全文获取类型
收费全文 | 766篇 |
免费 | 26篇 |
国内免费 | 1篇 |
专业分类
化学 | 681篇 |
晶体学 | 5篇 |
力学 | 6篇 |
数学 | 66篇 |
物理学 | 35篇 |
出版年
2023年 | 8篇 |
2022年 | 13篇 |
2021年 | 20篇 |
2020年 | 8篇 |
2019年 | 13篇 |
2018年 | 9篇 |
2017年 | 7篇 |
2016年 | 12篇 |
2015年 | 16篇 |
2014年 | 27篇 |
2013年 | 40篇 |
2012年 | 55篇 |
2011年 | 63篇 |
2010年 | 27篇 |
2009年 | 18篇 |
2008年 | 38篇 |
2007年 | 48篇 |
2006年 | 46篇 |
2005年 | 41篇 |
2004年 | 42篇 |
2003年 | 41篇 |
2002年 | 31篇 |
2001年 | 11篇 |
2000年 | 10篇 |
1999年 | 11篇 |
1998年 | 11篇 |
1997年 | 10篇 |
1996年 | 6篇 |
1995年 | 5篇 |
1994年 | 5篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1989年 | 3篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1982年 | 5篇 |
1981年 | 3篇 |
1979年 | 4篇 |
1977年 | 4篇 |
1975年 | 4篇 |
1959年 | 2篇 |
1937年 | 3篇 |
1932年 | 7篇 |
1928年 | 2篇 |
1927年 | 2篇 |
1925年 | 4篇 |
1911年 | 4篇 |
1908年 | 3篇 |
排序方式: 共有793条查询结果,搜索用时 17 毫秒
11.
Alain Adenier Eva Cabet-Deliry Sophie Griveau Florence Mercier Christine Vautrin-Ul 《Surface science》2006,600(21):4801-4812
This study investigates the spontaneous grafting of different para-substituted phenyl groups on carbon and metallic surfaces from diazonium salts solutions. Glassy carbon, nickel, zinc and iron plates were allowed to react with an acetonitrile solution of aryldiazonium tetrafluoroborate salt by simple dipping. The surfaces were characterized before and after their immersion by XPS and AFM to evidence the formation of a coating on the different materials. The results are indicative of the presence of substituted phenyl groups on all the investigated surfaces. This study also aims at correlating grafting efficiency with metal reactivities and diazonium salt electronic properties by means of AFM and FT-IRRAS. For this purpose, zinc and nickel were chosen due to their opposite reducing properties and two diazonium salts were selected with electron-donor or -withdrawing para-substituents. The results tend to indicate that redox properties of both partners (diazonium + metal) are of prime importance for grafting to occur. 相似文献
12.
Lionel Joucla Florence Popowycz Olivier Lozach Laurent Meijer Benoît Joseph 《Helvetica chimica acta》2007,90(4):753-763
The syntheses of paullone ( 1a ) and three paullone derivatives, including a sulfur analogue ( 2a ), a tricyclic derivative ( 2b ), and a ring‐enlarged variant ( 2c ), are described, Pd‐catalyzed intramolecular Heck reaction being the key step. The kinase‐inhibitory properties of the novel paullone analogues were investigated. 相似文献
13.
14.
M. Florence 《Transformation Groups》2006,11(2):161-176
Let k be a perfect field and G an algebraic group defined over k. Let X be a homogeneous space of G. We show the following:
if there exists a k-variety which is birational to X and which has a smooth k-rational point, then X also has a k-rational
point (Theorem 5.7). 相似文献
15.
