无线电   197094篇
  2021年   14765篇
  2020年   17396篇
  2019年   17539篇
  2016年   29606篇
  2015年   21844篇
  2014年   32920篇
  2013年   78960篇
  2012年   42673篇
  2011年   40265篇
  2010年   40034篇
  2009年   44534篇
  2008年   43107篇
  2007年   40184篇
  2006年   47985篇
  2005年   39066篇
  2004年   40414篇
  2003年   37666篇
  2002年   38740篇
  2001年   38336篇
  2000年   33450篇
  1999年   29876篇
  1998年   27900篇
  1997年   27682篇
  1996年   27108篇
  1995年   24830篇
  1994年   24318篇
  1993年   23692篇
  1992年   23742篇
  1991年   23850篇
  1990年   22599篇
  1989年   22184篇
  1988年   21367篇
  1987年   20023篇
  1986年   18929篇
  1985年   25427篇
  1984年   26509篇
  1983年   22413篇
  1982年   23839篇
  1981年   22980篇
  1980年   22242篇
  1979年   22214篇
  1978年   23450篇
  1977年   23020篇
  1976年   22710篇
  1975年   21391篇
  1974年   21099篇
  1973年   21604篇
  1972年   15768篇
  1968年   13457篇
  1967年   13480篇
排序方式: 共有10000条查询结果,搜索用时 718 毫秒
121.
Analog Integrated Circuits and Signal Processing - This paper presents the complete design of a phase locked loop-based clock synthesizer for reconfigurable analog-to-digital converters. The...  相似文献   
122.
Gawad  Dina A.  Elnaggar  Mai M.  Belal  Tarek S. 《Chromatographia》2022,85(7):617-628
Chromatographia - The present work deals with the optimization, validation and application of a versatile HPLC–DAD method for concurrent estimation of nine antimicrobials and proton pump...  相似文献   
123.

Sampling or task jitter affects the performance of digital control systems but realistic simulation of this effect has not been possible to date. Our previous work has developed a novel method to simulate sampling jitter in MATLAB/Simulink simulation software where the jitter is generated randomly. What has been missing is a way to capture sampling jitter from a target platform and then feed this timing information into the simulation. This paper presents a low-cost and novel solution to these problems. The method uses an Arduino board to capture task jitter from two different hardware platforms with multiple stressing conditions. Then the recorded performance data is used to drive realistic simulations of a control system. Measurement shows that the task jitter data does not follow any specific random distribution such as Gaussian or Uniform. Furthermore, very occasional timing patterns, which may not be picked up while testing a real system, can result in extreme controller responses. This novel method allows comparisons of different platforms and reduces the effort required to choose the most appropriate platform for full implementation.

  相似文献   
124.
We investigate the possibility of phantom crossing in the dark energy sector and the solution for the Hubble tension between early and late universe observations. We use robust combinations of different cosmological observations, namely the Cosmic Microwave Background (CMB), local measurement of Hubble constant (H0), Baryon Acoustic Oscillation (BAO) and SnIa for this purpose. For a combination of CMB+BAO data that is related to early universe physics, phantom crossing in the dark energy sector was confirmed at a 95% confidence level and we obtained the constraint H0=71.03.8+2.9 km/s/Mpc at a 68% confidence level, which is in perfect agreement with the local measurement by Riess et al. We show that constraints from different combinations of data are consistent with each other and all of them are consistent with phantom crossing in the dark energy sector. For the combination of all data considered, we obtained the constraint H0=70.25±0.78 km/s/Mpc at a 68% confidence level and the phantom crossing happening at the scale factor am=0.8510.031+0.048 at a 68% confidence level.  相似文献   
125.
David Hull     
Journal of Optimization Theory and Applications -  相似文献   
126.
Algebra and Logic - Unary functions definable in o-stable ordered groups of nonvaluational type are studied. Such functions are proved to be piecewise monotone and continuous.  相似文献   
127.
128.
Journal of Applied Mechanics and Technical Physics - A refined model of viscoelastic-plastic deformation of flexible plates with spatial reinforcement structures has been developed. Strains of the...  相似文献   
129.
General Relativity and Gravitation - In previous work, we established theoretical results concerning the effect of matter shells surrounding a gravitational wave (GW) source, and we now apply these...  相似文献   
130.
Set-Valued and Variational Analysis - R. Tyrell Rockafellar and his collaborators introduced, in a series of works, new regression modeling methods based on the notion of superquantile (or...  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