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   830篇
  免费   29篇
  国内免费   8篇
化学   654篇
晶体学   16篇
力学   15篇
数学   51篇
物理学   131篇
  2023年   3篇
  2022年   5篇
  2021年   11篇
  2020年   8篇
  2019年   12篇
  2018年   8篇
  2017年   6篇
  2016年   20篇
  2015年   23篇
  2014年   15篇
  2013年   44篇
  2012年   28篇
  2011年   47篇
  2010年   24篇
  2009年   40篇
  2008年   48篇
  2007年   51篇
  2006年   56篇
  2005年   43篇
  2004年   52篇
  2003年   35篇
  2002年   44篇
  2001年   21篇
  2000年   23篇
  1999年   11篇
  1998年   17篇
  1997年   11篇
  1996年   13篇
  1994年   6篇
  1993年   5篇
  1992年   12篇
  1991年   9篇
  1990年   9篇
  1989年   11篇
  1988年   4篇
  1987年   5篇
  1986年   7篇
  1985年   6篇
  1984年   6篇
  1983年   5篇
  1982年   7篇
  1981年   10篇
  1980年   9篇
  1979年   6篇
  1978年   3篇
  1977年   5篇
  1975年   4篇
  1974年   2篇
  1973年   7篇
  1972年   6篇
排序方式: 共有867条查询结果,搜索用时 15 毫秒
131.
132.
133.
We prove that there do not exist CR submanifolds Mn of maximal CR dimension of a complex projective space \({\mathbf{P}^{\frac{n+p}{2}}(\mathbf{C})}\) with flat normal connection D of M, when the distinguished normal vector field is parallel with respect to D. If D is lift-flat, then there exists a totally geodesic complex projective subspace \({\mathbf{P}^{\frac{n+1}{2}}(\mathbf{C})}\) of \({\mathbf{P}^{\frac{n+p}{2}}(\mathbf{C})}\) such that M is a real hypersurface of \({\mathbf{P}^{\frac{n+1}{2}}(\mathbf{C})}\).  相似文献   
134.
Summary: We developed a new method for synthesizing an organic-soluble permethylated cyclodextrin-based insulated molecular wire (IMW); this method involves the polymerization of a symmetrical linked inclusion complex as a monomer. This monomer was synthesized by dimerization of linked inclusion complexes at the terminal alkynyl groups by Glaser coupling. The polyrotaxane thus obtained is highly soluble in a variety of organic solvents and has a high covering ratio, regioregularity, and photoluminescence efficiency.  相似文献   
135.
Several criteria for existence of smooth densities of Wiener functionals are known in the framework of Malliavin calculus. In this article, we introduce the notion of generalized locally non-degenerate Wiener functionals and prove that they possess smooth densities. The result presented here unifies the earlier works by Shigekawa and Florit-Nualart. As an application, we prove that the law of the strong solution to a stochastic differential equation driven by Brownian motion admits a smooth density without an assumption of Lipschitz continuity for dispersion coefficients.  相似文献   
136.
Abstract

A generalized Fourier–Gauss transform is an operator acting in a Boson Fock space and is formulated as a continuous linear operator acting on the space of test white noise functions. It does not admit, in general, a unitary extension with respect to the norm of the Boson Fock space induced from the Gaussian measure with variance 1 but is extended to a unitary isomorphism if the Gaussian measure is replaced with the ones with different covariance operators. As an application, unitarity of a generalized dilation is discussed.  相似文献   
137.
We have realized the microscopic simulation of olefin polymerization, that is, the simulation of the catalytic polymerization (CP) reaction system composed of (pyridylamido)hafnium(IV) complex as the catalyst. For this purpose, we adopted Red Moon (RM) method, a novel molecular simulation method to simulate the complex reaction system. First, according to the previous research, with the help of the QM calculation, we proposed a model system and elementary processes and explained the theoretical treatment of the simulation by the RM method (the RM simulation). In addition, we also proposed a macroscopic simulation based on chemical kinetics simulation. Then, we performed two simulations and compared them in terms of the effective time evolution of the three macroscopic physical quantities, the number-average molecular weight Mn , the mass-average molecular weight Mw , and the molar-mass dispersity ĐM . The comparison showed that the two simulations are in quantitative or partially qualitative agreement with each other. Therefore, it is concluded that the RM simulation could not only simulate the CP reaction process microscopically, but also it is connected essentially to reproduce the time evolution of the macroscopic physical quantities on the basis of its microscopic simulation data. © 2018 Wiley Periodicals, Inc.  相似文献   
138.
We propose an improvement of the replica-exchange and replica-permutation methods, which we call the replica sub-permutation method (RSPM). Instead of considering all permutations, this method uses a new algorithm referred to as sub-permutation to perform parameter transition. The RSPM succeeds in reducing the number of combinations between replicas and parameters without the loss of sampling efficiency. For comparison, we applied the replica sub-permutation, replica-permutation, and replica-exchange methods to a β-hairpin mini protein, chignolin, in explicit water. We calculated the transition ratio and number of tunneling events in the parameter space, the number of folding–unfolding events, the autocorrelation function, and the autocorrelation time as measures of sampling efficiency. The results indicate that among the three methods, the proposed RSPM is the most efficient in both parameter and conformational spaces. © 2019 Wiley Periodicals, Inc.  相似文献   
139.
Embedded silicon carbon alloy (e-Si:C) technology for source and drain (S/D) is expected to improve nMOSFET drive current. The distribution and activation characteristics of arsenic in Si:C film and the interfacial solid-phase reaction of the Ni/Si:C system were studied with the aim of achieving the maximum improvement of the characteristics of e-Si:C S/D. It was clarified that the active carrier concentration of Si:C decreased with increasing carbon concentration compared to the control Si. There is concern that the low doping activation in Si:C increases series resistance of e-Si:C S/D nMOSFETs and degrades the performance gain expected from the strain effect.  相似文献   
140.
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