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   1362606篇
  免费   29681篇
  国内免费   7757篇
化学   685105篇
晶体学   20298篇
力学   75025篇
综合类   105篇
数学   242339篇
物理学   377172篇
  2021年   13503篇
  2020年   15945篇
  2019年   16078篇
  2018年   12689篇
  2016年   28013篇
  2015年   20784篇
  2014年   30499篇
  2013年   74458篇
  2012年   39374篇
  2011年   37085篇
  2010年   37441篇
  2009年   39627篇
  2008年   36133篇
  2007年   31857篇
  2006年   38078篇
  2005年   30487篇
  2004年   31626篇
  2003年   29462篇
  2002年   30430篇
  2001年   30220篇
  2000年   25986篇
  1999年   23074篇
  1998年   21224篇
  1997年   21202篇
  1996年   21221篇
  1995年   19302篇
  1994年   18713篇
  1993年   18282篇
  1992年   18387篇
  1991年   18700篇
  1990年   17812篇
  1989年   17871篇
  1988年   17359篇
  1987年   17365篇
  1986年   16308篇
  1985年   22692篇
  1984年   23874篇
  1983年   20032篇
  1982年   21702篇
  1981年   20911篇
  1980年   20241篇
  1979年   20478篇
  1978年   21752篇
  1977年   21363篇
  1976年   21132篇
  1975年   19831篇
  1974年   19477篇
  1973年   19990篇
  1972年   14471篇
  1967年   12639篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
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   
83.
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   
84.
Shavgulidze  N. E. 《Mathematical Notes》2021,110(1-2):297-300
Mathematical Notes -  相似文献   
85.
86.
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   
87.
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   
88.
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   
89.
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   
90.
David Hull     
Journal of Optimization Theory and Applications -  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