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   1309767篇
  免费   29614篇
  国内免费   7752篇
化学   648259篇
晶体学   20434篇
力学   74418篇
综合类   107篇
数学   240009篇
物理学   363906篇
  2021年   13463篇
  2020年   15899篇
  2019年   16016篇
  2018年   13010篇
  2016年   27884篇
  2015年   20776篇
  2014年   30346篇
  2013年   74174篇
  2012年   36291篇
  2011年   32517篇
  2010年   36775篇
  2009年   39466篇
  2008年   32255篇
  2007年   27815篇
  2006年   33386篇
  2005年   26609篇
  2004年   27949篇
  2003年   26580篇
  2002年   27655篇
  2001年   25959篇
  2000年   23166篇
  1999年   21759篇
  1998年   20729篇
  1997年   20772篇
  1996年   20984篇
  1995年   19101篇
  1994年   18536篇
  1993年   18060篇
  1992年   17775篇
  1991年   18077篇
  1990年   17310篇
  1989年   17387篇
  1988年   16958篇
  1987年   16988篇
  1986年   15878篇
  1985年   22343篇
  1984年   23654篇
  1983年   19878篇
  1982年   21593篇
  1981年   20830篇
  1980年   20190篇
  1979年   20251篇
  1978年   21623篇
  1977年   21197篇
  1976年   20855篇
  1975年   19526篇
  1974年   19181篇
  1973年   19650篇
  1972年   14126篇
  1967年   12371篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Physics of Atomic Nuclei - The muon puzzle is an excess of muon bundles generated by primary cosmic rays (PCR) at energies above 10 $${}^{17}$$ eV compared to estimations that assume even a heavy...  相似文献   
82.
Taherian  A.  Toutounian  F. 《Numerical Algorithms》2021,88(4):1831-1850
Numerical Algorithms - In this paper, the block generalized product-type bi-conjugate gradient (GPBi-CG) method for solving large, sparse nonsymmetric linear systems of equations with multiple...  相似文献   
83.
Shavgulidze  N. E. 《Mathematical Notes》2021,110(1-2):297-300
Mathematical Notes -  相似文献   
84.
85.
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   
86.
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   
87.
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   
88.
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   
89.
David Hull     
Journal of Optimization Theory and Applications -  相似文献   
90.
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