全文获取类型
收费全文 | 469篇 |
免费 | 12篇 |
国内免费 | 1篇 |
专业分类
化学 | 307篇 |
晶体学 | 2篇 |
力学 | 4篇 |
数学 | 77篇 |
物理学 | 92篇 |
出版年
2023年 | 5篇 |
2022年 | 5篇 |
2021年 | 6篇 |
2020年 | 6篇 |
2019年 | 4篇 |
2018年 | 8篇 |
2017年 | 5篇 |
2016年 | 13篇 |
2015年 | 8篇 |
2014年 | 13篇 |
2013年 | 37篇 |
2012年 | 35篇 |
2011年 | 30篇 |
2010年 | 18篇 |
2009年 | 23篇 |
2008年 | 23篇 |
2007年 | 25篇 |
2006年 | 23篇 |
2005年 | 19篇 |
2004年 | 16篇 |
2003年 | 18篇 |
2002年 | 8篇 |
2001年 | 8篇 |
2000年 | 9篇 |
1999年 | 6篇 |
1998年 | 4篇 |
1997年 | 6篇 |
1996年 | 5篇 |
1995年 | 4篇 |
1994年 | 5篇 |
1993年 | 5篇 |
1992年 | 6篇 |
1991年 | 6篇 |
1990年 | 4篇 |
1989年 | 4篇 |
1988年 | 4篇 |
1985年 | 5篇 |
1984年 | 5篇 |
1983年 | 2篇 |
1982年 | 4篇 |
1981年 | 4篇 |
1980年 | 5篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 4篇 |
1976年 | 2篇 |
1975年 | 5篇 |
1973年 | 6篇 |
1968年 | 3篇 |
1896年 | 1篇 |
排序方式: 共有482条查询结果,搜索用时 15 毫秒
131.
The stereospecific endo dimerization of cyclopentadiene takes place through an asynchronous and symmetrical bispericyclic transition structure, which shows a merging of the 4+2 and 2+4 cycloaddition paths. The shape of the transition structure testifies to the presence of attractive Salem/Houk secondary orbital interactions assisting the endo approach. 相似文献
132.
Daniel Grasseschi Andre L. A. Parussulo Vitor M. Zamarion Robson R. Guimares Koiti Araki Henrique E. Toma 《Journal of Raman spectroscopy : JRS》2014,45(9):758-763
A dicarboxybipyridine‐trimercaptotriazine ruthenium complex, primarily designed for dye solar cells, has been successfully employed for generating electrostatically stabilized gold colloids, because of its high negative charge and capability of binding to gold nanoparticles via the sulfur groups. Surprisingly, a strong surface‐enhanced Raman scattering enhancement has been observed for the isolated nanoparticles, exceeding those recorded after inducing agglomeration. Such unusual response has been ascribed to the predominant contribution of the charge‐transfer and resonance Raman mechanisms, more than compensating for the lack of the local hot spots, in relation to the agglomerated systems. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
133.
We show that the upper bound for the maximum number of independent elements of a \((v_r)\) configuration is given by \(\lfloor 2v/(r+1) \rfloor \) and that this bound is attained for all integer values of \(r\) by geometric configurations of points and lines in the Euclidean plane. This disproves a conjecture of Branko Grünbaum. 相似文献
134.
M. Vinceković D. Jurašin V. Tomašić M. Bujan 《Journal of Dispersion Science and Technology》2013,34(8):1099-1111
The interactions of alkylammonium chlorides (the number of carbon atom per chain was either 12, 14, or 16) with sodium cholate have been investigated by a combination of techniques including light and electron microscopy, surface tension, conductivity, light scattering, and microelectrophoretic measurements. The phase behavior has strongly depended on the molar ratio and actual concentration of oppositely charged surfactants. The change in the composition of the aggregates leads to a shape transformation from globular to elongated micelles to open and/or closed bilayers (vesicles) and precipitation. The length of micelles has been found to decrease dramatically with the concentration shift to the micellar regions of either surfactant. Upon a moderate excess of one surfactant, the mean hydrodynamic diameter of aggregates increases and wormlike micelles and/or open and closed bilayers are formed. Microscopic observations of alkylammonium cholates (novel catanionic surfactants precipitated in and/or close to equimolar region) have shown the presence of a variety of morphologies including twisted ribbons, tubules and bundles of tubules. 相似文献
135.
Pierangela Ciuffreda Fiamma Ronchetti Lucio Toma 《Journal of carbohydrate chemistry》2013,32(5):805-811
Abstract The α-D-glucopyranosyl-(1?>2)-L-rhamnopyranosyl sequence is present in some repeating units of bacterial polysaccharides,1 as those found in the Shigella type or in various Streptococcal strains. 相似文献
136.
