全文获取类型
收费全文 | 2412篇 |
免费 | 421篇 |
国内免费 | 688篇 |
专业分类
化学 | 2612篇 |
晶体学 | 57篇 |
力学 | 7篇 |
综合类 | 27篇 |
数学 | 4篇 |
物理学 | 814篇 |
出版年
2024年 | 11篇 |
2023年 | 52篇 |
2022年 | 98篇 |
2021年 | 119篇 |
2020年 | 167篇 |
2019年 | 103篇 |
2018年 | 90篇 |
2017年 | 126篇 |
2016年 | 119篇 |
2015年 | 132篇 |
2014年 | 152篇 |
2013年 | 252篇 |
2012年 | 203篇 |
2011年 | 151篇 |
2010年 | 148篇 |
2009年 | 142篇 |
2008年 | 152篇 |
2007年 | 215篇 |
2006年 | 165篇 |
2005年 | 154篇 |
2004年 | 149篇 |
2003年 | 108篇 |
2002年 | 86篇 |
2001年 | 62篇 |
2000年 | 66篇 |
1999年 | 45篇 |
1998年 | 39篇 |
1997年 | 36篇 |
1996年 | 26篇 |
1995年 | 37篇 |
1994年 | 22篇 |
1993年 | 28篇 |
1992年 | 17篇 |
1991年 | 9篇 |
1990年 | 14篇 |
1989年 | 13篇 |
1988年 | 5篇 |
1987年 | 4篇 |
1986年 | 2篇 |
1985年 | 2篇 |
排序方式: 共有3521条查询结果,搜索用时 359 毫秒
91.
Jaime González Velasco 《Central European Journal of Chemistry》2005,3(3):470-481
The analytical treatment of a model considering the electrooxidation of p-porous silicon layers under galvanostatic conditions
is able to give account of experimental facts such as the shape and location of the electroluminescence peak as well as of
the spectral shift of the electroluminescence peak produced by oxidation. The proposed model considers electroluminescence
to be the result of electron injection into the conduction band by an adsorbed intermediate produced by electrooxidation of
the surface coverage with hydrogen or siloxene of the silicon nanocrystallites. The access of holes to the surface is made
possible by low accumulation layer conditions and is the rate determining step in the electroluminescence mechanism. In this
way it is possible to give a satisfactory explanation to the shift towards the blue experimented by the electroluminiscence
emission maximum as a consequence of electrooxidation. 相似文献
92.
The composition, overall stability constant and molar absorptivity of the chelate of gallium(III) ion with semimethylthymol blue, SMTB, were determined spectrophotometrically in acetate buffer (pH 4.5–5). A violet Ga(SMTB) chelate was formed with logarithmic overall stability constant of 18.0±0.1 (I=0.1) and molar absorptivity of 4.25×104l mol–1cm–1 (max 580 nm). SMTB is proposed as a new reagent for the spectrophotometric determination of micro-molar amounts of gallium(III). The colour development depends on time, temperature, pH and buffer species. The interference of different cations, anions and organic acids on gallium(III) determination was also investigated. Beer's law was obeyed for 3.5–31.3 gGa(III)/25ml (0.14–1.25 g ml–1). SMTB was used for the spectrophotometric determination of gallium in different grade minerals and ores and the results were of acceptable error and relative standard deviation. Comparison between the two suggested methods and atomic absorption spectrometry for Ga(III) determination was carried out. 相似文献
93.
Toluidine blue(TB) is a good sensitizer for the polymerization of acrylnmide(AM) induced by He-Ne laser. With TB as a sensitizer and various alcoholamine as donors, the photoredox of TB and the polymerization kinetics of AM induced by He-Ne laser were investigated. It was found that either for the photoredox of TB or for the polymerization of AM, the activity of alcoholamine increases in the order of EOA相似文献
94.
