全文获取类型
收费全文 | 199篇 |
免费 | 1篇 |
专业分类
化学 | 81篇 |
晶体学 | 2篇 |
力学 | 16篇 |
数学 | 22篇 |
物理学 | 79篇 |
出版年
2022年 | 1篇 |
2021年 | 1篇 |
2020年 | 2篇 |
2019年 | 1篇 |
2018年 | 4篇 |
2017年 | 1篇 |
2016年 | 7篇 |
2015年 | 1篇 |
2014年 | 4篇 |
2013年 | 5篇 |
2012年 | 7篇 |
2011年 | 11篇 |
2010年 | 9篇 |
2009年 | 8篇 |
2008年 | 7篇 |
2007年 | 6篇 |
2006年 | 11篇 |
2005年 | 11篇 |
2004年 | 8篇 |
2003年 | 10篇 |
2002年 | 8篇 |
2001年 | 8篇 |
2000年 | 3篇 |
1999年 | 2篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1996年 | 3篇 |
1995年 | 3篇 |
1994年 | 5篇 |
1993年 | 3篇 |
1992年 | 4篇 |
1991年 | 3篇 |
1989年 | 3篇 |
1987年 | 1篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 5篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 4篇 |
1977年 | 4篇 |
1976年 | 4篇 |
1974年 | 3篇 |
1973年 | 1篇 |
1971年 | 1篇 |
1932年 | 2篇 |
1908年 | 2篇 |
1902年 | 2篇 |
排序方式: 共有200条查询结果,搜索用时 19 毫秒
31.
Abstract Spectroscopic properties of Ce3+ ions in GdAlO3 crystal are presented. At least three Ce3+ nonequivalent centres (multisites) are present in this crystal. Energy transfer from the Ce3+ main in the UV emitting centres to the Ce3+ green emitting centres is observed. Ce3+ fluorescence decays are either fast (1.5–20 ns) or slower due to complicated processes of energy transfer and migration (Ce3+)i → (Gd3+)n-steps → (Ce3+)j (energy transfer through Gd3+ sublattice). 相似文献
32.
S. Soriano C. Dufour K. Dumesnil Ph. Mangin 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,63(4):469-478
Below its ordering temperature (T
N
= 90 K), bulk bcc Eu has a helical magnetic state with propagation vectors along the three equivalent 〈100〉 directions. In
contrast, epitaxial (110)Eu films exhibit a unique magnetic ordering: the domain with a magnetic helix propagating along the
in-plane [001] direction vanishes on cooling, at the expense of other domains with helices propagating along [100] and [010].
This paper is devoted to the study of the stability of the magnetic domains in an external magnetic field using neutron scattering
experiments and macroscopic magnetization measurements. The helix propagating along the [001] direction can be restored by
the application of an external field along this direction. On the contrary, when a magnetic field is applied along an intermediate
direction, specifically [10], the domain with a helix propagating along [001] is suppressed. Both effects depend on the film thickness. They are explained
if one considers that, because of the low magnetic anisotropy of Eu, a helix with a propagation vector parallel to (or close
to) the applied magnetic field is energetically more favourable than cycloidal structures with unchanged propagation vectors.
Finally, the amplitudes of the propagation vectors and their directions (that are modified in films compared to bulk) do not
vary under magnetic field. 相似文献
33.
Prof. Marcus W. Drover Maeve C. Dufour Lindsay A. Lesperance-Nantau Rayni P. Noriega Dr. Kirill Levin Prof. Robert W. Schurko 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(49):11180-11186
Herein, we establish the preparation, characterization, and reactivity of a new diphosphine ligand, 1,2-bis(di(3-dicyclohexylboraneyl)propylphosphino)ethane (P2BCy4), a scaffold that contains four pendant boranes. An entryway into the coordination chemistry of P2BCy4 is established by using nickel, providing the octaboraneyl complex [Ni(P2BCy4)2]—this species contains a boron-rich secondary coordination sphere that reacts readily with Lewis bases. In the case of 4,4′-bipyridine, an air-sensitive coordination polymer is obtained. Characterization of this material by solid-state NMR and EPR spectroscopy reveals the presence of a charge-transfer polymer, which forms as a function of intramolecular Ni→4,4′-bpy electron transfer (ET), providing an array of oxidized nickel sites and reduced 4,4′-bpy radical anion sites. Notably, the related intermolecular reaction between the model fragments [Ni(dnppe)2] (dnppe=1,2-bis(di-n-propylphosphino)ethane) and a bis(boraneyl)-protected 4,4′-bpy, provides no ET. Overall, the P2BCy4 fragment provides a unique opportunity for Lewis base activation, in one case allowing for the facile construction of monomers for incorporation into redox-active macromolecules. 相似文献
34.
Galland S Rakotomanomana N Dufour C Mora N Dangles O 《Organic & biomolecular chemistry》2008,6(22):4253-4260
Hydroxycinnamic acids (HCAs) are among the most abundant dietary polyphenols. Recent bioavailability studies have shown that HCAs enter the blood circulation mainly as glucuronides, which are thus most likely to express their potential health effects. In this work, an efficient synthesis of HCA O-arylglucuronides is developed. As for many xenobiotics, the resilience of HCA O-arylglucuronides in plasma and subsequent delivery to tissues could be governed by their binding to human serum albumin (HSA). Hence, the affinity of HCA O-arylglucuronides for HSA and its possible binding site were investigated by fluorescence spectroscopy. HCA O-arylglucuronides turn out to be moderate HSA ligands (K in the range 1-4 x 10(4) M(-1)) that bind HSA in sub-domain IIA, competitively or noncompetitively with other sub-domain IIA ligands such as dansylamide and the flavonol quercetin. 相似文献
35.
