首页 | 官方网站   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   587219篇
  免费   4050篇
  国内免费   1214篇
数理化   592483篇
  2021年   5083篇
  2020年   5405篇
  2019年   6325篇
  2018年   13247篇
  2017年   13650篇
  2016年   14413篇
  2015年   6796篇
  2014年   11500篇
  2013年   24103篇
  2012年   21387篇
  2011年   29172篇
  2010年   21192篇
  2009年   21575篇
  2008年   26593篇
  2007年   28279篇
  2006年   19059篇
  2005年   19319篇
  2004年   17019篇
  2003年   15927篇
  2002年   15069篇
  2001年   15715篇
  2000年   12163篇
  1999年   9172篇
  1998年   8060篇
  1997年   7734篇
  1996年   7306篇
  1995年   6412篇
  1994年   6379篇
  1993年   6252篇
  1992年   6580篇
  1991年   7116篇
  1990年   6832篇
  1989年   6770篇
  1988年   6403篇
  1987年   6580篇
  1986年   6149篇
  1985年   7474篇
  1984年   7767篇
  1983年   6558篇
  1982年   6718篇
  1981年   6296篇
  1980年   6085篇
  1979年   6723篇
  1978年   6775篇
  1977年   6832篇
  1976年   6880篇
  1975年   6430篇
  1974年   6249篇
  1973年   6455篇
  1972年   5024篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.

The problem of the minimax testing of the Poisson process intensity \({\mathbf{s}}\) is considered. For a given intensity \({\mathbf{p}}\) and a set \(\mathcal{Q}\), the minimax testing of the simple hypothesis \(H_{0}: {\mathbf{s}} = {\mathbf{p}}\) against the composite alternative \(H_{1}: {\mathbf{s}} = {\mathbf{q}},\,{\mathbf{q}} \in \mathcal{Q}\) is investigated. The case, when the 1-st kind error probability \(\alpha \) is fixed and we are interested in the minimal possible 2-nd kind error probability \(\beta ({\mathbf{p}},\mathcal{Q})\), is considered. What is the maximal set \(\mathcal{Q}\), which can be replaced by an intensity \({\mathbf{q}} \in \mathcal{Q}\) without any loss of testing performance? In the asymptotic case (\(T\rightarrow \infty \)) that maximal set \(\mathcal{Q}\) is described.

  相似文献   
2.
3.
4.
5.
In this work, we have used the MuMax3 software to simulate devices consisting of a ferromagnetic thin film placed over a heavy metal thin film. The devices are two interconnected partial-disks where a Néel domain wall is formed in the disks junction. In our simulations we investigate devices with disk radius r=50 nm and different distance d between the disks centers (from d=12 nm to d=2R=100 nm). By applying strong sinusoidal external magnetic fields, we find a mechanism able to create, annihilate and even manipulate a skyrmion in each side of the device. This mechanism is discussed in terms of interactions between skyrmion and domain wall. The Néel domain wall formed in the center of the device interacts with the Néel skyrmion, leading to a process of transporting a skyrmion from one disk to the other periodically. Our results have relevance for potential applications in spintronics such as logical devices.  相似文献   
6.
7.
8.
The structure, chemical composition, and magnetic properties of electrochemically deposited nanocrystalline Co-Ni-Fe films were investigated using a number of techniques. A high saturation magnetic induction up to B s = 21 kG was attained. An enhancement of the saturation magnetization compared to the ideal anticipated one was revealed, which correlated with the nonlinear behavior of the structural phase composition and lattice parameters with the change of the composition. The text was submitted by the authors in English.  相似文献   
9.
Methods for phase stabilization of ammonium nitrate were sought for in order to considerably expand the application area of this oxidizing agent in various-purpose self-combustible formulations, including that in a new generation of gas-generating formulations for automobile air bags. New methods for stabilization of ammonium nitrate were studied and, in particular, a search was made for organic compounds that can stabilize ammonium nitrate even at their low content. The mechanism of phase state stabilization of ammonium nitrate by compounds of this kind was examined.  相似文献   
10.
Kinetic, sorption and selectivity properties of commercial adsorbents are improved by adding petroleum residues (tar asphaltene concentrates) 13% of whole mass. Obtained adsorbents can be used for selective extraction of nobel metals from multicomponent polymetallic solutions of heavy metals and fro sewages purification for removing arsenic.  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-23

京公网安备 11010802026262号