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   1511057篇
  免费   32111篇
  国内免费   8290篇
化学   654411篇
晶体学   20205篇
力学   74349篇
综合类   104篇
数学   239971篇
物理学   366610篇
无线电   195808篇
  2021年   14751篇
  2020年   17362篇
  2019年   17531篇
  2018年   13298篇
  2016年   29629篇
  2015年   21765篇
  2014年   32755篇
  2013年   78551篇
  2012年   39209篇
  2011年   35409篇
  2010年   39211篇
  2009年   44216篇
  2008年   38841篇
  2007年   35767篇
  2006年   42957篇
  2005年   34812篇
  2004年   36619篇
  2003年   34643篇
  2002年   35610篇
  2001年   34391篇
  2000年   30913篇
  1999年   28637篇
  1998年   27330篇
  1997年   27204篇
  1996年   26829篇
  1995年   24614篇
  1994年   24067篇
  1993年   23464篇
  1992年   23041篇
  1991年   23297篇
  1990年   22050篇
  1989年   21693篇
  1988年   20858篇
  1987年   19617篇
  1986年   18427篇
  1985年   24978篇
  1984年   26168篇
  1983年   22170篇
  1982年   23622篇
  1981年   22814篇
  1980年   22076篇
  1979年   21887篇
  1978年   23198篇
  1977年   22745篇
  1976年   22349篇
  1975年   21040篇
  1974年   20645篇
  1973年   21178篇
  1972年   15368篇
  1967年   13124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