F. Dufour M. Horiguchi A. B. Piunovskiy 《Stochastics An International Journal of Probability and Stochastic Processes》2016,88(7):1073-1098
In this paper, we study the infinite-horizon expected discounted continuous-time optimal control problem for Piecewise Deterministic Markov Processes with both impulsive and gradual (also called continuous) controls. The set of admissible control strategies is supposed to be formed by policies possibly randomized and depending on the past-history of the process. We assume that the gradual control acts on the jump intensity and on the transition measure, but not on the flow. The so-called Hamilton–Jacobi–Bellman (HJB) equation associated to this optimization problem is analyzed. We provide sufficient conditions for the existence of a solution to the HJB equation and show that the solution is in fact unique and coincides with the value function of the control problem. Moreover, the existence of an optimal control strategy is proven having the property to be stationary and non-randomized. 相似文献
36.
Dufour A Girods P Masson E Normand S Rogaume Y Zoulalian A 《Journal of chromatography. A》2007,1164(1-2):240-247
Two methods for the sampling and analysis of tar produced from wood pyrolysis were compared. The first method used a conventional cold-trapping technique in solvent-filled impingers followed by liquid injection. The second one is a new application of multibed solid-phase adsorbent (SPA) tubes followed by thermal desorption (TD). Both methods are based on gas chromatography (GC) coupled with mass spectrometry (MS). Quantification was performed with a well reproducible GC-MS method with three internal deuterated standards. The SPA/TD method offers several advantages. No solvent is required, the detection levels are improved, and gas chromatography separation is easier. Moreover, sampling time is reduced from about 1h (for the conventional cold-trapping technique in impingers) to a few seconds. No discrimination was observed between the two sampling methods for the 10 quantified compounds (aromatic compounds from benzene to phenanthrene and phenols) except for benzene. 相似文献
37.
Marianne Bérubé Dufour Dominique Derome Radu Zmeureanu 《Infrared Physics & Technology》2009,52(2-3):70-78
In situ determination of global air leakage of the building envelope is presently done with the fan depressurization test. During such test, infrared thermography could also be used to dimension unintentional small openings (cracks). In this study, thermography was used to measure in laboratory the surface temperature of single-layer walls subjected to air flow through surrogates of cracks. Two image-processing methods were developed and applied to a dataset of 36 thermograms recorded in laboratory. First, using the edge detection technique, the opening length and large width (more than 4 mm) can be graphically estimated with an error of less than 8%. Second, for smaller openings, correlations for two image-processing characteristics, peak height and missing attenuation, were established. These relationships result in estimation with a relative error of less than 4% of the widths of small cracks on thermograms. The development of correlations for the spectrum of conditions found on site could be a step towards in situ quantification of air leakage areas. 相似文献
38.
Katherine Nott Michel Paquot Samuel Dufour Marc Eeman Magali Deleu 《Colloids and surfaces. B, Biointerfaces》2009,69(2):268-275
Three kinds of derivatives of the M1 factor of virginiamycin have been synthesised: esters with long chain fatty acids, oximes with modified polar amino acids and bis-derivatives with both the ester and oxime function. The study of the surface tension time dependence of M1 and its derivatives has shown that it is necessary to enhance simultaneously the hydrophobicity and the hydrophilicity of M1 to render M1 surface-active. A structure/function relationship study of the surface-active bis-derivatives has shown that enhancing the hydrophobicity of the molecule led to slower adsorption kinetics, higher stability of the monolayers formed and a better capacity to penetrate a membrane model. The repulsive electrostatic forces due to the presence of charges on the amino acids linked to M1 lead to higher surface tensions, a greater molecular area at the interface and lower penetration into a membrane model.This study has demonstrated that modifying systematically the hydrophobicity and hydrophilicity of a non surface-active molecule allows the production of surface-active derivatives. 相似文献
39.
B. Beaubier J.-E. Dufour F. Hild S. Roux S. Lavernhe K. Lavernhe-Taillard 《Experimental Mechanics》2014,54(3):329-341
A new calibration procedure is proposed for a stereovision setup. It uses the object of interest as the calibration target, provided the observed surface has a known definition (e.g., its CAD model). In a first step, the transformation matrices needed for the calibration of the setup are determined assuming that the object conforms to its CAD model. Then the 3D shape of the surface of interest is evaluated by deforming the a priori given freeform surface. These two steps are performed via an integrated approach to stereoDIC. The measured 3D shape of a machined Bézier patch is validated against data obtained by a coordinate measuring machine. The feasibility of the calibration method’s application to large surfaces is shown with the analysis of a 2-m2 automotive roof panel. 相似文献
40.
A catalytic asymmetric oxidative iminium-allenamine cascade allows the use of propargyl alcohols as stable substrates and yields valuable chiral bicyclic 4H-chromenes. A subsequent Michael addition-condensation domino reaction provides complex tricyclic 4H-chromenes in a highly enantioselective fashion. 相似文献