全文获取类型
收费全文 | 1414篇 |
免费 | 62篇 |
国内免费 | 5篇 |
专业分类
化学 | 1172篇 |
晶体学 | 10篇 |
力学 | 4篇 |
数学 | 68篇 |
物理学 | 227篇 |
出版年
2023年 | 10篇 |
2022年 | 13篇 |
2021年 | 11篇 |
2020年 | 22篇 |
2019年 | 29篇 |
2018年 | 17篇 |
2017年 | 11篇 |
2016年 | 30篇 |
2015年 | 35篇 |
2014年 | 38篇 |
2013年 | 73篇 |
2012年 | 91篇 |
2011年 | 82篇 |
2010年 | 52篇 |
2009年 | 53篇 |
2008年 | 94篇 |
2007年 | 90篇 |
2006年 | 98篇 |
2005年 | 90篇 |
2004年 | 81篇 |
2003年 | 46篇 |
2002年 | 58篇 |
2001年 | 24篇 |
2000年 | 27篇 |
1999年 | 26篇 |
1998年 | 19篇 |
1997年 | 22篇 |
1996年 | 17篇 |
1995年 | 8篇 |
1994年 | 13篇 |
1993年 | 11篇 |
1992年 | 22篇 |
1991年 | 18篇 |
1990年 | 17篇 |
1989年 | 13篇 |
1988年 | 13篇 |
1987年 | 9篇 |
1986年 | 6篇 |
1985年 | 14篇 |
1984年 | 10篇 |
1983年 | 7篇 |
1982年 | 7篇 |
1979年 | 6篇 |
1976年 | 3篇 |
1975年 | 6篇 |
1974年 | 6篇 |
1972年 | 6篇 |
1969年 | 2篇 |
1968年 | 3篇 |
1967年 | 5篇 |
排序方式: 共有1481条查询结果,搜索用时 78 毫秒
141.
Kaori Kobayashi Takanori Matsui Shozo Tsunekawa 《Journal of Molecular Spectroscopy》2011,269(2):242-247
The trans-ethyl methyl ether molecule has three low-lying torsional modes, that is, two inequivalent methyl internal rotations and an asymmetric skeletal torsion. The internal rotations of the CCH3 and OCH3 methyl rotors and the skeletal torsion correspond to the vibrational modes, ν28, ν29 and ν30 respectively. In this study, the microwave absorption spectrum in the ν28 = 1 CCH3 torsional state was analyzed for the first time. Nine hundred fifty seven lines up to J = 48 and K = 4 were assigned, and the rotational, centrifugal distortion and internal rotational tunneling parameters were determined with the use of a tunneling matrix formalism. By combining the present results on the ν28 = 1 torsional state with those for the ν30 = 1 skeletal torsional state and the ν29 = 1 OCH3 torsional state, torsional couplings are estimated in order to understand quantitatively the inverted A/E sequence patterns observed for those three excited torsional states. 相似文献
142.
143.
This paper deals with the NOx removal with the help of a non-thermal surface plasma discharge in wet conditions. The gas treatment device consisting of a surface discharge and a wet-type reactor, was characterized through FTIR and electrical measurements. The ability of the proposed system for the cleaning of gas exhaust was studied. NOx as gaseous pollutant was decomposed effectively. To improve the chemical conversion, a coil was inserted in the electric circuit then a catalyst was placed in the plasma area. Results showed an improvement of NOx removal by an increase in radical species produced and synergistic effect, respectively. 相似文献
144.
Yasuko Ishizuka Hiroshi Nakanishi Takanori Shiraishi Yasuo Kogure Shoichi Kobayashi 《Journal of carbohydrate chemistry》2013,32(4):583-592
ABSTRACT 1H NMR spectra of some oligosaccharide substituted cyclodextrins composed of only α-D-glucose units are analysed. Chemical shifts of protons of each glucosyl group of the chain were determined by experiments with the HOHAHA pulse technique. In spite of the similar kinds of protons, dispersion of chemical shifts is observed. The most dispersed proton is the anomeric proton, and the largest change in the chemical shifts is 0.5 ppm. 相似文献
145.
