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   669篇
  免费   6篇
  国内免费   4篇
化学   478篇
晶体学   3篇
力学   8篇
数学   63篇
物理学   127篇
  2023年   4篇
  2022年   5篇
  2021年   6篇
  2019年   5篇
  2018年   11篇
  2017年   4篇
  2016年   8篇
  2015年   6篇
  2014年   8篇
  2013年   25篇
  2012年   30篇
  2011年   31篇
  2010年   24篇
  2009年   29篇
  2008年   35篇
  2007年   33篇
  2006年   52篇
  2005年   44篇
  2004年   29篇
  2003年   28篇
  2002年   20篇
  2001年   12篇
  2000年   8篇
  1999年   6篇
  1998年   15篇
  1997年   11篇
  1996年   11篇
  1995年   12篇
  1994年   4篇
  1992年   5篇
  1991年   4篇
  1988年   4篇
  1987年   5篇
  1986年   12篇
  1985年   15篇
  1984年   12篇
  1983年   5篇
  1982年   11篇
  1981年   8篇
  1980年   7篇
  1979年   11篇
  1978年   9篇
  1977年   6篇
  1976年   5篇
  1975年   3篇
  1974年   6篇
  1970年   4篇
  1967年   4篇
  1964年   5篇
  1962年   4篇
排序方式: 共有679条查询结果,搜索用时 0 毫秒
611.
612.
Let ξ =(ξ01,...) be a zero-one series. We shall study whether the Walsh series,
is the Walsh--Fourier series of some measure or not. This revised version was published online in June 2006 with corrections to the Cover Date.  相似文献   
613.
A phase-separated acidic ionic liquid affords to catalyze a reaction of pyrrole with benzaldehyde in dichloromethane, forming porphyrins in a comparable yield to the Lindsey method and is reusable at least ten times without loss of catalytic activity.  相似文献   
614.
We illustrate a general polymeric design of fluorescent logic gates, for example, AND, using temperature and pH as inputs.  相似文献   
615.
Five new alkaloids, dictyodendrins A-E (1-5), were isolated from the Japanese marine sponge Dictyodendrilla verongiformis as telomerase inhibitors. Their structures were elucidated by spectroscopic and chemical methods. Dictyodendrins are tyramine-based pyrrolocarbazole derivatives containing three or four p-hydroxybenzene groups. They inhibited telomerase completely at a concentration of 50 microg/mL.  相似文献   
616.
Ferroelectric polarization-reversal switching of vinylidene fluoride—trifluoroethylene copolymer with 73 mol % of vinylidene fluoride is investigated under a variety of conditions in an attempt to derive detailed information on the polarization reversal of the polymer. The electric-field dependence of switching time ts obeys an exponential law. The temporal change of switching current density J is presented in the form J/(Ps ? P) versus time (P is the polarization, and Ps is its saturation value), which is free of the depolarization-field effect and discriminates in a straightforward manner between acceleration and deceleration of switching. Effects of the annealing of samples upon ts are observed together with changes in the degree of crystallinity. Effects of space charge distribution upon ts are investigated by applying two successive pulses, positive and negative, with varied intervals tw between the two. The dynamics of space charge redistribution is elucidated from the tw dependence of the ts of the second pulse. The temperature dependence of ts indicates that the switching becomes critically fast as the phase-transition temperature is approached.  相似文献   
617.
MO quantities by CNDO/2 method on several valence isomeric ketenes and structurally corresponding allene molecules were calculated to evaluate the influence of structural feature on magnitude of back-donation of oxygen n-electrons in ketene, and to rationalize an unusual cycloaddition involved in diphenyl ketene.  相似文献   
618.
Grignard reagents react with acid chlorides in tetrahydrofuran at low temperature to produce ketones in excellent yields. The results reported here strongly indicate the importance of the solvent in Grignard reagent chemistry.  相似文献   
619.
Plasma-induced reaction in an aqueous solution of phenyl-containing amino acids resulted in the formation of several hydroxyphenyl amino acids, which was explained by the action of hydroxyl radicals generated by decomposition of water molecules by the high energy plasma.  相似文献   
620.
Fuzzy control algorithms are developed based on fuzzy models of systems. The control issues are posed as multiobjective optimization problems involving goals and constraints imposed on system's variables. Two basic design modes embrace on- and off-line modes of control development. The first type of design deals with the time and state-dependent objectives and pertains to control determination based upon the current state of the fuzzy model. The second design mode gives rise to an explicit form of a fuzzy controller that is learned based on a given list of state-control associations. Both the fuzzy models as well as fuzzy controllers are realized as logic processors.  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