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   327906篇
  免费   1251篇
  国内免费   693篇
数理化   329850篇
  2020年   1954篇
  2019年   2436篇
  2018年   18898篇
  2017年   19339篇
  2016年   12495篇
  2015年   3360篇
  2014年   4126篇
  2013年   7809篇
  2012年   12330篇
  2011年   25427篇
  2010年   16032篇
  2009年   16671篇
  2008年   20701篇
  2007年   25347篇
  2006年   6301篇
  2005年   11678篇
  2004年   8988篇
  2003年   9204篇
  2002年   6828篇
  2001年   5422篇
  2000年   4335篇
  1999年   3081篇
  1998年   2883篇
  1997年   2653篇
  1996年   2630篇
  1995年   2288篇
  1994年   2197篇
  1993年   2242篇
  1992年   2220篇
  1991年   2528篇
  1990年   2433篇
  1989年   2527篇
  1988年   2414篇
  1987年   2437篇
  1986年   2262篇
  1985年   2803篇
  1984年   2821篇
  1983年   2467篇
  1982年   2511篇
  1981年   2410篇
  1980年   2212篇
  1979年   2543篇
  1978年   2705篇
  1977年   2699篇
  1976年   2814篇
  1975年   2608篇
  1974年   2526篇
  1973年   2746篇
  1972年   2211篇
  1971年   2009篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
A finite support product of ω1 clones of Jensen's minimal Π21 singleton forcing is used to define a model in which any non-empty analytically definable set of reals contains an analytically definable real (the full basis theorem), but there is no analytically definable wellordering of the reals.  相似文献   
2.
3.
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   
4.
5.
6.
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   
7.
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   
8.
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   
9.
Experimental data on the effect of thallium and sodium impurities on the lattice heat conductivity of PbTe at room temperature are reported. Because the lattice of lead chalcogenides is strongly polarized near charged impurities, the effect of impurities on the lattice heat conductivity depends substantially on their charge state. This property of the material has been used to determine the charge state of the thallium impurity in PbTe. The results obtained argue for a model of quasi-local thallium-impurity states which assumes low electron-correlation energy at an impurity center. Fiz. Tverd. Tela (St. Petersburg) 40, 1206–1208 (July 1998)  相似文献   
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-23

京公网安备 11010802026262号