全文获取类型
收费全文 | 760篇 |
免费 | 51篇 |
专业分类
化学 | 576篇 |
晶体学 | 5篇 |
力学 | 15篇 |
数学 | 67篇 |
物理学 | 148篇 |
出版年
2023年 | 8篇 |
2022年 | 13篇 |
2021年 | 17篇 |
2020年 | 4篇 |
2019年 | 17篇 |
2018年 | 9篇 |
2017年 | 5篇 |
2016年 | 34篇 |
2015年 | 21篇 |
2014年 | 31篇 |
2013年 | 54篇 |
2012年 | 82篇 |
2011年 | 82篇 |
2010年 | 40篇 |
2009年 | 34篇 |
2008年 | 43篇 |
2007年 | 42篇 |
2006年 | 49篇 |
2005年 | 30篇 |
2004年 | 32篇 |
2003年 | 19篇 |
2002年 | 17篇 |
2001年 | 3篇 |
2000年 | 11篇 |
1999年 | 8篇 |
1998年 | 5篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1995年 | 3篇 |
1994年 | 8篇 |
1993年 | 3篇 |
1992年 | 4篇 |
1991年 | 6篇 |
1990年 | 3篇 |
1989年 | 3篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1979年 | 5篇 |
1978年 | 4篇 |
1977年 | 6篇 |
1975年 | 4篇 |
1961年 | 3篇 |
1956年 | 2篇 |
1954年 | 3篇 |
1927年 | 2篇 |
1890年 | 4篇 |
1887年 | 3篇 |
1871年 | 1篇 |
排序方式: 共有811条查询结果,搜索用时 0 毫秒
111.
Badr Benmansour Ludovic Stephan Jean-Yves Cabon Laure Deschamps Philippe Giamarchi 《Journal of fluorescence》2011,21(3):843-850
This work presents spectroscopic properties of some Endocrine Disrupting Compounds (EDCs), frequently found in food and in
natural water. Studied molecules belong to the groups of phenolic and phthalate EDCs. In a first part, we have examined their
absorption and fluorescence properties. Fluorescence emission wavelengths are about 300 nm for phenolic compounds and 360 nm
for phtalate compounds; main excitation wavelengths being comprised between 210 nm and 230 nm. Fluorescence lifetimes measured
are short (about 4 ns) and the fluorescence quantum yield has been determined. In a second part, to avoid the time consuming
solvent extraction step, an analytical application to evaluate the performance of a direct analysis by laser induced fluorescence
spectroscopy of ECDs traces in tap water and in raw water is presented. Good detection limits have been obtained, i.e.: 0.35 μg.L−1 of chlorophenol in tap water, which are always lower than the reported Predictive Non Efficient Concentration (PNEC). 相似文献
112.
Leininger P Ilakovac V Joly Y Schierle E Weschke E Bunau O Berger H Pouget JP Foury-Leylekian P 《Physical review letters》2011,106(16):167203
Resonant magnetic x-ray scattering near the vanadium L2,3-absorption edges has been used to investigate the low temperature magnetic structure of high quality BaVS3 single crystals. Below T(N)=31 K, the strong resonance revealed a triple-incommensurate magnetic ordering at the wave vector (0.226 0.226 ξ) in hexagonal notation, with ξ=0.033. The azimuthal-angle dependence of the scattering signal and time-dependent density functional theory simulations indicate an antiferromagnetic order within the ab plane with the spins polarized along a in the monoclinic structure. 相似文献
113.
In this Letter, we present a new experimental approach to investigate the effective temperature concept as a generalization of the fluctuation-dissipation theorem (FDT) for nonequilibrium systems. Simultaneous measurements of diffusion coefficient and sedimentation velocity of heavy colloids, embedded in a Laponite clay suspension, are performed with a fluorescence-recovery-based setup. This nonperturbative dual measurement, performed at a single time in a single sample, allows for a direct application of the FDT to the tracer velocity observable. It thus provides a well-defined derivation of the effective temperature in this ageing colloidal gel. For a wide range of concentrations and ageing times, we report no violation of the FDT, with effective temperature agreeing with bath temperature. This result is consistent with recent theoretical predictions on the coupling between the velocity observable and nonequilibrium gels dynamics. 相似文献
114.
