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   1519690篇
  免费   43618篇
  国内免费   19186篇
化学   767702篇
晶体学   17682篇
力学   85936篇
综合类   764篇
数学   275373篇
物理学   435037篇
  2021年   16269篇
  2020年   18997篇
  2019年   19373篇
  2018年   23307篇
  2017年   22170篇
  2016年   35297篇
  2015年   25392篇
  2014年   35447篇
  2013年   80949篇
  2012年   51409篇
  2011年   56505篇
  2010年   49568篇
  2009年   51487篇
  2008年   51250篇
  2007年   49181篇
  2006年   43493篇
  2005年   40420篇
  2004年   37793篇
  2003年   34725篇
  2002年   34010篇
  2001年   32059篇
  2000年   27689篇
  1999年   24872篇
  1998年   22840篇
  1997年   22572篇
  1996年   22690篇
  1995年   20524篇
  1994年   19825篇
  1993年   19143篇
  1992年   19208篇
  1991年   18737篇
  1990年   17828篇
  1989年   17694篇
  1988年   17234篇
  1987年   17093篇
  1986年   16074篇
  1985年   22507篇
  1984年   23694篇
  1983年   19734篇
  1982年   21457篇
  1981年   20618篇
  1980年   19898篇
  1979年   20207篇
  1978年   21525篇
  1977年   21122篇
  1976年   20922篇
  1975年   19659篇
  1974年   19331篇
  1973年   19882篇
  1972年   14324篇
排序方式: 共有10000条查询结果,搜索用时 641 毫秒
111.
Li  Mingjun  Zhu  Li 《应用数学和力学(英文版)》2021,42(8):1171-1182
This study is to numerically test the interfacial instability of ferrofluid flow under the presence of a vacuum magnetic field. The ferrofluid parabolized stability equations(PSEs) are derived from the ferrofluid stability equations and the Rosensweig equations, and the characteristic values of the ferrofluid PSEs are given to describe the ellipticity of ferrofluid flow. Three numerical models representing specific cases considering with/without a vacuum magnetic field or viscosity are created to mathematically examine the interfacial instability by the computation of characteristic values. Numerical investigation shows strong dependence of the basic characteristic of ferrofluid Rayleigh-Taylor instability(RTI) on viscosity of ferrofluid and independence of the vacuum magnetic field.For the shock wave striking helium bubble, the magnetic field is not able to trigger the symmetry breaking of bubble but change the speed of the bubble movement. In the process of droplet formation from a submerged orifice, the collision between the droplet and the liquid surface causes symmetry breaking. Both the viscosity and the magnetic field exacerbate symmetry breaking. The computational results agree with the published experimental results.  相似文献   
112.
International Journal of Theoretical Physics - Quantum coherence, coming from quantum superposition, occupies a significant position in the field of physics. We put forward a lower bound of the...  相似文献   
113.
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   
114.
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   
115.
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   
116.
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   
117.
David Hull     
Journal of Optimization Theory and Applications -  相似文献   
118.
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   
119.
120.
Huang  Renpei  Chen  Li  Yuan  Xiaoru 《显形杂志》2021,24(2):317-330
Journal of Visualization - Forecast calibration methods based on historical similar atmospheric state are effective means weather forecast accuracy. Conventional approaches search similar forecasts...  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