全文获取类型
收费全文 | 727篇 |
免费 | 21篇 |
国内免费 | 1篇 |
专业分类
化学 | 525篇 |
晶体学 | 20篇 |
力学 | 9篇 |
数学 | 40篇 |
物理学 | 155篇 |
出版年
2023年 | 5篇 |
2022年 | 5篇 |
2021年 | 4篇 |
2019年 | 8篇 |
2018年 | 10篇 |
2017年 | 10篇 |
2016年 | 15篇 |
2015年 | 20篇 |
2014年 | 13篇 |
2013年 | 47篇 |
2012年 | 37篇 |
2011年 | 39篇 |
2010年 | 29篇 |
2009年 | 20篇 |
2008年 | 28篇 |
2007年 | 28篇 |
2006年 | 39篇 |
2005年 | 39篇 |
2004年 | 33篇 |
2003年 | 30篇 |
2002年 | 24篇 |
2001年 | 14篇 |
2000年 | 14篇 |
1999年 | 13篇 |
1998年 | 8篇 |
1997年 | 10篇 |
1996年 | 8篇 |
1995年 | 7篇 |
1994年 | 10篇 |
1993年 | 6篇 |
1992年 | 5篇 |
1991年 | 10篇 |
1989年 | 13篇 |
1988年 | 12篇 |
1987年 | 11篇 |
1985年 | 12篇 |
1984年 | 10篇 |
1982年 | 11篇 |
1981年 | 9篇 |
1980年 | 12篇 |
1978年 | 7篇 |
1977年 | 11篇 |
1976年 | 4篇 |
1975年 | 3篇 |
1974年 | 6篇 |
1973年 | 5篇 |
1972年 | 4篇 |
1971年 | 3篇 |
1968年 | 5篇 |
1967年 | 3篇 |
排序方式: 共有749条查询结果,搜索用时 0 毫秒
91.
92.
Natural antioxidants. III. Antioxidative components isolated from rhizome of Curcuma longa L 总被引:2,自引:0,他引:2
S Toda T Miyase H Arichi H Tanizawa Y Takino 《Chemical & pharmaceutical bulletin》1985,33(4):1725-1728
93.
Takashi Toda Norihiko Shimazaki Toshio Mukai Chizuko Kabuto 《Tetrahedron letters》1980,21(41):4001-4004
The structure of a minor dimer () of 1-arylcycloheptatrienylidenethylene was determined by X-ray crystallography. Dehydration of and gave novel non-benzenoid aromatics---6,12-diarylazuleno[1,2-b]azulenes ( and ), whose electronic and NMR spectral properties were reported. 相似文献
94.
95.
96.
97.
Yoshio Iwakura Fujio Toda Yoshinori Torii Katsuaki Murata 《Journal of polymer science. Part A, Polymer chemistry》1968,6(4):785-791
Polyamideamines with a sequence of two amide and one amine linkage in a main chain were synthesized from the polyaddition of 2-isopropylidene-4-alkyl-3-oxazolin-5-ones and primary diamines. The polyaddition reaction proceeded through 1,4-conjugate addition of an amine group to 3-oxazolin-5-one and subsequent ring opening of the intermediate addition product with another amine. Although aliphatic diamines gave oily polymers, xylylenediamines afforded amorphous solid polymers. The reduced viscosities and polymer melt temperature of the polymers were 0.05–0.12 and 90–130°C., respectively. 相似文献
98.
99.
Ochiai M Nishi Y Mori T Tada N Suefuji T Frohn HJ 《Journal of the American Chemical Society》2005,127(30):10460-10461
Reported here for the first time are the synthesis, isolation, and characterization of hypervalent beta-haloalkenyl-lambda3-bromanes. Exposure of terminal alkynes to p-trifluoromethylphenyl(difluoro)-lambda3-bromane activated by BF3-i-Pr2O resulted in fluoro-lambda3-bromanation of the triple bonds in a Markovnikov fashion, yielding (E)-beta-fluoroalkenyl-lambda3-bromanes stereoselectively in good yields. 5-Chloro-1-pentynes undergo domino lambda3-bromanation-chlorine shift-fluorination or lambda3-bromanation-chlorine shift-alkyl shift-fluorination reaction, depending on the substituents and afford (E)-beta-chloroalkenyl-lambda3-bromanes stereoselectively in high yields. The beta-chloroalkenyl-lambda3-bromanes contain three kinds of halogen atoms, F, Cl, and Br, in the molecule. 相似文献
100.
Ochiai M Takeuchi Y Katayama T Sueda T Miyamoto K 《Journal of the American Chemical Society》2005,127(35):12244-12245
Reported here for the first time is the iodobenzene-catalyzed alpha-oxidation of ketones, in which diacyloxy(phenyl)-lambda3-iodanes generated in situ act as real oxidants of ketones and m-chloroperbenzoic acid serves as a terminal oxidant. Oxidation of a ketone with m-chloroperbenzoic acid in acetic acid in the presence of a catalytic amount of iodobenzene, BF3.Et2O, and water at room temperature under argon affords an alpha-acetoxy ketone in good yield. p-Methyl- and p-chloroiodobenzene also serve as efficient catalysts in this direct oxidation. We found that when the reaction was carried out in the absence of a catalytic amount of iodobenzene, Baeyer-Villiger oxidation of a ketone took place. It is noted that use of water and BF3.Et2O is crucial to the success of this alpha-acetoxylation. 相似文献