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   203881篇
  免费   1955篇
  国内免费   592篇
化学   102326篇
晶体学   3340篇
力学   9287篇
综合类   5篇
数学   22470篇
物理学   69000篇
  2021年   1655篇
  2020年   1797篇
  2019年   1998篇
  2018年   2699篇
  2017年   2601篇
  2016年   3765篇
  2015年   2304篇
  2014年   3613篇
  2013年   9084篇
  2012年   7240篇
  2011年   8735篇
  2010年   6041篇
  2009年   5909篇
  2008年   7911篇
  2007年   8081篇
  2006年   7724篇
  2005年   6892篇
  2004年   6426篇
  2003年   5653篇
  2002年   5494篇
  2001年   6424篇
  2000年   4932篇
  1999年   3794篇
  1998年   3038篇
  1997年   3045篇
  1996年   2791篇
  1995年   2613篇
  1994年   2464篇
  1993年   2337篇
  1992年   2691篇
  1991年   2671篇
  1990年   2600篇
  1989年   2396篇
  1988年   2449篇
  1987年   2448篇
  1986年   2279篇
  1985年   2960篇
  1984年   3215篇
  1983年   2631篇
  1982年   2801篇
  1981年   2771篇
  1980年   2637篇
  1979年   2727篇
  1978年   2821篇
  1977年   2819篇
  1976年   2886篇
  1975年   2670篇
  1974年   2644篇
  1973年   2776篇
  1972年   1763篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
931.
932.
In this paper we discuss Sobolev bounds on functions that vanish at scattered points in a bounded, Lipschitz domain that satisfies a uniform interior cone condition. The Sobolev spaces involved may have fractional as well as integer order. We then apply these results to obtain estimates for continuous and discrete least squares surface fits via radial basis functions (RBFs). These estimates include situations in which the target function does not belong to the native space of the RBF.

  相似文献   

933.
The influence of the discharge conditions on the dynamics of energy release is considered for pulsed arcs in air at initial pressures from 105 to 8×105 Pa and a low-voltage capacitor voltage of up to 400 V. A novel method for determining the resistance of the discharge channel in the final stage of a spark discharge is proposed. The method is applied to estimating the discharge channel parameters.  相似文献   
934.
A holographic screen that makes it possible to display 3D images by the method of point-focused aspects (of a scene to be displayed) or by projecting narrow line holograms is suggested and implemented. The image thus formed reconstructs only horizontal parallax, which allows one to cut the body of information necessary for 3D imaging. Projection through the screen and a way of recording the screen are considered.  相似文献   
935.
Mauricio D Garay 《Topology》2004,43(5):1081-1088
We introduce a cohomological approach to isochore deformation problems. We use this formulation in order to prove an isochore versal deformation theorem for holomorphic function germs.  相似文献   
936.
We find necessary and sufficient conditions for any two congruences on an antigroup of finite rank to be permutable.  相似文献   
937.
We describe hybrid manufacturing/remanufacturing systems with a long lead time for manufacturing and a short lead time for remanufacturing. We review the classes of inventory strategies for hybrid systems in the literature. These are all based on equal lead times. For systems with slow manufacturing and fast remanufacturing, we propose a new class. An extensive numerical experiment shows that the optimal strategy in the new class almost always performs better and often much better than the optimal strategies in all other classes.  相似文献   
938.
939.
Gamma-ray induced X-ray emission (GIXE) technique for elemental lead in-vivo tibial measurement using a large volume hyper pure germanium detector is presented with the most convenient source-sample-detector geometry. The system operates advantageously when several parameters are considered for a lower dead time operation. The detection limit (DL) is better that 3.5 μg/g of Ca. Results of in-vivo average tibial lead concentration for some of the monitored groups are: control 7 μg of lead per g of Ca; gasoline filling attendants 6 μg/g of Ca; custom office workers near the DL; industrial workers range from DL up to 84±3 μg/g of Ca, suggesting that lead accumulation in the bone does not represent a major health risk This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   
940.
A novel liquid scintillator system using metal β-diketonate chemistry based on loadings of indium, a target of current interest in low energy solar neutrino detection, is developed. The optical absorption, fluorescence and scintillation properties for this new system are described. The scintillation light output as found from the irradiation by low energy gamma-rays is presented. Notable light yields are found.  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