全文获取类型
收费全文 | 120篇 |
免费 | 0篇 |
专业分类
化学 | 73篇 |
力学 | 9篇 |
数学 | 11篇 |
物理学 | 27篇 |
出版年
2023年 | 2篇 |
2022年 | 1篇 |
2021年 | 5篇 |
2020年 | 3篇 |
2019年 | 5篇 |
2014年 | 3篇 |
2013年 | 8篇 |
2012年 | 16篇 |
2011年 | 11篇 |
2010年 | 7篇 |
2009年 | 3篇 |
2008年 | 5篇 |
2007年 | 3篇 |
2006年 | 8篇 |
2005年 | 5篇 |
2004年 | 5篇 |
2003年 | 1篇 |
2002年 | 3篇 |
2001年 | 3篇 |
2000年 | 6篇 |
1999年 | 5篇 |
1998年 | 5篇 |
1997年 | 1篇 |
1996年 | 3篇 |
1994年 | 1篇 |
1992年 | 1篇 |
1989年 | 1篇 |
排序方式: 共有120条查询结果,搜索用时 15 毫秒
81.
Poly(3,4-ethylenedioxythiophene) nanotubes (PEDOT NTs) flexible membrane was successfully fabricated by vapor deposition polymerization (VDP) mediated electrospinning for ammonia gas detection. PVA nanofibers (NFs) were electrospun as a core part and polyvinyl alcohol (PVA)/PEDOT coaxial nanocables (NCs) were prepared by VDP method via EDOT monomer adsorption onto the electrospun PVA NFs as templates. To obtain the PEDOT NTs membrane, the PVA NFs were removed from PVA/PEDOT coaxial NCs with distilled water. PVA/PEDOT coaxial NCs and PEDOT NTs had the conductivities of 71 and 61 S cm−1 and were applied as a transducer for ammonia gas detection in the range of 1-100 parts per million (ppm) of NH3 gas. They exhibited the minimum detectable level of ca. 5 parts per million (ppm) and fast response time (less than 1 s) towards ammonia gas. In a recovery time, the PEDOT NTs membrane sensor was ca. 30 s and shorter compared to that of the membrane sensor based on the PVA/PEDOT NCs (ca. 50 s). In addition, sensor performance of PEDOT NTs membrane was also undertaken as a function of membrane thickness. Thick membrane sensor (30 μm) had the enhanced sensitivity and the sensitivity on the membrane thickness was in the order of 30 μm > 20 μm > 10 μm at 60 ppm of NH3 gas. 相似文献
82.
Jae Ryong Kweon 《Journal of Differential Equations》2007,235(1):166-198
We are concerned with singularities and regularities of solutions for the Navier-Stokes system of incompressible flows on a polygonal domain with a concave vertex. We subtract the corner singularities by the Stokes operator from the solution velocity and pressure functions of the system. It is shown that the stress intensity factors are functions of time variable, belong to a fractional Sobolev space on the time interval and can be expressed in terms of given data. An increased regularity for the remainder is obtained. 相似文献
83.
Mi-Seon Shin Young-Jin Kang Hyun-A Chung Jung-Won Park Deok-Heon Kweon Woo Song Lee Yong-Jin Yoon Sung-Kyu Kim 《Journal of heterocyclic chemistry》1999,36(5):1135-1142
Some novel 3-halo-6-(4-substituted-phenoxy)pyridazines and 3,6-di-(4-substituted-phenoxy)pyridazines were synthesized from 3,6-dichloropyridazine or 3,6-diiodopyridazine. 3,6-Diiodopyridazine was prepared from 3,6-dichloropyridazine using hydriodic acid/iodine monochloride. 相似文献
84.
Jae Ryong Kweon 《Numerical Methods for Partial Differential Equations》2004,20(3):412-431
A linearized compressible viscous Stokes system is considered. The a posteriori error estimates are defined and compared with the true error. They are shown to be globally upper and locally lower bounds for the true error of the finite element solution. Some numerical examples are given, showing an efficiency of the estimator. © 2004 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 20: 412–431, 2004. 相似文献
85.
