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   1490篇
  免费   35篇
  国内免费   7篇
化学   1052篇
晶体学   4篇
力学   65篇
数学   235篇
物理学   176篇
  2023年   7篇
  2022年   19篇
  2021年   40篇
  2020年   30篇
  2019年   27篇
  2018年   23篇
  2017年   24篇
  2016年   44篇
  2015年   21篇
  2014年   41篇
  2013年   69篇
  2012年   68篇
  2011年   89篇
  2010年   52篇
  2009年   58篇
  2008年   82篇
  2007年   106篇
  2006年   97篇
  2005年   76篇
  2004年   87篇
  2003年   51篇
  2002年   53篇
  2001年   14篇
  2000年   20篇
  1999年   10篇
  1998年   17篇
  1997年   14篇
  1996年   14篇
  1995年   20篇
  1994年   9篇
  1993年   14篇
  1992年   12篇
  1991年   17篇
  1990年   9篇
  1989年   9篇
  1988年   17篇
  1987年   5篇
  1986年   5篇
  1985年   12篇
  1984年   14篇
  1983年   9篇
  1982年   9篇
  1981年   16篇
  1980年   16篇
  1979年   17篇
  1978年   7篇
  1977年   5篇
  1976年   13篇
  1975年   6篇
  1974年   8篇
排序方式: 共有1532条查询结果,搜索用时 15 毫秒
171.
We prove the simplicity and analyticity of the eigenvalues of the cubic oscillator Hamiltonian, $$\begin{array}{ll}H(\beta)=-\frac{d^2}{dx^2}+x^2+i\sqrt{\beta}x^3\end{array}$$ , for β in the cut plane ${\mathcal{C}_c:=\mathcal{C}\backslash \mathcal{R}_-}$ . Moreover, we prove that the spectrum consists of the perturbative eigenvalues {E n (β)} n ≥ 0 labeled by the constant number n of nodes of the corresponding eigenfunctions. In addition, for all ${\beta \in \mathcal{C}_c, E_n(\beta)}$ can be computed as the Stieltjes-Padé sum of its perturbation series at β = 0. This also gives an alternative proof of the fact that the spectrum of H(β) is real when β is a positive number. This way, the main results on the repulsive PT-symmetric and on the attractive quartic oscillators are extended to the cubic case.  相似文献   
172.
The use of hyperbolic numbers for studying space-time geometry and trigonometry is extended for demonstrating the Frenet’s formulas in space-time. By means of this introduction the twin paradox for non-uniformly accelerated motions is formalized in a straightforward way.  相似文献   
173.
174.
We consider a non-linear Stark effect as a model for localization and symmetry breaking of a molecule in a gas. By a comparison method with respect to the linear Stark effect, we prove the existence of level bifurcation and symmetry breaking at a critical value of the gas pressure exponentially small for large nuclear masses. Extending the Davies results, we confirm the predictions of Claverie-Jona Lasinio for pyramidal molecules as the ammonia one.  相似文献   
175.
176.
177.
In recent publications, we have defined complexes of differential forms on analytic spaces which are resolutions of the constant sheaf. These complexes were used to prove the existence of a mixed Hodge structure on the cohomology of analytic spaces which possess kählerian hypercoverings, in particular, projective algebraic varieties. We define an exterior product on these forms, which induces the cup product on the cohomology of analytic spaces. The main difficulty is to prove that this exterior product is functorial with respect to morphisms of analytic spaces. This exterior product can be used to prove that the cup product is compatible with the mixed Hodge structure on the cohomology.  相似文献   
178.
The Eu3+ complexes of the tripode and tetrapode ligands 1 and 2 , respectively, containing 2,2′-bipyridine coordinating units have been prepared. The UV absorption and luminescence spectra, lifetimes, and quantum yields have been measured under a variety of experimental conditions. The contributions of different paths to the decay of the luminescent excited state are evaluated, and the structures of the complexes are discussed on the basis of spectroscopic and photophysical data.  相似文献   
179.
A device to be obtained by depositing a columnar thin-film on a transparent substrate decorated periodically by an array of rectangular grooves is proposed as a narrowband, linear-polarization rejection filter. The rigorous coupled-wave approach is harnessed to calculate the reflectances and transmittances. High-quality filters of chosen materials and with less than 2 nm bandwidths can be designed with a vapor flux angle for deposition of the columnar thin-film as the controlling parameter.  相似文献   
180.
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