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   1401840篇
  免费   30563篇
  国内免费   8465篇
化学   712012篇
晶体学   20634篇
力学   75885篇
综合类   161篇
数学   245752篇
物理学   386424篇
  2021年   13626篇
  2020年   16072篇
  2019年   16160篇
  2018年   13790篇
  2016年   28539篇
  2015年   21113篇
  2014年   30669篇
  2013年   74920篇
  2012年   41753篇
  2011年   41008篇
  2010年   39152篇
  2009年   41005篇
  2008年   39435篇
  2007年   35781篇
  2006年   40497篇
  2005年   33486篇
  2004年   33573篇
  2003年   31130篇
  2002年   31824篇
  2001年   31530篇
  2000年   26771篇
  1999年   23495篇
  1998年   21427篇
  1997年   21374篇
  1996年   21348篇
  1995年   19364篇
  1994年   18825篇
  1993年   18394篇
  1992年   18616篇
  1991年   18887篇
  1990年   18034篇
  1989年   18061篇
  1988年   17632篇
  1987年   17559篇
  1986年   16536篇
  1985年   22943篇
  1984年   24053篇
  1983年   20178篇
  1982年   21820篇
  1981年   20997篇
  1980年   20389篇
  1979年   20684篇
  1978年   21883篇
  1977年   21537篇
  1976年   21368篇
  1975年   20046篇
  1974年   19761篇
  1973年   20238篇
  1972年   14696篇
  1967年   12823篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
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   
92.
David Hull     
Journal of Optimization Theory and Applications -  相似文献   
93.
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   
94.
Journal of Applied Mechanics and Technical Physics - A refined model of viscoelastic-plastic deformation of flexible plates with spatial reinforcement structures has been developed. Strains of the...  相似文献   
95.
Crystallography Reports - The recombinant С-terminal fragment of myomesin-2 was purified to a homogeneous state. The crystallization conditions for the С-terminal fragment of myomesin-2...  相似文献   
96.
Faul  Peter F. 《Semigroup Forum》2021,102(3):655-673
Semigroup Forum - It is well known that the set of isomorphism classes of extensions of groups with abelian kernel is characterized by the second cohomology group. In this paper we generalise this...  相似文献   
97.
Kumar  Sanjay  Jiwari  Ram  Mittal  R. C.  Awrejcewicz  Jan 《Nonlinear dynamics》2021,104(1):661-682
Nonlinear Dynamics - In this article, the authors simulate and study dark and bright soliton solutions of 1D and 2D regularized long wave (RLW) models. The RLW model occurred in various fields such...  相似文献   
98.
Mejjaoli  H.  Ben Saïd  S. 《Analysis Mathematica》2021,47(3):629-663
Analysis Mathematica - We introduce and study the k-Hankel Gabor transform. We investigate the localization operators for this transform. In particular, we study their trace class properties and we...  相似文献   
99.
Chen  C. Y.  Kao  C. L.  Huang  S. T.  Kuo  C. E.  Song  P. L.  Li  W. J.  Hsu  L. T.  Li  H. T. 《Chemistry of Natural Compounds》2022,58(1):107-109
Chemistry of Natural Compounds -  相似文献   
100.
Pentafluorosulfanyl (SF5)-containing compounds and corresponding analogs are a highly valuable class of fluorine-containing building blocks owing to their unique properties. The reason for that is the set of peculiar and tremendously beneficial characteristics they can impart on molecules once introduced onto them. Despite this, their application in distinct scientific fields remains modest, given the extremely harsh reaction conditions needed to access such compounds. The recent synthetic approaches via S−F, and C−SF5 bond formation as well as the use of SF5-containing building blocks embody a “stairway-to-heaven” loophole in the synthesis of otherwise-inaccessible chemical scaffolds only a few years ago. Herein, we report and evaluate the properties of the SF5 group and analogs, by summarizing synthetic methodologies available to access them as well as following applications in material science and medicinal chemistry since 2015.  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