全文获取类型
收费全文 | 362篇 |
免费 | 0篇 |
国内免费 | 2篇 |
专业分类
化学 | 312篇 |
晶体学 | 2篇 |
力学 | 4篇 |
数学 | 30篇 |
物理学 | 16篇 |
出版年
2022年 | 6篇 |
2021年 | 6篇 |
2020年 | 6篇 |
2019年 | 5篇 |
2017年 | 4篇 |
2016年 | 2篇 |
2015年 | 2篇 |
2014年 | 5篇 |
2013年 | 25篇 |
2012年 | 13篇 |
2011年 | 15篇 |
2010年 | 6篇 |
2009年 | 7篇 |
2008年 | 26篇 |
2007年 | 23篇 |
2006年 | 19篇 |
2005年 | 20篇 |
2004年 | 21篇 |
2003年 | 21篇 |
2002年 | 12篇 |
2001年 | 2篇 |
2000年 | 2篇 |
1999年 | 2篇 |
1998年 | 9篇 |
1997年 | 5篇 |
1996年 | 8篇 |
1995年 | 5篇 |
1994年 | 3篇 |
1993年 | 8篇 |
1991年 | 7篇 |
1990年 | 5篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 4篇 |
1985年 | 4篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1982年 | 5篇 |
1981年 | 3篇 |
1979年 | 4篇 |
1978年 | 11篇 |
1977年 | 2篇 |
1975年 | 4篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1972年 | 3篇 |
1970年 | 1篇 |
1969年 | 4篇 |
1955年 | 1篇 |
排序方式: 共有364条查询结果,搜索用时 15 毫秒
171.
Anne-Marie Alquie-Redon Jacky Vigneron Claude Lamy 《Journal of Electroanalytical Chemistry》1978,92(2):147-161
The voltammetric curves for a 2-step sequential reaction involving a 2nd order adsorption process (such as the catalytic mechanism met in the anodic oxidation of hydrogen) are investigated theoretically by computer calculations. Steady state cyclic voltammetry (s.s.c.v.) is particularly treated by repeating forward and backward sweeps as many times as necessary to reach the steady state. For both l.p.s.v. and s.s.c.v., the usual characteristic features are considered, i.e. EM, θM, iM as a function of sweep rate υ, especially in the range of υ, where the computed data fit the results derived from analytical solution (quasi-reversible charge transfer, and irreversible charge transfer). In s.s.c.v., indications are given to obtain the kinetic parameters (k1, k2, α) from experimental plots. 相似文献
172.
The effect of the chirality of the amino acid at position i + 2 on a β-turn was investigated by a grid scan ab initio calculation on the Ac-
-Pro-
-Ala-NH2 and Ac-
-Pro-
-Ala-NH2 blocked dipeptides. Th6-31G basis set was used to estimate the effect of the alanyl side chain on the conformation of the peptide backbone in a blocked dipeptide as a simple, but complete model for a reverse turn. This study provides a quantum mechanical evaluation of the ability of the NH at the i + 3 residue to form the H-bond that closes the 10 membered ring which stabilizes the turn. The lowest energy of all 64 probed conformations of the
-Ala containing peptide corresponded to a good type II β-turn with a hydrogen bond distance between the acetyl oxygen and the amide terminal hydrogen of 2.21 Å. A comparison with the nonblocked dipeptide ab initio study indicates that the presence of the end blocks enhances the propensity of the
-Ala-containing dipeptide for a type II β-turn, but does not seem to enhance the propensity of the
-Ala-containing dipeptide for a type I β-turn. The energies and geometric parameters for the lowest four optimized conformations identified by the grid scan search for each molecule have been calculated. 相似文献
173.
Cécile HubertChristian Alexandre Anne-Marie AubertinFrançois Huet 《Tetrahedron》2003,59(17):3127-3130
Nucleoside analogues 9 and 12 were obtained in good yields from alcohol 7 which, under Mitsunobu conditions, led to the title products after deprotection steps. 相似文献
174.
Serge Seube Anne-Marie Lamazoure Jean Sotiropoulos 《Journal of heterocyclic chemistry》1978,15(2):343-346
Diamines react with 3-dimercaptomethylenecamphor giving either a bis-oxothioamide or a heterocyclic compound via in oxoaminothioamide intermediate. In this last reaction, there is cleavage of both C? S bonds. Similarly, diamines react with β-oxothioamides to produce the same heterocyclic derivatives. In these reactions, a transamination is involved and the carbonyl group of camphor is preserved. A distinctly different reaction occurs when the same camphor derivatives are treated with hydrazine; thioxo- alcoylamino- or arylaminoindazoles are then obtained. Ring closure occurs on the carbonyl carbon of the camphor molecule. 相似文献
175.
