全文获取类型
收费全文 | 507篇 |
免费 | 16篇 |
国内免费 | 12篇 |
专业分类
化学 | 376篇 |
晶体学 | 5篇 |
力学 | 7篇 |
数学 | 83篇 |
物理学 | 64篇 |
出版年
2023年 | 3篇 |
2022年 | 3篇 |
2021年 | 6篇 |
2019年 | 11篇 |
2018年 | 5篇 |
2017年 | 5篇 |
2016年 | 13篇 |
2015年 | 10篇 |
2014年 | 14篇 |
2013年 | 32篇 |
2012年 | 41篇 |
2011年 | 47篇 |
2010年 | 20篇 |
2009年 | 15篇 |
2008年 | 32篇 |
2007年 | 35篇 |
2006年 | 23篇 |
2005年 | 31篇 |
2004年 | 30篇 |
2003年 | 34篇 |
2002年 | 17篇 |
2001年 | 9篇 |
2000年 | 8篇 |
1999年 | 4篇 |
1998年 | 4篇 |
1997年 | 10篇 |
1996年 | 3篇 |
1995年 | 4篇 |
1994年 | 4篇 |
1993年 | 3篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1981年 | 2篇 |
1980年 | 4篇 |
1979年 | 4篇 |
1978年 | 5篇 |
1977年 | 4篇 |
1976年 | 2篇 |
1975年 | 3篇 |
1974年 | 4篇 |
1973年 | 4篇 |
1971年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有535条查询结果,搜索用时 46 毫秒
101.
102.
103.
104.
Magennis SW Habtemariam A Novakova O Henry JB Meier S Parsons S Oswald ID Brabec V Sadler PJ 《Inorganic chemistry》2007,46(12):5059-5068
The dinuclear RuII arene complexes [{(eta6-arene)RuCl}2(mu-2,3-dpp)](PF6)2, arene=indan (1), benzene (2), p-cymene (3), or hexamethylbenzene (4) and 2,3-dpp=2,3-bis(2-pyridyl)pyrazine, have been synthesized and characterized. Upon irradiation with UVA light, complexes 1 and 2 readily underwent arene loss, while complexes 3 and 4 did not. The photochemistry of 1 was studied in detail. In the X-ray structure of [{(eta6-indan)RuCl}2(mu-2,3-dpp)](PF6)2 (1), 2,3-dpp bridges two RuII centers 6.8529(6) A apart. In water, aquation of 1 in the dark occurs with replacement of chloride with biexponential kinetics and decay constants of 100+/-1 min-1 and 580+/-11 min-1. This aquation was suppressed by 0.1 M NaCl. UV or visible irradiation of 1 in aqueous or methanolic solution led to arene loss. The fluorescence of the unbound arene is approximately 40 times greater than when it is complexed. Irradiation of 1 also had a significant effect on its interactions with DNA. The DNA binding of 1 is increased after irradiation. The non-irradiated form of 1 preferentially formed DNA adducts that only weakly blocked RNA polymerase, while irradiation of 1 transformed the adducts into stronger blocks for RNA polymerase. The efficiency of irradiated 1 to form DNA interstrand cross-links was slightly greater than that of cisplatin in both 10 mM NaClO4 and 0.1 M NaCl. In contrast, the interstrand cross-linking efficiency of non-irradiated 1 in 10 mM NaClO4 was relatively low. An intermediate amount of cross-linking was observed when the sample of DNA already modified by non-irradiated 1 was irradiated. DNA unwinding measurements supported the conclusion that both mono- and bifunctional adducts with DNA can form. These results show that photoactivation of dinuclear RuII arene complexes can simultaneously produce a highly reactive ruthenium species that can bind to DNA and a fluorescent marker (the free arene). Importantly, the mechanism of photoreactivity is also independent of oxygen. These complexes, therefore, have the potential to combine both photoinduced cell death and fluorescence imaging of the location and efficiency of the photoactivation process. 相似文献
105.
106.
107.
Elemental sulphur, a common constituent of marine sediments, has been shown to give dialkyl sulphides with the Grignard reagents commonly used to derivatize alkyltin species before their determination by gas chromatography with flame photometric detection (GC–FPD). Further, it has been demonstrated that even with the red filter for 610 nm (normally used for organotin compounds) fitted to the detector, sulphur compounds do give rise to an emission signal, which may be mistaken for tin emission from a pentylated or propylated alkyltin compound, as the respective retention times are in some cases quite close. © 1997 by John Wiley & Sons, Ltd. 相似文献
108.
109.
Iain Raeburn 《Acta Appl Math》2009,108(3):509-514
In recent joint work with Nadia Larsen, we gave a new proof of a theorem of Mallat which describes how to construct wavelets
from quadrature mirror filters. Our main innovation was to show how the scaling function associated to the filter can be used
to identify a particular direct limit of Hilbert spaces with L
2(ℝ). Here we show that wavelet-packet bases for L
2(ℝ) also fit naturally into the same direct-limit framework. 相似文献
110.
Benjamin Nabet Naomi E. Leonard Iain D. Couzin Simon A. Levin 《Journal of Nonlinear Science》2009,19(4):399-435
We analyze a continuous-time model of a multi-agent system motivated by simulation studies on dynamics of decision making
in animal groups in motion. Each individual moves at constant speed in the plane and adjusts its heading in response to relative
headings of others in the population. The population includes two subgroups that are “informed” such that individuals in each
subgroup have a preferred direction of motion. The model exhibits fast and slow time scales allowing for a reduction in the
dimension of the problem. The stable solutions for the reduced model correspond to compromise by individuals with conflicting
preferences. We study the global phase space for the proposed reduced model by computing equilibria and exploring stability
and bifurcations.
B. Nabet’s and N.E. Leonard’s work is supported in part by AFOSR grant FA9550-07-1-0-0528 and ONR grants N00014-02-1-0826
and N00014-04-1-0534.
I.D. Couzin’s work was supported by the Royal Society, Balliol College and EPSRC grants GR/S04765/01 and GR/T11234/01, a Searle
Scholar Award and DARPA grant HR001-05-1-0057.
S.A. Levin’s work was supported in part by DARPA grant HR0011-05-1-0057 and NSF grant EF-0434319. 相似文献