全文获取类型
收费全文 | 380篇 |
免费 | 22篇 |
国内免费 | 8篇 |
专业分类
化学 | 182篇 |
晶体学 | 1篇 |
力学 | 18篇 |
数学 | 140篇 |
物理学 | 69篇 |
出版年
2023年 | 2篇 |
2022年 | 4篇 |
2021年 | 9篇 |
2020年 | 12篇 |
2019年 | 17篇 |
2018年 | 14篇 |
2017年 | 7篇 |
2016年 | 15篇 |
2015年 | 10篇 |
2014年 | 19篇 |
2013年 | 38篇 |
2012年 | 28篇 |
2011年 | 23篇 |
2010年 | 16篇 |
2009年 | 13篇 |
2008年 | 24篇 |
2007年 | 14篇 |
2006年 | 20篇 |
2005年 | 15篇 |
2004年 | 13篇 |
2003年 | 8篇 |
2002年 | 11篇 |
2001年 | 4篇 |
2000年 | 6篇 |
1999年 | 2篇 |
1998年 | 4篇 |
1997年 | 2篇 |
1996年 | 3篇 |
1995年 | 7篇 |
1994年 | 2篇 |
1993年 | 6篇 |
1992年 | 5篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1985年 | 3篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1973年 | 4篇 |
1885年 | 1篇 |
排序方式: 共有410条查询结果,搜索用时 187 毫秒
101.
Christian A. Rivera Mourad Heniche François Bertrand Roland Glowinski Philippe A. Tanguy 《国际流体数值方法杂志》2012,69(3):653-670
A parallel sliding mesh algorithm for the finite element simulation of viscous fluid flows in agitated tanks is presented. Lagrange multipliers are used at the sliding interfaces to enforce the continuity between the fixed and moving subdomains. The novelty of the method consists of the coupled solution of the resulting velocity–pressure‐Lagrange multipliers system of equations by an ILU(0)‐QMR solver. A penalty parameter is introduced for both the interface and the incompressibility constraints to avoid pivoting problems in the ILU(0) algorithm. To handle the convective term, both the Newton–Raphson scheme and the semi‐implicit linearization are tested. A penalty parameter is introduced for both the interface and the incompressibility constraints to avoid the failure of the ILU(0) algorithm due to the lack of pivoting. Furthermore, this approach is versatile enough so that it allows partitioning of sliding and fixed subdomains if parallelization is required. Although the sliding mesh technique is fairly common in CFD, the main advantage of the proposed approach is its low computational cost due to the inexpensive and parallelizable calculations that involve preconditioned sparse iterative solvers. The method is validated for Couette and coaxial stirred tanks. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
102.
103.
104.
Importance of Outer‐Sphere and Aggregation Phenomena in the Relaxation Properties of Phosphonated Gadolinium Complexes with Potential Applications as MRI Contrast Agents
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Dr. Mourad Elhabiri Dr. Sabah Abada Mohamadou Sy Dr. Aline Nonat Dr. Philippe Choquet Dr. David Esteban‐Gómez Dr. Claudio Cassino Dr. Carlos Platas‐Iglesias Prof. Mauro Botta Dr. Loïc J. Charbonnière 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(17):6535-6546
A series composed of a tetra‐, a tris‐ and a bisphosphonated ligand based on a pyridine scaffold ( L4 , L3 and L2 , respectively) was studied within the frame of lanthanide (Ln) coordination. The stability constants of the complexes formed with lanthanide cations (Ln=La, Nd, Eu, Gd, Tb, Er and Lu) were determined by potentiometry in aqueous solutions (25.0 °C, 0.1 M NaClO4), showing that the tetraphosphonated complexes are among the most stable LnIII complexes reported in the literature. The complexation of L4 was further studied by different titration experiments using mass spectrometry and various spectroscopic techniques including UV/Vis absorption, and steady state and time‐resolved luminescence (Ln=Eu and Tb). Titration experiments confirmed the formation of highly stable [Ln L4 ] complexes. 31P NMR experiments of the Lu L4 complex revealed an intramolecular interconversion process which was studied at different temperatures and was rationalized by DFT modelling. The relaxivity properties of the GdIII complexes were studied by recording their 1H NMRD profiles at various temperatures, by temperature dependent 17O NMR experiments (Gd L4 ) and by pH dependent relaxivity measurements at 0.47 T (Gd L3 and Gd L2 ). In addition to the high relaxivity values observed for all complexes, the results showed an important second‐sphere contribution to relaxivity and pH dependent variations associated with the formation of aggregates for Gd L2 and Gd L3 . Finally, intravenous injection of Gd L4 to a mouse was followed by dynamic MRI imaging at 1.5 T, which showed that the complex can be immediately found in the blood stream and rapidly eliminated through the liver and in large part through the kidneys. 相似文献
105.
