全文获取类型
收费全文 | 156篇 |
免费 | 30篇 |
国内免费 | 31篇 |
专业分类
化学 | 157篇 |
晶体学 | 3篇 |
力学 | 2篇 |
数学 | 10篇 |
物理学 | 45篇 |
出版年
2024年 | 1篇 |
2023年 | 3篇 |
2022年 | 5篇 |
2021年 | 6篇 |
2020年 | 6篇 |
2019年 | 4篇 |
2018年 | 4篇 |
2017年 | 6篇 |
2016年 | 3篇 |
2015年 | 9篇 |
2014年 | 14篇 |
2013年 | 16篇 |
2012年 | 11篇 |
2011年 | 15篇 |
2010年 | 8篇 |
2009年 | 10篇 |
2008年 | 21篇 |
2007年 | 14篇 |
2006年 | 11篇 |
2005年 | 11篇 |
2004年 | 4篇 |
2003年 | 4篇 |
2002年 | 9篇 |
2000年 | 2篇 |
1999年 | 1篇 |
1998年 | 3篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1993年 | 3篇 |
1991年 | 1篇 |
1989年 | 4篇 |
1988年 | 1篇 |
1984年 | 1篇 |
排序方式: 共有217条查询结果,搜索用时 15 毫秒
11.
In this paper, we establish existence theorems of quasivariational inclusion problems; from them, we establish existence theorems
of mathematical programs with quasivariational inclusion constraint, bilevel problems, mathematical programs with equilibrium
constraint and semi-infinite problems.
This research was supported by the National Science Council of the Republic of China. The authors express their gradtitude
to the referees for valuable suggestions. 相似文献
12.
Chien‐Kuo Hsieh Feng‐Chun Lo Gene‐Hsiang Lee Shie‐Ming Peng Wen‐Feng Liaw 《中国化学会会志》2000,47(1):103-107
Complex fac‐[Fe(CO)3(TePh)3]? was employed as a “metallo chelating” ligand to synthesize the neutral (CO)3Mn(μ‐TePh)3Fe(CO)3 obtained in a one‐step synthesis by treating fac‐[Fe(CO)3(TePh)3]? with fac‐[Mn‐(CO)3(CH3CN)3]+. It seems reasonable to conclude that the d6 Fe(II) [(CO)3Fe(TePh)3]? fragment is isolobal with the d6 Mn(I) [(CO)3Mn(TePh)3]2? fragment in complex (CO)3Mn(μ‐TePh)3Fe(CO)3. Addition of fac‐[Fe(CO)3(TePh)3]? to the CpNi(I)(PPh3) in THF resulted in formation of the neutral CpNi(TePh)(PPh3) also obtained from reaction of CpNi(I)(PPh3) and [Na][TePh] in MeOH. This investigation shows that fac‐[Fe(CO)3(TePh)3]? serves as a tridentate metallo ligand and tellurolate ligand‐transfer reagent. The study also indicated that the fac‐[Fe(CO)3(SePh)3]? may serve as a better tridentate metallo ligand and chalcogenolate ligand‐transfer reagent than fac‐[Fe(CO)3(TePh)3]? in the syntheses of heterometallic chalcogenolate complexes. 相似文献
13.
Yi-Lin Yu Edvin Skaljo Hoa Le Minh Zabih Ghassemlooy 《Fiber and Integrated Optics》2013,32(5-6):383-394
AbstractThis article presents a novel bidirectional wavelength reconfigurable optical network utilizing a remotely pumped erbium-doped fiber amplifier and tunable fiber Bragg gratings. The system is experimentally demonstrated at a 10-Gb/s per channel over 20-km fiber span that verifies the metro-network range system performance. The achieved power penalty is less than 1 dB when compared to the back-to-back transmission link. An example of practical application where the proposed module is used as an add/drop multiplexer and a remote node in the bidirectional wavelength division multiplexing passive optical network system is described. 相似文献
14.
Keh-Yi Lee Chia-Chen Tsai Tsong-Cheng Weng Yi-Lin Kuo Chih-Wei Kao Kuei-Yuan Chen Yu-Jen Lin 《Fiber and Integrated Optics》2006,25(1):29-40
There are several key factors that affect the transmission characteristics of the 90° (L-shaped) bent photonic crystal waveguides. The first factor is the direct coupling efficiency from the incident lights into the waveguides. The second one is the bandgap deviations of the photonic crystals. And the third factor is the optical reflections in the bent corners. In this article, we compare three types of L-shaped bent photonic crystal waveguides. One is the original type, which has an abrupt right-angle bend. Another is an improved 90° bend with a 45°-mirror. The other is an L-shaped bent photonic crystal waveguide with a 45°-transitional section. We investigate their respective frequency responses and observe the improvements in the total transmission efficiencies provided by the latter types. 相似文献
15.