Jung‐Won Park Deok‐Heon Kweon Young‐Jin Kang Woo Song Lee Su‐Dong Cho Yong‐Jin Yoon 《Journal of heterocyclic chemistry》2000,37(1):5-10
This paper presents the synthesis of some novel acyclonucleosides involving pyrrolo[2,3‐c]pyridazine and 4‐hydroxybutyl side chain. 相似文献
86.
87.
Structural and magnetic properties of silicon/aluminum-added and -free FeCoNi magnetic alloy nanofibers with nanogranular
phases prepared by electrospinning and subsequent annealing of the PVP-blended ternary metal precursors in hydrogen atmosphere
were investigated. The FeCoNi magnetic alloy nanofibers with evenly distributed nanocrystalline phases were formed, which
are identified as γ-Fe1−x
Ni
x
binary phase with face-centered cubic structure and α-CoFe phase with body-centered cubic structure. At elevated temperature,
the α → γ structural martensitic transformation in the FeCoNi ternary alloys occurred due to the inhomogeneities in composition
of the matrix during annealing of the alloy with metastable α-phase. In the Si/Al-added FeCoNi nanofibers, more than two phases
with complicated-boundaries of the grains in and/or outside the nanofibers were formed as crystalline phases and amorphous
phase. The amorphous phase consisted of Si and/or Al acted as an inhibitor diminishing α → γ transformation as well as an
interparticle insulation layer. At low annealing temperature of 450 °C, the Si/Al-added nanofiber mainly consisted of metastable
α-phase with a low-crystallinity surface structure and very small diameter of 13 nm was formed and showed an unexpectedly
high coercivity, which attributed to the surface effects and/or high surface/volume ratio. 相似文献
88.
Kyungwook Min Daniel J. Valco Anna Oldani Keunsoo Kim Jacob Temme Chol-Bum M. Kweon Tonghun Lee 《Proceedings of the Combustion Institute》2019,37(4):5003-5011
The reactivity of six kerosene based control fuels, specifically formulated for cetane number variation, are investigated by measuring ignition delay time in a heated rapid compression machine. Cetane numbers vary from 30 to 55 (increment of 5) while holding other properties relatively constant by adjusting chemical group composition. Main cetane variation was controlled through the distribution of normal alkanes and isoalkanes, which was fine-tuned using additives. Other fuel properties such as density, viscosity, H/C ratio, etc. were balanced using cyclic compounds and aromatics. Fuels were tested in the RCM at compressed pressures of Pc=?10 and 20?bar, equivalence ratios of ??=?0.25, 0.5 and 1.0, in the low to intermediate temperature range (620?K?≤?Tc?≤?730?K). Relations between cetane number and ignition delay time have been evaluated at multiple test conditions, and further analysis on multistage ignition has been conducted. Ignition delay times of fuels with higher cetane numbers are shorter at these temperatures for most conditions. First stage ignition delay time measurements have been observed to be relatively insensitive to Pc, ?, and fuel type, while deviations in overall ignition delay times are mainly attributed to second stage ignition delay time, impacted by variations in the first stage temperature. Control fuels of this type offer an opportunity to be used in practical experiments to determine the impact of cetane number on combustion dynamics. 相似文献
89.
A simple and successful design for a panoramic stereo system that uses a single camera and multiple mirrors is presented. A wide-baseline stereo enhances the three-dimensional reconstruction accuracy even with a single camera. The feasibility of the system as a practical stereo sensor has been demonstrated with experiments in an indoor environment. 相似文献
90.
An evolution compressible Stokes system is studied in a bounded cylindrical region . The initial datum of pressure is assumed to have a jump at a specified curve C0 in Ω. As predicted by the Rankine-Hugoniot conditions, the pressure and velocity derivatives have jump discontinuities along the characteristic plane of the curve C0 directed by an ambient velocity vector. An explicit formula for the jump discontinuity is presented. The jump decays exponentially in time, more rapidly for smaller viscosities. Under suitable conditions of the data, a regularity of the solution is established in a compact subregion of Q away from the jump plane. 相似文献