全文获取类型
收费全文 | 308篇 |
免费 | 11篇 |
专业分类
化学 | 254篇 |
晶体学 | 8篇 |
力学 | 9篇 |
数学 | 9篇 |
物理学 | 39篇 |
出版年
2022年 | 1篇 |
2021年 | 11篇 |
2020年 | 6篇 |
2019年 | 5篇 |
2018年 | 4篇 |
2017年 | 3篇 |
2016年 | 4篇 |
2015年 | 9篇 |
2014年 | 7篇 |
2013年 | 21篇 |
2012年 | 33篇 |
2011年 | 40篇 |
2010年 | 15篇 |
2009年 | 19篇 |
2008年 | 14篇 |
2007年 | 17篇 |
2006年 | 15篇 |
2005年 | 19篇 |
2004年 | 16篇 |
2003年 | 18篇 |
2002年 | 17篇 |
2001年 | 5篇 |
2000年 | 5篇 |
1999年 | 2篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1991年 | 1篇 |
1988年 | 1篇 |
1982年 | 2篇 |
1980年 | 1篇 |
1978年 | 1篇 |
排序方式: 共有319条查询结果,搜索用时 31 毫秒
91.
Christelle Der Loughian Loïc Tadrist Jean-Marc Allain Julien Diener Bruno Moulia Emmanuel de Langre 《Comptes Rendus Mecanique》2014,342(1):1-7
Model plants are extensively used in biological studies, and their mechanical behaviour needs to be better understood, in relation to studies in mechanoperception for instance. We present here the first approach to derive experimentally the modal parameters of two of these plants, Arabidopsis thaliana and Populus tremula × alba. A classical sinusoidal sweep excitation is used, with a measurement of displacements based on LKT optical flow tracking, followed by a bi-orthogonal decomposition (BOD). This allows us to estimate several modal frequencies for each plant, as well as the corresponding spatial localizations of deformation. Analyzing the modal frequencies, we show that global and local modes correspond to distinct ranges of frequencies and depend differently on plant size. Possible phenotyping applications are then discussed. 相似文献
92.
Dominique Bazin Arnaud Dessombz Christelle Nguyen Hang Korng Ea Frédéric Lioté John Rehr Christine Chappard Stephan Rouzière Dominique Thiaudière Solen Reguer Michel Daudon 《Journal of synchrotron radiation》2014,21(1):136-142
Osteoporosis represents a major public health problem through its association with fragility fractures. The public health burden of osteoporotic fractures will rise in future generations, due in part to an increase in life expectancy. Strontium‐based drugs have been shown to increase bone mass in postmenopausal osteoporosis patients and to reduce fracture risk but the molecular mechanisms of the action of these Sr‐based drugs are not totally elucidated. The local environment of Sr2+ cations in biological apatites present in pathological and physiological calcifications in patients without such Sr‐based drugs has been assessed. In this investigation, X‐ray absorption spectra have been collected for 17 pathological and physiological calcifications. These experimental data have been combined with a set of numerical simulations using the ab initioFEFF9 X‐ray spectroscopy program which takes into account possible distortion and Ca/Sr substitution in the environment of the Sr2+ cations. For selected samples, Fourier transforms of the EXAFS modulations have been performed. The complete set of experimental data collected on 17 samples indicates that there is no relationship between the nature of the calcification (physiological and pathological) and the adsorption mode of Sr2+ cations (simple adsorption or insertion). Such structural considerations have medical implications. Pathological and physiological calcifications correspond to two very different preparation procedures but are associated with the same localization of Sr2+versus apatite crystals. Based on this study, it seems that for supplementation of Sr at low concentration, Sr2+ cations will be localized into the apatite network. 相似文献
93.
