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   179篇
  免费   3篇
化学   102篇
晶体学   2篇
力学   10篇
数学   12篇
物理学   56篇
  2022年   2篇
  2021年   6篇
  2020年   5篇
  2019年   8篇
  2018年   10篇
  2017年   8篇
  2016年   6篇
  2015年   6篇
  2014年   4篇
  2013年   3篇
  2012年   5篇
  2011年   11篇
  2010年   9篇
  2009年   8篇
  2008年   13篇
  2007年   9篇
  2006年   3篇
  2005年   8篇
  2004年   2篇
  2003年   5篇
  2002年   3篇
  2001年   6篇
  2000年   3篇
  1999年   3篇
  1998年   1篇
  1997年   1篇
  1996年   1篇
  1995年   8篇
  1994年   2篇
  1993年   1篇
  1991年   1篇
  1989年   1篇
  1988年   1篇
  1986年   2篇
  1985年   1篇
  1984年   2篇
  1983年   1篇
  1981年   4篇
  1980年   1篇
  1978年   1篇
  1976年   4篇
  1975年   1篇
  1973年   2篇
排序方式: 共有182条查询结果,搜索用时 15 毫秒
11.
In the interaction with H2O2 in an alkaline medium, Cu(OH)2 forms terminal Cu–OOH and bridging peroxo complexes with the -1,1 and -2:2 structures. It was found that the terminal peroxide is active in the reactions of H2O2 decomposition, diphenol oxidation, and nitrile conversion into acid amides. The promoting effect of ammonia on these reactions was found. A possible mechanism is discussed.  相似文献   
12.
An anomalously large increase was found in the rate of cleavage of 4-nitrophenyl 4-toluenesulfonate (13000 times) and diethylphosphate (550 times) by the zwitterionic micelles of 1-cetyl-3-(2-hydroxyiminopropyl)imidazolium chloride and bromide. Detailed kinetic and thermodynamic analysis of these processes made it possible to establish that the main factor responsible for the high rates of reaction in the micellar phase is the concentration of the reagents.  相似文献   
13.
A series of palladium complexes of general formula [(Acac)PdL1L2]+A, where L1, L2 = phosphines and A = BF4, CF3SO3, were synthesized. Preliminary studies show that the complexes are active in selective dimerization of styrene and addition polymerization of norbornene.  相似文献   
14.
The problem of supersonic swirling flow past a blunt body is studied numerically on the basis of the complete Navier-Stokes equations.St. Petersburg. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 6, pp. 158–160, November–December, 1994.  相似文献   
15.
The need for high quality crystals constantly rise. It is especially obvious in connection with the evolution of electronics and optoelectronics. At the present time all the basic methods for crystal growing are known. So the question arises – what further developments are needed to create further advances? Without doubt first of all it is necessary to speak about perfecting crystal growing equipment. Perfecting modern equipment will enhance and accommodate the results of our understanding of the crystallization physics and provide solutions to the various physical tasks at the atomic and macroscopic levels. Each new step in the process of perfecting the technology and production processes demands large intellectual and material inputs. The continual updating of pullers requires constructive solutions and control systems. Mathematical modelling of the methods of crystallization enables one to more rapidly create the software for the digital systems which are a feature of the latest achievements of physics, that is IT engineering and the modern theory of automatic control.Here we consider the problem of mathematical modelling of crystallization processes from the melt by Czochralski, Liquid Encapsulated Czochralski and Floating Zone methods based on linearization of three conservation laws: the heat, mass and the growth angle constancy is reviewed in depth. Special attention is given to the problem of the dynamical analysis of these processes in open and closed states and to the synthesis of the digital control of crystal diameter for the weight technique. The main problems discussed involve the determination of the parameters required for calculating such control systems together with the use of the multichannel parametric PID regulator involving the state variable observer concept. In addition briefly considered are the problems of digital filtering of the measurement noise based on multidimentional Kalman filters and the determination of mechanical stability limits for static menisci.  相似文献   
16.
The aldol condensation of formaldehyde and the lower carbohydrate dihydroxyacetone in a neutral aqueous medium is effectively catalyzed by solid compounds (hydroxylapatite and calcium phosphate and carbonate), natural minerals (apatite and vivianite), and soluble phosphates. In excess formaldehyde, the decrease in the concentration of the lower carbohydrate is described by a first-order rate law with respect to dihydroxyacetone. The major products of the reaction between formaldehyde and dihydroxyacetone in the presence of the above catalysts are erythrulose (45–50% selectivity) and 3-pentulose (35–40% selectivity). Branched pentulose and hexulose are also identified among the reaction products.  相似文献   
17.
Scientific Research Institute of Applied Mathematics and Mechanics, 634050 Tomsk. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, No. 2, pp. 3–7, March–April, 1995  相似文献   
18.
19.
Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 5, pp. 113–116, September–October, 1989.  相似文献   
20.
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