My-Loan-Phung Le Fannie Alloin Pierre Strobel Jean-Claude Lepr��tre Laure Cointeaux Carlos P��rez del Valle 《Ionics》2011,18(9):817-827
Ionic liquids, ILs, based on fluorinated pyrrolidinium and piperidinium ammonium cations and imide anion were prepared and characterized. The physicochemical and electrochemical properties of these ILs including melting point, glass transition and degradation temperatures, viscosity, ionic conductivity, and electrochemical stability were determined and compared to alkyl pyrrolidinium and piperidinium ILs. The incorporation of a CF3 group instead of a CH3 induces an increase of the IL viscosity, thus a conductivity decrease. However, good ionic conductivity is obtained with fluorinated pyrrolidinium IL. Cyclic amine ILs with propyl alkyl chain or fluorinated ammonium exhibit very high electrochemical stability toward oxidation. The effect of the addition of LiTFSI on the IL properties was studied with the same methodology. 相似文献
115.
Gilles Aubert Laure Blanc-Féraud Daniele Graziani 《Applied Mathematics and Optimization》2013,67(1):73-96
The paper is concerned with the analysis of a new variational model to restore point-like and curve-like singularities in biological images. To this aim we investigate the variational properties of a suitable energy which governs these pathologies. Finally in order to realize numerical experiments we minimize, in the discrete setting, a regularized version of this functional by fast descent gradient scheme. 相似文献
116.
In this paper, we give the expression and the asymptotic behaviour of the physical solution of a time harmonic wave equation set in a periodic waveguide. This enables us to define a radiation condition and show well-posedness of the Helmholtz equation set in a periodic waveguide. 相似文献
117.
9-Membered rings are readily constructed through a radical addition-cyclisation sequence on a 1,6-dien-3-ol system followed by a Grob-type fragmentation. 相似文献
118.
In this work, we are interested in the numerical approximation of an eigenvalue problem arising from the computation of guided modes in integrated optics waveguides which are particular cases of open waveguides. 相似文献
119.
In this paper we show, by using dyadic approximations, the existence of a geometric rough path associated with a fractional
Brownian motion with Hurst parameter greater than 1/4. Using the integral representation of fractional Brownian motions, we
furthermore obtain a Skohorod integral representation of the geometric rough path we constructed. By the results in [Ly1],
a stochastic integration theory may be established for fractional Brownian motions, and strong solutions and a Wong-Zakai
type limit theorem for stochastic differential equations driven by fractional Brownian motions can be deduced accordingly.
The method can actually be applied to a larger class of Gaussian processes with covariance functions satisfying a simple decay
condition.
Received: 11 May 2000 / Revised version: 20 March 2001 / Published online: 11 December 2001 相似文献
120.
Marie‐Laure Louillat‐Habermeyer Rongwei Jin Prof. Dr. Frederic W. Patureau 《Angewandte Chemie (International ed. in English)》2015,54(13):4102-4104
A method was developed for the direct dehydrogenative construction of C? N bonds between unprotected phenols and a series of cyclic anilines without resorting to any kind of metal activation of either substrate and without the use of halides. The resulting process relies on the exclusively organic activation of molecular oxygen and the subsequent oxidation of the aniline substrate. This allows the coupling of ubiquitous phenols, thus furnishing aminophenols through an atom‐economical and most sustainable dehydrogenative amination method. This new reactivity, which relies on the intrinsic organic reactivity of cumene in what can be seen as a modified Hock activation process of oxygen, is expected to have a large impact on the formation of C? N bonds in organic synthesis. 相似文献