杂合型全局优化法优化水分子团簇结构 总被引:2,自引:0,他引:2
基于遗传算法、快速模拟退火及共轭梯度方法提出了一种快速的杂合型全局优化方法(fast hybrid global optimization algorithm, FHGOA),并将这一方法应用于TIP3P和TIPS2模型水分子团簇(H2O)n结构的优化.在进行TIP3P模型水分子团簇结构的优化过程中,发现了能量比文献值更低的团簇结构,且执行效率有较大提高.把该方法应用到优化TIPS2模型的水分子团簇,发现最优结构和采用TTM2-F模型优化的水分子团簇结构在n < 17时完全相同,为全表面结构;而在n=17、19、22时为单中心水分子笼状结构;在n=25、27时为双中心水分子笼状结构.说明随着团簇中水分子个数的增加,采用TIPS2和TTM2-F势能函数优化的团簇最优结构有相同的变化趋势. 相似文献
16.
A novel conductive biocomposite film (MWCNTs–DNA–cyt c) which contains multi-walled carbon nanotubes (MWCNTs) along with the incorporation of DNA and cytochrome c (cyt c) has been synthesized on glassy carbon electrode (GCE), gold (Au), indium tin oxide (ITO) and screen printed carbon electrode (SPCE) by potentiostatic methods. The presence of both MWCNTs and DNA in the biocomposite film enhances the surface coverage concentration (Γ), increases the electron transfer rate constant (Ks) up to 21% and decreases the degradation of cyt c during the cycling. The biocomposite film also exhibits a promising enhanced electrocatalytic activity towards the reduction of halogen oxyanions and oxidation of biochemical compounds such as ascorbic acid and l-cysteine. The cyclic voltammetry has been used for the measurement of electroanalytical properties of analytes by means of biocomposite film modified GCEs. The sensitivity of MWCNTs–DNA–cyt c modified GCE possess higher values than the values obtained for DNA–cyt c film modified GCE. Further, the reduction potentials of halogen oxyanions Epc, clearly shows that the activity of the biocomposite is dependent on the electronegativity of halogen oxyanions. Electrochemical quartz crystal microbalance studies revealed the enhancements in the functional properties of MWCNTs, DNA and cyt c. We have studied the surface morphology of the biocomposite films using scanning electron microscopy and atomic force microscopy, which revealed that DNA and cyt c have been incorporated on MWCNTs. Finally, the flow injection analysis has been used for the amperometric detection of analytes at MWCNTs–DNA–cyt c film modified SPCE. 相似文献
17.
Jie‐Ren Shie 《先进技术聚合物》2008,19(1):73-83
This study analyzed contour distortions, wear and tensile properties of polypropylene (PP) components applied in the interior coffer of automobiles. A hybrid method integrating a trained generalized regression neural network (GRNN) and a sequential quadratic programming (SQP) method is proposed to determine an optimal parameter setting of the injection‐molding process. The specimens were prepared under different injection‐molding conditions by changing melting temperatures, injection speeds, and injection pressures. Average contour distortions at six critical locations, wear and tensile properties were selected as the quality targets. Sixteen experimental runs, based on a Taguchi orthogonal array table, were utilized to train the GRNN and then the SQP method was applied to search for an optimal setting. The trained GRNN was capable of predicting average contour distortions, wear and tensile properties at various injection‐molding conditions. In addition, the analysis of variance (ANOVA) was implemented to identify significant factors for the molding process and the proposed algorithm was compared with traditional schemes like the Taguchi method and the design of experiments (DOE) approach. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
18.
The quantum states are presented in these processions of fabricating poly-Si films. Amorphous silicon films prepared by PECVD has been crystallized by conventional furnace annealing (FA) and rapid thermal annealing (RTA), respectively. It is found that the thin films grain size present quantum states with the increasing of the gas flow ratios of SiH4, H2 mixture, substrate temperatures, frequency power, annealing temperature and time. 相似文献
19.
A route to the total synthesis of koumine has been suggested. Five 4-substituted 1, 2-d hydropyridine derivatives, which are supposed to be a conjugated diene of Diels-Alder reaction to produce the isoquinuclidine ring of koumine, have been synthesized. Only two of them were found to be able to undergo the Diels-Alder reaction. The stereochemistry of the reaction product has also been examined. 相似文献
20.