146.
Decomposition of Benzene in Air in a Plasma Reactor: Effect of Reactor Type and Operating Conditions 总被引:2,自引:0,他引:2
Ogata A. Miyamae K. Mizuno K. Kushiyama S. Tezuka M. 《Plasma Chemistry and Plasma Processing》2002,22(4):537-552
The decomposition of benzene was carried out in two types of plasma reactors packed with BaTiO3 pellets: one reactor had two stainless steel electrodes (SUS reactor), and the other reactor had a glass layer between two concentric electrodes (GL reactor). The decomposition efficiency and the suppression of formation of N2O and NOx were greater in the GL reactor than in the SUS reactor. In contrast, the suppression of O3 formation and the oxidation to COx in the SUS reactor were superior to those in the GL reactor. The effect of wa eform and frequency of applied ac power was in estigated for each reactor. 相似文献
147.
Taichi Nakano Takashi Miyamoto Takanori Endoh Makoto Shimotani Naoki Ashida Toshishige Morioka Yutaka Takahashi 《应用有机金属化学》2004,18(2):65-67
The palladium‐catalyzed silastannation of acetylenes with tributyl(trimethylsilyl)stannane in the presence of triethylphosphite is reported for the first time. The reaction occurs at room temperature to give (Z)‐silyl(stannyl)ethenes in high yields. The protodemetallation of the resulting adducts with HCl–tetraethylammonium chloride is described first, which demonstrates that the reaction is governed only by the stability of a carbonium ion arising from the protonation to (Z)‐silyl(stannyl)ethenes rather than the hard and soft acid and base principle, i.e. the β‐cation stabilization effect (σ–π stabilization one) of a stannyl group in the carbonium ion is rather significant. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
148.
149.
Dr. Oscar Tutusaus Dr. Rana Mohtadi Dr. Timothy S. Arthur Dr. Fuminori Mizuno Dr. Emily G. Nelson Prof. Yulia V. Sevryugina 《Angewandte Chemie (International ed. in English)》2015,54(27):7900-7904
Unlocking the full potential of rechargeable magnesium batteries has been partially hindered by the reliance on chloride‐based complex systems. Despite the high anodic stability of these electrolytes, they are corrosive toward metallic battery components, which reduce their practical electrochemical window. Following on our new design concept involving boron cluster anions, monocarborane CB11H12? produced the first halogen‐free, simple‐type Mg salt that is compatible with Mg metal and displays an oxidative stability surpassing that of ether solvents. Owing to its inertness and non‐corrosive nature, the Mg(CB11H12)2/tetraglyme (MMC/G4) electrolyte system permits standardized methods of high‐voltage cathode testing that uses a typical coin cell. This achievement is a turning point in the research and development of Mg electrolytes that has deep implications on realizing practical rechargeable Mg batteries. 相似文献
150.
C‐Selective and Diastereoselective Alkyl Addition to β,γ‐Alkynyl‐α‐imino Esters with Zinc(II)ate Complexes 下载免费PDF全文
Dr. Manabu Hatano Kenji Yamashita Mai Mizuno Orie Ito Prof. Dr. Kazuaki Ishihara 《Angewandte Chemie (International ed. in English)》2015,54(9):2707-2711
Since umpolung α‐imino esters contain three electrophilic centers, regioselective alkyl addition with traditional organometallic reagents has been a serious problem in the practical synthesis of versatile chiral α‐amino acid derivatives. An unusual C‐alkyl addition to α‐imino esters using a Grignard reagent (RMgX)‐derived zinc(II)ate was developed. Zinc(II)ate complexes consist of a Lewis acidic [MgX]+ moiety, a nucleophilic [R3Zn]? moiety, and 2 [MgX2]. Therefore, the ionically separated [R3Zn]? selectively attacks the imino carbon atom ,which is most strongly activated by chelation of [MgX]+. In particular, chiral β,γ‐alkynyl‐α‐imino esters can strongly promote highly regio‐ and diastereoselective C‐alkylation because of structural considerations, and the corresponding optically active α‐quaternary amino acid derivatives are obtained within 5 minutes in high to excellent yields. 相似文献