Laetitia Ancel Agnieszka Niedźwiecka Colette Lebrun Christelle Gateau Pascale Delangle 《Comptes Rendus Chimie》2013,16(6):515-523
Lanthanide-binding peptides are very attractive for the design of bioprobes. Indeed, they combine the amazing properties of lanthanide ions, such as their time-resolved luminescence (Eu, Tb) or electronic relaxation (Gd) to the characteristics of the peptide scaffold, such as large solubility in water and ability to recognize biological substrates. Peptides derived from natural amino acids are reviewed in a first section. Some of their lanthanide complexes have already demonstrated their efficiency in determining protein structures and functions. Then, we will show how insertion of chelating unnatural amino acids modulates peptide-lanthanide complexes properties, such as luminescence and stability. 相似文献
94.
SMC (sheet molding compound) is a composite based on fibers‐reinforced unsaturated polyester (UP) resin molded usually at 140°C to 170°C under a pressure of 60 to 100 bars. In order to develop new SMC formulations that can be molded at lower temperature (100°C) for economic and environmental reasons, the formulation of the composite had to be completely modified, both to allow a rapid reaction at 100°C, but also to avoid a vitrification phenomenon due to the fact that the glass transition temperature (Tg) of the SMC parts becomes, during the molding process, higher than the mold temperature. In this paper, the relation between the molding temperature, the glass transition temperature, and the final conversion of UP resin/styrene formulations has been underlined. The Tg of the cured resin was decreased by two different ways. The first way involved the reduction of the crosslinking density of the UP resin by using a blend of two resins, a pure maleic and a more flexible one. This blend allows to adjust the Tg over a temperature range from 197°C (Tg of the pure UP resin) to 75°C (Tg of the pure flexible resin). The second way consisted in the addition of butyl methacrylate (BuMA), a reactive plasticizer, to the formulation, allowing a decrease of the final material's Tg from 197°C to 130°C by replacing 35 wt% of styrene by BuMA. These two methods allow to obtain a final conversion of 99% after 8 minutes of molding at 100°C. 相似文献
95.
Stephane Parola Martine Verdenelli Catherine Sigala Jean-Pierre Scharff Karine Velez Christelle Veytizou Jean-François Quinson 《Journal of Sol-Gel Science and Technology》2003,26(1-3):803-806
Sol-gel coatings on non-oxide substrates can be used to prevent high temperature degradation and to improve wet corrosion resistance. Alumina coatings were investigated. The starting precursor was aluminium sec-butoxide, modified with chelating ligands such as 2,4-pentanedione or acrylic acid to prevent its precipitation in the presence of water. Stainless steel plates and Hi-Nicalon SiC fibers are often utilized in different kinds of applications and thus were selected as substrates. Thin films were deposited from the modified alkoxide solutions using dip-coating techniques. The parameters governing the process such as the aging of the sols, the viscosity, the withdrawal rate and the thermal treatment were investigated. The films were characterized (morphology, thickness) and showed an interesting behaviour as protection barrier in an aggressive medium. 相似文献
96.
Hureau C Groni S Guillot R Blondin G Duboc C Anxolabéhère-Mallart E 《Inorganic chemistry》2008,47(20):9238-9247
The two pentadentate amino-pyridine ligands L5(2) and L5(3) (L5(2) and L5(3) stand for the N-methyl-N,N',N'-tris(2-pyridylmethyl)ethane-1,2-diamine and the N-methyl-N,N',N'-tris(2-pyridylmethyl)propane-1,3-diamine, respectively) were used to synthesize four mononuclear Mn(II) complexes, namely [(L5(2))MnCl](PF6) (1(PF6)), [(L5(3))MnCl](PF6) (2(PF6)), [(L5(2))Mn(OH2)](BPh4)2 (3(BPh4)2), and [(L5(3))Mn(OH2)](BPh4)2 (4(BPh4)2). The X-ray diffraction studies revealed different configurations for the ligand L5(n) (n = 2, 3) depending on the sixth exogenous ligand and/or the counterion. Solid state high-field electron paramagnetic resonance spectra were recorded on complexes 1-4 as on previously described mononuclear Mn(II) systems with tetra- or hexadentate amino-pyridine ligands. Positive and negative axial zero-field splitting (ZFS) parameters D were determined whose absolute values ranged from 0.090 to 0.180 cm(-1). Density-functional theory calculations were performed unraveling that, in contrast with chloro systems, the spin-spin and spin-orbit coupling contributions to the D-parameter are comparable for mixed N,O-coordination sphere complexes. 相似文献
97.
