全文获取类型
收费全文 | 712篇 |
免费 | 36篇 |
国内免费 | 3篇 |
专业分类
化学 | 501篇 |
晶体学 | 8篇 |
力学 | 17篇 |
数学 | 107篇 |
物理学 | 118篇 |
出版年
2023年 | 4篇 |
2022年 | 12篇 |
2021年 | 13篇 |
2020年 | 23篇 |
2019年 | 13篇 |
2018年 | 6篇 |
2017年 | 11篇 |
2016年 | 20篇 |
2015年 | 22篇 |
2014年 | 20篇 |
2013年 | 30篇 |
2012年 | 60篇 |
2011年 | 58篇 |
2010年 | 44篇 |
2009年 | 20篇 |
2008年 | 59篇 |
2007年 | 44篇 |
2006年 | 37篇 |
2005年 | 35篇 |
2004年 | 23篇 |
2003年 | 18篇 |
2002年 | 17篇 |
2001年 | 9篇 |
2000年 | 7篇 |
1999年 | 5篇 |
1998年 | 8篇 |
1997年 | 6篇 |
1996年 | 4篇 |
1995年 | 7篇 |
1994年 | 5篇 |
1993年 | 6篇 |
1992年 | 10篇 |
1991年 | 7篇 |
1990年 | 4篇 |
1989年 | 8篇 |
1988年 | 6篇 |
1986年 | 3篇 |
1985年 | 7篇 |
1984年 | 8篇 |
1983年 | 9篇 |
1982年 | 3篇 |
1980年 | 4篇 |
1978年 | 4篇 |
1977年 | 3篇 |
1976年 | 4篇 |
1975年 | 3篇 |
1974年 | 7篇 |
1973年 | 2篇 |
1939年 | 3篇 |
1924年 | 2篇 |
排序方式: 共有751条查询结果,搜索用时 15 毫秒
91.
Etienne MA Aucoin JP Fu Y McCarley RL Hammer RP 《Journal of the American Chemical Society》2006,128(11):3522-3523
We have prepared two peptides based on the hydrophobic core (Lys-Leu-Val-Phe-Phe) of amyloid beta-protein (Abeta) that contain alpha,alpha-disubstituted amino acids at alternating positions, but differ in the positioning of the oligolysine chain (AMY-1, C-terminus; AMY-2, N-terminus). We have studied the effects of AMY-1 and AMY-2 on the aggregation of Abeta and find that, at stoichiometric concentrations, both peptides completely stop Abeta fibril growth. Equimolar mixtures of AMY-1 and Abeta form only globular aggregates as imaged by scanning force microscopy and transmission electron microscopy. These samples show no signs of protofibrillar or fibrillar material even after prolonged periods of time (4.5 months). Also, 10 mol % of AMY-1 prevents Abeta self-assembly for long periods of time; aged samples (4.5 months) show only a few protofibrillar or fibrillar aggregates. Circular dichroism spectroscopy of equimolar mixtures of AMY-1 and Abeta show that the secondary structure of the mixture changes over time and progresses to a predominantly beta-sheet structure, which is consistent with the design of these inhibitors preferring a sheet-like conformation. Changing the position of the charged tail on the peptide, AMY-2 interacts with Abeta differently in that equimolar mixtures form large ( approximately 1 mum) globular aggregates which do not progress to fibrils, but precipitate out of solution. The differences in the aggregation mediated by the two peptides is discussed in terms of a model where the inhibitors act as cosurfactants that interfere with the native ability of Abeta to self-assemble by disrupting hydrophobic interactions either at the C-terminus or N-terminus of Abeta. 相似文献
92.
Kuśtrowski P Chmielarz L Dziembaj R Cool P Vansant EF 《The journal of physical chemistry. A》2005,109(2):330-336
The novel mesoporous templated silicas (MCM-48, SBA-15, MCF, and MSU) were used as supports for transition metal (Cu, Cr, or Fe) oxides. The catalysts were synthesized using the incipient wetness impregnation, and characterized by low-temperature N2 sorption, DRIFT, photoacoustic IR spectroscopy, UV-vis diffuse reflectance spectroscopy, and temperature-programmed desorption of ammonia. It was shown that the preparation method used results in different distributions and dimensions of the transition metal oxide clusters on the inert support surface. The prepared catalysts were tested in the reaction of oxidative dehydrogenation of ethylbenzene in the presence of nitrous oxide. The iron-containing catalysts showed the highest catalytic activity. The presence of isolated Fe3+ was found to be the most important factor influencing the ethylbenzene conversion. The undesirable effect of the increase in selectivity toward CO2 was observed for the samples with the highest concentrations of acidic surface sites. 相似文献
93.
