全文获取类型
收费全文 | 110篇 |
免费 | 6篇 |
专业分类
化学 | 89篇 |
力学 | 5篇 |
物理学 | 22篇 |
出版年
2023年 | 1篇 |
2021年 | 3篇 |
2020年 | 6篇 |
2019年 | 3篇 |
2018年 | 2篇 |
2017年 | 1篇 |
2016年 | 2篇 |
2015年 | 4篇 |
2014年 | 2篇 |
2013年 | 3篇 |
2012年 | 14篇 |
2011年 | 11篇 |
2010年 | 4篇 |
2009年 | 3篇 |
2008年 | 6篇 |
2007年 | 7篇 |
2006年 | 11篇 |
2005年 | 7篇 |
2004年 | 6篇 |
2003年 | 2篇 |
2002年 | 3篇 |
2001年 | 2篇 |
1997年 | 1篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1990年 | 1篇 |
1987年 | 1篇 |
1984年 | 2篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1974年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有116条查询结果,搜索用时 15 毫秒
21.
JS Park Y Hirana S Mouri Y Miyauchi N Nakashima K Matsuda 《Journal of the American Chemical Society》2012,134(35):14461-14466
Understanding of electronic and optical features of single-walled carbon nanotubes (SWNTs) has been a central issue in science and nanotechnology of carbon nanotubes. We describe the detection of both the positive trion (positively charged exciton) and negative trion (negatively charged exciton) as a three-particle bound state in the SWNTs at room temperature by an in situ photoluminescence spectroelectrochemistry method for an isolated SWNT film cast on an ITO electrode. The electrochemical hole and electron dopings enable us to detect such trions on the SWNTs. The large energy difference between the singlet bright exciton and the negative and positive trions showing a tube diameter dependence is determined by both the exchange splitting energy and the trion binding energy. In contrast to conventional compound semiconductors, on the SWNTs, the negative trion has almost the same binding energy to the positive trion, which is attributed to nearly identical effective masses of the holes and electrons. 相似文献
22.
Imran M. Zainuddin Masatoshi Yasuda Takehiko Horio Shuji Matsusaka 《Particle & Particle Systems Characterization》2012,29(1):8-15
The flowability of powders with different mass median diameters ranging from micrometers to nanometers was measured using the vibration shear tube method. In the measurement system used in this study, the powder was discharged through a narrow gap between a vibrating tube edge and a flat bottom surface, where each particle could experience high shear forces to overcome the adhesion and friction forces. The vibration amplitude was increased during the measurement, and the mass of particles discharged was measured at constant time intervals. From the relationship between the mass flow rate and the vibration acceleration, static and dynamic properties of the powders were evaluated using the critical vibration acceleration, characteristic mass flow rate, and gradient of mass flow rate. The correlation between the static and dynamic properties was studied in detail. 相似文献
23.
Khatayevich D So CR Hayamizu Y Gresswell C Sarikaya M 《Langmuir : the ACS journal of surfaces and colloids》2012,28(23):8589-8593
The systematic control over surface chemistry is a long-standing challenge in biomedical and nanotechnological applications for graphitic materials. As a novel approach, we utilize graphite-binding dodecapeptides that self-assemble into dense domains to form monolayer-thick long-range-ordered films on graphite. Specifically, the peptides are rationally designed through their amino acid sequences to predictably display hydrophilic and hydrophobic characteristics while maintaining their self-assembly capabilities on the solid substrate. The peptides are observed to maintain a high tolerance for sequence modification, allowing control over surface chemistry via their amino acid sequence. Furthermore, through a single-step coassembly of two differently designed peptides, we predictably and precisely tune the wettability of the resulting functionalized graphite surfaces from 44° to 83°. The modular molecular structures and predictable behavior of short peptides demonstrated here give rise to a novel platform for functionalizing graphitic materials that offers numerous advantages, including noninvasive modification of the substrate, biocompatible processing in an aqueous environment, and simple fusion with other functional biological molecules. 相似文献
24.
K Watanabe Y Nishimura T Nomoto N Umemoto Z Zhang B Zhang J Kuroyanagi Y Shimada T Shintou M Okano T Miyazaki T Imamura T Tanaka 《BMC neuroscience》2012,13(1):101
ABSTRACT: BACKGROUND: Successful delivery of compounds to the brain and retina is a challenge in the development of therapeutic drugs and imaging agents. This challenge arises because internalization of compounds into the brain and retina is restricted by the blood--brain barrier (BBB) and blood-retinal barrier (BRB), respectively. Simple and reliable in vivo assays are necessary to identify compounds that can easily cross the BBB and BRB. METHODS: We developed six fluorescent indoline derivatives (IDs) and examined their ability to cross the BBB and BRB in zebrafish by in vivo fluorescence imaging. These fluorescent IDs were administered to live zebrafish by immersing the zebrafish larvae at 7--8 days post fertilization in medium containing the ID, or by intracardiac injection. We also examined the effect of multidrug resistance proteins (MRPs) on the permeability of the BBB and BRB to the ID using MK571, a selective inhibitor of MRPs. RESULTS: The permeability of these barriers to fluorescent IDs administered by simple immersion was comparable to when administered by intracardiac injection. Thus, this finding supports the validity of drug administration by simple immersion for the assessment of BBB and BRB permeability to fluorescent IDs. Using this zebrafish model, we demonstrated that the length of the methylene chain in these fluorescent IDs significantly affected their ability to cross the BBB and BRB via MRPs. CONCLUSIONS: We demonstrated that in vivo assessment of the permeability of the BBB and BRB to fluorescent IDs could be simply and reliably performed using zebrafish. The structure of fluorescent IDs can be flexibly modified and, thus, the permeability of the BBB and BRB to a large number of IDs can be assessed using this zebrafish-based assay. The large amount of data acquired might be useful for in silico analysis to elucidate the precise mechanisms underlying the interactions between chemical structure and the efflux transporters at the BBB and BRB. In turn, understanding these mechanisms may lead to the efficient design of compounds targeting the brain and retina. 相似文献
25.
