全文获取类型
收费全文 | 1030篇 |
免费 | 14篇 |
专业分类
化学 | 745篇 |
晶体学 | 7篇 |
力学 | 12篇 |
数学 | 22篇 |
物理学 | 258篇 |
出版年
2023年 | 6篇 |
2021年 | 8篇 |
2020年 | 10篇 |
2019年 | 13篇 |
2017年 | 4篇 |
2016年 | 7篇 |
2015年 | 14篇 |
2014年 | 19篇 |
2013年 | 45篇 |
2012年 | 51篇 |
2011年 | 51篇 |
2010年 | 24篇 |
2009年 | 31篇 |
2008年 | 66篇 |
2007年 | 65篇 |
2006年 | 66篇 |
2005年 | 49篇 |
2004年 | 50篇 |
2003年 | 34篇 |
2002年 | 40篇 |
2001年 | 21篇 |
2000年 | 21篇 |
1999年 | 10篇 |
1998年 | 9篇 |
1996年 | 12篇 |
1995年 | 11篇 |
1994年 | 16篇 |
1993年 | 12篇 |
1992年 | 14篇 |
1991年 | 14篇 |
1990年 | 15篇 |
1989年 | 10篇 |
1988年 | 15篇 |
1987年 | 23篇 |
1986年 | 10篇 |
1985年 | 14篇 |
1984年 | 13篇 |
1983年 | 7篇 |
1982年 | 9篇 |
1981年 | 15篇 |
1980年 | 11篇 |
1979年 | 15篇 |
1978年 | 16篇 |
1977年 | 10篇 |
1976年 | 11篇 |
1975年 | 5篇 |
1974年 | 8篇 |
1973年 | 11篇 |
1970年 | 4篇 |
1966年 | 4篇 |
排序方式: 共有1044条查询结果,搜索用时 15 毫秒
121.
Yokoe H Mitsuhashi C Matsuoka Y Yoshimura T Yoshida M Shishido K 《Journal of the American Chemical Society》2011,133(23):8854-8857
Enantiocontrolled total syntheses of the breviones A, B, and C have been accomplished using a highly diastereoselective oxidative coupling of an α-pyrone with a tricyclic diene prepared from an optically pure Wieland-Miescher ketone derivative through the 7-endo-trig mode of acyl radical cyclization. 相似文献
122.
Eiichi Masumoto Hiroshi Maruoka Fumi Okabe Sho Nishida Yuki Yoshimura Toshihiro Fujioka Kenji Yamagata 《Journal of heterocyclic chemistry》2011,48(1):96-104
Dihydropyridazinones 4a , 4b , N‐substituted dihydropyrazoles 5b , 5c , 5d , and O‐substituted pyrazoles 6a , 6b , 6c , 6d have been synthesized starting from spirocyclopropanepyrazole derivative 2 . Treatment of 2 with α‐chloro esters, e.g., methyl chloroacetate, ethyl chloroacetate, isopropyl chloroacetate, and tert‐butyl chloroacetate, in potassium carbonate/sodium iodide system caused ring opening and subsequent C‐ or N‐attack nucleophilic substitution to give the corresponding dihydropyridazinones 4a , 4b and N‐substituted dihydropyrazoles 5b , 5c , 5d . On the other hand, in the absence of sodium iodide, O‐substituted pyrazoles 6a , 6b , 6c , 6d were obtained from 2 via an O‐attack nucleophilic substitution. J. Heterocyclic Chem., 2011. 相似文献
123.
Ohno O Chiba T Todoroki S Yoshimura H Maru N Maekawa K Imagawa H Yamada K Wakamiya A Suenaga K Uemura D 《Chemical communications (Cambridge, England)》2011,47(46):12453-12455
Novel sesquiterpene alkaloids, halichonines A (1), B (2), and C (3), were identified from the marine sponge Halichondria okadai Kadota. By spectroscopic analyses and synthesis, their structures were revealed to include a 6,6-bicyclic ring system and two prenylated amine moieties. In addition, 2 induced apoptosis in HL60 human leukemia cells. 相似文献
124.
125.
We have investigated the pressure-induced Raman spectral changes of 1-ethyl-3-methylimidazolium tetrafluoroborate ([emim][BF4]). We found that [emim][BF4] did not crystallize up to 1.2 GPa. The Raman CH stretching spectra arising from the CH3 groups of the ethyl-chain and the CH3 group adjacent to the imidazolium-ring in [emim]+ cation largely changed against pressure. Moreover, the Raman intensity of the CH2 (N) bending band arising from the alkyl-chain drastically changes with increasing pressure, but that of the imidazolium-ring in-plane bending band arising from the imidazolium-ring is independent of pressure. Our results show that the environment around the alkyl-chain of [emim][BF4] is largely perturbed rather than that around the imidazolium-ring upon compression. 相似文献
126.
Toshihiro Yoshimura Yusuke Tamenori Nozomu Iwasaki Hiroshi Hasegawa Atsushi Suzuki Hodaka Kawahata 《Journal of synchrotron radiation》2013,20(5):734-740
Magnesium K‐edge X‐ray absorption near‐edge structure (XANES) spectra have been investigated to develop a systematic understanding of a suite of Mg‐bearing geological materials such as silicate and carbonate minerals, sediments, rocks and chemical reagents. For the model compounds the Mg XANES was found to vary widely between compounds and to provide a fingerprint for the form of Mg involved in geologic materials. The energy positions and resonance features obtained from these spectra can be used to specify the dominant molecular host site of Mg, thus shedding light on Mg partitioning and isotope fractionation in geologic materials and providing a valuable complement to existing knowledge of Mg geochemistry. 相似文献
127.
H. Wada H. Nakamura E. Fukami K. Yoshimura M. Shiga Y. Nakamura 《Journal of magnetism and magnetic materials》1987,70(1-3):17-19
The thermal expansion and low temperature and low temperature specific heat were measured for Y1−xScxMn2. The results are discussed in terms of spin fluctuations and compared with those of Y(Mn1−xAlx)2, which show al local moment character. It is revealed that Y1−xScxMn2 is a typical nearly antiferromagnet in which giant spin fluctuations are thermally excited. 相似文献
128.
Fumihiko Nakano 《Journal of statistical physics》2006,123(4):803-810
In this note we show that, a simple combination of deep results in the theory of random Schrödinger operators yields a quantitative estimate of the fact that the localization centers become far apart, as corresponding energies are close together. 相似文献
129.
130.