全文获取类型
收费全文 | 113篇 |
免费 | 0篇 |
专业分类
化学 | 76篇 |
晶体学 | 1篇 |
力学 | 5篇 |
数学 | 15篇 |
物理学 | 16篇 |
出版年
2021年 | 2篇 |
2020年 | 1篇 |
2018年 | 2篇 |
2015年 | 3篇 |
2014年 | 1篇 |
2012年 | 4篇 |
2011年 | 7篇 |
2010年 | 4篇 |
2009年 | 1篇 |
2008年 | 7篇 |
2007年 | 4篇 |
2006年 | 7篇 |
2005年 | 3篇 |
2004年 | 3篇 |
2003年 | 5篇 |
2002年 | 6篇 |
2000年 | 3篇 |
1999年 | 2篇 |
1998年 | 1篇 |
1997年 | 5篇 |
1996年 | 3篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1992年 | 1篇 |
1991年 | 4篇 |
1990年 | 1篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1979年 | 1篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1974年 | 3篇 |
1973年 | 4篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1969年 | 2篇 |
1968年 | 2篇 |
1957年 | 1篇 |
1935年 | 1篇 |
1934年 | 1篇 |
1931年 | 1篇 |
排序方式: 共有113条查询结果,搜索用时 15 毫秒
51.
52.
53.
Contel M Villuendas PR Fernández-Gallardo J Alonso PJ Vincent JM Fish RH 《Inorganic chemistry》2005,44(26):9771-9778
This fluorous biphasic catalysis (FBC) contribution was focused on the synthesis and characterization of new fluorous soluble R(f)-Cu(II) carboxylate complexes containing nonfluoroponytailed ligands and defines their role as precatalysts for the FBC oxidation of alkenols and alcohols in the presence of 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO)/O(2). In this FBC approach, we have utilized the phase-switching technique of Vincent et al. (J. Am. Chem. Soc. 2002, 124, 12942) to solubilize the nonfluoroponytailed ligands, N-1,4,7-Me(3)TACN, 2, and N-1,4,7-pentamethyldiethylenetriamine (PMDETA), 3, by reaction with a fluorous solvent-soluble copper (II) dimeric complex, [Cu({C(8)F(17)(CH(2))(2)}(2)CHCO(2))(2)](2), 1. Moreover, the reaction of nonfluoroponytailed ligands 2 and 3 with 1 afforded new perfluoroheptane-soluble Cu(II) complexes, [Cu({C(8)F(17)(CH(2))(2)}(2)CHCO(2))(2)(2)], 4, and [Cu({C(8)F(17)(CH(2))(2)}(2)CHCO(2))(2) (3)], 5, respectively. The known Cu(II) complex, 1, was further characterized by electron paramagnetic resonance (EPR) spectroscopy confirming its dimeric structure, while 4 and 5 were characterized by elemental analysis, IR, diffuse reflectance UV-vis, and EPR spectroscopy. Furthermore, 1, 4, and 5 were evaluated as precatalysts for alkenol and alcohol oxidation. The oxidation reactions of alkenols and alcohols in the presence of TEMPO/O(2) proceeded under FBC conditions for 1, 4, and 5, but 1-octanol was unreactive under single-phase FBC conditions at 90 degrees C with TEMPO/O(2). The thermomorphic property of 5, soluble in chlorobenzene/toluene at 90 degrees C but insoluble at room temperature, was also evaluated in the selective oxidation of p-nitrobenzyl alcohol to p-nitrobenzaldehyde. Plausible mechanisms concerning these FBC/thermomorphic oxidation reactions will be discussed. 相似文献
54.
Ionkin AS Marshall WJ Fish BM Schiffhauer MF McEwen CN 《Chemical communications (Cambridge, England)》2008,(42):5432-5434
The first stable enols in 1,2-dihydrophosphetes and were synthesized and structurally characterized with intermolecular hydrogen bonds to phosphoryl groups in 10-membered dimeric structures; in contrast, trivalent analogue exists in keto-form, where such stabilization by hydrogen bonds is not feasible. 相似文献
55.
56.
Alexander Fish 《Israel Journal of Mathematics》2011,184(1):477-504
We introduce a new class of “random“ subsets of natural numbers, WM sets. This class contains normal sets (sets whose characteristic function is a normal binary sequence). We establish necessary and sufficient conditions for solvability of systems of linear equations within every WM set and within every normal set. We also show that any partition-regular system of linear equations with integer coefficients is solvable in any WM set. 相似文献
57.
58.
Margaret C. Etter Zofia Urbańczyk-Lipkowska Patricia A. Fish Thomas W. Panunto Paul W. Baures James S. Frye 《Journal of chemical crystallography》1988,18(4):311-325
The hydrogen bond patterns ofo-alkoxybenzoic acids have been shown previously to involve intramolecular hydrogen bonds. In this paper we show thato-methoxybenzoic acid (I) and o-ethoxybenzoic acid (II) both exist as monomers with intramolecular hydrogen bonds in solution but that, in the solid-state,I crystallizes as hydrogen-bonded dimers whileII crystallizes with an intramolecular hydrogen bond. The correlation between solution and solid-state hydrogen bond patterns is made using solution and solid-state IR and NMR methods and by correlating the solid-state patterns with known X-ray crystal structures. The crystal structure ofI is reported here. Crystal data: monoclinicP21/n;a=7.002(2),b=14.945(9),c=7.719(4) Å,=115.44(3)°,Z=4,V=729.4 Å3, andR=0.046 (1660 reflections). 相似文献
59.
The thermal changes taking place at the sites of Fe-Co metal inclusions in synthetic diamond grains have been investigated using Mössbauer spectroscopy on as-grown samples and samples annealed at 970–1370 K. The spectra show the presence of Fe-Co and (Fe-Co)-C complexes. The temperature-dependent results suggest that the latter are due to reactions at the metal inclusion-diamond interface, and may be a signature of the processes leading to strength loss in the grains. 相似文献
60.
M. Beiglbck V. Bergelson T. Downarowicz A. Fish 《Topology and its Applications》2009,156(16):2565-2571
Rado's Theorem characterizes the systems of homogeneous linear equations having the property that for any finite partition of the positive integers one cell contains a solution to these equations. Furstenberg and Weiss proved that solutions to those systems can in fact be found in every central set. (Since one cell of any finite partition is central, this generalizes Rado's Theorem.) We show that the same holds true for the larger class of D-sets. Moreover we will see that the conclusion of Furstenberg's Central Sets Theorem is true for all sets in this class. 相似文献