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   1374643篇
  免费   30122篇
  国内免费   7683篇
化学   687510篇
晶体学   20560篇
力学   75537篇
综合类   106篇
数学   248385篇
物理学   380350篇
  2021年   13683篇
  2020年   16177篇
  2019年   16358篇
  2018年   14455篇
  2017年   12850篇
  2016年   29265篇
  2015年   21532篇
  2014年   31118篇
  2013年   75827篇
  2012年   40466篇
  2011年   38520篇
  2010年   38838篇
  2009年   40995篇
  2008年   36913篇
  2007年   32910篇
  2006年   37436篇
  2005年   30438篇
  2004年   31291篇
  2003年   29165篇
  2002年   30017篇
  2001年   29562篇
  2000年   25464篇
  1999年   22909篇
  1998年   21300篇
  1997年   21257篇
  1996年   21344篇
  1995年   19364篇
  1994年   18845篇
  1993年   18392篇
  1992年   18474篇
  1991年   18674篇
  1990年   17881篇
  1989年   17891篇
  1988年   17443篇
  1987年   17423篇
  1986年   16384篇
  1985年   22788篇
  1984年   23993篇
  1983年   20139篇
  1982年   21784篇
  1981年   20995篇
  1980年   20342篇
  1979年   20571篇
  1978年   21816篇
  1977年   21402篇
  1976年   21122篇
  1975年   19775篇
  1974年   19410篇
  1973年   19869篇
  1972年   14340篇
排序方式: 共有10000条查询结果,搜索用时 140 毫秒
101.
102.
Russian Physics Journal - The specific features of the sorption activity of silver nanoparticles (AgNPs) on biodegradable polymers of natural (collagen) and artificial (polyamide 6.6) origin have...  相似文献   
103.
104.
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   
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.
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   
107.
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   
108.
David Hull     
Journal of Optimization Theory and Applications -  相似文献   
109.
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   
110.
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