全文获取类型
收费全文 | 880篇 |
免费 | 109篇 |
国内免费 | 250篇 |
专业分类
化学 | 940篇 |
晶体学 | 12篇 |
力学 | 15篇 |
综合类 | 2篇 |
数学 | 2篇 |
物理学 | 268篇 |
出版年
2024年 | 8篇 |
2023年 | 14篇 |
2022年 | 32篇 |
2021年 | 32篇 |
2020年 | 47篇 |
2019年 | 34篇 |
2018年 | 31篇 |
2017年 | 40篇 |
2016年 | 43篇 |
2015年 | 35篇 |
2014年 | 43篇 |
2013年 | 76篇 |
2012年 | 55篇 |
2011年 | 62篇 |
2010年 | 35篇 |
2009年 | 68篇 |
2008年 | 70篇 |
2007年 | 86篇 |
2006年 | 71篇 |
2005年 | 62篇 |
2004年 | 38篇 |
2003年 | 51篇 |
2002年 | 37篇 |
2001年 | 33篇 |
2000年 | 35篇 |
1999年 | 23篇 |
1998年 | 18篇 |
1997年 | 13篇 |
1996年 | 12篇 |
1995年 | 13篇 |
1994年 | 6篇 |
1993年 | 2篇 |
1992年 | 4篇 |
1991年 | 4篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1985年 | 3篇 |
排序方式: 共有1239条查询结果,搜索用时 855 毫秒
11.
《Electroanalysis》2003,15(14):1192-1197
The investigation of the electrochemical reduction processes of C6H5SSC6H5 and C6H5SH in CH3CN using cyclic voltammetry indicates a different behavior on GC and Au electrodes. On GC surface adsorption phenomena are absent, the electrochemical reduction process is irreversible and diffusion controlled. For both the starting molecules the same species, C6H5S?, is formed upon reduction. The E° values of the reduction processes were determined by convolution method and the standard free energy of the S? S bond of C6H5SSC6H5 estimated. On Au surface instead, a self‐assembled monolayer of C6H5SAuads originated after the S? S or S? H bond breaking can be observed by simply dipping the electrode in solution of C6H5SSC6H5 and C6H5SH, respectively. The properties of the SAM were investigated by electrochemical reduction of the adsorbed thiolates. On Au electrode the reduction processes involve C6H5SAuads and give rise to desorbed C6H5S?. A neutral radical is obtained by electrochemical oxidation of thiolate anion. It reacts rapidly with the electrode surface to give the S‐Au bond again. 相似文献
12.
13.
Dispersion of copper(Ⅱ) phthalocyanine (CuPc), copper(Ⅱ) phthalocyaninesulfonate (CuPcS) and cobalt(Ⅱ)phthalocyaninetetrasulfonate (CoPcTS) on the surface of titanium dioxide was investigated by XRD, XPS, FT-IR and UV-Vis techniques. Results show that interaction between CuPc and TiO2 was very weak and CuPc was difficult to disperse on the surface of the support. While partly sulfurized CuPcS could be dispersed on the surface of support through sulfo-groups and its dispersion capacity was determined to be 0.085 g CuPcS/g TiO2. Completely sulfurlzed CoPcTS could also be dispersed on the surface of TiO2 as a monolayer and its dispersion capacity was 0.12 g CoPcTS/g TiO2. Interactions of the sulfo-groups as well as the electrons of CoPcTS with the surface of TiO2 could be evidenced by FT-IR characterization. Therefore, it was suggested that CoPcTS molecules be adsorbed on the surface of TiO2 in a flat-lying mode while CuPcS in a slanting one. UV-Vis spectra show that the dispersed CuPcS and CoPcTS molecules exist in both forms of monomers and dimers. 相似文献
14.
15.
The surface pressure vs. mokcular surface area relations for dipalmitoyl phosphatidylcholine (DPPC) insoluble monolayer and sodium deoxycholate (SDC) adsorbed monolayer,L and D1, respectively, were obtained from the analyses of surface tensions measured by the Wilhelmy glass plate. Also, D1 was obtained by a drop-weight method. Next, the surface pressure time course,(t), of the SDC aq. was measured by the Wilhelmy plate before and after DPPC was spread on the liquid surface. At DPPC spreading,(t) jumped to a maximum,, and decreased along an exponential curve. The values of with various surface amounts of DPPC and bulk concentrations of SDC were analyzed using a dual surface-region model. The model enabled the estimation of. For better fitting, modified relations were constructed in place of D1. The exponential decrease of(t) was also observed on the SDC adsorbed monolayer which was rapidly compressed by a moving barrier. The(t) relaxation rate constants of the SDC monolayers which were compressed by DPPC spreading and the moving barrier agreed with each other, suggesting a desorption of SDC from the surface. 相似文献
16.