Paolini J Leandri C Desjobert JM Barboni T Costa J 《Journal of chromatography. A》2008,1193(1-2):37-49
Chemical composition of volatile fractions of nine commercial hydrolats and corresponding essential oils obtained using an industrial process were studied. The hydrolat volatile fractions were reported for the first time. A comparative study of those obtained, on the one hand, by liquid-liquid extraction (LLE) and, on the other hand, using five solid-phase microextraction (SPME) fibers and also purge-and-trap-automatic thermal desorption (P&T-ATD) was conducted with analysis performed by GC and GC/MS. The use of various techniques has resulted in a change of chromatographic profile of the hydrolat volatile fractions. Quantitative differences were established between chemical compositions of headspace and those obtained by a conventional method (LLE). Statistical analyses were carried out to summarize the results. 相似文献
98.
Free Superoxide is an Intermediate in the Production of H2O2 by Copper(I)‐Aβ Peptide and O2 下载免费PDF全文
Dr. Karine Reybier Sara Ayala Dr. Bruno Alies Dr. João V. Rodrigues Susana Bustos Rodriguez Dr. Giovanni La Penna Dr. Fabrice Collin Dr. Cláudio M. Gomes Dr. Christelle Hureau Prof. Dr. Peter Faller 《Angewandte Chemie (International ed. in English)》2016,55(3):1085-1089
Oxidative stress is considered as an important factor and an early event in the etiology of Alzheimer's disease (AD). Cu bound to the peptide amyloid‐β (Aβ) is found in AD brains, and Cu‐Aβ could contribute to this oxidative stress, as it is able to produce in vitro H2O2 and HO. in the presence of oxygen and biological reducing agents such as ascorbate. The mechanism of Cu‐Aβ‐catalyzed H2O2 production is however not known, although it was proposed that H2O2 is directly formed from O2 via a 2‐electron process. Here, we implement an electrochemical setup and use the specificity of superoxide dismutase‐1 (SOD1) to show, for the first time, that H2O2 production by Cu‐Aβ in the presence of ascorbate occurs mainly via a free O2.? intermediate. This finding radically changes the view on the catalytic mechanism of H2O2 production by Cu‐Aβ, and opens the possibility that Cu‐Aβ‐catalyzed O2.? contributes to oxidative stress in AD, and hence may be of interest. 相似文献
99.
Dr. Viacheslav Shkirskiy Dr. Eric Levillain Dr. Christelle Gautier 《Chemphyschem》2021,22(11):1074-1078
A new method to follow in-situ grafting kinetics of diazonium compounds based on imposing small amplitude high frequency AC oscillations at grafting potential, is outlined. This enables the time-resolved measurements of capacitive impedance concomitantly with the growth of the organic layer at the working electrode. The impedance values were quantitatively correlated with the ex-situ (from voltammograms) and in-situ (from quartz crystal microbalance) measured surface coverages, providing a validation of the new methodology. The versatility of the developed approach was demonstrated on the grafting via reduction of 4-nitrobenzenediazonium on Au and glassy carbon (GC) substrates and via deposition of in-situ generated diazonium salts from 1-aminoanthraquinone and 4-ferrocenylaniline on GC. The capacitive impedance measurements are simple, fast, and non-destructive, making it an appealing methodology for an exploration of grafting kinetics of a wide range of diazonium salts. 相似文献
100.
Bouzina Abdeslem Berredjem Malika Belhani Billel Bouacida Sofiane Marminon Christelle Le Borgne Marc Bouaziz Zouhair Aissaoui Mohamed 《Research on Chemical Intermediates》2021,47(4):1359-1376
Research on Chemical Intermediates - We demonstrate here a rapid and comfortable synthetic sequence to benzothiadiazinone dioxide (six-membered cyclic sulfamide) derivatives, analogues of... 相似文献