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   1330269篇
  免费   29726篇
  国内免费   7752篇
化学   662487篇
晶体学   20332篇
力学   74581篇
综合类   109篇
数学   242158篇
物理学   368080篇
  2021年   13564篇
  2020年   15998篇
  2019年   16107篇
  2018年   12694篇
  2016年   27957篇
  2015年   20902篇
  2014年   30547篇
  2013年   74656篇
  2012年   37470篇
  2011年   34139篇
  2010年   37023篇
  2009年   39461篇
  2008年   33613篇
  2007年   29275篇
  2006年   35278篇
  2005年   28006篇
  2004年   29195篇
  2003年   27636篇
  2002年   28788篇
  2001年   27225篇
  2000年   24147篇
  1999年   22190篇
  1998年   20928篇
  1997年   20986篇
  1996年   21109篇
  1995年   19183篇
  1994年   18640篇
  1993年   18196篇
  1992年   17975篇
  1991年   18318篇
  1990年   17445篇
  1989年   17540篇
  1988年   17092篇
  1987年   17105篇
  1986年   16005篇
  1985年   22451篇
  1984年   23765篇
  1983年   19935篇
  1982年   21661篇
  1981年   20890篇
  1980年   20255篇
  1979年   20367篇
  1978年   21709篇
  1977年   21281篇
  1976年   21008篇
  1975年   19678篇
  1974年   19337篇
  1973年   19783篇
  1972年   14292篇
  1967年   12543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