全文获取类型
收费全文 | 156篇 |
免费 | 5篇 |
国内免费 | 1篇 |
专业分类
化学 | 135篇 |
晶体学 | 1篇 |
力学 | 4篇 |
数学 | 5篇 |
物理学 | 17篇 |
出版年
2023年 | 1篇 |
2022年 | 1篇 |
2021年 | 2篇 |
2019年 | 3篇 |
2018年 | 1篇 |
2017年 | 3篇 |
2016年 | 2篇 |
2015年 | 1篇 |
2014年 | 5篇 |
2013年 | 3篇 |
2012年 | 8篇 |
2011年 | 10篇 |
2010年 | 6篇 |
2009年 | 7篇 |
2008年 | 10篇 |
2007年 | 8篇 |
2006年 | 14篇 |
2005年 | 10篇 |
2004年 | 10篇 |
2003年 | 7篇 |
2002年 | 8篇 |
2001年 | 1篇 |
2000年 | 4篇 |
1998年 | 2篇 |
1997年 | 3篇 |
1996年 | 1篇 |
1995年 | 3篇 |
1994年 | 2篇 |
1993年 | 3篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1985年 | 2篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 2篇 |
排序方式: 共有162条查询结果,搜索用时 31 毫秒
61.
Toshikatsu Koga Akihiro Hirashima Yuji Ueda Mutsuo Morita 《Theoretical chemistry accounts》1982,62(1):55-67
For a one-electron homonuclear diatomic system with arbitrary nuclear charge Z, the change in the nature of diatomic interaction and its density origin are quantitatively examined as a function of Z by the method of binding/antibinding analyses based on the Hellmann-Feynman theorem. In the Isg ground state, two energy extrema, potential barrier at a large internuclear distance and potential minimum at a smaller distance, appear for 1<Z<1.44. The binding part of the partitioned Hellmann-Feynman forces suffers little effect of Z, and these two extrema are attributed respectively to the increase in the nuclear repulsion and to the decrease in the antibinding part of the partitioned forces. In the antibonding 2pu state, a stable molecule is formed for Z<1. This appearance of the bonding nature is shown to have its origin in the binding part which is almost unchanged by the decrease of Z. 相似文献
62.
63.
Tatsuzawa F Saito N Miyoshi K Shinoda K Shigihara A Honda T 《Chemical & pharmaceutical bulletin》2004,52(5):631-633
A new diacylated 8-C-glucosylanthocyanin was isolated from the purple flowers of Tricyrtis formosana 'Fujimusume' as one of the major anthocyanins along with four known pigments. The structure of this pigment was determined to be 8-C-(6-O-trans-sinapoyl)-beta-glucopyranosylcyanidin 3-O-(6-O-malonyl-beta-glucopyranoside) by chemical and spectroscopic methods. In addition, four known pigments, 8-C-glucosylcyanidin 3-malonylglucoside, cyanidin 3-glucoside, cyanidin 3-rutinoside and cyanidin 3-malonylglucoside, were identified as the major anthocyanins in the flowers. 相似文献
64.
Shigeki Sasaki Shouji Nakashima Fumi Nagatsugi Yoshitsugu Tanaka Masao Hisatome Minoru Maeda 《Tetrahedron letters》1995,36(52):9521-9524
A new artificial nucleobase (1) was designed for the selective formation of a triple-complex with a cytosine-guanine base pair at the major groove site. It has been proved based on the 1D- and 2D 1H-NMR spectra that the protected 2′-oxy-1 (7) forms a triplex complex with the GC pair selectively. 相似文献
65.
An enantiopure phosphonothioic acid showed a unique and superior chiral recognition ability, arising from its P-stereogenicity, for racemic 1-phenylethylamine derivatives through diastereomeric crystallization. Spherical molecular clusters, associated by hydrogen bonds and CH/pi interactions, aggregated with high symmetry in the less-soluble diastereomeric salts. 相似文献
66.
Tetsuo Yamasaki Eiji Kawaminami Fumi Uchimura Tadashi Okawara Mitsuru Furukawa 《Journal of heterocyclic chemistry》1991,28(4):859-865
The reaction of 5(4)-amino-4(5)-chloropyridazin-3(2H)-ones 1 (9 ) with methyl dithiocarbamates 2 gave 2-arylaminothiazolo[4,5-d]pyridazinones 3 (10 ). Treatment of 5(4)-alkylamino-4(5)-chloropyridazin-3(2H)-ones 5 (12 ) with 2 afforded the corresponding 2-aryliminothiazolo[4,5-d]pyridazinones 6 (13 ). Cyclization of 1a with phenylisothiocyanate produced 2-amino- and 2-iminothiazolo[4,5-d]pyridazinones 3a and 16 . 相似文献
67.
Masao Kunioka Fumi Ninomiya Masahiro Funabashi 《Polymer Degradation and Stability》2006,91(9):1919-1928
The methods for producing reference test materials for biodegradation evaluation tests have been studied. Mechanical crushing at low temperature of polymer pellets using dry ice was selected for the method of producing polymer powder of poly(lactic acid) (PLA). The powders were fractionated using 60 mesh (250 μm) and 120 mesh (125 μm) sieves. The size distributions were then measured. The average diameter of the PLA particles obtained by this method was 214.2 μm. The biodegradation speeds of these PLA polymer powders were evaluated by two methods based on the international standard and one in vitro method based on the enzymatic degradation. First, the degree of biodegradation for this PLA powder was 91% for 35 days in a controlled compost determined by a method based on ISO 14855-1 (JIS K6953) at 58 °C managed by the Mitsui Chemical Analysis and Consulting Service, Inc. (Japan). Second, these polymer powders were measured for biodegradation by the Microbial Oxidative Degradation Analyzer (MODA) in a controlled compost at 58 °C and 70 °C based on ISO/DIS 14855-2 under many conditions. The degree of biodegradation for this PLA powder was approximately 80% for 50 days. In addition, the polymer powders were biodegraded by Proteinase K which is a PLA degradation enzyme. This polymer powder was suitable as a reference material for the evaluation methods of biodegradation. 相似文献
68.
Kenji Yamagata Fumi Okabe Motoyoshi Yamazaki Yoshinobu Tagawa 《Monatshefte für Chemie / Chemical Monthly》2002,133(5):643-651
Summary. The reaction of 2-amino-4,5-dihydro-3-furancarboxamides with morpholine in the presence of acetic acid in pyridine or under
the influence of ammonium acetate gave the corresponding 3-diaminomethylene-4,5-dihydro-2(3H )-furanones; 4,5-dihydro-2-morpholino-3-furancarboxamides were not isolated. One of the former reacted with benzylamine to
give (E )- and (Z )-3-(amino-(benzylamino)-methylene)-4,5-dihydro-4-phenyl-2(3H )-furanones and 2-benzylamino-4,5-dihydro-4-phenyl-3-furancarboxamide.
Received October 4, 2001. Accepted October 10, 2001 相似文献
69.
70.
The reactions of 2‐amino‐4,5‐dihydro‐3‐furancarboxarnides 1a,b with cyanomethylene compounds (such as alkyl cyanoacetates and malononitrile) gave the corresponding ring‐opened products 2a‐f. Compounds 2a‐d reacted with methanesulfonic acid to give the corresponding α‐alkylidene‐γ‐butyrolactones 3a‐d. On the other hand, treatment of 2e,f with methanesulfonic acid yielded 3‐pyridinecarbonitrile derivatives 4a,b. 相似文献