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   1588472篇
  免费   32329篇
  国内免费   8268篇
化学   705624篇
晶体学   20366篇
力学   75553篇
综合类   107篇
数学   245475篇
物理学   383477篇
无线电   198467篇
  2021年   14799篇
  2020年   17436篇
  2019年   17608篇
  2018年   14057篇
  2016年   30259篇
  2015年   22058篇
  2014年   33035篇
  2013年   79128篇
  2012年   43828篇
  2011年   42666篇
  2010年   41209篇
  2009年   45513篇
  2008年   44982篇
  2007年   42616篇
  2006年   48816篇
  2005年   40682篇
  2004年   41563篇
  2003年   38593篇
  2002年   39218篇
  2001年   39061篇
  2000年   33911篇
  1999年   30080篇
  1998年   27981篇
  1997年   27734篇
  1996年   27153篇
  1995年   24870篇
  1994年   24336篇
  1993年   23750篇
  1992年   23826篇
  1991年   23974篇
  1990年   22709篇
  1989年   22274篇
  1988年   21494篇
  1987年   20112篇
  1986年   19016篇
  1985年   25521篇
  1984年   26575篇
  1983年   22458篇
  1982年   23874篇
  1981年   23009篇
  1980年   22257篇
  1979年   22260篇
  1978年   23465篇
  1977年   23046篇
  1976年   22731篇
  1975年   21453篇
  1974年   21127篇
  1973年   21638篇
  1972年   15771篇
  1967年   13477篇
排序方式: 共有10000条查询结果,搜索用时 328 毫秒
121.
Crystallography Reports - The crystal and molecular structures of Cl–C6H4–O–C16H33 (I) have been studied, and its differential scanning calorimetry (DSC) study is performed....  相似文献   
122.
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   
123.
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   
124.

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   
125.
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   
126.
David Hull     
Journal of Optimization Theory and Applications -  相似文献   
127.
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   
128.
129.
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   
130.
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   
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