Amina Chnirheb Mourad Harir Basem Kanawati Agnes Fekete Mohammed El Azzouzi Norbert Hertkorn Philippe Schmitt-Kopplin 《Analytical and bioanalytical chemistry》2010,398(5):2325-2334
The hydrolysis of the herbicide safener mefenpyrdiethyl (1-(2, 4-dichlorophenyl)-4, 5-dihydro-5-methyl-1H-pyrazole-3,5-dicarboxylic acid diethyl ester) was investigated in aqueous solutions in the pH range from 2 to 9 and the temperature
range from 298 to 323 K. The kinetics of hydrolysis were pseudo first order and were found to be strongly pH and temperature
dependent. While near-constant in acidic medium, the hydrolysis rates strongly increased in alkaline pH, and total hydrolysis
was observed at pH 11. Two main hydrolysis products, mefenpyrethyl (monoester) and mefenpyr (dicarboxylic acid) were isolated
by ultrahigh-pressure liquid chromatography (UHPLC) and characterized using high-resolution Fourier transform ion cyclotron
resonance mass spectroscopy (ICR-FT/MS) as well as 1H, 13C and 2D NMR analyses. Additionally, a density functional theory (DFT) investigation explained the stability of the pesticide
at pH 7 and the high reactivity of the pesticide in alkaline medium. The key nucleophilic reaction partner is hydroxyl ions
instead of neutral water molecules. Furthermore, the calculated activation barrier for hydrolysis in alkaline medium is in
agreement with the extrapolated and experimentally determined activation barrier at pH 14. 相似文献
106.
In natural waters, fluoride ions are necessary and beneficial for the human being. At higher level of F− in water, it is toxic and detrimental to human health, leading to serious problems such as dental and skeleton fluorosis.
According to the World Health Organization, the acceptable concentrations of fluoride in potable water are in the range of
0.7–1.5 mg L−1. Various treatment technologies for fluoride removal from water have been used such as ion exchange, adsorption and membrane
processes. In the present study, removal of fluoride ions from aqueous solutions was investigated using a polyamide thin film
composite nanofiltration membrane denoted as HL 2514 T from Osmonics Company. Through this membrane, the mechanism of transport
was investigated. The Kedem–Katchelsky model was applied in order to determine phenomenological parameters σ and P
s, respectively, the reflection coefficient of the membrane and the solute permeability of ions. The convective and diffusive
parts of the mass transfer were quantified. The retention of monovalent and bivalent salts by this membrane shows that it
is negatively charged. In the second part, retention of fluoride anions was investigated. Results show that the retention
of fluoride by HL membrane exceeds 80%. The influence of the chemical parameters (feed concentration and ionic strength) and
the physical parameters (applied pressure and recovery) on the elimination of fluoride was studied. 相似文献
107.
Jordan Pohn Mourad Heniche Louis Fradette Michael Cunningham Timothy McKenna 《Macromolecular Symposia》2011,302(1):133-141
Summary: A hybrid multi-zonal/computational fluid dynamics (CFD) framework is currently being developed to aid in the scale-up of high solid content latex production and processing. Poly3D, a commercial laminar CFD code tailored to modelling the mixing of non-Newtonian fluids, has been coupled to a population balance model via a customized interface. CFD is used to generate flow fields inside a series of reactors; this information is then transferred to a multi-zone population balance model to assess the impact of non-homogenous mixing on the evolution of the latex particle size distribution (PSD) when concentrated latex suspension is altered via the addition of a coagulant. The rheological properties of high solid content latexes are sensitive to changes in the PSD, so the flow field is periodically updated if significant changes in the rheological properties of the latex are detected in any of the zones. The details of the models comprising the framework are presented and the utility of the framework is demonstrated. 相似文献
108.
We consider the stability in an inverse problem of determining the potential q entering the wave equation in a bounded smooth domain of Rd from boundary observations. The observation is given by a hyperbolic (dynamic) Dirichlet to Neumann map associated to a wave equation. We prove a log-type stability estimate in determining q from a partial Dirichlet to Neumann map provided that q is a priori known in a neighbourhood of the boundary of the spatial domain and satisfies an additional condition. Next, we use this result to establish a stability estimate related to the multidimensional Borg-Levinson theorem. 相似文献
109.
Alaa A. Hassan Aboul‐Fetouh E. Mourad Kamal M. El‐Shaieb Ashraf H. Abou‐Zied 《Journal of heterocyclic chemistry》2006,43(2):471-475
110.
Labonte L Pagnoux D Roy P Bahloul F Zghal M Melin G Burov E Renversez G 《Optics letters》2006,31(12):1779-1781
A simple self-referenced nondestructive method is proposed for measuring the cutoff wavelength of microstructured optical fibers (MOFs). It is based on the analysis of the time-dependent optical power transmitted through a bow-tie slit rotating in the far-field pattern of the fiber under test. As a first demonstration, the cutoff wavelength of a 2 m MOF sample is found to be close to that provided by numerical predictions (approximately 25 nm higher). Because of the high dynamics of the measurement, the uncertainty is limited to Dlambda= +/-10 nm. 相似文献