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   28815篇
  免费   812篇
  国内免费   236篇
化学   19600篇
晶体学   129篇
力学   664篇
综合类   1篇
数学   5411篇
物理学   4058篇
  2022年   183篇
  2021年   282篇
  2020年   360篇
  2019年   328篇
  2018年   282篇
  2017年   297篇
  2016年   610篇
  2015年   628篇
  2014年   668篇
  2013年   1428篇
  2012年   1438篇
  2011年   1739篇
  2010年   965篇
  2009年   831篇
  2008年   1501篇
  2007年   1495篇
  2006年   1587篇
  2005年   1415篇
  2004年   1348篇
  2003年   1112篇
  2002年   1066篇
  2001年   460篇
  2000年   418篇
  1999年   398篇
  1998年   390篇
  1997年   438篇
  1996年   403篇
  1995年   363篇
  1994年   399篇
  1993年   350篇
  1992年   328篇
  1991年   326篇
  1990年   287篇
  1989年   285篇
  1988年   264篇
  1987年   227篇
  1986年   257篇
  1985年   373篇
  1984年   373篇
  1983年   318篇
  1982年   351篇
  1981年   326篇
  1980年   342篇
  1979年   273篇
  1978年   304篇
  1977年   281篇
  1976年   225篇
  1975年   191篇
  1974年   200篇
  1973年   166篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
A new parallel storm surge model, the Parallel Environmental Model (PEM), is developed and tested by comparisons with analytic solutions. The PEM is a 2‐D vertically averaged, wetting and drying numerical model and can be operated in explicit, semi‐implicit and fully implicit modes. In the implicit mode, the propagation, Coriolis and bottom friction terms can all be treated implicitly. The advection and diffusion terms are solved with a parallel Eulerian–Lagrangian scheme developed for this study. The model is developed specifically for use on parallel computer systems and will function accordingly in either explicit of implicit modes. Storm boundary conditions are based on a simple exponential decay of pressure from the centre of a storm. The simulated flooding caused by a major Category 5 hurricane making landfall in the Indian River Lagoon, Florida is then presented as an example application of the PEM. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   
62.
A column-switching high-performance liquid chromatographic method with fluorescence detection was developed for the simultaneous determination of four benzamide-type anti-psychotic drugs: sulpiride, tiapride, sultopride and metoclopramide in human serum. In this method, a TSKgel Super-ODS column was used as an analytical column, and a TSKgel G 2000SW was prepared as a pretreatment column. Under the optimized analytical conditions, four benzamide-type anti-psychotic drugs were eluted within 18 min. The detection limits (S/N = 3) for sulpiride, tiapride, sultopride and metoclopramide are 1 ng/ml, 4 ng/ml, 2 ng/ml and 0.5 ng/ml, respectively. Finally, the method was applied to the determination of sulpiride in human serum samples obtained after a single oral dose of sulpiride.  相似文献   
63.
Duality principles in Gabor theory such as the Ron–Shen duality principle and the Wexler–Raz biorthogonality relations play a fundamental role for analyzing Gabor systems. In this article we present a general approach to derive duality principles in abstract frame theory. For each sequence in a separable Hilbert space we define a corresponding sequence dependent only on two orthonormal bases. Then we characterize exactly properties of the first sequence in terms of the associated one, which yields duality relations for the abstract frame setting. In the last part we apply our results to Gabor systems.  相似文献   
64.
Deformation quantization is a powerful tool for quantizing theories with bosonic and fermionic degrees of freedom. The star products involved generate the mathematical structures which have recently been used in attempts to analyze the algebraic properties of quantum field theory. In the context of quantum mechanics they provide a quantization procedure for systems with either bosonic or fermionic degrees of freedom. We illustrate this procedure for a number of physical examples, including bosonic, fermionic, and supersymmetric oscillators. We show how non-relativistic and relativistic particles with spin can be naturally described in this framework.  相似文献   
65.
Since a comprehensive survey published in 1999 [1] much work was done in standardizing measuring methods to characterize the surface geometry of dispersed and/or porous solids and to certify reference materials. The present paper is an extension of a short communication [2]. It gives a survey on existing standards and reports on new drafts and proposals.  相似文献   
66.
67.
68.
We exhibit timelike geodesic paths for a metric, introduced by Bonnor [11] and considered also by Steadman [13], and show that coordinate time runs backward along a portion of these geodesics.  相似文献   
69.
70.
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