全文获取类型
收费全文 | 1275篇 |
免费 | 47篇 |
国内免费 | 8篇 |
专业分类
化学 | 921篇 |
晶体学 | 5篇 |
力学 | 20篇 |
数学 | 223篇 |
物理学 | 161篇 |
出版年
2020年 | 19篇 |
2019年 | 14篇 |
2018年 | 15篇 |
2016年 | 33篇 |
2015年 | 18篇 |
2014年 | 29篇 |
2013年 | 44篇 |
2012年 | 42篇 |
2011年 | 40篇 |
2010年 | 28篇 |
2009年 | 20篇 |
2008年 | 33篇 |
2007年 | 32篇 |
2006年 | 30篇 |
2005年 | 38篇 |
2004年 | 26篇 |
2003年 | 36篇 |
2002年 | 28篇 |
2001年 | 24篇 |
2000年 | 12篇 |
1999年 | 15篇 |
1998年 | 14篇 |
1997年 | 22篇 |
1996年 | 25篇 |
1995年 | 22篇 |
1994年 | 20篇 |
1993年 | 16篇 |
1992年 | 18篇 |
1991年 | 27篇 |
1990年 | 19篇 |
1989年 | 23篇 |
1988年 | 16篇 |
1987年 | 28篇 |
1986年 | 22篇 |
1985年 | 21篇 |
1984年 | 37篇 |
1983年 | 19篇 |
1982年 | 19篇 |
1981年 | 17篇 |
1980年 | 21篇 |
1979年 | 18篇 |
1978年 | 28篇 |
1977年 | 24篇 |
1976年 | 17篇 |
1975年 | 19篇 |
1974年 | 15篇 |
1973年 | 17篇 |
1972年 | 16篇 |
1971年 | 14篇 |
1970年 | 13篇 |
排序方式: 共有1330条查询结果,搜索用时 15 毫秒
71.
Siegfried Bosch 《Inventiones Mathematicae》1973,19(3):165-218
Ohne Zusammenfassung 相似文献
72.
73.
74.
Power spectra of discrete dynamical systems at the threshold of chaos contain line series obeying Sω ∞ ω for small ω. We explain in terms of the Feigenbaum rescaling parameter α. Another parameter β related to the noise strength of states of periodic chaos and recently numerically determined by Huberman and Zisook is related to α as well. 相似文献
75.
76.
Described is the first enantioselective synthesis of (-)-gilbertine (2), a member of the uleine-type family, and the determination of the absolute configuration of this natural product is reported. The key step employs a cationic cascade reaction for a tetrahydropyrane and piperidine ring formation and the construction of the pentacyclic framework in one step. The synthetic strategy utilizes the Shibasaki reaction to build up the first stereogenic center. A formylation reaction of a 3-substituted cyclohexanone derivative was achieved, giving only the desired regioisomer. The Japp-Klingemann Fischer indole protocol was used successfully as a convergent synthetic approach for the construction of the desired tetrahydrocarbazole (20). Furthermore, an unexpected behavior of this 2,3-disubstituted cyclohexanone derivative during an epimerization process was investigated, resulting in different chemical behavior of the enantiomers and the racemate. The diastereomeric resolution was achieved via the cationic cascade reaction, demonstrating the versatility of this approach. Significantly, the synthetic 17-step sequence was easy to execute, giving (-)-gilbertine in 5.5% overall yield. 相似文献
77.
Jérôme Chabert Siegfried Echterhoff Hervé Oyono-Oyono 《Geometric And Functional Analysis》2004,14(3):491-528
We study the connection between the Baum-Connes conjecture
for a locally compact group G with coeefficient A and the Künneth
formula for the K-theory of tensor products by the corresponding crossed
product
. The main tool for this is obtained by an application of
a general reduction procedure which allows us to analyze certain functors
connected to the topological K-theory of a group in terms of their restrictions
to compact subgroups. We also discuss several other interesting
applications of this method, including a general extension result for the
Baum-Connes conjecture. 相似文献
78.
79.
The dinuclear copper(I) complex [Cu(2)L(1)(CH(3)CN)(2)](ClO(4))(2) (1, L(1) = 3,6,9,17,20,23-hexaazatricyclo[23.3.1.1]triaconta-1(29),2,9,11(30),12(13),14,16,23,25,27-decaene) has been structurally characterized. As previously described, intramolecular ligand hydroxylation (at the aromatic ring) was observed when 1 was reacted with dioxygen. A stopped-flow analysis of the reaction of 1 with dioxygen under different conditions did not allow a "dioxygen intermediate" to be spectroscopically detected. Detailed NMR and electrochemical data on 1 are also presented and evaluated for the first time. No copper(II) complexes of L(1) could be characterized due to hydrolysis of the compounds. In contrast, complex 2-differing from 1 only in an increase in the size of the chelate rings-did not undergo intramolecular hydroxylation when it was oxidized. The crystal structure of 2 is also described. 相似文献
80.
8-alpha-Acetoxyverrol (4), the first open chain example of the trichothecenes with oxygenation at C-8, was isolated from cultures of Aphanocladium spectabile. The compound doses the biosynthetic gap to the macrocyclic verrucarins. 相似文献