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   5901篇
  免费   127篇
化学   3231篇
晶体学   31篇
力学   131篇
数学   1352篇
物理学   1283篇
  2021年   35篇
  2020年   45篇
  2019年   50篇
  2018年   141篇
  2017年   128篇
  2016年   201篇
  2015年   144篇
  2014年   197篇
  2013年   477篇
  2012年   295篇
  2011年   402篇
  2010年   213篇
  2009年   193篇
  2008年   335篇
  2007年   331篇
  2006年   307篇
  2005年   226篇
  2004年   196篇
  2003年   141篇
  2002年   134篇
  2001年   96篇
  2000年   80篇
  1999年   57篇
  1998年   52篇
  1997年   48篇
  1996年   49篇
  1995年   47篇
  1994年   28篇
  1993年   41篇
  1992年   56篇
  1991年   43篇
  1990年   48篇
  1989年   52篇
  1988年   48篇
  1987年   48篇
  1986年   41篇
  1985年   60篇
  1984年   67篇
  1983年   64篇
  1982年   61篇
  1981年   41篇
  1980年   53篇
  1979年   47篇
  1978年   68篇
  1977年   39篇
  1976年   52篇
  1975年   41篇
  1974年   48篇
  1973年   40篇
  1972年   33篇
排序方式: 共有6028条查询结果,搜索用时 15 毫秒
1.
Nonlinear Dynamics - Two types of constitutive equations consisting of instantaneous and power type hereditary contributions are proposed in order to model generalized capacitor (inductor). The...  相似文献   
2.
Journal of Solid State Electrochemistry - The synergistic effects between two Keggin-type heteropoly acids (HPAs) and carbon surface were examined and elucidated. An improved high rate capability...  相似文献   
3.
Nonlinear Dynamics - We generalize previously obtained solutions to the generalized nonlinear Schrödinger equation (NLSE) with cubic-quintic nonlinearity and distributed coefficients to obtain...  相似文献   
4.
Strontium-based medications, such as strontium ranelate, have been suggested to have therapeutic effects in patients with osteoporosis. Strontium salts available off-shelf in stores across North America are assumed to provide similar effects as strontium ranelate and thus should lead to similar distributions of elemental strontium incorporated in bone. The objective of this study was to compare the spatial distribution of strontium in animal bones following the administration of strontium ranelate and strontium citrate. Seventeen-week-old Sprague–Dawley rats were split into three groups over 10 weeks and given 625 mg/kg/day of strontium ranelate and 676 mg/kg/day of strontium citrate; the control group received no additional supplementary strontium. The humeri were collected from all animals, and strontium distribution was mapped using 2D micro-XRF and 3D dual energy K-edge subtraction (KES) imaging. 2D and 3D elemental mapping methods demonstrated that strontium delivered during treatment by both salts had the same spatial distribution. 3D elemental strontium maps of treated animal bones showed that strontium was largely observed in the trabecular regions under the epiphyseal (growth) plate. The thickness of the strontium layers in both the strontium ranelate and strontium citrate sample was not significantly different (p = .9201). 2D micro-XRF and 3D dual-energy KES images effectively elucidated the spatial distribution of elemental strontium in calcified tissue. These methods provide a novel approach to evaluating the potential efficacy of strontium supplements in the treatment of osteoporosis.  相似文献   
5.
ABSTRACT

We consider the nonsteady flow of a micropolar fluid in a thin (or long) curved pipe via rigorous asymptotic analysis. Germano's reference system is employed to describe the pipe's geometry. After writing the governing equations in curvilinear coordinates, we construct the asymptotic expansion up to a second order. Obtained in the explicit form, the asymptotic approximation clearly demonstrates the effects of pipe's distortion, micropolarity and the time derivative. A detailed study of the boundary layers in space is provided as well as the construction of the divergence correction. Finally, a rigorous justification of the proposed effective model is given by proving the error estimates.  相似文献   
6.
7.
8.
9.
10.
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