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   1489166篇
  免费   32742篇
  国内免费   8749篇
化学   643600篇
晶体学   19995篇
力学   73916篇
综合类   128篇
数学   238362篇
物理学   358816篇
无线电   195840篇
  2021年   14918篇
  2020年   17474篇
  2019年   17630篇
  2016年   29125篇
  2015年   21772篇
  2014年   32888篇
  2013年   78683篇
  2012年   38184篇
  2011年   33034篇
  2010年   38175篇
  2009年   43510篇
  2008年   36910篇
  2007年   33268篇
  2006年   42024篇
  2005年   33106篇
  2004年   35314篇
  2003年   33697篇
  2002年   35076篇
  2001年   33255篇
  2000年   30191篇
  1999年   28415篇
  1998年   27322篇
  1997年   27220篇
  1996年   26866篇
  1995年   24648篇
  1994年   24105篇
  1993年   23445篇
  1992年   22946篇
  1991年   23141篇
  1990年   21927篇
  1989年   21587篇
  1988年   20709篇
  1987年   19513篇
  1986年   18321篇
  1985年   24859篇
  1984年   26107篇
  1983年   22116篇
  1982年   23578篇
  1981年   22786篇
  1980年   22054篇
  1979年   21819篇
  1978年   23175篇
  1977年   22709篇
  1976年   22314篇
  1975年   20957篇
  1974年   20615篇
  1973年   21131篇
  1972年   15355篇
  1968年   13076篇
  1967年   13121篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Shavgulidze  N. E. 《Mathematical Notes》2021,110(1-2):297-300
Mathematical Notes -  相似文献   
102.
103.
A formal computation proving a new operator identity from known ones is, in principle, restricted by domains and codomains of linear operators involved, since not any two operators can be added or composed. Algebraically, identities can be modelled by noncommutative polynomials and such a formal computation proves that the polynomial corresponding to the new identity lies in the ideal generated by the polynomials corresponding to the known identities. In order to prove an operator identity, however, just proving membership of the polynomial in the ideal is not enough, since the ring of noncommutative polynomials ignores domains and codomains. We show that it suffices to additionally verify compatibility of this polynomial and of the generators of the ideal with the labelled quiver that encodes which polynomials can be realized as linear operators. Then, for every consistent representation of such a quiver in a linear category, there exists a computation in the category that proves the corresponding instance of the identity. Moreover, by assigning the same label to several edges of the quiver, the algebraic framework developed allows to model different versions of an operator by the same indeterminate in the noncommutative polynomials.  相似文献   
104.
Journal of Communications Technology and Electronics - Abstract—The matrix coefficients of projection models of strip lines obtained using the Chebyshev basis are presented as a sum of...  相似文献   
105.
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   
106.
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   
107.
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   
108.
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   
109.
David Hull     
Journal of Optimization Theory and Applications -  相似文献   
110.
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   
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