全文获取类型
收费全文 | 776篇 |
免费 | 10篇 |
专业分类
化学 | 581篇 |
晶体学 | 8篇 |
力学 | 20篇 |
数学 | 42篇 |
物理学 | 135篇 |
出版年
2022年 | 6篇 |
2021年 | 8篇 |
2020年 | 8篇 |
2019年 | 14篇 |
2018年 | 12篇 |
2017年 | 9篇 |
2016年 | 12篇 |
2015年 | 8篇 |
2014年 | 10篇 |
2013年 | 31篇 |
2012年 | 30篇 |
2011年 | 58篇 |
2010年 | 32篇 |
2009年 | 32篇 |
2008年 | 48篇 |
2007年 | 55篇 |
2006年 | 49篇 |
2005年 | 51篇 |
2004年 | 44篇 |
2003年 | 33篇 |
2002年 | 41篇 |
2001年 | 6篇 |
2000年 | 13篇 |
1999年 | 8篇 |
1998年 | 12篇 |
1997年 | 11篇 |
1996年 | 13篇 |
1995年 | 4篇 |
1994年 | 12篇 |
1993年 | 5篇 |
1992年 | 9篇 |
1991年 | 7篇 |
1990年 | 4篇 |
1989年 | 6篇 |
1988年 | 3篇 |
1986年 | 4篇 |
1985年 | 10篇 |
1984年 | 6篇 |
1983年 | 6篇 |
1982年 | 5篇 |
1981年 | 12篇 |
1980年 | 6篇 |
1979年 | 6篇 |
1978年 | 4篇 |
1977年 | 3篇 |
1976年 | 4篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1967年 | 3篇 |
1966年 | 2篇 |
排序方式: 共有786条查询结果,搜索用时 15 毫秒
91.
That there is a close connection between crude (or suspended) Hopf invariants and the reduced diagonal map has long been known. In this paper we build on a classical result of Boardman and Steer (1967) to explore some further relationships in terms of conic structures. In a related result we show that certain Toda brackets contain crude Hopf invariants as elements. In particular, using this latter observation, detection of crude Hopf invariants can be carried out. 相似文献
92.
The rotational time correlation function (RTCF) of solute benzene molecules in the ionic liquid (1-butyl-3-methylimidazolium chloride) has been studied using classical molecular dynamics simulation. The effect of solvent charge on the functional form of RTCF was investigated by comparing four force fields for the solvent where the total charge on the anion and the cation was set to ±1e, ±0.7e, ±0.5e, and 0, respectively. For all three charged solvent models, the RTCF exhibits a long-time tail where the relaxation rate exhibits a significant slowdown. This feature is strengthened by higher solvent charges as well as lower temperatures, indicating the influence of the strong Coulombic fields arising from the solvent charges. The long-time tail is caused by the extraordinarily slow solvent structural relaxation of ionic liquids compared to the time scale of their local vibrational and librational dynamics. 相似文献
93.
Kurono N Ohtsuga K Wakabayashi M Kondo T Ooka H Ohkuma T 《The Journal of organic chemistry》2011,76(24):10312-10318
Kinetic resolution of sterically hindered racemic α-tert-alkyl-α-hydroxy esters is performed by enantiomer-selective carbamoylation with the t-Bu-Box-Cu(II) catalyst (Box = bis(oxazoline)). The reaction with 0.5 equiv of n-C(3)H(7)NCO is carried out with a substrate-to-catalyst molar ratio of 500-5000 at -20 to 25 °C. The high enantiomer-discrimination ability of the catalyst achieves an excellent stereoselectivity factor (s = k(fast)/k(slow)) of 261 in the best case. A catalytic cycle for this reaction is proposed. 相似文献
94.
