全文获取类型
收费全文 | 1564篇 |
免费 | 56篇 |
国内免费 | 2篇 |
专业分类
化学 | 1320篇 |
晶体学 | 22篇 |
力学 | 12篇 |
数学 | 74篇 |
物理学 | 194篇 |
出版年
2023年 | 12篇 |
2022年 | 18篇 |
2021年 | 26篇 |
2020年 | 20篇 |
2019年 | 25篇 |
2018年 | 20篇 |
2017年 | 18篇 |
2016年 | 35篇 |
2015年 | 25篇 |
2014年 | 40篇 |
2013年 | 87篇 |
2012年 | 77篇 |
2011年 | 104篇 |
2010年 | 48篇 |
2009年 | 49篇 |
2008年 | 115篇 |
2007年 | 116篇 |
2006年 | 104篇 |
2005年 | 141篇 |
2004年 | 97篇 |
2003年 | 67篇 |
2002年 | 70篇 |
2001年 | 22篇 |
2000年 | 19篇 |
1999年 | 10篇 |
1998年 | 24篇 |
1997年 | 15篇 |
1996年 | 25篇 |
1995年 | 11篇 |
1994年 | 12篇 |
1993年 | 7篇 |
1992年 | 5篇 |
1991年 | 7篇 |
1989年 | 8篇 |
1988年 | 5篇 |
1987年 | 3篇 |
1986年 | 6篇 |
1985年 | 13篇 |
1984年 | 14篇 |
1983年 | 6篇 |
1982年 | 20篇 |
1981年 | 10篇 |
1980年 | 17篇 |
1979年 | 5篇 |
1978年 | 11篇 |
1977年 | 8篇 |
1976年 | 5篇 |
1975年 | 5篇 |
1974年 | 6篇 |
1973年 | 3篇 |
排序方式: 共有1622条查询结果,搜索用时 15 毫秒
201.
The ozonolysis of 2-phenyloxazoles having the good leaving group as an anion at C-5 position gave mainly N-benzoylisocyanate ( 2 ) with the formation of carbon dioxide. 相似文献
202.
Hideki Sakurai Yoshiyasu Kamiyama Yasuhiro Nakadaira 《Journal of organometallic chemistry》1977,131(1):147-152
1,1,2,2-Tetramethyl-1,2-disilacyclopentane undergoes the SiSi/SiSi metathesis reaction with vinyl- or ethynyl-substituted disilanes in the presence of a palladium complex. 相似文献
203.
New procedures for preparation of trimethylsilylsodium and trimethylsilylpotassium, which gave coupling products with primary and secondary alkyl chlorides in high yields, are reported. 相似文献
204.
205.
Omori Hideki Maeda Yoshiaki Miyazaki Naoya Yoshioka Akira 《Letters in Mathematical Physics》1998,46(2):171-180
It is well known that the Moyal bracket gives a unique deformation quantization of the canonical phase space R2n up to equivalence. In his presentation of an interesting deformation quantization of the Poisson algebra of Laurent polynomials, Ovsienko discusses the equivalences of deformation quantizations of these algebras. We show that under suitable conditions, deformation quantizations of this algebra are equivalent. Though Ovsienko showed that there exists a deformation quantization of the Poisson algebra of Laurent polynomials which is not equivalent to the Moyal product, this is not correct. We show this equivalence by two methods: a direct construction of the intertwiner via the star exponential and a more standard approach using Hochschild 2-cocycles. 相似文献
206.
Four new dicyclopentadienyltitanium(IV) metallocycles, Cp2TiCH2XCH2 (X = SiMe2OSiMe2, SiMe2CH2SiMe2, SiMe2SiMe2, and SiMe2SiMe2SiMe2) are prepared and characterized. 相似文献
207.
208.
209.
Arsenic has been applied to many electronic devices such as electrophotoreceptors, gallium arsenide (GaAs) semiconductors and solid-state image pickup devices. For electrophotoreceptors selenium–arsenic (Se? As) alloys are coated onto the conductive substrate of the receptors. Arsenic is mostly used in electophotoreceptors in electronic devices. During the coating process, a part of the gaseous arsenic is released through an exhaust system. In order to avoid arsenic being discharged to the atmosphere, bag filters and high-efficiency particulate air filters are set before the exhaust port. Any arsenic which still exists in the waste water after washing tools and jigs from the coating process is collected by sedimentation before discharging. The Ames salmonella/microsome plate test for As2Se3 indicated no mutagenic activity under the test system used. For the safety of workers engaged in arsenic-related jobs, they received a medical examination once every six months. No negative trends from the examination was found in 428 men who received the examination from Autumn 1980 to Spring 1987. 相似文献
210.
New asymmetric bis(oxazoline) (Box) ligand bearing amide group at the oxazoline 4-position, (S,S)-2,2′-methylenebis(4-tert-butylcarbamoyl-2-oxazoline) (1S), was designed and synthesized for selective catalytic reaction. The crystal structure of the ternary copper complex, consisting of 1S and N-benzoyl-N-phenyl-hydroxylamine, demonstrated interligand interactions, such as hydrogen bonding and CH-π interaction. Catalytic performance of the copper complex with 1S was investigated for an asymmetric Diels-Alder reaction using benzylidene-2-acetylpyridine and 1,3-cyclohexadiene (CHD). The reaction product was enantio-pure endo-(pyridin-2-yl)(3-phenylbicyclo[2,2,2]oct-5-ene-2-yl)methanone (BPCD), of which crystal structure was analyzed by the X-ray method. No stereo- and enantio-isomer of BPCD was detected by chiral HPLC analysis. Introduction of hydrogen bonding site into 1S can promote the Diels-Alder reaction even though using poor reactive CHD. Without 1S, this reaction did not give any product. Addition of 2-propanol to this reaction system inhibited the formation of BPCD, indicating that the designed interligand interaction sites, especially hydrogen bonding, play an important role for catalytic performance. 相似文献