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   8531篇
  免费   1327篇
  国内免费   669篇
化学   5736篇
晶体学   87篇
力学   503篇
综合类   36篇
数学   996篇
物理学   3169篇
  2024年   22篇
  2023年   163篇
  2022年   285篇
  2021年   296篇
  2020年   365篇
  2019年   303篇
  2018年   274篇
  2017年   260篇
  2016年   422篇
  2015年   428篇
  2014年   467篇
  2013年   600篇
  2012年   788篇
  2011年   750篇
  2010年   530篇
  2009年   488篇
  2008年   550篇
  2007年   418篇
  2006年   456篇
  2005年   332篇
  2004年   262篇
  2003年   220篇
  2002年   172篇
  2001年   137篇
  2000年   146篇
  1999年   174篇
  1998年   154篇
  1997年   127篇
  1996年   131篇
  1995年   112篇
  1994年   95篇
  1993年   79篇
  1992年   78篇
  1991年   76篇
  1990年   44篇
  1989年   38篇
  1988年   39篇
  1987年   35篇
  1986年   28篇
  1985年   21篇
  1984年   20篇
  1983年   20篇
  1982年   9篇
  1981年   14篇
  1980年   9篇
  1977年   6篇
  1976年   10篇
  1975年   9篇
  1973年   8篇
  1972年   6篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
931.
932.
933.
934.
935.
The micro mechanism of anti-Stokes fluorescent cooling was investigated on molecular or ionic scale. A new conception of single molecule-photon cryocooler (SMPC) was given, and the smallest cryocooler in the world was predicted. We described SMPC and its running principle in detail. The quantum transition processes of SMPC and the largest cooling coefficient that SMPC can get in an optical transition were given. Also we studied the random property of SMPC in cooling processes. The thermodynamic behavior of single Yb3+ ion as a photon cryocooler was imitated.  相似文献   
936.
In wireless networks, Connected Dominating Sets (CDSs) are widely used as virtual backbones for communications. On one hand, reducing the backbone size will reduce the maintenance overhead. So how to minimize the CDS size is a critical issue. On the other hand, when evaluating the performance of a wireless network, the hop distance between two communication nodes, which reflect the energy consumption and response delay, is of great importance. Hence how to minimize the routing cost is also a key problem for constructing the network virtual backbone. In this paper, we study the problem of constructing applicable CDS in wireless networks in terms of size and routing cost. We formulate a wireless network as a Disk-Containment Graph (DCG), which is a generalization of the Unit-Disk Graph (UDG), and we develop an efficient algorithm to construct CDS in such kind of graphs. The algorithm contains two parts and is flexible to balance the performance between the two metrics. We also analyze the algorithm theoretically. It is shown that our algorithm has provable performance in minimizing the CDS size and reducing the communication distance for routing.  相似文献   
937.
The canonical brain storm optimization (BSO) employs clustering, creating and selecting operators, which are all connected and have great impacts on the optimization performance. In this paper, the state-of-the-art search strategies are introduced and the potential strengths and weaknesses of these strategies in the BSO algorithm are analyzed and compared from the perspective of the analytical model rather than any metaphors. The numerical experiments are carried out to artificially amplify and highlight the performance of various strategies. Finally, the progressive directions of the BSO algorithm are discussed for further research.  相似文献   
938.
939.
940.
In this paper, we discuss the globalization of some kind of modified Levenberg-Marquardt methods for nonsmooth equations and their applications to nonlinear complementarity problems. In these modified Levenberg-Marquardt methods, only an approximate solution of a linear system at each iteration is required. Under some mild assumptions, the global convergence is shown. Finally, numerical results show that the present methods are promising.  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