全文获取类型
收费全文 | 1914篇 |
免费 | 51篇 |
国内免费 | 6篇 |
专业分类
化学 | 1413篇 |
晶体学 | 15篇 |
力学 | 23篇 |
综合类 | 1篇 |
数学 | 103篇 |
物理学 | 416篇 |
出版年
2021年 | 17篇 |
2020年 | 19篇 |
2019年 | 25篇 |
2018年 | 16篇 |
2017年 | 14篇 |
2016年 | 26篇 |
2015年 | 35篇 |
2014年 | 36篇 |
2013年 | 87篇 |
2012年 | 96篇 |
2011年 | 115篇 |
2010年 | 55篇 |
2009年 | 39篇 |
2008年 | 104篇 |
2007年 | 118篇 |
2006年 | 104篇 |
2005年 | 88篇 |
2004年 | 73篇 |
2003年 | 78篇 |
2002年 | 81篇 |
2001年 | 56篇 |
2000年 | 46篇 |
1999年 | 23篇 |
1998年 | 16篇 |
1997年 | 9篇 |
1996年 | 17篇 |
1995年 | 12篇 |
1994年 | 24篇 |
1993年 | 22篇 |
1992年 | 23篇 |
1991年 | 24篇 |
1990年 | 24篇 |
1989年 | 17篇 |
1988年 | 23篇 |
1987年 | 31篇 |
1986年 | 23篇 |
1985年 | 35篇 |
1984年 | 23篇 |
1983年 | 14篇 |
1982年 | 19篇 |
1981年 | 14篇 |
1980年 | 15篇 |
1979年 | 20篇 |
1978年 | 24篇 |
1977年 | 20篇 |
1976年 | 20篇 |
1975年 | 25篇 |
1974年 | 23篇 |
1973年 | 18篇 |
1972年 | 10篇 |
排序方式: 共有1971条查询结果,搜索用时 812 毫秒
51.
The mechanisms of nitrosation of acetone through sodium enolate [CH3CO1CH2]-Na+ (1) or naked enolate [CH3CO1CH2]- (2) with methyl nitrite CH3O3NO2 (3), and the reactivity of the syn-form of 3 (syn-3) during the C-N bond formation process were investigated using ab initio molecular orbital (MO) methods. Our results have demonstrated the predominant formation of E-1-hydroxyimino-2-oxo-propane CH3COCH=NOH (4E) when the complex [CH3CO1CH2NO2(O3CH3)]-Na+ was produced kinetically via a metal-chelated pericyclic transition state (TS(CHELATED)), in which the O3 atom of syn-3 was coordinated to the Na+ atom of 1. 相似文献
52.
53.
54.
Kenji Kojima Kusuo Nishiyama Kanetada Nagamine Hironobu Ikeda 《Hyperfine Interactions》1993,78(1-4):429-433
The site diluted finite spin cluster system Rb2CO
x
Mg1–x
F4 (x=0.15, 0.4, 0.5) has been investigated by the +SR technique. Muon spin relaxation was observed in these diluted magnetic systems in a weak longitudinal field of 100 G. By reducing temperature below 100 K, the experimental data show features of slowing down phenomena of the Co electron moments in the finite spin clusters. 相似文献
55.
H. Shiromaru T. Moriwaki H. Ikeda Y. Achiba 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1993,26(Z1):216-218
A simple threshold electron analyzer was constructed and laser photodetachment threshold electron spectra of Si– and Si
4
–
were measured. 相似文献
56.
Eietsu Hasegawa Shinya Takizawa Akira Yamaguchi Naoki Chiba Hiroshi Ikeda 《Tetrahedron》2006,62(27):6581-6588
Photoinduced electron-transfer reactions of several ketone substrates were studied to evaluate the utilities of 1,6-bis(dimethylamino)pyrene (BDMAP), 1,6-dimethoxypyrene (DMP), 9,10-bis(dimethylamino)anthracene (BDMAA), and 9,10-dimethoxyanthracene (DMA) as electron-donating sensitizers cooperating with 2-aryl-1,3-dimethylbenzimidazolines. BDMAP and DMP generally led higher conversion of ketones and better yield of reduction products compared to BDMAA and DMA. 相似文献
57.
Carbazoledioxazines with an angular type structure (5,15-dialkyl-7,17-dialkyloxy-9,19-dichloro-5,15-dihydrodiindolo[2,3-c:2′,3′-n]triphenodioxazines) were selectively synthesized by electrochemical oxidative ring closure of precursors (2,5-bis(9-alkyl-2-alkyloxy-3-carbazolylamino)-3,6-dichloro-1,4-benzoquinones). The structure was confirmed by 1H-nmr and other instrumental analyses. Their thermal properties and solubilities were investigated and were compared with those of carbazoledioxazines with a linear type structure. 相似文献
58.
M. Ueshima K. Sano M. Ikeda K. Yoshino J. Okamura 《Research on Chemical Intermediates》1998,24(2):133-141
The selective catalytic oxidation (SCO) of ammonia to N2 was studied by using a series of noble metal-V2O5-WO3 catalysts supported on titania-silica (TS) prepared by coprecipitation method. In the V2O5-WO3 catalyst system, the use of TS as a support was very effective to enhance catalytic activity compared with TiO2 or SiO2 alone. The addition of a slight amount of Pd and Ir to V2O5-WO3/TS catalyst caused also remarkable enhancement of the catalytic activity without decreasing the selectivity to N2. The present catalysts provide remarkably high catalytic performance for SCO of ammonia to N2 under the practical reaction conditions for an industrial application. 相似文献
59.
利用色相色谱/质谱联用技术,傅立叶红外及裂解-气相色谱/质谱联用技术,对印刷用上光油的关键成分进行了分析,共鉴定出7种挥发性组分,2种高分子聚合物。 相似文献
60.
Hiroshi Ikeda Takumi Sugiyama Akihiko Ueno 《Journal of inclusion phenomena and macrocyclic chemistry》2007,57(1-4):83-87
A new chemosensor for larger guests was prepared. The new chemosensor bears hydrophobic units at the primary hydroxy side
and a dansyl unit at the secondary hydroxy side of β-cyclodextrin. Due to the hydrophobic units, the new chemosensor is sensitive
to large or slender guests such as SDS and insensitive to 1-adamantanol, which is a good guest for the natural β-CD. 相似文献