Stamp collapse in soft lithography 总被引:1,自引:0,他引:1
Huang YY Zhou W Hsia KJ Menard E Park JU Rogers JA Alleyne AG 《Langmuir : the ACS journal of surfaces and colloids》2005,21(17):8058-8068
We have studied the so-called roof collapse in soft lithography. Roof collapse is due to the adhesion between the PDMS stamp and substrate, and it may affect the quality of soft lithography. Our analysis accounts for the interactions of multiple punches and the effect of elastic mismatch between the PDMS stamp and substrate. A scaling law among the stamp modulus, punch height and spacing, and work of adhesion between the stamp and substrate is established. Such a scaling law leads to a simple criterion against the unwanted roof collapse. The present study agrees well with the experimental data. 相似文献
94.
Ben Yahia H Gaudin E Darriet J Banks M Kremer RK Villesuzanne A Whangbo MH 《Inorganic chemistry》2005,44(9):3087-3093
A new magnetic oxide, CuMnVO4, was prepared, and its crystal structure was determined by single-crystal X-ray diffraction. The magnetic properties of CuMnVO4 were characterized by magnetic susceptibility and specific heat measurements, and the spin exchange interactions of CuMnVO4 were analyzed on the basis of spin-polarized electronic band structure calculations. CuMnVO4 contains MnO4 chains made up of edge-sharing MnO6 octahedra containing high-spin Mn2+ cations. Our work shows that CuMnVO4 undergoes a three-dimensional antiferromagnetic transition at approximately 20 K. Both the intrachain and interchain spin exchanges are antiferromagnetic, and the interchain spin exchange is not negligible compared to the intrachain spin exchange. 相似文献
95.
Etienne M Grosso D Boissière C Sanchez C Walcarius A 《Chemical communications (Cambridge, England)》2005,(36):4566-4568
We provide the first electrochemical evidence of permeability changes in continuous mesoporous TiO2 thin film electrodes induced by nanocrystallisation. 相似文献
96.
It is well known under the name of ‘periodic homogenization’ that, under a centering condition of the drift, a periodic diffusion process on Rd converges, under diffusive rescaling, to a d-dimensional Brownian motion. Existing proofs of this result all rely on uniform ellipticity or hypoellipticity assumptions on the diffusion. In this paper, we considerably weaken these assumptions in order to allow for the diffusion coefficient to even vanish on an open set. As a consequence, it is no longer the case that the effective diffusivity matrix is necessarily non-degenerate. It turns out that, provided that some very weak regularity conditions are met, the range of the effective diffusivity matrix can be read off the shape of the support of the invariant measure for the periodic diffusion. In particular, this gives some easily verifiable conditions for the effective diffusivity matrix to be of full rank. We also discuss the application of our results to the homogenization of a class of elliptic and parabolic PDEs. 相似文献
97.
Distributions of simultaneous fiber failures—bursts—in loaded fiber bundles are studied considering inertia and damping. Resulting burst size distributions have universal properties: all approach the power law DΔΔ−2.5 for larger burst sizes Δ. Momentary burst size distributions evolve with increasing damage and do not follow power laws but are still universal. Finally, it is briefly outlined how to use distribution progression to assess damage state. 相似文献
98.
Karolien De Wael Sandra Van Vlierberghe Hans Buschop Peter Dubruel Bart Vekemans Etienne Schacht Laszlo Vincze Annemie Adriaens 《Surface and interface analysis : SIA》2009,41(5):389-393
The aim of the present paper is to characterize a cross‐linked horse heart cytochrome c (HHC) film on cysteamine‐modified gold electrodes. The HHC film was deposited using 1‐ethyl‐3‐(3‐dimethylaminopropyl)‐carbodiimide (EDC) as a coupling agent. Attenuated total reflection infrared (ATR‐IR) spectroscopic analyses were performed to characterize the newly formed surface on a qualitative and conformational level. The film thickness was measured using a noncontact optical surface profiler, while quantitative data and information on the heterogeneity of the film were obtained by means of synchrotron radiation X‐ray micro fluorescence (SR micro‐XRF). Results indicate that, in addition to electrochemical studies, spectroscopic analysis methods are essential to gain insight in the effect of immobilization strategies on protein conformations. The latter is of relevance in the development and optimization of biosensors. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
99.
Etienne Airiau Thomas Spangenberg Nicolas Girard Dr. Angèle Schoenfelder Jessica Salvadori Maurizio Taddei Prof. André Mann Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(35):10938-10948
The development of hydroformylative domino reactions of easily accessible vinyl acetamides is described. Extremely regioselective hydroformylation of terminal double bounds provides a transient N‐acyliminium that can be trapped by various nucleophiles to give several aza‐heterocylic scaffolds in a diastereoselective manner. 相似文献
100.
Structural transformations induced in gamma and alpha globulins under influence of gamma irradiation using doses of 2.5 and
24 kGy were studied by differential scanning calorimetry (DSC) and thermogravimetry (TG, DTG). Thermal decomposition of the
globulins irradiated in water suspensions occurs at higher temperatures, in comparison to the reference non-irradiated samples.
This was related to formation of covalent linkages in the irradiated proteins, apart to chemical changes induced in amino-acids.
Essential modification of thermal decomposition was detected already after irradiation with a dose of 2.5 kGy performed for
water suspensions. Irradiation of solid native proteins induces decrease in decomposition temperature and gives evidence of
proteins degradation. 相似文献