全文获取类型
收费全文 | 259篇 |
免费 | 17篇 |
国内免费 | 2篇 |
专业分类
化学 | 215篇 |
晶体学 | 1篇 |
数学 | 3篇 |
物理学 | 59篇 |
出版年
2023年 | 4篇 |
2022年 | 6篇 |
2021年 | 11篇 |
2020年 | 10篇 |
2019年 | 12篇 |
2018年 | 8篇 |
2017年 | 8篇 |
2016年 | 11篇 |
2015年 | 11篇 |
2014年 | 8篇 |
2013年 | 18篇 |
2012年 | 17篇 |
2011年 | 27篇 |
2010年 | 7篇 |
2009年 | 8篇 |
2008年 | 17篇 |
2007年 | 11篇 |
2006年 | 11篇 |
2005年 | 11篇 |
2004年 | 4篇 |
2003年 | 5篇 |
2002年 | 4篇 |
2001年 | 4篇 |
1997年 | 1篇 |
1996年 | 3篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1984年 | 4篇 |
1983年 | 1篇 |
1982年 | 3篇 |
1980年 | 4篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1976年 | 3篇 |
1975年 | 4篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1969年 | 1篇 |
1968年 | 2篇 |
1966年 | 1篇 |
1963年 | 1篇 |
排序方式: 共有278条查询结果,搜索用时 250 毫秒
261.
Nakade S Kanzaki T Kubo W Kitamura T Wada Y Yanagida S 《The journal of physical chemistry. B》2005,109(8):3480-3487
Performance of dye-sensitized solar cells (DSCs) was investigated depending on the compositions of the electrolyte, i.e., the electrolyte with a different cation such as Li(+), tetra-n-butylammonium (TBA(+)), or 1,2-dimethyl-3-propylimidazolium (DMPIm(+)) in various concentrations, with and without 4-tert-butylpyridine (tBP), and with various concentrations of the I(-)/I(3)(-) redox couple. Current-voltage characteristics, electron lifetime, and electron diffusion coefficient were measured to clarify the effects of the constituents in the electrolyte on the charge recombination kinetics in the DSCs. Shorter lifetimes were found for the DSCs employing adsorptive cations of Li(+) and DMPIm(+) than for a less-adsorptive cation of TBA(+). On the other hand, the lifetimes were not influenced by the concentrations of the cations in the solutions. Under light irradiation, open-circuit voltages of DSCs decreased in the order of TBA(+)> DMPIm(+) > Li(+), and also decreased with the increase of [Li(+)]. The decreases of open-circuit voltage (V(oc)) were attributed to the positive shift of the TiO(2) conduction band potential (CBP) by the surface adsorption of DMPIm(+) and Li(+). These results suggest that the difference of the free energies between that of the electrons in the TiO(2) and of I(3)(-) has little influence on the electron lifetimes in the DSCs. The shorter lifetime with the adsorptive cations was interpreted with the thickness of the electrical double layer formed by the cations, and the concentration of I(3)(-) in the layer, i.e., TBA(+) formed thicker double layer resulting in lower concentration of I(3)(-) on the surface of the TiO(2). The addition of 4-tert-butylpyridine (tBP) in the presence of Li(+) or TBA(+) showed no significant influence on the lifetime. The increase of V(oc) by the addition of tBP into the electrolyte containing Li(+) and the I(-)/I(3)(-) redox couple was mainly attributed to the shift of the CBP back to the negative potential by reducing the amount of adsorbed Li cations. 相似文献
262.
Ozawa F Okamoto H Kawagishi S Yamamoto S Minami T Yoshifuji M 《Journal of the American Chemical Society》2002,124(37):10968-10969
The (pi-allyl)palladium complex bearing an sp2-hybridized phosphorus ligand (DPCB-OMe: 1,2-bis(4-methoxyphenyl)-3,4-bis[(2,4,6-tri-tert-butylphenyl)phosphinidene]cyclobutene) efficiently catalyzes direct conversion of allylic alcohols in the absence of activating agents of alcohols such as Lewis acids. N-Allylation of aniline proceeds at room temperature to afford monoallylated anilines in 90-97% yields. C-Allylation of active methylene compounds is also successful at 50 degrees C using a catalytic amount of pyridine as a base, giving monoallylation products in 85-95% yields. The catalytic mechanism involving hydrido- and (pi-allyl)palladium intermediates has been proposed on the basis of stoichiometric examinations using model compounds of presumed intermediates. 相似文献
263.
Makoto Takeishi Toshio Watanabe Shogo Niino Shigeru Hayama 《Journal of polymer science. Part A, Polymer chemistry》1980,18(10):3081-3088
Copper(II), nickel(II), cobalt(II), and zinc(II) accelerated the carboxylate-catalyzed hydrolyses of 2,4-dinitrophenyl isonicotinate (DNPI) and 2,4-dinitrophenyl picolinate (DNPP). The rate enhancement effect of the metal ions in the partially neutralized poly(methacrylic acid)- or poly(acrylic acid)-catalyzed hydrolysis of DNPI was greater than that in the monomeric acetate ion-catalyzed hydrolysis of this ester. This feature of the reactions was explained by the formation of a ternary complex composed of the polymer, the metal ion, and the substrate, in which the metal ion serves as a template for the nucleophilic reaction between the carboxylate groups along the polymer chain and the coordinated substrate. In DNPP the metal ion effect on the polycarboxylate-catalyzed hydrolysis was smaller than that on the acetate ion-catalyzed hydrolysis. This was interpreted as the result of differences in the structure of the complex. 相似文献
264.