Rotational motion of a nitroxide radical, peroxylamine disulfonate (PADS), dissolved in room temperature ionic liquids (RTILs) was studied by analyzing electron paramagnetic resonance spectra of PADS in various RTILs. We determined physical properties of PADS such as the hyperfine coupling constant (A), the temperature dependence of anisotropic rotational correlation times (τ(∥) and τ(⊥)), and rotational anisotropy (N). We observed that the A values remain unchanged for various RTILs, which indicates negligible interaction between the N-O PADS group and the cation of RTIL. Large N values suggest strong interaction of the negative sulfonyl parts of PADS with the cations of RTILs. Most of the τ(∥), τ(⊥), and (τ(∥)τ(⊥))(1/2) values are within the range calculated on the basis of a hydrodynamic theory with stick and slip boundary conditions. It was deduced that this theory could not adequately explain the measured results in some RTILs with smaller BF(4) and PF(6) anions. 相似文献
95.
Xie Jian Imanishi Nobuyuki Hirano Atsushi Takeda Yashuo Yamamoto Osamu Zhao Xin-Bing Cao Gao-Shao 《Journal of Solid State Electrochemistry》2011,15(9):2031-2039
Ag and Ag2O thin films have been prepared by radio frequency magnetron sputtering on Cu substrates and have been characterized by X-ray
diffraction, scanning electron microscope and atomic force microscope. The electrochemical performance of the thin films has
been studied by galvanostatic cycling and cyclic voltammetry. The potential dependence of Li-ion chemical diffusion coefficients,
[(D)\tilde]\textLi {\widetilde{D}_{\text{Li}}} , of the films has been determined by galvanostatic intermittent titration technique and electrochemical impedance spectroscopy.
It is found that Li-ion chemical diffusion coefficients of the Ag film range from 10−16 to 3 × 10−14 cm2 s−1. The Ag/Li2O composite that is formed from Ag2O after the first cycle exhibits higher
[(D)\tilde]\textLi {\widetilde{D}_{\text{Li}}} values than the Ag film, especially at a low Li-intercalation content. The phase transitions in the two-phase region cause
a significant decrease of chemical diffusion coefficients. 相似文献
96.
Takahito Itoh Motoka Ikeda Nobuyuki Hirata Yuji Moriya Zhaoyin Wen Yoshiaki Ichikawa Masataka Kubo Osamu Yamamoto 《Ionics》2002,8(1-2):44-52
Terminal-acetylated hyperbranched poly(ethylene glycol) derivatives containing diethylene, triethylene, and hexaethylene and
3,5-dioxybenzoate branching units (poly-Ac1a, poly-Ac1b, and poly-Ac1c) were synthesized. Electrochemical and thermal properties of the hyperbranched polymer electrolytes with lithium salts such
as LiCF3SO3 and LiN(CF3SO2)2, the composite hyperbranched polymer electrolytes with LiN(CF3SO2)2 containing α-LiAlO2 and γ-LiAlO2 fillers, and the hyperbranched polymer blended poly(ethylene oxide) electrolytes with LiN(CF3SO2)2 were investigated and discussed.
Paper presented at the 8th EuroConference on Ionics, Carvoeire, Algarve, Portugal, Sept. 16–22, 2001. 相似文献
97.
98.
99.
Karl-Heinz Hoffmann Nobuyuki Kenmochi Marek Niezgdka 《Journal of Mathematical Analysis and Applications》1992,170(2)
The paper is devoted to questions of an analysis of the large-time solutions to a class of two-phase Stefan problems with delay in the source terms of the governing equations. The case of one space dimension is considered. Results on the asymptotic behaviour of the solutions at t → ∞ are established. 相似文献
100.
Kumio Okaichi Nobuyuki Kajitani Katuko Nakajima Keiichi Nozu † Takeo Ohnishi † 《Photochemistry and photobiology》1989,50(1):69-73
Irradiation by health lamp (HL) light (280–320 nm) more efficiently induced cell killing and mutation in a radiation sensitive mutant (TW8) of Dictyostelium discoideum as compared with the parental wild-type strain (NC4). This light as well as a germicidal lamp-light (254 nm) produced pyrimidine dimers. The dimers were removed from DNA molecules by excision repair in NC4, but more slowly in TW8. It is suggested that pyrimidine dimers are the main DNA damage caused by HL light in D. discoideum , and that this results in cell killing and induced mutation. 相似文献