全文获取类型
收费全文 | 262篇 |
免费 | 15篇 |
国内免费 | 3篇 |
专业分类
化学 | 203篇 |
晶体学 | 4篇 |
数学 | 40篇 |
物理学 | 33篇 |
出版年
2023年 | 1篇 |
2021年 | 5篇 |
2020年 | 5篇 |
2019年 | 4篇 |
2018年 | 5篇 |
2017年 | 5篇 |
2016年 | 5篇 |
2015年 | 6篇 |
2014年 | 8篇 |
2013年 | 18篇 |
2012年 | 21篇 |
2011年 | 26篇 |
2010年 | 11篇 |
2009年 | 17篇 |
2008年 | 19篇 |
2007年 | 8篇 |
2006年 | 16篇 |
2005年 | 17篇 |
2004年 | 13篇 |
2003年 | 15篇 |
2002年 | 14篇 |
2001年 | 2篇 |
2000年 | 2篇 |
1999年 | 3篇 |
1998年 | 1篇 |
1997年 | 2篇 |
1996年 | 6篇 |
1995年 | 2篇 |
1994年 | 4篇 |
1993年 | 3篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1974年 | 1篇 |
排序方式: 共有280条查询结果,搜索用时 31 毫秒
21.
Pere Ara 《Proceedings of the American Mathematical Society》2001,129(4):1041-1049
We show that two -algebras are strongly Morita equivalent if and only if their Pedersen ideals are Morita equivalent as rings with involution.
22.
An optical mm-wave demultiplexer is presented. Double sideband modulation with suppressed optical carrier and filtering properties of dual overwritten fiber Bragg gratings are the fundamentals for optical demultiplexing of mm-wave radio-on-fiber signals: using a single optical carrier, Millimeter-wave signals of 20 and 40 GHz frequencies carrying independent data are created, transmitted over fiber, demultiplexed and wireless distributed to be detected and data recovered in a mobile unit. Double sideband modulation with suppressed optical carrier yields no power penalty due to chromatic dispersion, while the filtering properties of the dual overwritten fiber Bragg gratings allow less than −40 dB electrical power interchannel leakage. Independent 2.5 Gb/s On-Off-keyed data have been successfully transmitted through the 20 and 40 GHz channels. 相似文献
23.
Ibon Alkorta Fernando Blanco Pere M. Deyà José Elguero Carolina Estarellas Antonio Frontera David Quiñonero 《Theoretical chemistry accounts》2010,126(1-2):1-14
This review covers two aspects concerning cooperativity in multiple weak bonds: a summary of literature results and a theoretical study of a complete series of model complexes. All the 15 combination of five weak bonds were explored: hydrogen bonds, hydric bonds, dihydrogen bonds, halogen bonds and ion–π interactions. Since in several cases there were no examples reported, a systematic exploration has been carried out on simple models at the MP2/aug-cc-pVTZ level. The results thus obtained have been analyzed using the atoms in molecules methodology. 相似文献
24.
25.
Miró P Pierrefixe S Gicquel M Gil A Bo C 《Journal of the American Chemical Society》2010,132(50):17787-17794
Uranyl-peroxide nanoclusters display different topologies based on square, pentagonal and hexagonal building blocks. Computed complexation energies of different cations (Li(+), Na(+), K(+), Rb(+), and Cs(+)) with [UO(2)(O(2))(H(2)O)](n) (n = 4, 5, and 6) macrocycles suggest a strong cation templating effect. The inherent bent structure of a U-O(2)-U model dimer is demonstrated and justified through the analysis of its electronic structure, as well as of the inherent curvature of the four-, five-, and six-uranyl macrocyles. The curvature is enhaced by cation coordination, which is suggested to be the driving force for the self-assembly of the nanocapsules. 相似文献
26.
Konstantin E. Komolov Mònica Aguilà Darwin Toledo Joan Manyosa Pere Garriga Karl-Wilhelm Koch 《Analytical and bioanalytical chemistry》2010,397(7):2967-2976
Surface plasmon resonance spectroscopy allows the study of protein interaction dynamics in real-time. Application of this
technique to G-protein coupled receptors, the largest family of receptors involved in signal transduction, has been complicated
by their low level of expression and the critical dependence of their native conformation on the hydrophobic transmembrane
lipid environment. Here, we investigate and compare three different strategies to immobilize rhodopsin, a prototypical G-protein
coupled receptor on a sensor chip surface using antibodies and a lectin for receptor capturing. By further probing of different
experimental conditions (pH, detergent type) we identified the optimal factors to maintain rhodopsin in a functional conformation
and extended this approach to recombinant rhodopsin that was heterologously expressed in COS cells. Functional operation of
rhodopsin on the sensor chip surface was proven by its activation and subsequent light-stimulated G-protein coupling. The
influence of these experimental parameters on the association and dissociation kinetics of G-protein receptor coupling was
determined. Thereby, we found that the kinetics of Gt interaction were not changed by the strategy of immobilization or the type of detergent. Regeneration of opsin directly on
a chip allowed recycling of the immobilized native and recombinant receptor. Thus, the approach provides an experimental framework
for choosing the most suitable conditions for the solubilization, immobilization, and for functional tests of rhodopsin on
a biosensor surface. 相似文献
27.
Linear and nonlinear optical properties of carbon nanotube-coated single-mode optical fiber gratings
Villanueva GE Jakubinek MB Simard B Oton CJ Matres J Shao LY Pérez-Millán P Albert J 《Optics letters》2011,36(11):2104-2106
Single-wall carbon nanotube deposition on the cladding of optical fibers has been carried out to fabricate an all-fiber nonlinear device. Two different nanotube deposition techniques were studied. The first consisted of repeatedly immersing the optical fiber into a nanotube supension, increasing the thickness of the coating in each step. The second deposition involved wrapping a thin film of nanotubes around the optical fiber. For both cases, interaction of transmitted light through the fiber core with the external coating was assisted by the cladding mode resonances of a tilted fiber Bragg grating. Ultrafast nonlinear effects of the nanotube-coated fiber were measured by means of a pump-probe pulses experiment. 相似文献
28.
29.
X-ray fluorescence analyses were used to determine the potassium contents of silicate minerals with K2O concentrations between 1 and 13 wt.%. This method is based on lithium tetraborate fused glass discs with 50 mg of sample at 1:120 dilution. The results show that this high-dilution minimises matrix effects and that both precision and accuracy are below 1.5% for all the silicate minerals analysed, whatever their composition. This analytical procedure is useful for K determination in small samples of mineral separates needed to establish K–Ar geochronology, without using acid digestion. 相似文献
30.
We give an example of a domain such that the sequence of iterated symmetric rings of quotients does not stabilize. This answers
a question of Passman.
The work of the first author has been partially supported by CICYT PB 86-0353-C02-01 and that of the second author by CICYT
PB87-0703 and the Institut d’Estudis Catalans. 相似文献