Daniel Demoulin Anne-Marie Armbruster Bernard Pullman 《Theoretical chemistry accounts》1978,48(2):143-153
A quantum molecular study by the SCFab initio method of the interaction of glyoxal with guanine provides for the formation of a stable covalent adduct in which the glyoxal
fragment forms a complementary cyclic ring attached to the imino N1 and amino N2 atoms of guanine with the concomitant migration of the N-bonded H atoms to the oxygens of glyoxal. The reaction should proceed
in two steps. The most plausible mechanism involves as the first step the interaction of a carbonyl group of glyoxal with
the amino group of guanine followed by a similar interaction at the imino group of guanine, rather than the reverse order
of interactions. The respective energy barriers are 49.7 and 63.9 kcal/mole. The intermediate product is also more stable
when the adduct occurs first at N2:30.7 kcal/mole versus 17.9 kcal/mole for the adduct at N1. 相似文献
176.
Anne-Marie Wifladt Grethe Wibetoe W. Lund 《Fresenius' Journal of Analytical Chemistry》1997,357(1):92-96
A method was developed for the determination of Sb in wine by electrothermal atomic absorption spectrometry, based on preconcentration
by hydride generation with collection directly in the graphite furnace. Thiourea was added for prereduction of Sb(V) to Sb(III).
The hydride was directly generated from diluted wine. Palladium was used as modifier in the collection step; the overall efficiency
of the hydride/trapping system was found to be 67%. Sb was determined in several samples of red wine; the concentrations found
were in the range 0.6 to 5.7 μg/L Sb. The detection limit of the method was 39 pg Sb, corresponding to 0.13 μg/L Sb in wine
when 0.3 mL wine was analyzed.
Received: 3 November 1995/Revised: 22 February 1996/Accepted: 24 February 1996 相似文献
177.
Dendrimers are hyperbranched nanosized and precisely defined molecules, attracting increasing attention each year due to their numerous properties in catalysis, materials science, and biology. This tutorial review concerns the use of dendrimers as catalysts and focuses more precisely on their properties as enantioselective catalysts. Emphasis is put on chiral phosphine complexes constituting the core or the end groups of various types of dendrimers. The effect of the location of the catalytic entities, the effect of the size (generation) and the nature of the dendritic skeleton on the enantiomeric excesses are discussed. 相似文献
178.
Deloncle R Coppel Y Rebout C Majoral JP Caminade AM 《Magnetic resonance in chemistry : MRC》2008,46(5):493-496
Two series of small generation dendrimers built with phosphorus atoms at each branching point and various types of nitrogen atoms at natural abundance of (15)N within the branches are characterized by a gradient enhanced GHNMQC (gradient hydrogen-nitrogen multiple quantum coherence) (1)H-(15)N NMR technique. The first series contains two types of nitrogen atoms, included in phosphorhydrazone linkages (CH=NNMe-P(S)), whereas the second series contains four types of nitrogen atoms included in azobenzene linkages (Ar-N=N-Ar') in addition to the phosphorhydrazone. The influence of the trans/cis isomerization of the azo bond on the (15)N NMR has also been studied. Despite the low solubility of the azobenzene-containing dendrimers, which renders the detection of some signals difficult, (15)N NMR appears as a very sensitive tool to detect chemical changes in the dendritic structure. 相似文献
179.
Hogan AM Tricotet T Meek A Khokhar SS O'Shea DF 《The Journal of organic chemistry》2008,73(15):6041-6044
The enantioselective carbolithiation of ortho-substituted (E)-beta-methylstyrenes provides access to chiral lithiated intermediates with broad synthetic potential. Specifically, beta-methylstyrenes with o-aminomethyl, ether, and oxazoline groups have been employed in the synthesis of chiral aromatics and heteroaromatics such as isoquinolines, isoquinolinones, benzofurans, and isobenzofuranones. 相似文献
180.
In a first step towards chemical sensors using molecular imprinted materials, the complexing characteristics of diethyl 4-nitrobenzylphosphonate, an organophosphate pesticide analogue, have been studied. Two molecules have been assessed as potential interacting moieties, specifically a fluoroalcohol and an aromatic acid. The interactions have been first characterized by regular methods, such as 1H, 31P NMR and IR spectroscopy. These showed a stoichiometry 1/1 for both complexes and association constants, respectively, close to 40 ± 10 and 12 ± 2 M−1. In a second step, isothermal titration calorimetry was used and a method was developed to obtain low-association constants. The association constant could be obtained for the fluoroalcohol ligand and was found equal to 63 ± 0.7 M−1. For the acidic molecule, an appropriate model could not be found, preventing the evaluation of this constant. 相似文献