Dr. Yoshinori Tokairin Yuhei Shigeno Dr. Jianlin Han Prof. Dr. Gerd-Volker Röschenthaler Dr. Hiroyuki Konno Dr. Hiroki Moriwaki Vadim A. Soloshonok 《ChemistryOpen》2020,9(1):93-96
Four differently substituted chiral Ni(II)-complexes of dehydroalanine Schiff base were prepared and reacted with BrCF2COOEt/Cu under the standard reaction conditions. The observed diastereoselectivity was found to depend on the degree and pattern of chlorine substitution for hydrogen in the structure of the dehydroalanine complexes. The unsubstituted complex gave the ratio of diastereomers (S)(2S)/(S)(2R) of 66/34. On the other hand, introduction of chlorine atoms in the strategic positions on the chiral ligands allowed to achieve a practically attractive diastereoselectivity of (∼98.5/1.5). Diastereomerically pure major product was disassembled to prepare 9-fluorenylmethyloxycarbonyl (Fmoc) derivative of (S)-4,4-difluoroglutamic acid. 相似文献
26.
Nobuhito Imanaka Toshiyuki Masui Yuhei Mayama Kazuhiko Koyabu 《Journal of solid state chemistry》2005,178(11):3601-3603
Crystalline yttrium oxycarbonate, Y2O2CO3, was synthesized by our original flux method using the 0.476Li2CO3-0.270Na2CO3-0.254K2CO3 eutectic mixture at 450 °C. The oxycarbonate was characterized by X-ray powder diffraction (XRD), thermogravimetric analysis (TGA), and Fourier-transfer infrared spectroscopy (FT-IR). The Y2O2CO3 prepared by the flux method was a crystalline single phase of hexagonal rare earth oxycarbonate (type-II). This is the first report on the single-phase synthesis of crystalline hexagonal type-II Y2O2CO3. 相似文献
27.
This communication presents studies that illustrated nitroso Diels-Alder adduct has been obtained in uniformly high enantioselectivity via a tandem nitroso aldol/Michael reaction using an amine catalyst. The regiochemical outcome of this construction is documented to be the opposite to that of the normal nitroso aldol reaction, which has been determined by X-ray analysis. The reaction of the enone with silver-BINAP catalyst has also been investigated in conjunction with the control of regiochemistry in a stepwise process. 相似文献
28.
Hitoshi Ito Yumi Ohki Yuhei Watanabe Hiromi Sunaga Isao Ishigaki 《Radiation Physics and Chemistry》1993,42(4-6):597-600
Relative sensitivities of endospores of Bacillus pumilus E601, B. subtilis IAM1069, B. megaterium S31 and B. brevis S5 to gamma rays, converted X rays (bremsstrahlung) and electron beams were examined in order to estimate the conditions in which converted X rays kill Bacillus spores. The radiation sensitivities to gamma rays and electron beams of each strain dried on glass fiber filter without additives were found to be almost equivalent, and D values were obtained as follows: 1.5–1.6 kGy for B. pumilus, 1.4–1.5 kGy for B. subtilis, 1.9–2.0 kGy for B. megaterium and 1.6–2.0 kGy for B. brevis. The radiation sensitivities of endospores of each strain to electron beams were slightly lower than those to gamma rays in the dry condition with additives of 2% peptone + 1 % glycerin on glass fiber filters. The increase of radiation resistance in the presence of additives was also observed with X rays, and it was on an intermediate level between those with gamma rays and electron beams. In the dry condition using cellulose filter paper, only the radiation resistances of B. megaterium and B. brevis in the presence of additives B. megaterium and B. brevis in the presence of additives were increased. 相似文献
29.
Isao Kaetsu Fumio Yoshii Yuhei Watanabe 《Journal of polymer science. Part A, Polymer chemistry》1978,16(10):2645-2650
Radiation-induced polymerization of glass-forming monomers such as 2-hydroxyethyl methacrylate and glycidyl methacrylate under high pressure was studied. The glass transition temperature of these monomers was heightened by increased pressure. The temperature dependence of polymerizability showed a characteristic relation; similar to those in supercooled-phase polymerization under normal pressure, that had a maximum at Tv which shifted to higher levels of temperature as well as to Tg under high pressure. Polymerizability in the supercooled state also increased under increased pressure. 相似文献
30.
Gururaj M. ShivashimpiShyam S. Pandey Rie WatanabeNaotaka Fujikawa Yuhei OgomiYoshihiro Yamaguchi Shuzi Hayase 《Tetrahedron letters》2012,53(40):5437-5440
Aiming toward the development of far-red sensitive organic dyes, unsymmetrical squaraine dye bearing direct cyanoacrylate functionalized indole ring has been synthesized and characterized along with its utilization as photosensitizer for dye-sensitized solar cells. Upon dye-sensitized solar cell fabrication, this sensitizer exhibits its potentiality as a good far-red sensitive dye having photoconversion efficiency of 5.03% under the simulated solar irradiation at AM 1.5 conditions. This opens up further possibility to design efficient far-red sensitive dyes by judicious implementation of suitable donor moieties with extended π-conjugation. 相似文献