全文获取类型
收费全文 | 149篇 |
免费 | 4篇 |
专业分类
化学 | 87篇 |
晶体学 | 2篇 |
力学 | 4篇 |
数学 | 13篇 |
物理学 | 47篇 |
出版年
2022年 | 1篇 |
2021年 | 3篇 |
2020年 | 3篇 |
2019年 | 1篇 |
2018年 | 3篇 |
2016年 | 2篇 |
2015年 | 5篇 |
2014年 | 4篇 |
2013年 | 10篇 |
2012年 | 3篇 |
2011年 | 3篇 |
2010年 | 1篇 |
2008年 | 4篇 |
2007年 | 3篇 |
2006年 | 1篇 |
2005年 | 4篇 |
2004年 | 2篇 |
2003年 | 1篇 |
2002年 | 1篇 |
2001年 | 3篇 |
2000年 | 9篇 |
1999年 | 3篇 |
1998年 | 1篇 |
1997年 | 2篇 |
1996年 | 3篇 |
1995年 | 4篇 |
1993年 | 3篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1984年 | 1篇 |
1983年 | 4篇 |
1982年 | 3篇 |
1981年 | 1篇 |
1980年 | 10篇 |
1979年 | 7篇 |
1978年 | 3篇 |
1977年 | 4篇 |
1976年 | 3篇 |
1975年 | 3篇 |
1974年 | 3篇 |
1972年 | 3篇 |
1971年 | 6篇 |
1968年 | 1篇 |
1961年 | 1篇 |
1960年 | 1篇 |
1928年 | 2篇 |
1880年 | 1篇 |
1865年 | 2篇 |
排序方式: 共有153条查询结果,搜索用时 46 毫秒
1.
2.
Deerenberg S Schrekker HS van Strijdonck GP Kamer PC van Leeuwen PW Fraanje J Goubitz K 《The Journal of organic chemistry》2000,65(16):4810-4817
A series of chiral phosphine-phosphite ligands 1-6 have been synthesized and used in the enantioselective palladium-catalyzed reaction of rac-1,3-diphenyl-2-propenyl acetate with dimethyl malonate as nucleophile. Ligands 1a, 2, 3, 5a, 6a, and 6b have been synthesized starting from racemic tert-butylphenylphosphinoborane. The use of dynamically resolved Li phosphide (-)-sparteine provided the optically pure ligands. Crystals of the allylpalladium (6a) complex were obtained, suitable for X-ray crystal structure determination. The X-ray crystal structure of the allylpalladium (6a) complex revealed a longer palladium-carbon bond distance trans to the phosphine moiety indicating that the attack of the nucleophile takes place at the carbon trans to the phosphine moiety. This was confirmed by the fact that the phosphine moiety did not affect the enantioselectivity directly. Under mild reaction conditions, enantioselectivities up to 83% were obtained (25 degrees C) with ligand 1e. Systematic variation of the ligand bridge and the phosphite moiety showed that the configuration of the product is controlled by the atropisomerism of the biphenyl substituent at the phosphite moiety. The conformation of the biphenyl group, in turn, is controlled by the substituent at the chiral carbon in the bridge. Ligands with large bite angles yielded higher enantioselectivities. 相似文献
3.
William L. Jolly 《Journal of organometallic chemistry》1979,172(2):C33-C35
Substitution of the hydrogen atoms of the cyclopentadienyl ring of (N, N-dimethylaminomethyl)cymantrene by deuterium changes the direction of orientation of metalation of this amine. 相似文献
4.
P.W. Jolly C. Krüger R. Salz J.C. Sekutowski 《Journal of organometallic chemistry》1979,165(3):C39-C42
The stoichiometric reaction between allene, zerovalent nickel and a chelating diphosphane leads to the formation of a bis-methylenenickelacyclopentane derivative whose structure has been established by X-ray crystallography. 相似文献
5.
Bis ( η1, η2-allyl) palladium phosphine complexes react with carbon dioxide and sulphur dioxide by insertion into the palladium-carbon σ-bond to give η3-allylpalladium-carboxylate and -S-sulphinate complexes. 相似文献
6.
When core ionization of an atom in a molecule causes significant changes in bond orders, the core-hole ion is formed in a strained configuration. This strain causes vibrational broadening of the core line. The core-hole ion can be represented as an ordinary chemical species by applying the equivalent cores approximation. Then simple rules of classical valence bond theory can be used to predict changes in the weighting of resonance structures and corresponding changes in bond orders. Thus qualitative changes in relative linewidths can be predicted. 相似文献
7.
B. Henc P.W. Jolly R. Salz S. Stobbe G. Wilke R. Benn R. Mynott K. Seevogel R. Goddard C. Krüger 《Journal of organometallic chemistry》1980,191(2):449-475
A series of 1 : 1 adducts have been prepared by treating the bis-η3-allyl complexes of nickel, palladium and platinum with tertiary phosphines. Investigations of their structure in solution as well as in the crystal have shown that both 18-electron (η3-allyl)2ML complexes as well as 16-electron (η1-allyl)-(η3-allyl)ML complexes may be formed. 相似文献
8.
P. Jolly K. V. Sane R. P. Saxena P. K. Srivastava 《International journal of quantum chemistry》1982,21(6):1051-1055
When a Padé-type function is used as a trial function, it is necessary to investigate the location of singularities and the zeros of the optimized function. It is shown that an unacceptable wave function can sometimes yield numerically acceptable values because of the nature of the integration procedure. It is also shown that it is possible to remove the undesirable features of a lower order form by invoking the next approximation. 相似文献
9.
Petra DG Kamer PC Spek AL Schoemaker HE van Leeuwen PW 《The Journal of organic chemistry》2000,65(10):3010-3017
A new class of efficient catalysts was developed for the asymmetric transfer hydrogenation of unsymmetrical ketones. A series of chiral N,S-chelates (6-22) was synthesized to serve as ligands in the iridium(I)-catalyzed reduction of ketones. Both formic acid and 2-propanol proved to be suitable as hydrogen donors. Sulfoxidation of an (R)-cysteine-based aminosulfide provided a diastereomeric ligand family containing a chiral sulfur atom. The two chiral centers of these ligands showed a clear effect of chiral cooperativity. In addition, aminosulfides containing two asymmetric carbon atoms in the backbone were synthesized. Both the sulfoxide-containing beta-amino alcohols and the aminosulfides derived from 1,2-disubstituted amino alcohols gave rise to high reaction rates and moderate to excellent enantioselectivities in the reduction of various ketones. The enantioselective outcome of the reaction was favorably affected by selecting the most appropriate hydrogen donor. Enantioselectivities of up to 97% were reached in the reduction of aryl-alkyl ketones. 相似文献
10.
Anthony Jolly Dandan Miao Maxime Daigle Prof. Dr. Jean-François Morin 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(12):4652-4661
The solution-phase synthesis is one of the most promising strategies for the preparation of well-defined graphene nanoribbons (GNRs) in large scale. To prepare high quality, defect-free GNRs, cycloaromatization reactions need to be very efficient, proceed without side reaction and mild enough to accommodate the presence of various functional groups. In this Minireview, we present the latest synthetic approaches for the synthesis of GNRs and related structures, including alkyne benzannulation, photochemical cyclodehydrohalogenation, Mallory and Pd- and Ni-catalyzed reactions. 相似文献