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排序方式: 共有134条查询结果,搜索用时 15 毫秒
81.
Kwan Kim Hyang Bong Lee Dongha Shin Hyunwoo Ryoo Ji Won Lee Kuan Soo Shin 《Journal of Raman spectroscopy : JRS》2011,42(12):2112-2118
In order to resolve the dispute on the origin of the b2‐type bands in the surface‐enhanced Raman scattering (SERS) of 4‐aminobenzenethiol (4‐ABT), we have measured its SERS spectra under a variety of conditions, including variable temperature and rotation, electrochemistry, and pH, as well as in the presence of a reducing agent. For comparison, the SERS spectra of 4‐nitrobenzenethiol (4‐NBT) and methyl orange (MO), a prototype azo compound, were also measured. First, we found that 4‐ABT on Ag is not subjected to photoreaction, although 4‐NBT is highly photoreactive on a silver surface. In the electrochemical environment, b2‐type bands of 4‐ABT lost their intensity at very negative potentials, but the intensity recovered immediately upon raising the potential. In addition, b2‐type bands were observed under rotation even after lowering the potential. The disappearance and reappearance of the b2‐type bands could also be observed by bringing the sample of 4‐ABT on Ag into contact consecutively with a borohydride solution and water. This is because the surface potential of Ag is lowered by contact with a borohydride solution. Besides, we found that not only the normal Raman but also the SERS spectral features of 4‐ABT are hardly affected by pH variation, while the spectral features of MO are greatly affected, especially in the region of the NN stretching vibration, suggesting that the possibility of a photoconversion of 4‐ABT to an azo compound is low. Altogether, the b2‐type bands were attributed to 4‐ABT, appearing in conjunction with the chemical enhancement mechanism in SERS. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
82.
Cheon Seoung Ryoo 《Applied mathematics and computation》2010,216(11):3365-3369
In [8], we proposed some numerical verification methods for automatic proof of the existence of solution for obstacle problems. In this paper we propose a new iterative algorithm to automatically prove the existence of solutions for some generalized obstacle problems. 相似文献
83.
Sangwoo Ryu Hyung Cheoul Shim Jun Tae Song Ilhwan Kim Hyewon Ryoo Seungmin Hyun Jihun Oh 《Particle & Particle Systems Characterization》2019,36(1)
Increasing the surface area to improve chemical activity is an unending task from conventional catalysis to recently emerging electrochemical energy conversion and storage. Here, a simple, vacuum‐deposition‐based method to form nanoporous structures of metals is reported. By utilizing thermal evaporation at a high pressure, fractal‐like nanoporous structures of Sn with porosity exceeding 98% are synthesized. The obtained nanostructure consists of nanoparticle aggregates, and the morphology can be controlled by adjusting the working pressure. The formation of the nanoporous structure is explained by homogeneous nucleation and diffusion‐limited aggregation, where nanoparticles produced by the repeated collisions of evaporated atoms adhere to the substrate without diffusion, forming porous aggregates. Due to the easy oxidation of Sn, the constituent nanoparticles are covered with amorphous SnOx and crystalline SnO phases. When the nanoporous Sn/SnOx aggregates are applied to a lithium‐ion battery anode through direct deposition on a Cu foil current collector without binders or conducting additives, the nanoporous Sn/SnOx anode shows greatly enhanced cyclability and exceptional rate performance compared to those of a dense Sn thin film anode. The approach investigated in this work is expected to provide a new platform to other fields that require highly porous structures. 相似文献
84.
Hee-Jin Ryoo Hee-Tak Kim Young-Gi Lee Jung-Ki Park Seong-In Moon 《Journal of Solid State Electrochemistry》1998,3(1):1-6
The thermal and electrochemical characteristics of plasticized polymer electrolytes composed of poly(acrylonitrile-co-methyl methacrylate) [P(AN-co-MMA)], a plasticizer [a mixture of ethylene carbonate and propylene carbonate], and LiCF3SO3 were investigated. The incorporation of a MMA unit into the matrix polymer was effective for an increase in the compatibility
between the matrix polymer and the plasticizer. The comparative investigation of the interfacial resistance of the Li/polymer
electrolyte/Li cell for the PAN-based and the P(AN-co-MMA)-based polymer electrolytes showed that the MMA unit could improve the stability of the polymer electrolyte toward the
Li electrode, which is probably due to the enhanced adhesion of the polymer electrolyte to the Li electrode.
