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   1957篇
  免费   32篇
  国内免费   23篇
化学   1576篇
晶体学   18篇
力学   17篇
数学   80篇
物理学   321篇
  2022年   7篇
  2021年   23篇
  2020年   23篇
  2019年   18篇
  2018年   17篇
  2017年   12篇
  2016年   23篇
  2015年   20篇
  2014年   33篇
  2013年   68篇
  2012年   99篇
  2011年   112篇
  2010年   71篇
  2009年   75篇
  2008年   108篇
  2007年   116篇
  2006年   119篇
  2005年   132篇
  2004年   115篇
  2003年   107篇
  2002年   90篇
  2001年   31篇
  2000年   18篇
  1999年   31篇
  1998年   30篇
  1997年   23篇
  1996年   36篇
  1995年   20篇
  1994年   12篇
  1993年   13篇
  1992年   16篇
  1991年   14篇
  1990年   8篇
  1989年   18篇
  1988年   16篇
  1987年   18篇
  1986年   7篇
  1985年   22篇
  1984年   28篇
  1983年   10篇
  1982年   27篇
  1981年   24篇
  1980年   19篇
  1979年   26篇
  1978年   22篇
  1977年   26篇
  1976年   16篇
  1975年   14篇
  1974年   13篇
  1973年   20篇
排序方式: 共有2012条查询结果,搜索用时 656 毫秒
141.
We report the development of a novel form of diffraction-based 3D microscopy to overcome resolution barriers inherent in high-resolution electron microscopy and tomography. By combining coherent electron diffraction with the oversampling phasing method, we show that the 3D structure of a nanocrystal can be determined ab initio at a resolution of 1 A from 29 simulated noisy diffraction patterns. This new form of microscopy can be used to image the 3D structures of nanocrystals and noncrystalline samples, with resolution limited only by the quality of sample diffraction.  相似文献   
142.
The objective of this study was to assess the effect of comprehensive exercise program widely accepted as a community-based physical intervention for the prevention of falling in the elderly persons on their controlling standing balance. Twenty-six community-dwelling elderly persons (13 males and females; 69.8 ± 2.8 years old) participated in this study. Daily exercise was comprised of walking for more than 30 min, stretching, muscle strengthening and balance exercise without exercise equipments. The intervention was continued for three months. Indicators of standing balance related to static balance, dynamic balance and postural response were measured before and after the intervention. As an effect of the intervention on static balance, the sway of center of pressure (COP) in the static stance significantly increased. In the dynamic balance, significant improvements were observed in one leg standing time, the 10-m gait time, functional reach. Additionally, the maximal movable length of COP which subjects can move voluntarily to right and left significantly increased. In the postural response, the integrated electromyography (IEMG) induced by postural response for sudden postural perturbation significantly decreased in the lower leg muscles. Since less muscular activities were sufficient to maintain posture, it was suggested that postural response was elicited more efficiently following the intervention. This study suggested that the comprehensive exercise program, which has been widely introduced as community-based interventions for the prevention of falling, have extensive effects on the control of standing balance covering static balance, dynamic balance and postural response in the elderly persons.  相似文献   
143.
144.
145.
146.
147.
An X-ray topographic method utilizing non-parallel (+,-) setting for measuring lattice mismatches between epitaxial films and substrates is reported. This method gives quantitative as well as topographical information on lattice distortions in a distorted crystal and allows us to study any reflection from various crystals, in which the fractional variation of lattice spacing, δd/d, is of the order of 10-4?10-5. Examples of applications are lattice mismatches between epitaxial magnetic garnet films and (111) gadolinium garnet (GGG) substrates. The spacing of the epitaxial film was slightly larger along the [111] direction than that of the substrate and the apparent crystal symmetry of the epitaxial film is rhombohedral.  相似文献   
148.
149.
The first titanium phosphate nanotubes with alternating interlayer spacings have been successfully prepared and characterized. The synthesis is accomplished in a reverse microemulsion formed in an amine extraction system. TEM data from samples made after different times of reaction suggest a scrolling-formation mechanism.  相似文献   
150.
Use of the grid points of the Gauss-Legendre numerical quadrature is examined as the exponent parameters of the basis functions of atomic Hartree-Fock wavefunctions. Calculations on He, Be, and Ne have been performed and reasonably accurate wavefunctions are obtained using 20 grid points or basis functions per symmetry species without any optimization of non-linear parameters.  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