D. Duracher F. Sauzedde A. Elaissari A. Perrin C. Pichot 《Colloid and polymer science》1998,276(3):219-231
Cationic hydrophilic copolymer latexes were synthesized at 70 °C either by batch or two-step emulsifier-free emulsion poly-merization
of styrene (St), N-iso-propylacrylamide (NIPAM), and aminoethylmethacrylate hydro-chloride (AEM) using 2,2′-azobis (2-amidinopropane) dihydrochloride
as initiator. At first, batch polymerization kinetics were followed by gas chromatography (GC), revealing that NIPAM rapidly
homopolymerized, before the polymerization of styrene had started. Particle size analysis by quasi-elastic light scattering
(QELS) and transmission electron microscopy (TEM) showed that monodispersed particles were obtained with the formation of
a poly[NIPAM] rich shell. Adding a small amount of the cationic monomer caused a strong decrease of the particle size without
affecting the size monodispersity. When a shot process was used, a narrow particle size distribution was maintained, provided
that the monomer addition was performed at a relatively high conversion of the first batch step. The poly[NIPAM] rich shell
layer was larger with the shot process, but increasing the amino-containing monomer in the recipe resulted in a dramatic decrease
of the thickness. Combination of transmission, scanning and atomic force microscopy techniques showed that these hydrophilic
particles exhibited odd-shaped structures, the unevenness being dependent upon the performed process. Kinetic data and particle
morphology information were inferred for discussion of the polymerization mechanism of this system.
Received: 21 August 1997 Accepted: 22 October 1997 相似文献
16.
2-(2- and 3-Pyridyl)anilines (1, 2), 2,2-dimethyl-N-[2-(2- and 3-pyridyl)phenyl]propanamides (3, 4), and 2-, 3- and 4-(2-methoxyphenyl)pyridines (7-9) are readily synthesized using cross-coupling reactions. Whereas the amines 1, 2 undergo side reactions, the corresponding amides 3, 4 are deprotonated with lithium 2,2,6,6-tetramethylpiperidide (LTMP): the compound 3 at C6' under in situ quenching, and the compound 4 at C4'. When the ether 7 is subjected to the same reagent, lithiation occurs at C6'. 相似文献
17.
Using concentration measurements based on high performance liquid chromatography, we have investigated the kinetics of reaction between single-stranded oligonucleotides containing a d(GpG) sequence, i.e., d(GG), d(TGG), d(TTGG), and d(CTGGCTCA), and the platinum complexes cis-[Pt(NH(3))(2)(H(2)O)(2)](2+) (1) and [Pt(NH(3))(3)(H(2)O)](2+) (2). The rate constants for the substitution of one aqua ligand of platinum in 1 or 2 by each guanine of the oligonucleotides were individually measured, as well as, for 1, those for the subsequent conversion of the monoadducts to the diadduct. For the platination of d(GG) and d(TGG), the rate constants are similar for the 5'- and 3'-guanines. The longer oligonucleotides d(TTGG) and d(CTGGCTCA) are platinated slightly faster on the 5'-G than on the 3'-G. 2 shows a similar slight preference for the 5'-guanine, but it reacts by a factor of 4-10 more slowly than 1. For both complexes, the platination rate constants increase with increasing oligonucleotide length. Platination of the 5'-G by 1 is 1 order of magnitude faster on d(CTGGCTCA) than on d(GG). Concerning the chelation step giving the GG diadduct of 1, the longer the oligonucleotide, the larger is the ratio between the rates of the cyclization of the 3'- and 5'-monoadducts k(3)(')(c) and k(5)(')(c): k(3)(')(c)/k(5)(')(c) equals 1.4 for d(GG) and 3.3 for d(CTGGCTCA). 相似文献
18.
Florence Robaut Alexandre Crisci Madeleine Durand-Charre Danielle Jouanne 《Microscopy and microanalysis》2006,12(4):331-334
The carbon contents in carburized steels were investigated by electron probe microanalysis (EPMA) for a range of carbon levels in the solid solution less than 1 wt%. This article describes the difficulties encountered with the classic analytical procedure using the k ratio of X-ray intensities and the phi(rhoz) model. Here, a suitable calibration curve method is presented with emphasis on the metallographic study of standard specimens and on the carbon decontamination of samples. 相似文献
19.
Alan S.F. BoydGraeme Cooke Florence M.A. DuclairoirVincent M. Rotello 《Tetrahedron letters》2003,44(2):303-306
We have investigated the electrochemically controlled hydrogen bonding interactions between tetrathiafulvalene host 3 and guests 4 or 5. Stabilisation of the 3+ state is dependent upon the nature of the guest species, whereas both guests prevent precipitation of the electrochemically generated 32+ species at the working electrode via hydrogen bonded molecular recognition processes. 相似文献
20.
The enantioselective monoreduction of 2-alkyl 1,3-diketones by dynamic kinetic resolution using optically active ruthenium catalysts allowed the preparation of the C14-C25 fragment of bafilomycin A1. 相似文献