In situ polarized Fourier transform IR external reflection spectra of Langmuir monolayers of zinc stearate and zinc 12-hydroxystearate
on a water surface were recorded for various surface areas, and their molecular structures were estimated. In the zinc stearate
monolayer, the wavenumbers and the absorbances of the antisymmetric and symmetric methylene stretching bands did not change
during monolayer compression, which means that orientational and conformational changes of the hydrocarbon chain did not occur.
However, wavenumber changes of the antisymmetric and symmetric carboxylate stretching bands were observed during surface compression.
The change in the binding nature of the zinc cation to the carboxylate group was speculated. Moreover, it was elucidated that
the structure of the hydrocarbon chain in the zinc 12-hydroxystearate monolayer was different from that in the zinc stearate
monolayer.
Received: 21 March 2001 Accepted: 6 July 2001 相似文献
17.
XRD,DTA,比表面测定等结果表明,制备方法对MoO3/ZrO2结构有决定性影响.仲钼酸铵浸渍仅经干燥的Zr(OH)4再经高温焙烧所得团体超强酸MoO3/ZrO2(Ⅰ)与浸渍晶态ZrO2所得部分氧化催化剂MoO3/ZrO2(Ⅱ)的载体形态有明显不同.(1)MoO3/ZrO2(Ⅰ)的比表面数倍于MoO3/ZrO2(Ⅱ);(2)MoO3含量增加时,MoO3/ZrO2(Ⅰ)的比表面逐步增大至一极大值再缓缓下降,而MoO3/ZrO2(Ⅱ)的比表面随MoO3含量增加而单调下降;(3)在MoO3/ZrO2(Ⅰ)中,ZrO2以介稳四方相存在,而在MoO3/ZrO2(Ⅱ)中则是稳定的单斜相.在此基础上研究了事先引入的活性组分在载体织构形成过程中的作用,包括延迟ZrO2晶化,阻碍晶粒长大及与之相关的相变等,并讨论了MoO3/ZrO2(Ⅰ)中MoO3最佳含量的科学含义. 相似文献
18.
《Electroanalysis》2003,15(20):1577-1583
Laccase enzymes from two different sources, namely, tree laccase from Rhus vernicifera and fungal laccase from Coriolus hirsutus were used for the development of biosensor for catechol. Laccase was immobilized onto the amine terminated thiol monolayers on gold surface by glutaraldehyde coupling. From the different thiol monolayers investigated, cystamine was found to be optimal with respect to sensitivity, stability, reproducibility, and other electrochemical properties of the enzyme electrode. Linear calibration in the range between 1 and 400 μM for catechol was obtained for fungal laccase covalently coupled on the electrode surface. The kinetic parameters determined using the Lineweaver‐Burk and Eadie‐Hofstee plots were Km=0.65 mM and Vmax=24.5 μA for fungal laccase compared to Km=5.4 mM and Vmax=6.6 μA for tree laccase on cystamine monolayer. The electrode showed good stability for 1 month without loosing appreciable activity when stored dry in a refrigerator at ?20 °C. 相似文献
19.
Michael?Sch?ferlingEmail author Michael?Riepl Petra?Pavlickova Hubert?Paul Dev?Kambhampati Bo?Liedberg 《Mikrochimica acta》2003,142(4):193-203
Two different types of -substituted alkanethiol/disulfide compounds have been used to prepare monolayer architectures on gold serving as platforms for the immobilization of receptor probe molecules – antibodies. These are: (i) carboxylic acid alkanethiols post-reacted with amino biotin to generate streptavidin surfaces, and (ii) N-hydroxysuccinimide-terminated disulfide surfaces. The properties of the monolayers, with and without attached receptor probe molecules, were analysed using infrared spectroscopy, ellipsometry, fluorescence scanning and atomic force microscopy. Several experimental parameters, such as condensation reagents, additives, probe and target concentrations and immobilization time, were systematically varied to determine the dynamic range and to optimize the sensitivity and signal-to-noise ratio of the biochip platforms. Fluorescence screening using Cy5-labelled antigens finally demonstrated that both surfaces could be successfully employed to immobilize the antibodies. The pros and cons of the two approaches are also discussed.Received November 15, 2002; accepted March 25, 2003
Published online July 28, 2003 相似文献
20.
Monodisperse, cationic polymer particles bearing quaternary ammonium groups effectively self-organized on hydrophobic solid substrates such as alkylated glass plates and polymer films to form particle monolayers. With an increase of the particle surface charge density, the surface coverage decreased and the morphology of particle monolayers changed from aggregated type to dispersed type. The dispersed type of particle monolayers having a relatively regular particle distance was formed at higher temperature. The self-organization behaviors on alkylated glass plates were different from those on unmodified glass plates through electrostatic interaction. The formation of particle monolayers on alkylated glass plates occurred only over a certain latex concentration range in contrast with that on unmodified glass plate. The adhesive strength of particle monolayers was enhanced by annealing at temperatures above the glass transition temperature (T
g) of the particles. Lens-shaped particle monolayers were fabricated by annealing the dispersed type of particle monolayers. 相似文献