Belardini A Larciprete MC Centini M Fazio E Sibilia C Chiappe D Martella C Toma A Giordano M Buatier de Mongeot F 《Physical review letters》2011,107(25):257401
Here we report the experimental observation of circular dichroism in the second-harmonic field (800-400 nm conversion) generated by self-organized gold nanowire arrays with subwavelength periodicity (160 nm). Such circular dichroism, raised by a nonlinear optical extrinsic chirality, is the evident signature of the sample morphology. It arises from the curvature of the self-assembled wires, producing a lack of symmetry at oblique incidence. The results were compared, both in the optical linear and nonlinear regime, with a reference sample composed of straight wires. Despite the weak extrinsic optical chirality of our samples (not observable by our optical linear measurements), high visibility (more than 50%) was obtained in the second-harmonic generated field. 相似文献
137.
Aida Taira Toma Takahiro Kanada Satoshi 《Journal of Solid State Electrochemistry》2020,24(6):1415-1425
Journal of Solid State Electrochemistry - It is well known that reducing particle size and/or hollowing the particles improves the electrochemical performance, especially the rate capability, of... 相似文献
138.
Shifting Chemical Equilibria in Flow—Efficient Decarbonylation Driven by Annular Flow Regimes 下载免费PDF全文
Dr. Bernhard Gutmann Dr. Petteri Elsner Dr. Toma Glasnov Dr. Dominique M. Roberge Prof. Dr. C. Oliver Kappe 《Angewandte Chemie (International ed. in English)》2014,53(43):11557-11561
To efficiently drive chemical reactions, it is often necessary to influence an equilibrium by removing one or more components from the reaction space. Such manipulation is straightforward in open systems, for example, by distillation of a volatile product from the reaction mixture. Herein we describe a unique high‐temperature/high‐pressure gas/liquid continuous‐flow process for the rhodium‐catalyzed decarbonylation of aldehydes. The carbon monoxide released during the reaction is carried with a stream of an inert gas through the center of the tubing, whereas the liquid feed travels as an annular film along the wall of the channel. As a consequence, carbon monoxide is effectively vaporized from the liquid phase into the gas phase and stripped from the reaction mixture, thus driving the equilibrium to the product and preventing poisoning of the catalyst. This approach enables the catalytic decarbonylation of a variety of aldehydes with unprecedented efficiency with a standard coil‐based flow device. 相似文献
139.
Nardjes Mouas Toma Jean‐Claude Daran Hocine Merazig Eric Manoury 《Acta Crystallographica. Section C, Structural Chemistry》2014,70(5):460-464
In our ongoing development of ferrocene ligands, 1‐dimethylamino‐2‐(diphenylphosphinothioyl)ferrocene is being used as a convenient building block to obtain racemic or enantiomerically pure ligands. Using this building block in large excess allowed the formation of several by‐products, two of which have already been reported; the structure of a third by‐product, namely 1‐(diphenylphosphinothioyl)‐2‐{[(diphenylphosphinothioyl)sulfanyl]methyl}ferrocene, [Fe(C5H5)(C30H25P2S3)], is presented here. The crystal structure is built up from a ferrocene unit, with one of the cyclopentadienyl (Cp) rings substituted in the 1‐ and 2‐positions by a protected diphenylphosphinothioyl group and a [(diphenylphosphinothioyl)sulfanyl]methyl fragment, –CH2SP(=S)Ph2. There are C—H...S interactions which result in the formation of chains parallel to the c axis. After desulfurization, the crude material was then reacted with Pd and Pt (M) precursors [MCl2(CH3CN)2] to yield two isostructural dinuclear complexes arranged around twofold axes, namely (R,R/S,S)‐bis{μ‐[2‐(diphenylphosphanyl)ferrocen‐1‐yl]methanethiolato‐κ3P,S:S}bis[chloridopalladium(II)] pentane disolvate, [Pd2{Fe(C5H5)(C18H15PS)}2Cl2]·2C5H12, and the platinum(II) analogue, (R,R/S,S)‐bis{μ‐[2‐(diphenylphosphanyl)ferrocen‐1‐yl]methanethiolato‐κ3P,S:S}bis[chloridoplatinum(II)] toluene monosolvate, [Pt2{Fe(C5H5)(C18H15PS)}2Cl2]·C7H8, in which the two metal atoms present a slightly distorted square‐planar geometry formed by two bridging S atoms and P and Cl atoms. The P,S‐chelating ligand results from the rupture of one of the P—S bonds in the starting ligand. These dinuclear complexes display a butterfly geometry. Surprisingly, only the (R,R/S,S) diastereoisomer has been isolated. 相似文献
140.
The synthesis of the methyl esters of racemic trans and cis 4-guanidinocyclohexylglycine as rigid analogues of (D, L)-arginine methyl ester is described. 相似文献