全文获取类型
收费全文 | 1168篇 |
免费 | 53篇 |
国内免费 | 6篇 |
专业分类
化学 | 761篇 |
晶体学 | 7篇 |
力学 | 32篇 |
数学 | 190篇 |
物理学 | 237篇 |
出版年
2023年 | 9篇 |
2022年 | 20篇 |
2021年 | 26篇 |
2020年 | 33篇 |
2019年 | 36篇 |
2018年 | 25篇 |
2017年 | 14篇 |
2016年 | 37篇 |
2015年 | 46篇 |
2014年 | 45篇 |
2013年 | 66篇 |
2012年 | 94篇 |
2011年 | 111篇 |
2010年 | 57篇 |
2009年 | 51篇 |
2008年 | 88篇 |
2007年 | 73篇 |
2006年 | 58篇 |
2005年 | 49篇 |
2004年 | 41篇 |
2003年 | 29篇 |
2002年 | 22篇 |
2001年 | 10篇 |
2000年 | 13篇 |
1999年 | 7篇 |
1998年 | 13篇 |
1997年 | 6篇 |
1995年 | 8篇 |
1994年 | 5篇 |
1993年 | 9篇 |
1992年 | 7篇 |
1991年 | 4篇 |
1990年 | 4篇 |
1989年 | 4篇 |
1988年 | 5篇 |
1987年 | 6篇 |
1986年 | 3篇 |
1985年 | 9篇 |
1984年 | 12篇 |
1983年 | 3篇 |
1981年 | 5篇 |
1979年 | 4篇 |
1978年 | 6篇 |
1977年 | 6篇 |
1976年 | 6篇 |
1975年 | 3篇 |
1974年 | 3篇 |
1973年 | 3篇 |
1971年 | 4篇 |
1969年 | 5篇 |
排序方式: 共有1227条查询结果,搜索用时 15 毫秒
91.
We study reduction of generalized complex structures. More precisely, we investigate the following question. Let J be a generalized complex structure on a manifold M, which admits an action of a Lie group G preserving J. Assume that M0 is a G-invariant smooth submanifold and the G-action on M0 is proper and free so that MG?M0/G is a smooth manifold. Under what condition does J descend to a generalized complex structure on MG? We describe a sufficient condition for the reduction to hold, which includes the Marsden–Weinstein reduction of symplectic manifolds and the reduction of the complex structures in Kähler manifolds as special cases. As an application, we study reduction of generalized Kähler manifolds. 相似文献
92.
Cartigny B Azaroual N Imbenotte M Mathieu D Parmentier E Vermeersch G Lhermitte M 《Talanta》2008,74(4):1075-1078
The determination and quantification of glyphosate in serum using (1)H NMR spectroscopy is reported. This method permitted serum samples to be analysed without derivatization or any other sample pre-treatment, using 3-trimethylsilyl 2,2',3,3'-tetradeuteropropionic acid (TSP-d(4)) as a qualitative and quantitative standard. Characterization of the herbicide N-(phosphonomethyl)glycine was performed by analysing chemical shifts and coupling constant patterns. Quantification was performed by relative integration of CH(2)-P protons to the TSP-d(4) resonance peak. The method was tested for repeatability (n=5) and yielded coefficients of variation of 1% and 3%, respectively: detection and quantification limits were also determined and were 0.03 and 0.1mmol/L, respectively. The method was applied to the quantification of glyphosate in a case of acute poisoning. 相似文献
93.
Highly concentrated colloidal suspensions exhibit a discontinuous shear-thickening behaviour. The transition from a low to a high viscosity state is associated to a large energy dissipation. This effect could find applications in structural damping while the viscosity increase brings added stiffness. In the present work, highly concentrated suspensions of monodisperse spherical silica particles in polyethylene glycol were selected for their strong thickening at low critical shear rates. Their damping properties were characterized by measuring the energy dissipated per cycle at low frequency (below 2 Hz) during oscillatory tests using a rheometer. The influence of parameters such as particle concentration, size and frequency was investigated. Damping was found to overcome that of benchmark elastomeric materials only in high frequencies and high strain domains. 相似文献
94.
Amandine Cournet Marie-Line Délia Alain Bergel Christine Roques Mathieu Bergé 《Electrochemistry communications》2010,12(4):505-508
Most bacteria known to be electrochemically active have been harvested in the anodic compartments of microbial fuel cells (MFCs) and are able to use electrodes as electron acceptors. The reverse phenomenon, i.e. using solid electrodes as electron donors, is not so widely studied. To our knowledge, most of the electrochemically active bacteria are Gram-negative. The present study implements a transitory electrochemical technique (cyclic voltammetry) to study the microbial catalysis of the electrochemical reduction of oxygen. It is demonstrated that a wide range of aerobic and facultative anaerobic bacteria are able to catalyze oxygen reduction. Among these electroactive bacteria, several were Gram-positive. The transfer of electrons was direct since no activity was obtained with the filtrate. These findings, showing a widespread property among bacteria including Gram-positive ones, open new and interesting routes in the field of electroactive bacteria research. 相似文献
95.
Philippe Gros Sabine Choppin Julien Mathieu Yves Fort 《The Journal of organic chemistry》2002,67(1):234-237
The determination of the initial deprotonation site of 2-chloro- and 2-methoxypyridine during reaction with BuLi-LiDMAE has been investigated. A series of experiments on deuterated regioisomers revealed a direct lithiation at C-6 excluding a potential first classical ortholithiation and lithium equilibration in the reaction medium. These results suggested that the formation of lithium aggregates at the neighboring of the pyridinic nitrogen atom favored BuLi delivery at C-6 as well as 6-lithio intermediate stabilization. 相似文献
96.
The osp(N, 2) extension of the AKNS scheme is reconsidered. It leads to a general class of integrable nonlinear evolution equations for 2+N(N–1)/2 commuting and 2N anticommuting fields. by reduction, various osp(N, 2) versions of the Korteweg-de Vries equation can be obtained. One of these is shown to be bi-Hamiltonian and its second Hamiltonian structure corresponds to the classical limit of the so(N) superconformal algebra. The nonlinear Schrödinger and modified Korteweg-de Vries reductions are also briefly discussed.Work supported by NSerc and FCAR. 相似文献
97.
Reda Moubah Silviu Colis Mathieu Gallart Guy Schmerber Pierre Gilliot Aziz Dinia 《Journal of luminescence》2012,132(2):457-460
Recent studies on the physical properties of Ca3Co2O6 nanometric samples have shown that their properties are significantly different from those of the bulk samples. The origin of this change is not trivial. We have carried out optical measurements on Ca3Co2O6 thin films with different thicknesses in order to characterize their electronic structure using optical spectroscopy measurements. The absorption spectra show a dependence on the film thickness that is correlated to the grain size in the polycrystalline layers. We found that the optical band gap increases from 1.3 to 1.55 eV when the thickness changes from 35 to 100 nm. The change in the band gap evolution with the film thickness is discussed in terms of both the amorphous effect and the grain size in the Ca3Co2O6 thin films. Finally, we show that these results are consistent with recent measurements concerning magnetic and electrical properties of Ca3Co2O6 nanometric samples. 相似文献
98.
Mathieu Baillif Alexandre Gabard 《Proceedings of the American Mathematical Society》2008,136(3):1105-1111
We analyze the relationship between Hausdorffness and homogeneity in the frame of manifolds not confined to be Hausdorff. We exhibit examples of homogeneous non-Hausdorff manifolds and prove that a Lindelöf homogeneous manifold is Hausdorff.
99.
100.