全文获取类型
收费全文 | 164篇 |
免费 | 4篇 |
专业分类
化学 | 82篇 |
晶体学 | 2篇 |
数学 | 4篇 |
物理学 | 80篇 |
出版年
2023年 | 1篇 |
2022年 | 3篇 |
2021年 | 9篇 |
2020年 | 5篇 |
2019年 | 4篇 |
2018年 | 1篇 |
2017年 | 1篇 |
2016年 | 4篇 |
2015年 | 3篇 |
2014年 | 2篇 |
2013年 | 3篇 |
2012年 | 15篇 |
2011年 | 20篇 |
2010年 | 14篇 |
2009年 | 9篇 |
2008年 | 13篇 |
2007年 | 8篇 |
2006年 | 9篇 |
2005年 | 3篇 |
2004年 | 4篇 |
2003年 | 11篇 |
2002年 | 2篇 |
2001年 | 1篇 |
2000年 | 1篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1994年 | 3篇 |
1993年 | 5篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1990年 | 3篇 |
1989年 | 1篇 |
1981年 | 1篇 |
排序方式: 共有168条查询结果,搜索用时 15 毫秒
71.
Dae-Won Lee Jung-Jun Oh Young-Moo Park Hee Jun Eom Sung Ho Yeom In Kyu Song Kwan-Young Lee 《Research on Chemical Intermediates》2008,34(8-9):817-825
A poly(methacrylamide-co-methylmethacrylate) (abbreviated PMAA-MMA) polymer support was studied for supporting a heteropolyacid (tungstophosphoric acid, H3PW12O40) with its surface positively charged in the polymerization step. PMAA-MMA supports could be obtained in a porous form by eliminating template reagent molecules (benzylmalonic acid) combined with properly selected monomer (methacrylamide). The amount of amine groups in PMAA-MMA directly determined the amount of H3PW12O40 impregnated, because the amine groups induced a positive charge on the PMAA-MMA surface. Finally, H3PW12O40/PMAA-MMA showed better acid catalytic activities than unsupported H3PW12O40 in alkylation of 1,3,5-trimethylbenzene with cyclohexene, which confirmed that PMAA-MMA supported H3PW12O40 effectively. 相似文献
72.
73.
74.
Tae Sung Eom Kyung Hwan Kim Chung Wung Bark 《Molecular Crystals and Liquid Crystals》2014,600(1):39-46
In this work, we report for the first time the improvement of the photovoltaic characteristics of dye-sensitized solar cells (DSSCs) by doping TiO2 with Fe2O3. DSSCs were fabricated using various percentages of Fe2O3-doped TiO2 composite nanoparticles. The Fe2O3-doped DSSCs exhibited a maximum conversion efficiency of 5.76% because of the effective electron transport. DSSCs based on Fe2O3-doped TiO2 films showed better photovoltaic performance than cells fabricated with only TiO2 nanoparticles. This result was attributed to the prevention of recombination between electrons in the TiO2 conduction band with the dye or electrolytes. A mechanism was suggested based on impedance results, which indicated improved electron transport at the interface of the TiO2/dye/electrolyte. 相似文献
75.
Han Young Eom So-Young Park Min Kyung Kim Joon Hyuk Suh Hyesun Yeom Jung Won Min Unyong Kim Jeongmi Lee Jeong-Rok Youm Sang Beom Han 《Journal of chromatography. A》2010,1217(26):4347-4354
Saikosaponins are triterpene saponins derived from the roots of Bupleurum falcatum L. (Umbelliferae), which has been traditionally used to treat fever, inflammation, liver diseases, and nephritis. It is difficult to analyze saikosaponins using HPLC-UV due to the lack of chromophores. Therefore, evaporative light scattering detection (ELSD) is used as a valuable alternative to UV detection. More recently, a charged aerosol detection (CAD) method has been developed to improve the sensitivity and reproducibility of ELSD. In this study, we compared CAD and ELSD methods in the simultaneous analysis of 10 saikosaponins, including saikosaponins-A, -B1, -B2, -B3, -B4, -C, -D, -G, -H and -I. A mixture of the 10 saikosaponins was injected into the Ascentis® Express C18 column (100 mm × 4.6 mm, 2.7 μm) with gradient elution and detection with CAD and ELSD by splitting. We examined various factors that could affect the sensitivity of the detectors including various concentrations of additives, pH and flow rate of the mobile phase, purity of nitrogen gas and the CAD range. The sensitivity was determined based on the signal-to-noise ratio. The best sensitivity for CAD was achieved with 0.1 mM ammonium acetate at pH 4.0 in the mobile phase with a flow rate of 1.0 mL/min, and the CAD range at 100 pA, whereas that for ELSD was achieved with 0.01% acetic acid in the mobile phase with a flow rate at 0.8 mL/min. The purity of the nitrogen gas had only minor effects on the sensitivities of both detectors. Finally, the sensitivity for CAD was two to six times better than that of ELSD. Taken together, these results suggest that CAD provides a more sensitive analysis of the 10 saikosaponins than does ELSD. 相似文献
76.
Eom K Jung H Lee G Park J Nam K Lee SW Yoon DS Yang J Kwon T 《Chemical communications (Cambridge, England)》2012,48(7):955-957
We report the reversible nanomechanical actuation of a microcantilever driven by the light irradiation-induced conformational changes of i-motif DNA chains, which are functionalized on the cantilever's surface. It is shown that light irradiation-driven nanomechanical actuation can be manipulated using DNA hybridization and/or ionic concentrations. 相似文献
77.
78.
Grigoriev A Do DH Kim DM Eom CB Adams B Dufresne EM Evans PG 《Physical review letters》2006,96(18):187601
Domain wall motion during polarization switching in ferroelectric thin films is fundamentally important and poses challenges for both experiments and modeling. We have visualized the switching of a Pb(Zr, Ti)O(3) capacitor using time-resolved x-ray microdiffraction. The structural signatures of switching include a reversal in the sign of the piezoelectric coefficient and a change in the intensity of x-ray reflections. The propagation of polarization domain walls is highly reproducible from cycle to cycle of the electric field. Domain wall velocities of 40 m s(-1) are consistent with the results of other methods, but are far less than saturation values expected at high electric fields. 相似文献
79.
An ultra-stable visible laser source (VLS) was generated by the second harmonic of a selectively injection-locked distributed feedback (DFB) laser from an optical frequency comb with acetylene-stabilized laser seeding. For the second-harmonic generation (SHG) of the injection-locked DFB laser, we used periodically poled lithium niobate (PPLN) crystal and generated the VLS at a region of 771 nm, which was discretely locked to a spacing of 25 GHz within the PPLN bandwidth (180 GHz). The frequency stability of this source was estimated to be 1.1 × 10− 12 with an average time of 1 s. 相似文献
80.
We examine the effect of vacancies on the doping of Si nanocrystals with B atoms. The electronic structure problem is solved in real space using pseudopotentials constructed within density functional theory. In the absence of vacancies, we find that it is energetically favorable for B dopants to be placed at or near the nanocrystal surface. However, in the presence of a vacancy, the B dopant can be stabilized within the nanocrystal as the vacancy effectively relieves the dopant induced stress. 相似文献