Eric W. Bohannan Xuerong Gao Kimberly R. Gaston Christopher D. Doss Chariklia Sotiriou-Leventis Nicholas Leventis 《Journal of Sol-Gel Science and Technology》2002,23(3):235-245
This study shows that conventional photolithography can be applied for patterning native or organic dye-doped silica films (0.5 m thick) obtained via a base-catalyzed sol-gel process. Photoresist was spin-coated onto high optical quality xerogel films, soft-baked, exposed to UV irradiation through a photomask, and developed with a commercial photoresist developing solution. Etching away of the photoresist-unprotected areas of the silica films was carried out with a dilute HF solution, while the remaining unexposed photoresist was removed with acetone. Interdigitated array patterns with features as small as 0.5 mm show a smooth surface and extremely sharp interfaces. Densification of the films at 550°C for 2 h decreases the film thickness by 11%, increases the refractive index from 1.420 to 1.456, and allows for well-defined patterning down to length scales of 10 m. Since the densification conditions are incompatible with organic dopants, it is demonstrated that sol-gel films can be doped after pattering (post-doping) by adsorption of cationic dyes from solution. Scanning electron microscopy reveals that the microstructure of patterned sol-gel films is similar to that of bulk monoliths, indicating that the photolithographic procedure is not harmful to the film quality. All patterned films demonstrate highly regular light diffraction patterns. 相似文献
95.
A new type of inorganic biosensor is introduced. The sensor comprises glucose oxidase enzymes encapsulated in a sol-gel-derived
Prussian blue-silicate hybrid network. Glucose is detected by the biocatalytic reduction of oxygen followed by catalytic reduction
of hydrogen peroxide by the Prusian blue catalyst. The sol-gel silicate entails a rigid encapsulating matrix, the Prussian
blue provides chemical catalysis and charge mediation from the reduction site to the supporting electrode, and the enzyme
is responsible for the biocatalysis. The feasibility of a dual optical/electrochemical mode of analysis is also demonstrated. 相似文献
96.
本文提出在原子吸收光谱测定中,采用Smith-Hieftje法校正背景时,空心阴极灯供电条件(即最佳宽窄脉冲电流)的选择依据和选择方法;并给出24个常见元素的宽窄脉冲电流的选定结果。 相似文献
97.
98.
Zhi Qiang LIU Qi FANG* Wen Tao YU Gang XUE Du Xia CAO Dong WANG Guang Ming XIA Min Hua JIANG State Key Laboratory of Crystal Materials Shandong University Jinan 《中国化学快报》2002,13(10)
In common fluorescence process, molecular excitation is caused by the absorption of at least a single photon with shorter wavelength. When certain laser is used as the pump source, some compounds can be excited by simultaneous absorption of at least two photons and then the emission of up-converted fluorescence may occur. This process is called two-photon excited fluorescence (TPEF)1,2. Because of several advantages of TPEF, including intrinsic high three-dimensional resolution and the p… 相似文献
99.
Three highly sensitive spectrophotometric methods for the determination of platinum(IV) have been developed, based on its colour reactions with molybdate and basic dyes (BD) in aqueous solution in the presence of poly(vinyl alcohol). Platinum(IV) reacts with molybdate and BD to form ion — association complexes of composition (BD)2[Pt (MoO4)3]. The molar absorptivities are between 6.83 × 105 and 9.51 × 105 dm3mol–1cm–1, the highest value being found with nile blue. Suitable conditions for the reactions and the effects of foreign ions were investigated. The methods can be applied to the spectrophotometric determination of trace amounts of platinum(IV) in some catalysts and ores. 相似文献
100.
《Electroanalysis》2005,17(3):210-222
Presented in this work is the first step towards an enzymeless/mediatorless glucose sensor. We first observed remarkable electrocatalytic oxidation of glucose using combinative ruthenium oxide (RuOx)‐Prussian blue (PB) analogues (designated as mvRuOx‐RuCN, mv: mixed valent) at ca. 1.1 V (vs. Ag/AgCl) in acidic media (pH 2 Na2SO4/H2SO4). Individual RuOx and PB analogs failed to give any such catalytic response. A high ruthenium oxidation state (i.e., oxy/hydroxy‐RuVII, E°≈1.4 V vs. RHE), normally occurring in strong alkaline conditions at RuOx‐based electrodes, was electrogenerated and stabilized (without any conventional disproportionation reaction) in the mvRuOx‐RuCN matrix for glucose catalysis. Detail X‐ray photoelectron spectroscopic studies can fully support the observation. The catalyst was chemically modified onto a disposable screen‐printed carbon electrode and employed for the amperometric detection of glucose via flow injection analysis (FIA). This system has a linear detection range of 0.3–20 mM with a detection limit and sensitivity of 40 μM (S/N=3) and 6.2 μA/(mM cm2), respectively, for glucose. Further steps towards the elimination of interference and the extendibility to neutral pHs were addressed. 相似文献