全文获取类型
收费全文 | 680篇 |
免费 | 29篇 |
国内免费 | 2篇 |
专业分类
化学 | 523篇 |
晶体学 | 6篇 |
力学 | 6篇 |
数学 | 100篇 |
物理学 | 76篇 |
出版年
2022年 | 7篇 |
2021年 | 8篇 |
2020年 | 12篇 |
2019年 | 14篇 |
2018年 | 6篇 |
2017年 | 9篇 |
2016年 | 12篇 |
2015年 | 21篇 |
2014年 | 20篇 |
2013年 | 30篇 |
2012年 | 32篇 |
2011年 | 44篇 |
2010年 | 25篇 |
2009年 | 26篇 |
2008年 | 40篇 |
2007年 | 38篇 |
2006年 | 34篇 |
2005年 | 40篇 |
2004年 | 28篇 |
2003年 | 27篇 |
2002年 | 33篇 |
2001年 | 10篇 |
2000年 | 15篇 |
1999年 | 8篇 |
1998年 | 11篇 |
1997年 | 10篇 |
1996年 | 19篇 |
1995年 | 5篇 |
1994年 | 4篇 |
1993年 | 9篇 |
1992年 | 6篇 |
1991年 | 5篇 |
1990年 | 6篇 |
1989年 | 6篇 |
1987年 | 5篇 |
1986年 | 7篇 |
1985年 | 9篇 |
1984年 | 2篇 |
1983年 | 5篇 |
1982年 | 8篇 |
1981年 | 10篇 |
1980年 | 8篇 |
1978年 | 6篇 |
1977年 | 6篇 |
1976年 | 7篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1973年 | 5篇 |
1971年 | 2篇 |
1970年 | 2篇 |
排序方式: 共有711条查询结果,搜索用时 31 毫秒
51.
Christiane Becker Michael Hodenius Gitta Blendinger Antonio Sechi Thomas Hieronymus Detlef Müller-Schulte Thomas Schmitz-Rode Martin Zenke 《Journal of magnetism and magnetic materials》2007
A challenge for future applications in nanotechnology is the functional integration of nano-sized materials into cellular structures. Here we investigated superparamagnetic Fe3O4 iron oxide nanoparticles coated with a lipid bilayer for uptake into cells and for targeting subcellular compartments. It was found that magnetic nanoparticles (MNPs) are effectively taken up into cells and make cells acquire magnetic activity. Biotin-conjugated MNPs were further functionalized by binding of the fluorescent tag streptavidin–fluorescein isothiocyanate (FITC) and, following uptake into cells, shown to confer magnetic activity and fluorescence labeling. Such FITC-MNPs were localized in the lysosomal compartment of cells which suggests a receptor-mediated uptake mechanism. 相似文献
52.
Stefan Eibl Andrew Fitch Michela Brunelli Alexander Dominic Evans Philip Pattison Marie Plazanet Mark Robert Johnson Christiane Alba‐Simionesco Helmut Schober 《Acta Crystallographica. Section C, Structural Chemistry》2009,65(6):o278-o280
The title compound, C10H18, a decalin stereoisomer, crystallizes with Z′ = 0.5 in the space group P21/n. The trans‐decalin molecule is located on an inversion centre with both rings in a chair conformation, making for a quasi‐flat overall shape. Despite the absence of hydrogen bonds, it crystallizes easily. In this work the unknown crystal structure of trans‐decalin has been solved and refined using X‐ray powder diffraction data. 相似文献
53.
54.
FT-IR spectroscopy and SFM were used to investigate the growth of thin films of the organic semiconductor 3,4,9,10-perylenetetracarboxylicdianhydride (PTCDA) deposited by vacuum sublimation onto various substrates, i.e. Ag(111) layers on mica, KBr(100), mica, oxidized Si, and TiO2 nanoparticles on Si. Layer thicknesses of PTCDA varied from 10 to 1500 nm.The anhydride vibrations of PTCDA differ for the used substrates, which can be connected to the orientation of the molecules relative to the substrate surface and the film morphology as detected in the SFM pictures. 相似文献
55.
Christiane Werner Frederik Wegener Stephan Unger Salvador Nogués Pierrick Priault 《Rapid communications in mass spectrometry : RCM》2009,23(16):2428-2438
Recent advances in understanding the metabolic origin and the temporal dynamics in δ13C of dark‐respired CO2 (δ13Cres) have led to an increasing awareness of the importance of plant isotopic fractionation in respiratory processes. Pronounced dynamics in δ13Cres have been observed in a number of species and three main hypotheses have been proposed: first, diurnal changes in δ13C of respiratory substrates; second, post‐photosynthetic discrimination in respiratory pathways; and third, dynamic decarboxylation of enriched carbon pools during the post‐illumination respiration period. Since different functional groups exhibit distinct diurnal patterns in δ13Cres (ranging from 0 to 10‰ diurnal increase), we explored these hypotheses for different ecotypes and environmental (i.e. growth light) conditions. Mass balance calculations revealed that the effect of respiratory substrates on diurnal changes in δ13Cres was negligible in all investigated species. Further, rapid post‐illumination changes in δ13Cres (30 min), which increased from 2.6‰ to 5‰ over the course of the day, were examined by positional 13C‐labelling to quantify changes in pyruvate dehydrogenase (PDH) and Krebs cycle (KC) activity. We investigated the origin of these dynamics with Rayleigh mass balance calculations based on theoretical assumptions on fractionation processes. Neither the estimated changes of PDH and KC, nor decarboxylation of a malate pool entirely explained the observed pattern in δ13Cres. However, a Rayleigh fractionation of 12C‐discriminating enzymes and/or a rapid decline in the decarboxylation rate of an enriched substrate pool may explain the post‐illumination peak in δ13Cres. These results are highly relevant since δ13Cres is used in large‐scale carbon cycle studies. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
56.
