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   170715篇
  免费   2309篇
  国内免费   713篇
化学   91928篇
晶体学   2461篇
力学   7604篇
综合类   7篇
数学   17703篇
物理学   54034篇
  2021年   991篇
  2020年   1112篇
  2019年   1126篇
  2018年   1153篇
  2017年   1167篇
  2016年   2329篇
  2015年   1909篇
  2014年   2484篇
  2013年   7685篇
  2012年   6264篇
  2011年   7935篇
  2010年   4882篇
  2009年   5030篇
  2008年   7299篇
  2007年   7282篇
  2006年   7007篇
  2005年   6533篇
  2004年   5852篇
  2003年   5044篇
  2002年   4953篇
  2001年   6026篇
  2000年   4558篇
  1999年   3474篇
  1998年   2624篇
  1997年   2617篇
  1996年   2567篇
  1995年   2275篇
  1994年   2161篇
  1993年   2025篇
  1992年   2343篇
  1991年   2308篇
  1990年   2021篇
  1989年   2005篇
  1988年   2028篇
  1987年   1960篇
  1986年   1871篇
  1985年   2774篇
  1984年   2752篇
  1983年   2206篇
  1982年   2391篇
  1981年   2272篇
  1980年   2226篇
  1979年   2173篇
  1978年   2243篇
  1977年   2199篇
  1976年   2129篇
  1975年   2118篇
  1974年   2023篇
  1973年   2105篇
  1972年   1199篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
By using two sections of erbium doped fiber and a fiber optical reflector, a novel, highly efficient L bandamplifier is demonstrated with significantly power-conversion-efficiency enhancement and the gain increasing of as much as 13 dB.  相似文献   
142.
The energy loss effect in nuclear matter, which is a nuclear effect apart from the nuclear effect on the parton distribution as in deep-inelastic scattering process, can be measured best by the nuclear dependence of the high energy nuclear Drell-Yan process. By means of the nuclear parton distribution studied only with lepton deep-inelastic scattering experimental data, the measured Drell-Yan production cross sections for 800 GeV proton incident on a variety of nuclear targets are analyzed within the Glauber framework which takes into account the energy loss of the beam proton. It is shown that the theoretical results with considering the energy loss effect are in good agreement with the FNAL E866 data.Arrival of the final proofs: 24 June 2003  相似文献   
143.
144.
Equilibrium Problems with Applications to Eigenvalue Problems   总被引:5,自引:0,他引:5  
In this paper, we consider equilibrium problems and introduce the concept of (S)+ condition for bifunctions. Existence results for equilibrium problems with the (S)+ condition are derived. As special cases, we obtain several existence results for the generalized nonlinear variational inequality studied by Ding and Tarafdar (Ref. 1) and the generalized variational inequality studied by Cubiotti and Yao (Ref. 2). Finally, applications to a class of eigenvalue problems are given.  相似文献   
145.
146.
The European Physical Journal C - The ALICE experiment at the CERN LHC will be dedicated to the investigation of heavy ion reactions at the highest energies. The main objective is the study of...  相似文献   
147.
148.
To further evaluate the causality between endogenous pyrogen (EP)-induced fever and cyclic adenosine-3',5'-monophosphate (cyclic AMP) level, the effects of sodium salicylate (SS) on the febrile response and increased levels of cyclic AMP in both cerebrospinal fluid (c.s.f.) and plasma during EP-induced fever in rabbits were observed. The results suggest that cyclic AMP is probably involved in the central mediation of EP-induced fever and that increased concentration of cyclic AMP in c.s.f. associated with EP-induced fever is not the result of temperature elevation but appears to be caused by the increased synthesis in the central nervous system. In addition it is confirmed that blood is impossibly a contributory source of increased cyclic AMP in c.s.f. during EP fever, and that SS may act subsequent to the increase in cyclic AMP.  相似文献   
149.
The effect of traffic noise on sleep of young adults in their homes   总被引:1,自引:0,他引:1  
The disturbance of sleep by traffic noise is a major problem area in noise pollution. Extensive laboratory tests using multichannel electroencephalograms (EEG) have been carried out by many workers to determine the general response of people when exposed to noise during sleep. An experimental technique for obtaining results in people's homes has been developed using a simplified one-channel EEG. The responses of six people in the age range 19-24 were measured. A significant correlation was found between sleep disturbance and traffic noise when the noise is expressed in EPNdB. In the home experiments the subjects appeared to be approximately 10 dB less sensitive to noises than laboratory subjects for similar noise exposure. There also appeared to be some adaptation to the noise exposure; however, only one subject was tested for a period of 20 days and was insufficient to give definite results on adaptation.  相似文献   
150.
In the framework of stochastic volatility models we examine estimators for the integrated volatility based on the pth power variation (i.e. the sum of pth absolute powers of the log‐returns). We derive consistency and distributional results for the estimators given high‐frequency data, especially taking into account what kind of process we may add to our model without affecting the estimate of the integrated volatility. This may on the one hand be interpreted as a possible flexibility in modelling, for example adding jumps or even leaving the framework of semimartingales by adding a fractional Brownian motion, or on the other hand as robustness against model misspecification. We will discuss possible choices of p under different model assumptions and irregularly spaced data. Copyright © 2005 John Wiley & Sons, Ltd.  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