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   356397篇
  免费   2066篇
  国内免费   641篇
化学   170372篇
晶体学   5410篇
力学   18521篇
综合类   9篇
数学   52554篇
物理学   112238篇
  2019年   2291篇
  2018年   11088篇
  2017年   11869篇
  2016年   8211篇
  2015年   3411篇
  2014年   4388篇
  2013年   10777篇
  2012年   12034篇
  2011年   21169篇
  2010年   13568篇
  2009年   13463篇
  2008年   18861篇
  2007年   22218篇
  2006年   9055篇
  2005年   13928篇
  2004年   10448篇
  2003年   9878篇
  2002年   7944篇
  2001年   7474篇
  2000年   5964篇
  1999年   4396篇
  1998年   3897篇
  1997年   3861篇
  1996年   3758篇
  1995年   3434篇
  1994年   3580篇
  1993年   3266篇
  1992年   3732篇
  1991年   3736篇
  1990年   3672篇
  1989年   3541篇
  1988年   3656篇
  1987年   3543篇
  1986年   3359篇
  1985年   4444篇
  1984年   4730篇
  1983年   3959篇
  1982年   4091篇
  1981年   4017篇
  1980年   3990篇
  1979年   3975篇
  1978年   4293篇
  1977年   4140篇
  1976年   4229篇
  1975年   3897篇
  1974年   3938篇
  1973年   4127篇
  1972年   2883篇
  1971年   2399篇
  1970年   2205篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
We study the stability of the results of the three-neutrino oscillation analysis of atmospheric and reactor neutrino data under departures of the one dominant mass scale approximation. In order to do so we perform the analysis of atmospheric and reactor neutrino data in terms of three-neutrino oscillations where the effect of both mass differences is explicitly considered. We study the allowed parameter space resulting from this analysis as a function of the mass splitting hierarchy parameter which parameterizes the departure from the one dominant mass scale approximation. We consider schemes with both direct and inverted mass ordering. Our results show that in the analysis of the atmospheric data the derived range of the largest mass splitting, , is stable, while the allowed ranges of mixing angles and are wider than those obtained in the one dominant mass scale approximation. Inclusion of the CHOOZ reactor data in the analysis results in the reduction of the parameter space in particular for the mixing angles. As a consequence the final allowed ranges of the parameters from the combined analysis are only slightly broader than when obtained in the one dominant mass scale approximation. Received: 31 May 2002 / Revised version: 10 July 2002 / Published online: 31 October 2002  相似文献   
992.
993.
A new method for studying the kinetics of the expansion of explosion products based on measuring the time elapsed from explosion initiation to the short-circuiting of the discharge gap by the products was proposed. It was revealed that, at the initial stage of expansion of the silver azide explosion products, they move with uniform acceleration, a behavior suggestive that, during this period, the exothermic reaction 2N3 → 3N2 occurs.  相似文献   
994.
Monstrous Branes     
 We study D-branes in the bosonic closed string theory whose automorphism group is the Bimonster group (the wreath product of the Monster simple group with ℤ2). We give a complete classification of D-branes preserving the chiral subalgebra of Monster invariants and show that they transform in a representation of the Bimonster. Our results apply more generally to self-dual conformal field theories which admit the action of a compact Lie group on both the left- and right-moving sectors. Received: 20 February 2002 / Accepted: 17 August 2002 Published online: 19 December 2002 Communicated by R.H. Dijkgraaf  相似文献   
995.
996.
997.
The influence of a large signal on the characteristics of a small signal near the frequency of the former is experimentally studied for the case of their simultaneous propagation through a resonant transmission line based on backward volume magnetostatic waves. The effects observed are caused by the excitation of spin waves in a ferromagnetic film at different large-signal frequencies and by the back influence of excited spin-wave packets on the amplitude and phase characteristics of the small signal.  相似文献   
998.
For two types of qutrits specified by the dynamical symmetry SU(3) and SU(2), we consider the difference in entanglement caused by the lack of quantum observables in the latter case. In particular, we show that the SU(2) qutrits can have specific separable entanglement caused by quantum correlations of intrinsic degrees of freedom in a single party without interparty correlations.  相似文献   
999.
The order-disorder phase transition in vanadium monoxide of substoichiometric compositions VOy has been studied for the first time in situ by the Faraday method with a pendulum magnetic balance of the Domenically type. A minimum is found on the temperature dependence of the magnetic susceptibility of vanadium monoxide of different compositions at a temperature of about 700 K. X-ray diffraction analysis performed before and after measuring the magnetic susceptibility confirmed the change in the structure of vanadium monoxide and the possibility of atom-vacancy processes upon cooling and heating of the samples.  相似文献   
1000.
Schemes and calculated characteristics of effective logic elements with two inputs for classical ground-state computations are reported. These elements have a high threshold (0.48) and perform a desired logical operation in a wide range of input signals.  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