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   1644篇
  免费   61篇
  国内免费   54篇
化学   418篇
晶体学   6篇
力学   320篇
综合类   7篇
数学   510篇
物理学   498篇
  2023年   8篇
  2022年   11篇
  2021年   19篇
  2020年   17篇
  2019年   73篇
  2018年   65篇
  2017年   46篇
  2016年   54篇
  2015年   60篇
  2014年   63篇
  2013年   93篇
  2012年   31篇
  2011年   53篇
  2010年   56篇
  2009年   98篇
  2008年   109篇
  2007年   74篇
  2006年   113篇
  2005年   113篇
  2004年   116篇
  2003年   101篇
  2002年   105篇
  2001年   23篇
  2000年   24篇
  1999年   27篇
  1998年   25篇
  1997年   17篇
  1996年   9篇
  1995年   10篇
  1994年   3篇
  1993年   7篇
  1992年   2篇
  1990年   2篇
  1989年   5篇
  1988年   3篇
  1986年   6篇
  1985年   10篇
  1984年   8篇
  1983年   2篇
  1982年   5篇
  1981年   16篇
  1980年   16篇
  1979年   6篇
  1978年   9篇
  1977年   10篇
  1976年   8篇
  1975年   10篇
  1974年   6篇
  1973年   3篇
  1957年   2篇
排序方式: 共有1759条查询结果,搜索用时 15 毫秒
101.
Let a open subset of n , n3, and an open. Existence and unicity are proved for the Dirichlet problem
It is assumed that the linear part of satisfy the conditions of Hervé, (·,u,u): ×× n satisfy Carathéodory's condition and structure conditions (H1), (H2) and (H3) below. Let H denote the sheaf of L-solutions, we prove that (,H) is a nonlinear Bauer harmonic space.  相似文献   
102.
Given D a domain in , G an open set in and E a subset of D verifying the harmonic analogue of Local Polynomial Condition of Leja at some point in D. We prove that if f(x, y) is a complex function defined on D × G such that– f(x, ) is harmonic on G for every fixed x E,– f(, y) is harmonic on D for every fixed y G,then f is harmonic in (x, y) on D × G.  相似文献   
103.
We analyze the asymptotic behavior of the rescaled solution to the linear Korteweg–de Vries equation when the initial conditions are supposed to be random and weakly dependent. By means of the method of moments we prove the Gaussianity of the limiting process and we present its correlation function. The same technique is applied to the analysis of another third-order heat-type equation.  相似文献   
104.
The strictly thermal spectrum in dragging coordinate system and the tunneling radiation characteristics of stationary axisymmetry Kerr-Newman de Sitter black hole is studied. The result shows that the tunneling rates at the event and cosmological horizon are related to the change of Bekenstein-Hawking entropy and that the factual radiation spectrum is not strictly pure thermal. Thus an exact correction to the Hawking thermal spectrum is present.  相似文献   
105.
In the late 1940s and the 1950s, Norwegian nuclear scientists, engineers, and administrators were deeply split over their nation’s goals, organization, politics, and tools for research in nuclear physics. One faction was determined to build a nuclear reactor in Norway, while another fiercely opposed the reactor plans and focused on particle accelerators. The first faction comprised scientific entrepreneurs and research technologists, the second academic scientists, most of whom began their research careers in nuclear physics in the 1930s. To understand this conflict, I trace the development of nuclear research in Norway from the early 1930s to the mid-1950s, placing it within an international context. Roland Wittje is working on his habilitation thesis in the History of Science Unit at the University of Regensburg, Germany.  相似文献   
106.
In an earlier article, Ghosh derived the density for the distance between two points uniformly and independently distributed in a rectangle. This article extends that work to include the case where the two points lie in two different rectangles in a lattice. This density allows one to find the expected value of certain functions of this distance between rectangles analytically or by one-dimensional numerical integration.

In the case of isotropic spatial models or spatial models with geometric anisotropy terms for agricultural experiments one can use these theoretical results to compute the covariance between the yields in different rectangular plots. As the numerical integration is one-dimensional these results are computed quickly and accurately. The types of covariance functions used come from the Matérn and power families of processes. Analytic results are derived for the de Wijs process, a member of both families and for the power models also.

Software in R is available. Examples of the code are given for fitting spatial models to the Fairfield Smith data. Other methods for the estimation of the covariance matrices are discussed and their pros and cons are outlined.  相似文献   
107.
Brandy and other aged distillates are a rich source of polyphenols. For brandies, contact with wood during ageing makes an important contribution to their polyphenols content. This paper describes the use of a previously devised ultra performance LC (UPLC) method to study the polyphenols content of Brandy de Jerez. UPLC is a new technique in LC offering several potential advantages, especially the reduction of time. Analyses of brandy performed by HPLC were repeated by UPLC. A special UPLC analytical column (Acquity UPLC BEH C18 column, 100×2.1 mm), with a particle size of 1.7 μm, forms part of this system. Using the UPLC system enabled the time needed for analysis to be reduced to one tenth of the time needed in the conventional HPLC system. In conclusion, the separation factor results of the UPLC were compared to those obtained using HPLC methods; this demonstrated that simple, high efficiency UPLC gradients are viable and advantageous substitutes for traditional analysis of polyphenols in brandy by HPLC. The method enabled 14 phenolic compounds to be identified and determined in 33 different commercial brandies, and this allowed them to be differentiated in function of quality.  相似文献   
108.
An iterative resolution method for inverse Cauchy problems is presented. The successive iterations satisfy the equilibrium equations exactly. Numerical simulations prove the accuracy of the method and its ability to solve Cauchy problems when the domain boundary is not regular. To cite this article: A. Cimetière et al., C. R. Mecanique 333 (2005).  相似文献   
109.
In the Shubnikov–de Haas oscillation spectrum of doped InAs/AlSb structures, high-amplitude peaks are established at combination frequencies. It is demonstrated that they are caused by a significant contribution of intersubband scattering to the processes of electron-electron interaction. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 32–38, December, 2008.  相似文献   
110.
P. Seibt 《K-Theory》1990,4(2):143-155
Local (cyclic) homology of filtered associative algebras is defined and discussed. In the commutative case, it fits naturally in the setting of (formal) de Rham cohomology; we thus obtain a satisfactory complement to a result of Feigin and Tsygan. There is a spectral sequence from discrete (cyclic) homology of the associated graded algebra to local (cyclic) homology of the original filtered algebra; we exhibit manageable conditions on its convergence.  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