265.
Kuniyuki Motojima Shogo Kozaki 《International Journal of Infrared and Millimeter Waves》2001,22(6):923-939
Spatial transfer function for wide band wireless communication system is analyzed by using FDTD and DFT method. Ray-based method is not sufficiently accurate, when the size of objects on the propagating path is comparable to the wavelength. In our proposed method, the tranfser function can be obtained exactly by using the FDTD method. For the numerical examples, the transfer functions in an aperture of the waveguide are calculated by proposed procedure. Furthermore, experimental verification is made by using two-dimensional propagation system, which is constructed of copper plates, antennas and vector network analyzer. The proposed algorithm is valid for estimating of the spatial transfer function. 相似文献
266.
Katsuya Ichihashi Daisuke Konno Kseniya Yu. Maryunina Katsuya Inoue Kazuhiro Toyoda Shogo Kawaguchi Yoshiki Kubota Yoko Tatewaki Tomoyuki Akutagawa Takayoshi Nakamura Sadafumi Nishihara 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(13):4213-4216
Artificial ion channels are of increasing interest because of potential applications in biomimetics, for example, for realizing selective ion permeability through the transport and/or exchange of selected ions. However, selective ion transport and/or exchange in the crystalline state is rare, and to the best of our knowledge, such a process has not been successfully combined with changes in the physical properties of a material. Herein, by soaking single crystals of Li2([18]crown‐6)3[Ni(dmit)2]2(H2O)4 ( 1 ) in an aqueous solution containing K+, we succeeded in complete ion exchange of the Li+ ions in 1 with K+ ions in the solution, while maintaining the crystalline state of the material. This ion exchange with K+ was selectively conducted even in mixed solutions containing K+ as well as Na+/Li+. Furthermore, remarkable changes in the physical properties of 1 resulted from the ion exchange. Our finding enables not only the realization of selective ion permeability but also the development of highly sensitive biosensors and futuristic ion exchange agents, for example. 相似文献
267.
Nakanishi T Inatomi Y Murata H Shigeta K Iida N Inada A Murata J Farrera MA Iinuma M Tanaka T Tajima S Oku N 《Chemical & pharmaceutical bulletin》2005,53(2):229-231
A new 4alpha-aryltetralin-type lignan called burseranin (1) and a known analogous lignan picropolygamain (2) were isolated along with known triterpenes, lupeol and epi-lupeol from the methanol extract of stems of Bursera graveolens, which showed a remarkable inhibitory activity against human HT1080 fibrosarcoma cells. The whole structure of 1 was established based on combined spectral studies and the absolute structure for 2 was first confirmed by CD spectral evidence. In addition, cytotoxic activities of the stem (methanol) extract and its components are evaluated in this paper. 相似文献
268.
Shogo Aoyama 《Zeitschrift fur Physik C Particles and Fields》1986,32(1):113-119
The differential geometry of Kähler group manifolds will be thoroughly interpreted through Killing potentials. This enables us to reformulate the four dimensional gauged supersymmetric σ-model on Kähler group manifolds by Killing potentials. In the reformulation the Lagrangian will take a simple form in which the isometry of the manifolds is linearly manifest. The scalar curvature of the manifolds will be ascribed to the spontaneous breaking of supersymmetry in the model. 相似文献
269.
Yusuke Mizokawa Hiroshi Iwasaki Ryusuke Nishitani Shogo Nakamura 《Journal of Electron Spectroscopy and Related Phenomena》1978,14(2):129-141
The binding energies of Ga 3d, As 3d, Ga L3M4,5M4,5 and O 1s in Ga, As, GaAs, Ga2O3, As2O3 and As2O5 are reevaluated by means of ESCA. The calibration lines of the C 1s and the Au 4f gave different binding energies for the compound materials. In order to determine the absolute binding energies, the chemical shifts in Auger and photoelectron lines from a layered structure composed of thin layer oxide and substrate of a defined material were used. An energy calibration curve, E(Ga 3d) vs. ΔE(GA LMM - Ga 3d), was found to be useful for determination of binding energies in the material which contains gallium. In the case of the GaAs sample, both the chemical etching and the ion bombardment effects on the chemical structure of the GaAs surface are also discussed. 相似文献
270.
Dr. Ryou Kubota Keisuke Nakamura Shogo Torigoe Prof. Dr. Itaru Hamachi 《ChemistryOpen》2020,9(1):67-79
Multicomponent supramolecular hydrogels are promising scaffolds for applications in biosensors and controlled drug release due to their designer stimulus responsiveness. To achieve rational construction of multicomponent supramolecular hydrogel systems, their in-depth structural analysis is essential but still challenging. Confocal laser scanning microscopy (CLSM) has emerged as a powerful tool for structural analysis of multicomponent supramolecular hydrogels. CLSM imaging enables real-time observation of the hydrogels without the need of drying and/or freezing to elucidate their static and dynamic properties. Through multiple, selective fluorescent staining of materials of interest, multiple domains formed in supramolecular hydrogels (e. g. inorganic materials and self-sorting nanofibers) can also be visualized. CLSM and the related microscopic techniques will be indispensable to investigate complex life-inspired supramolecular chemical systems. 相似文献