Received: 14 July 1997 / Accepted: 14 May 1998 相似文献
85.
A simple and simultaneous analysis method for four (anionic, amphoteric, nonionic, and cationic) classes of surfactants in shampoo and hair conditioner was newly developed. Analysis of the surfactants was performed using a reversed-phase HPLC (RPLC) combined with evaporative light scattering detection (ELSD) without any pre-treatment. An optimum analysis condition for the resolution of both four main surfactant mixtures used in shampoo and five main surfactants used in hair conditioner could be established under a gradient mobile phase condition with acetonitrile, tetrahydrofuran and water. The detection limits were 2.5-30 μg mL−1 except for SLES (150 μg mL−1), and the calibration curves, i.e. the log-log plots, were linear in the working range of 2.5-5250 μg mL−1 with R2 values of above 0.998. The observed precision was less than 5% R.S.D. The elution peaks were identified by a liquid chromatography-mass spectrometer (LC-MS) equipped with an electrospray interface operating in mixed-mode. 相似文献
86.
Lan-Young?Hong Tae-Ho?Yoon Hyang-Im?Ryoo Sang-Hee?Jung Dong-Pyo?KimEmail author 《Journal of Sol-Gel Science and Technology》2011,57(3):279-286
The mesoporous inorganic–organic SiO2–TiO2–PEG hybrid resin systems with various useful functionalities were directly synthesized by a binary sol–gel reaction of TEOS–TiCl4 and the subsequent chelation with a chatecholic compound (dihydroxy benzene), dihydroxy-m-benzenedisulfonic acid disodium
salt, on the surface Ti ion of the ordered mesoporous SBA-15 network structure, respectively. Moreover, the hybrid resins
consisting of polyethylene glycol and a silane coupling agent exhibited the controlled wettability, excellent coating processibility
on various substrates with strong abrasion resistance. Furthermore, the transparent and low viscous resin showed the successful
performance to fabricate various nanoscale patterns with the feature size down to 170 nm by imprint lithography. Based on
the excellent patternability, nanofluidics with 100 nm of the narrowest dimension channel height was fabricated to employ
a capillary electrophoresis for separation DNAs without gel matrix. In addition, the presence of sulfonic acid in the resin
also showed the solid acid catalytic performance. These results reveal that the developed hybrid materials are very useful
as an imprint resin as well as versatile microchemical applications. 相似文献
87.
88.
89.
Toyohide Takeuchi Takuya Kimura Ji-Ye Jin Chuzo Fujimoto Kazutoku Ohta Kwang-Pill Lee Je-Jeong Ryoo Seong-Ho Choi 《Analytical sciences》2003,19(9):1265-1267
A pressure-controlled on-column injection method was developed for microcolumn liquid chromatography. The system was assembled from a syringe pump, a Model M-445 Six-Way Micro Selection Valve, a separation column and a UV detector. The injection volume could be regulated by changing the applied pressure and/or the sample loading time. The system was evaluated in the ion-exchange mode. The system was applied to the determination of anions in river-water samples. 相似文献
90.
A branch-and-reduce approach to global optimization 总被引:4,自引:0,他引:4
This paper presents valid inequalities and range contraction techniques that can be used to reduce the size of the search space of global optimization problems. To demonstrate the algorithmic usefulness of these techniques, we incorporate them within the branch-and-bound framework. This results in a branch-and-reduce global optimization algorithm. A detailed discussion of the algorithm components and theoretical properties are provided. Specialized algorithms for polynomial and multiplicative programs are developed. Extensive computational results are presented for engineering design problems, standard global optimization test problems, univariate polynomial programs, linear multiplicative programs, mixed-integer nonlinear programs and concave quadratic programs. For the problems solved, the computer implementation of the proposed algorithm provides very accurate solutions in modest computational time. 相似文献