全文获取类型
收费全文 | 163篇 |
免费 | 4篇 |
国内免费 | 1篇 |
专业分类
化学 | 105篇 |
力学 | 8篇 |
数学 | 25篇 |
物理学 | 30篇 |
出版年
2021年 | 1篇 |
2020年 | 3篇 |
2019年 | 6篇 |
2018年 | 1篇 |
2016年 | 6篇 |
2015年 | 3篇 |
2014年 | 5篇 |
2013年 | 8篇 |
2012年 | 5篇 |
2011年 | 17篇 |
2010年 | 5篇 |
2009年 | 14篇 |
2008年 | 10篇 |
2007年 | 15篇 |
2006年 | 12篇 |
2005年 | 8篇 |
2004年 | 6篇 |
2003年 | 9篇 |
2002年 | 7篇 |
2001年 | 2篇 |
1999年 | 3篇 |
1998年 | 2篇 |
1997年 | 1篇 |
1996年 | 4篇 |
1995年 | 3篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1981年 | 1篇 |
排序方式: 共有168条查询结果,搜索用时 46 毫秒
1.
2.
Natividad Gálvez Belén Fernández Purificación Sánchez Julia Morales-Sanfrutos Francisco Santoyo-González Rafael Cuesta Ruperto Bermejo Miguel Clemente-León Eugenio Coronado Alejandra Soriano-Portillo José M. Domínguez-Vera 《Solid State Sciences》2009,11(4):754-759
We have covalently coupled fluorophore 4-(2-hydroxyethoxy)-7-nitro-2,1,3-benzoxadiazole (NBD) to the external ferritin shell through lysine residues. An increase in the luminescence quantum yield of the fluorescent ferritin particles and a blue shift in its emission peak compared to individual fluorophore were observed. The study of the particles by transmission electron microscopy showed that the native iron core ferritin is intact and that no degradation occurs during chemical functionalization of the protein shell. The NBD-labeled ferritin particles are water soluble, which allowed their controlled deposition by the Langmuir–Blodgett (LB) technique. Superparamagnetic and fluorescent properties of the particles are preserved within the LB film. 相似文献
3.
4.
Rafael Cuesta Paloma Arranz‐Mascars John N. Low Christopher Glidewell 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(8):918-921
In the title compound, [Na(C5H5N4O3)]·2H2O, each Na cation is linked to three C5H4N4O3? anions and two water molecules, forming approximately octahedral NaNO5 units; the cations and the anions form molecular ladders, and each ladder is linked to four neighbouring ladders by O—H?O and O—H?N hydrogen bonds. 相似文献
5.
How cooperation emerges in human societies is still a
puzzle. Evolutionary game theory has been the standard framework to
address this issue. In most models, every individual plays with all
others, and then reproduces and dies according to what she earns.
This amounts to assuming that selection takes place at a slow pace
with respect to the interaction time scale. We show that, quite generally, if selection speeds up, the evolution outcome
changes
dramatically. Thus, in games such as Harmony, where cooperation is
the only equilibrium and the only rational outcome, rapid selection
leads to dominance of defectors. Similar non trivial phenomena arise
in other binary games and even in more complicated settings such as
the Ultimatum game. We conclude that the rate of selection is a key
element to understand and model the emergence of cooperation, and one
that has so far been overlooked. 相似文献
6.
Runge–Kutta based convolution quadrature methods for abstract, well-posed, linear, and homogeneous Volterra equations, non
necessarily of sectorial type, are developed. A general representation of the numerical solution in terms of the continuous
one is given. The error and stability analysis is based on this representation, which, for the particular case of the backward
Euler method, also shows that the numerical solution inherits some interesting qualitative properties, such as positivity,
of the exact solution. Numerical illustrations are provided. 相似文献
7.