Hermann Ehrlich Thomas Hanke René Born Christiane Fischer Andrej Frolov Tobias Langrock Ralf Hoffmann Uwe Schwarzenbolz Thomas Henle Paul Simon Dorin Geiger Vasily V. Bazhenov Hartmut Worch 《Journal of membrane science》2009
In the present work, we show for the first time, that N?-carboxymethyllysine is the major product of the in vitro non-enzymatic glycation reaction between fibrillar collagen and glucuronic acid. Dual diffusion membrane system was effectively used for oriented crystal growth of octacalcium phosphate/hydroxyapatite on the biomimetically carboxymethylated collagen fibrils. We hypothesize that the function of biomimetically carboxymethylated collagen is to increase the local concentration of corresponding ions in such a way that a critical nucleus of ions can be formed, leading to the formation of the mineral under specific micro-environment conditions achieved by using diffusion membrane system. 相似文献
57.
Frauke Schimmele Christiane Kaiser Susanne Pitsch Helmut Sitzmann 《Chemie in Unserer Zeit》2016,50(4):234-243
Reactions of the alkaline earth metals magnesium, calcium, strontium, and barium with water, phenolphthalein solution, diluted extract of red cabbage, diluted hydrochloric acid, or ammonia are well suited for a demonstration of the increase in reactivity within this group of metals with increasing atomic number. If the alkali metals lithium and sodium are included, the reactivity of six s‐block elements can be demonstrated in test tubes with small amounts of chemicals. 相似文献
58.
Hofmann CC Lindner SM Ruppert M Hirsch A Haque SA Thelakkat M Köhler J 《Physical chemistry chemical physics : PCCP》2010,12(43):14485-14491
A flexible organic triad consisting of two perylene bisimide antennas covalently linked to a [60]fullerene by flexible spacers has been synthesized and studied by electrochemistry, steady-state and time-resolved spectroscopy. We found that π-π-stacking of the two antenna subunits has considerable impact on the photophysics of the system and leads to a reduction of the effective light-harvesting efficiency of the assembly. This finding is important for light harvesting in flexible materials based on the dye antenna-fullerene concept. 相似文献
59.
Brodie-Linder N Le Caër S Alam MS Renault JP Alba-Simionesco C 《Physical chemistry chemical physics : PCCP》2010,12(42):14188-14195
Measurement of H(2) production from electron irradiation (10 MeV) on SBA-15 materials has shown that adsorbed water is attacked preferentially. Silanol groups are only attacked when they are in the majority with respect to adsorbed water, however they are much less efficient at producing H(2). The comparison between water content before and after electron irradiation and the corresponding H(2) production indicates that water desorption is the main route to adsorbed water loss for SBA-15 materials. On the other hand, surface silanol groups are more susceptible to attack, leading to H(2) production when SBA-15 samples have undergone extensive thermal treatment. Electron irradiation of SBA-15-Cu materials has shown that the presence of Cu(II) on the surface reduces and inhibits the production of H(2.) This inhibiting power affects adsorbed water bonded to grafted copper but not surface silanol groups. 相似文献
60.
The problem of two‐dimensional tracer advection on the sphere is extremely important in modeling of geophysical fluids and has been tackled using a variety of approaches. A class of popular approaches for tracer advection include ‘incremental remap’ or cell‐integrated semi‐Lagrangian‐type schemes. These schemes achieve high‐order accuracy without the need for multistage integration in time, are capable of large time steps, and tend to be more efficient than other high‐order transport schemes when applied to a large number of tracers over a single velocity field. In this paper, the simplified flux‐form implementation of the Conservative Semi‐LAgrangian Multi‐tracer scheme (CSLAM) is reformulated using quadratic curves to approximate the upstream flux volumes and Gaussian quadrature for integrating the edge flux. The high‐order treatment of edge fluxes is motivated because of poor accuracy of the CSLAM scheme in the presence of strong nonlinear shear, such as one might observe in the midlatitudes near an atmospheric jet. Without the quadratic treatment of upstream edges, we observe at most second‐order accuracy under convergence of grid resolution, which is returned to third‐order accuracy under the improved treatment. A shallow‐water barotropic instability also reveals clear evidence of grid imprinting without the quadratic correction. Consequently, these tests reveal a problem that might arise in tracer transport near nonlinearly sheared regions of the real atmosphere, particularly near cubed‐sphere panel edges. Although CSLAM is used as the foundation for this analysis, the conclusions of this paper are applicable to the general class of incremental remap schemes. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献