全文获取类型
收费全文 | 479篇 |
免费 | 40篇 |
国内免费 | 1篇 |
专业分类
化学 | 375篇 |
晶体学 | 2篇 |
力学 | 22篇 |
数学 | 52篇 |
物理学 | 69篇 |
出版年
2023年 | 5篇 |
2022年 | 6篇 |
2021年 | 9篇 |
2020年 | 22篇 |
2019年 | 18篇 |
2018年 | 15篇 |
2017年 | 8篇 |
2016年 | 16篇 |
2015年 | 20篇 |
2014年 | 31篇 |
2013年 | 33篇 |
2012年 | 46篇 |
2011年 | 37篇 |
2010年 | 19篇 |
2009年 | 19篇 |
2008年 | 26篇 |
2007年 | 28篇 |
2006年 | 29篇 |
2005年 | 30篇 |
2004年 | 25篇 |
2003年 | 20篇 |
2002年 | 15篇 |
2001年 | 4篇 |
2000年 | 6篇 |
1999年 | 2篇 |
1998年 | 5篇 |
1997年 | 1篇 |
1996年 | 4篇 |
1995年 | 1篇 |
1994年 | 3篇 |
1993年 | 6篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1988年 | 1篇 |
1985年 | 2篇 |
1911年 | 1篇 |
1874年 | 4篇 |
排序方式: 共有520条查询结果,搜索用时 31 毫秒
511.
[reaction: see text] A formal [2+2+2] process has been devised that allows the stereocontrolled formation of ring-fused piperidines from allylsilanes possessing an oxime moiety. The cascade involves an intermolecular radical addition of an alpha-iodoacetate onto an allylsilane double bond, which is followed by a 5-exo-trig cyclization onto an oxime and is completed by the formation of the amide bond by nucleophilic attack of the amine onto the ester function. 相似文献
512.
Coquière D Cadeau H Rondelez Y Giorgi M Reinaud O 《The Journal of organic chemistry》2006,71(11):4059-4065
In our quest for the elaboration of supramolecular models of metallo-enzyme active sites, we became interested in developing new methodologies for the selective functionalization of the large rim of calix[6]arenes. Here, we describe a novel reaction, i.e. the ipso-chlorosulfonylation of calixarene derivatives. The process has been found to be highly efficient, selective and versatile. The regioselectivity is controlled by the nature of the O-substituents at the small rim. Indeed, when O-alkylated by a protonable imidazole group, the aromatic rings are deactivated toward an electrophilic attack and the anisol units can be selectively ipso-chlorosulfonylated under mild conditions (rt). Performing the reaction at a higher temperature allowed the per-chlorosulfonylation to take place. Hence, the synthesis of various sulfonate and sulfonamide derivatives is reported. Finally, a combination of ipso-nitration and chlorosulfonylation allows the per-functionalization of the aromatic units at the large rim in selective alternate positions. Overall, this novel methodology opens new routes to a variety of calixarenes, allowing the tuning of their physical properties without drastically altering their hydrophobic conic cavities. 相似文献
513.
Fractional Laplacian phase transitions and boundary reactions: A geometric inequality and a symmetry result 总被引:1,自引:0,他引:1
Yannick Sire 《Journal of Functional Analysis》2009,256(6):1842-3402
We deal with symmetry properties for solutions of nonlocal equations of the type
514.
Alain Hdoux Jeong‐Ah Seo Yannick Guinet Laurent Paccou 《Journal of Raman spectroscopy : JRS》2012,43(1):16-23
Cold‐ and heat‐induced β‐lactoglobulin (BLG) transformations have been analyzed in the presence of 4 M urea, from Raman spectroscopy investigations carried out simultaneously in the low wavenumber range (10–400 cm−1) and in the amide I region (1500–1800 cm−1). These investigations show common features between the denaturation processes at low and high temperatures. The denatured states are reached via an intermediate state characterized by a soft tertiary structure without detectable conformational changes. This intermediate is intimately connected with a tetrahedral hydrogen‐bond structure of water which extends over a limited range. It is shown that the disruption of the hydrogen‐bond network of D2O has an important consequence on the solvent dynamics, which controls protein dynamics and is characterized by an anharmonic behavior. By monitoring the amide I mode, conformational changes are detected at low temperature (below 5 °C) and determined to be similar to those detected at high temperature in the presence of urea near 65 °C, and in the absence of urea near 80 °C. The conformational changes are described as a loss of α‐helix structures and a concomitant formation of β‐sheets. The temperature dependence of the amide I wavenumber in BLG dissolved in the 4 M urea aqueous solution was interpreted on the basis of a two‐state model, leading to the protein stability curve related to its molecular conformation. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
515.
Yannick Gorsse Angelo Iollo Haysam Telib Lisl Weynans 《Journal of computational physics》2012,231(23):7780-7794
We present a finite-volume scheme for compressible Euler flows where the grid is cartesian and it does not fit to the body. The scheme, based on the definition of an ad hoc Riemann problem at solid boundaries, is simple to implement and it is formally second order accurate. Error convergence rates with respect to several exact test cases are investigated and examples of flow solutions in one, two and three dimensions are presented. 相似文献
516.
517.
518.
Dr. Conor T. Kelly Sean Dunne Dr. Irina A. Kühne Dr. Andrew Barker Dr. Kane Esien Dr. Solveig Felton Dr. Helge Müller-Bunz Dr. Yannick Ortin Prof. Grace G. Morgan 《Angewandte Chemie (International ed. in English)》2023,62(18):e202217388
Reversible proton-induced spin state switching of an FeIII complex in solution is observed at room temperature. A reversible magnetic response was detected in the complex, [FeIII(sal2323)]ClO4 ( 1 ), using Evans’ method 1H NMR spectroscopy which indicated cumulative switching from low-spin to high-spin upon addition of one and two equivalents of acid. Infrared spectroscopy suggests a coordination-induced spin state switching (CISSS) effect, whereby protonation displaces the metal-phenoxo donors. The analogous complex, [FeIII(4-NEt2-sal2323)]ClO4 ( 2 ), with a diethylamino group on the ligand, was used to combine the magnetic change with a colorimetric response. Comparison of the protonation responses of 1 and 2 reveals that the magnetic switching is caused by perturbation of the immediate coordination sphere of the complex. These complexes constitute a new class of analyte sensor which operate by magneto-modulation, and in the case of 2 , also yield a colorimetric response. 相似文献
519.
Ren delobel Serge Bourbigot Michel Le Bras Yannick Schmidt Jean -Marie Leroy 《Macromolecular Symposia》1993,74(1):59-69
A method allowing the determination of the formulation leading to the best fire retardancy properties is presented in the case of intumescent systems. The method consists in the determination of invariant physicochemical parameters deduced from TG analysis: invariant activation energy and invariant preexponentiel factor. The relation between the values given by an evaluation test (LOI) and the invariant activation energy is then discussed. 相似文献
520.