Juan Francisco GonzálezElena de la Cuesta Carmen Avendaño 《Tetrahedron letters》2003,44(23):4395-4398
Addition of aldehyde dimethyl acetals (here acetaldehyde) to unisolated O-trimethylsilyl derivatives of 1-acetyl-3-arylmethylpiperazine-2,5-diones (here 2,5-dimethoxyphenyl), in the presence of TMSOTf as the catalyst, gave nearly quantitatively the corresponding N-methoxyalkyl derivatives which, under acidic treatment, gave in very good yield through a Pictet-Spengler-type reaction involving N-acyliminium cations (6S*,11aR*)-2-acetyl-6-alkyl-3,6,11,11a-tetrahydro-2H-pyrazino[1,2-b]isoquinoline-1,4-diones. Epimerization of the 11a-stereocentre was accomplished by radical bromination, spontaneous hydrobromide elimination and catalytic hydrogenation, to give the (6S*,11aS*)-isomers. We propose these compounds as precursors of tetrahydroisoquinoline antitumour antibiotics. 相似文献
8.
Cuesta L Huertos MA Morales D Pérez J Riera L Riera V Miguel D Menéndez-Velazquez A García-Granda S 《Inorganic chemistry》2007,46(7):2836-2845
Complexes [Re(ONCMe2)(CO)3(bipy)] (1) and [Re(ONCMe2)(CO)3(phen)] (2), synthesized by reaction of the respective triflato precursors [Re(OTf)(CO)3(N-N)] (N-N = bipy, phen) with KONCMe2, feature O-bonded monodentate oximato ligands. Compound [Re(CO)3(phen)(HONCMe2)]BAr'4 (3), with a monodentate N-bonded oxime ligand, was prepared by reaction of [Re(OTf)(CO)3(phen)], HONCMe2, and NaBAr'4. Deprotonation of 3 afforded 2. The oximato complexes reacted with p-tolylisocyanate, p-tolylisothiocyanate, maleic anhydride, and tetracyanoethylene, affording the products of the insertion of the electrophile into the Re-O bond, compounds 4-7. One representative of each type of compound was fully characterized, including single-crystal X-ray diffraction. The reactions of 1 and 2 with dimethylacetylenedicarboxylate were found to involve first an insertion as the ones mentioned above but followed by incorporation of water, loss of acetone, and formation of the charge-separated neutral amido complexes 9 and 10. The structure of 9 and 10 was determined by X-ray diffraction, and key features of their electronic distribution were studied using a topological analysis of the electron density as obtained from the Fourier map. 相似文献
9.
Corzana F Cuesta I Freire F Revuelta J Torrado M Bastida A Jiménez-Barbero J Asensio JL 《Journal of the American Chemical Society》2007,129(10):2849-2865
Aminoglycosides are clinically relevant antibiotics that participate in a large variety of molecular recognition processes involving different RNA and protein receptors. The 3-D structures of these policationic oligosaccharides play a key role in RNA binding and therefore determine their biological activity. Herein, we show that the particular NH2/NH3(+)/OH distribution within the antibiotic scaffold modulates the oligosaccharide conformation and flexibility. In particular, those polar groups flanking the glycosidic linkages have a significant influence on the antibiotic structure. A careful NMR/theoretical analysis of different natural aminoglycosides, their fragments, and synthetic derivatives proves that both hydrogen bonding and charge-charge repulsive interactions are at the origin of this effect. Current strategies to obtain new aminoglycoside derivatives are mainly focused on the optimization of the direct ligand/receptor contacts. Our results strongly suggest that the particular location of the NH2/NH3(+)/OH groups within the antibiotics can also modulate their RNA binding properties by affecting the conformational preferences and inherent flexibility of these drugs. This fact should also be carefully considered in the design of new antibiotics with improved activity. 相似文献
10.
Cuesta A 《Journal of the American Chemical Society》2006,128(41):13332-13333
We have used cyanide-modified Pt(111) electrodes to investigate the size and geometry of the minimum atomic ensemble necessary for the oxidation of methanol on Pt electrodes. Poison formation on cyanide-modified Pt(111) is completely inhibited, the corresponding electrooxidation reaction proceeding, hence, exclusively through the reactive intermediate pathway. These results suggest that formation of adsorbed CO would require the presence of at least three contiguous Pt atoms. 相似文献