全文获取类型
收费全文 | 55篇 |
免费 | 1篇 |
专业分类
化学 | 51篇 |
晶体学 | 1篇 |
力学 | 1篇 |
数学 | 1篇 |
物理学 | 2篇 |
出版年
2022年 | 3篇 |
2021年 | 1篇 |
2019年 | 2篇 |
2016年 | 1篇 |
2015年 | 1篇 |
2013年 | 3篇 |
2012年 | 6篇 |
2011年 | 3篇 |
2010年 | 2篇 |
2009年 | 1篇 |
2007年 | 2篇 |
2006年 | 1篇 |
2005年 | 4篇 |
2004年 | 1篇 |
2003年 | 6篇 |
2002年 | 3篇 |
2001年 | 1篇 |
1999年 | 1篇 |
1998年 | 2篇 |
1996年 | 1篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1983年 | 1篇 |
1978年 | 2篇 |
1970年 | 1篇 |
1969年 | 2篇 |
1965年 | 1篇 |
1964年 | 1篇 |
排序方式: 共有56条查询结果,搜索用时 15 毫秒
51.
An analytical method has been proposed to optimise the small-signaloptical gain of CO2-N2 gasdynamic lasers (gdl) employing two-dimensional (2D) wedge nozzles. Following our earlier work the equations governing the steady, inviscid, quasi-one-dimensional
flow in the wedge nozzle of thegdl are reduced to a universal form so that their solutions depend on a single unifying parameter. These equations are solved
numerically to obtain similar solutions for the various flow quantities, which variables are subsequently used to optimize
the small-signal-gain. The corresponding optimum values like reservoir pressure and temperature and 2D nozzle area ratio also
have been predicted and graphed for a wide range of laser gas compositions, with either H2O or He as the catalyst. A large number of graphs are presented which may be used to obtain the optimum values of small signal
gain for a wide range of laser compositions without further computations. 相似文献
52.
The structure of the alkaloid thalicmine has been proved to be 1,2-methylenedioxy-3,9,10-trimethoxyaporphine by a synthesis of the racemic form of the alkaloid on classical lines. 相似文献
53.
Shanmugasundaram M Wu MS Jeganmohan M Huang CW Cheng CH 《The Journal of organic chemistry》2002,67(22):7724-7729
Diynes 1a-c [X(CH(2)Ctbd1;CCO(2)Me)(2): X = (CH(2))(2), 1a, X = CH(2), 1b and X = O, 1c] undergo [2 + 2 + 2] ene-diyne cycloaddition reactions with a variety of allenes (n-butylallene 2a, phenylallene 2b, (4-chlorophenyl)allene 2c, (4-bromophenyl)allene 2d, (3-methoxyphenyl)allene 2e, 1-naphthylallene 2f, cyclohexylallene 2g and cyclopentylallene 2h) in the presence of Ni(dppe)Br(2) and Zn powder in CH(3)CN at 80 degrees C for 8 h to give the corresponding polysubstituted benzene derivatives 4a-l in good to excellent yields. Under similar reaction conditions, unsymmetrical diynes 5a-c (HCtbd1;CCH(2)XCH(2)Ctbd1;CCO(2)Me) react with allenes 2 to afford exclusively the corresponding meta-isomers 6a-g in 73-86% yields. The catalytic reaction is highly regioselective and completely chemoselective. This synthetic method is compatible with many functional groups such as Cl, Br, and OMe on the phenyl group of the allene moiety and an ether linkage in a diyne moiety. In this catalytic reaction, allenes are synthetically equivalent to terminal alkynes. Interestingly, unsymmetrical diyne 7 (MeCtbd1;C(CH(2))(4)Ctbd1;CCO(2)Me) undergoes 2:1 cocyclotrimerization with allenes 2a and 2g to afford the corresponding polysubstituted benzene derivatives 9a,b in 87% and 82% yields, respectively. A plausible mechanism involving a nickelacycloheptadiene intermediate is proposed to account for this nickel-catalyzed reaction. 相似文献
54.
55.
Daylight photocatalysis by carbon-modified titanium dioxide 总被引:38,自引:0,他引:38
56.