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   265篇
  免费   5篇
  国内免费   2篇
化学   85篇
晶体学   2篇
力学   2篇
数学   152篇
物理学   31篇
  2023年   1篇
  2022年   2篇
  2021年   5篇
  2020年   2篇
  2019年   4篇
  2018年   2篇
  2017年   4篇
  2016年   5篇
  2015年   4篇
  2014年   7篇
  2013年   39篇
  2012年   22篇
  2011年   13篇
  2010年   13篇
  2009年   14篇
  2008年   18篇
  2007年   8篇
  2006年   14篇
  2005年   12篇
  2004年   2篇
  2003年   7篇
  2002年   16篇
  2001年   4篇
  2000年   2篇
  1999年   1篇
  1998年   2篇
  1997年   2篇
  1996年   8篇
  1995年   1篇
  1994年   3篇
  1993年   3篇
  1992年   1篇
  1990年   1篇
  1989年   3篇
  1986年   1篇
  1985年   2篇
  1984年   2篇
  1983年   3篇
  1982年   3篇
  1981年   5篇
  1980年   1篇
  1979年   1篇
  1978年   1篇
  1977年   1篇
  1976年   2篇
  1975年   1篇
  1973年   1篇
  1970年   1篇
  1948年   2篇
排序方式: 共有272条查询结果,搜索用时 171 毫秒
71.
The existence of life on a free-floating planet is conditioned by the existence of an optically thick atmosphere. This may ensure the long-term thermal stability of a (liquid) solvent on the surface of that body. Requirements to be fulfilled by a hypothetic gas constituent of a free-floating planet atmosphere are studied. The four gases analyzed here (nitrogen, carbon dioxide, methane and ethane) are candidates. They may induce a higher opacity than molecular hydrogen, which has been considered in previous research. The paper deals with preparation of tables of Rosseland mean opacity values. Selection of the ranges of temperature and pressure is guided by life existence considerations. The range of temperatures involved (50 to 650 K) is lower than usually found in the literature. The tables may be useful for studies related to free-floating planets, where the usage of absorption opacity is a straightforward way to compute the energy flux in the atmosphere. Also, the results are useful in all cases where radiation is transferred through dense layers of the gases considered in this paper.  相似文献   
72.
In this paper we prove the internal feedback stabilization of steady-state solutions of semilinear parabolic equations and introduce a controller synthesis methodology based on finite element approximations of the original PDEs. Numerical tests are given for some one- and two-dimensional nonlinear parabolic equations.  相似文献   
73.
In the present work we show that the local generalized monotonicity of a lower semicontinuous set-valued operator on some certain type of dense sets ensures the global generalized monotonicity of that operator. We achieve this goal gradually by showing at first that the lower semicontinuous set-valued functions of one real variable, which are locally generalized monotone on a dense subsets of their domain are globally generalized monotone. Then, these results are extended to the case of set-valued operators on arbitrary Banach spaces. We close this work with a section on the global generalized convexity of a real valued function, which is obtained out of its local counterpart on some dense sets.  相似文献   
74.
We give a formula for the one-parameter strongly continuous semigroups ${e^{-tL^{\lambda}}}We give a formula for the one-parameter strongly continuous semigroups e-tLl{e^{-tL^{\lambda}}} and e-t [(A)\tilde]{e^{-t \tilde{A}}}, t > 0 generated by the generalized Hermite operator Ll, l ? R\{0}{L^{\lambda}, \lambda \in {\bf R}\backslash \{0\}} respectively by the generalized Landau operator ?. These formula are derived by means of pseudo-differential operators of the Weyl type, i.e. Weyl transforms, Fourier-Wigner transforms and Wigner transforms of some orthonormal basis for L 2(R 2n ) which consist of the eigenfunctions of the generalized Hermite operator and of the generalized Landau operator. Applications to an L 2 estimate for the solutions of initial value problems for the heat equations governed by L λ respectively ?, in terms of L p norm, 1 ≤ p ≤ ∞ of the initial data are given.  相似文献   
75.
In the present paper, using a Picard Type method of approximation, we investigate the global existence of mild solutions for a class of Ito Type stochastic differential equations whose coefficients satisfy conditions more general than the Lipschitz and linear growth ones.  相似文献   
76.
The paper studies the motion laws influence over the VIPAS1 industrial robot working. The motion differential equations, that govern the motion robot were established. Using them we can study the direct problem for the robot dynamics. There are the given motion laws for the accelerated and decreasing motion having triangular, trapezoidal and parabolic forms. The graphics of the forces and moments give us the possibility to make some recommandations under energetic aspects, for the optimal solutions about the VIPAS1 industrial robot. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   
77.
A series of cyclometallated 2-phenylpyridine Pt(II) complexes having N-benzoyl thiourea derivatives as ancillary ligands were prepared and characterised by elemental analysis, IR and UV–Vis spectroscopy, 1H and 13C NMR spectroscopy as well as by X-ray diffraction on single-crystal. All complexes were obtained as a single isomer with N atom of the 2-phenylpyridine ligand and S atom of the N-benzoyl thiourea derivatives coordinated in trans positions to the platinum metal as evidenced by using X-ray crystallography and NMR spectroscopy. All Pt(II) complexes show good luminescence properties at room temperature, both in dichloromethane solution and in solid state.  相似文献   
78.
We prove the existence of a solution for the obstacle problem associated with the Kolmogorov operator corresponding to the stopping-time problem for stochastic Navier–Stokes equations in 2-D.  相似文献   
79.
The SEM microfractographies of Zircaloy-4 are studied by the time-series method. We first develop a computer application which associates a time series to each SEM micrograph. Furthermore, we will apply the phase space embedding technique to reconstruct the attractor and to compute the autocorrelation dimension. Using the fractal analysis technique, the SEM microfractographies of the fracture surface of the Zircaloy-4 samples have been analyzed.   相似文献   
80.
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