全文获取类型
收费全文 | 472篇 |
免费 | 10篇 |
专业分类
化学 | 419篇 |
力学 | 2篇 |
数学 | 6篇 |
物理学 | 55篇 |
出版年
2021年 | 4篇 |
2020年 | 8篇 |
2019年 | 5篇 |
2018年 | 8篇 |
2016年 | 6篇 |
2014年 | 7篇 |
2013年 | 46篇 |
2012年 | 24篇 |
2011年 | 23篇 |
2010年 | 9篇 |
2009年 | 14篇 |
2008年 | 10篇 |
2007年 | 16篇 |
2006年 | 17篇 |
2005年 | 24篇 |
2004年 | 15篇 |
2003年 | 11篇 |
2002年 | 13篇 |
2001年 | 13篇 |
2000年 | 5篇 |
1999年 | 5篇 |
1998年 | 4篇 |
1996年 | 8篇 |
1995年 | 5篇 |
1994年 | 3篇 |
1992年 | 7篇 |
1991年 | 5篇 |
1990年 | 4篇 |
1989年 | 4篇 |
1988年 | 4篇 |
1987年 | 4篇 |
1986年 | 4篇 |
1985年 | 3篇 |
1984年 | 11篇 |
1982年 | 5篇 |
1981年 | 9篇 |
1980年 | 12篇 |
1979年 | 9篇 |
1978年 | 19篇 |
1977年 | 9篇 |
1976年 | 8篇 |
1975年 | 5篇 |
1974年 | 4篇 |
1973年 | 3篇 |
1972年 | 3篇 |
1969年 | 5篇 |
1968年 | 7篇 |
1967年 | 11篇 |
1966年 | 3篇 |
1965年 | 6篇 |
排序方式: 共有482条查询结果,搜索用时 15 毫秒
121.
The synthesis of optically active lipopeptide derivatives has been accomplished by the use of chiral glycerol derivatives. Lipopeptide derivatives with (R)-glycerol moieties showed higher mitogenic activities than those with the (S)-configuration. N-2,2,2-Trichloroethoxycarbonyl lipopeptide derivatives increased mitogenic activity. 相似文献
122.
Yasuo Kita Taizo Uno Yoshiaki Inaki Kiichi Takemoto 《Journal of polymer science. Part A, Polymer chemistry》1981,19(2):477-485
Photodimerization of thymine bases present on the side chain of acryloyl and methacryloyl-type polymers was studied in dimethyl sulfoxide, dimethylformamide, and dimethyl sulfoxide—ethylene glycol mixture. Quantum efficiencies for photodimerization and quenching with isoprene were influenced by the solvents. The self-association of thymine bases estimated from their ultraviolet (UV) spectra and intrinsic viscosity were related to the effect of solvent on the photodimerization. 相似文献
123.
Naomichi Furukawa Toshiaki Yoshimura Masami Ohtsu Takeshi Akasaka Shigeru Oae 《Tetrahedron》1980,36(1):73-80
The Michael type additions of diphenyl N-unsubstituted sulfimide (free sulfimide) to various electrophilic olefins were carried out. The reaction with cis- and trans-dibenzoylethylene, dimethyl-fumarate, dimethylmaleate, benzalacetophenone and benzalacetone gave mainly the corresponding trans-2-acylaziridines and trans-enaminoketones. However, phenyl vinyl sulfone or acrylonitrile afforded not the corresponding aziridine but diphenyl-N-2-cyano or N-2-phenylsulfonylethylsulfimide, a simple Michael adduct When optically active (+)-(R)-o-methoxyphenyiphenyl free sulfimide was treated with such an α,β-unsaturated carbonyl compound as benzalacetopbenone, an optically active 2-acylazindine, i.e., (-)-trans-2-benzoyl-3-phenylaziridine was obtained in ca 30% optical purity and its absolute configuration was assigned as (2R,3S) upon chemical transformation to the configuration-ally known 2-phenyl-2-benzoylamino-1-ethanol or by comparing its CD spectrum with that of (1R,2R)-1-phenyl-2-benzoyl-cyclopropane. Meanwhile, (-)-(S)-o-methoxyphenylphenyl free sulfimide was found to react with benzalacetophenone to afford (+)-trans-2-benzoyl-3-phenylaziridine of 25% optical purity. Effects of solvent and temperature on both die distribution of the products ratio and the optical yield were examined. 相似文献
124.
Chuzo Iwata Yoshiji Takemoto Hitoshi Kubota Takeshi Kuroda Takeshi Imanishi 《Tetrahedron letters》1985,26(27):3231-3234
(±)-Oxylubimin (1), the highest oxidized spirovetivane-type phytoalexin, was totally synthesized with high stereoselectivity using a novel method for α′-hydroxylation of α,β-unsaturated ketones. 相似文献
125.
126.
127.
Naomichi Furukawa Kunihiko Akutagawa Toshiaki Yoshimura Shigeru Oae 《Tetrahedron letters》1981,22(40):3989-3992
N-(Arenesulfonyl) sulfilimines can be oxidized to the corresponding sulfoximes in high yields with sodium hypochlorite in an AcOEt-H2O two phase system in the presence of quaternary ammonium salts as catalysts. 相似文献
128.
129.
M. Miyata K. Morioka K. Takemoto 《Journal of polymer science. Part A, Polymer chemistry》1977,15(12):2987-2996
Postirradiation polymerization of 2,3-dimethylbutadiene in deoxycholic acid canal complexes was studied under various reaction conditions. The polymerization was carried out in degassed sealed tubes since the atmosphere had a large effect upon the polymer yield. Addition of 2,3-dimethylbutane led to a sharp drop in polymer yield, while hydroquinone showed little effect on the polymerization. The rate of postirradiation polymerization was found to increase with increase in reaction temperature and irradiation dose. The apparent activation energy was obtained as 13.7 kcal/mole in a temperature range between ?14 and 30°C. Existence of living free radicals having a long lifetime, the gradual change of the monomer into the polymer within the canals, and the effective spatial control in canals are discussed on the basis of the postirradiation polymerization behavior, nature of the adducts, and the structure of the polymers. 相似文献