全文获取类型
收费全文 | 353篇 |
免费 | 19篇 |
国内免费 | 5篇 |
专业分类
化学 | 263篇 |
晶体学 | 1篇 |
力学 | 15篇 |
数学 | 39篇 |
物理学 | 59篇 |
出版年
2023年 | 2篇 |
2022年 | 5篇 |
2021年 | 17篇 |
2020年 | 22篇 |
2019年 | 11篇 |
2018年 | 19篇 |
2017年 | 7篇 |
2016年 | 18篇 |
2015年 | 11篇 |
2014年 | 14篇 |
2013年 | 27篇 |
2012年 | 21篇 |
2011年 | 20篇 |
2010年 | 16篇 |
2009年 | 7篇 |
2008年 | 24篇 |
2007年 | 19篇 |
2006年 | 15篇 |
2005年 | 15篇 |
2004年 | 10篇 |
2003年 | 7篇 |
2002年 | 14篇 |
2000年 | 3篇 |
1999年 | 3篇 |
1998年 | 5篇 |
1997年 | 2篇 |
1996年 | 5篇 |
1995年 | 5篇 |
1994年 | 4篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1990年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 7篇 |
1983年 | 2篇 |
1982年 | 4篇 |
1981年 | 4篇 |
1978年 | 1篇 |
1972年 | 2篇 |
1971年 | 1篇 |
排序方式: 共有377条查询结果,搜索用时 15 毫秒
251.
Flavio U. Coelho Dieter Happel 《Proceedings of the American Mathematical Society》1997,125(5):1283-1291
Quasitilted algebras are generalizations of tilted algebras. As a main result we show here that the Auslander-Reiten quiver of such an algebra has a preprojective component
252.
Pier Luigi Silvestrelli Francesco Ancilotto Flavio Toigo Carlo Sbraccia Takashi Ikeda Mauro Boero 《Chemphyschem》2005,6(9):1889-1893
The interaction of water with alkanethiolate chains is studied from first principles. A detailed analysis is performed by optimizing the structure of small water clusters, one-dimensional water chains, and ordered and disordered thin water layers adsorbed on hydroxyl(OH)- and methyl(CH3)-terminated alkanethiol monolayers. The hydrophilic/hydrophobic character of these two different substrates is investigated by means of an energetic analysis combined with hydrogen-bond counting. On the hydrophilic OH-terminated alkanethiol surface, zigzag, one-dimensional water chains and disordered thin water layers are the energetically favored structures. The ab initio results can be used to determine the optimal value of the empirical parameters characterizing a suitable force field to be used in classic molecular dynamics simulations. 相似文献
253.
254.
Elias P. Ferreira-Neto Flavio L. S. de Carvalho Sajjad Ullah Vinicius C. Zoldan André A. Pasa Adriano Lopes de Souza Liliane C. Battirola Petra Rudolf Sara Aldabe Bilmes Ubirajara P. Rodrigues-Filho 《Journal of Sol-Gel Science and Technology》2013,66(3):363-371
Supramolecular interactions between nitrogenated groups in hybrid ormosils bearing phosphotungstate nanocatalyst were used to tune the photocatalytical activity of these class-II hybrid materials obtained through sol–gel chemistry. Surface chemistry and morphology of the materials was studied by scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy and water contact angle measurements. The photocatalytic efficiency of these hybrid films, measured by the degradation of crystal violet over-layer deposited on ormosils films, is higher for ormosils bearing neutral, more polar and less H-bonding nitrile groups than those bearing alkylamine/alkylammonium functionalities, despite the lower W/Si atomic ratio on the surface and lower tungsten percentage of the pure nitrile bearing ormosils. Such higher surface reactivity of the nitrile bearing ormosils is due to weaker interaction with the phosphotungstate and the lower activity of amine bearing ormosils is attributed to the competition among reversible photochromism and photocatalysis pathways in these materials. 相似文献
255.
Pei Su Hang Hu Daisy Unsihuay Di Zhang Tiziano Dainese Rosa E. Diaz Jongsu Lee Don K. Gunaratne Haiyan Wang Flavio Maran Jianguo Mei Julia Laskin 《Angewandte Chemie (International ed. in English)》2020,59(20):7711-7716
The design of functional interfaces is central to both fundamental and applied research in materials science and energy technology. We introduce a new, broadly applicable technique for the precisely controlled high‐throughput preparation of well‐defined interfaces containing polyatomic species ranging from small ions to nanocrystals and large protein complexes. The mass‐dispersive deposition of ions onto surfaces is achieved using a rotating‐wall mass analyzer, a compact device which enables the separation of ions using low voltages and has a theoretically unlimited mass range. We demonstrate an efficient deposition of singly charged Au144(SC4H9)60 ions (33.7 kDa), which opens up exciting opportunities for the structural characterization of nanocrystals and their assemblies using transmission electron microscopy. Our approach also enables the high‐throughput deposition of mass‐selected ions from multicomponent mixtures, which is of interest to the controlled preparation of surface gradients and rapid screening of molecules in mixtures for a specific property. 相似文献
256.
A Novel Sensor Based on Manganese azo‐Macrocycle/Carbon Nanotubes to Perform the Oxidation and Reduction Processes of Two Diphenol Isomers
下载免费PDF全文
![点击此处可从《Electroanalysis》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Saimon Moraes Silva Fernando Mota de Oliveira Danielle Diniz Justino Lauro Tatsuo Kubota Auro Atsushi Tanaka Flavio Santos Damos Rita de Cássia Silva Luz 《Electroanalysis》2014,26(3):602-611
The present work describes the development of a selective and sensitive voltammetric sensor for simultaneous determination of catechol (CC) and hydroquinone (HQ), based on a glassy carbon (GC) electrode modified with manganese phthalocyanine azo‐macrocycle (MnPc) adsorbed on multiwalled carbon nanotubes (MWCNT). Scanning electron microscopy and scanning electrochemical microscopy were used to characterize the composite material (MnPc/MWCNT) on the glassy carbon electrode surface. The modified electrode showed excellent electrochemical activity towards the simultaneous oxidation and reduction of CC and HQ. On the MnPc/MWCNT/GC electrode, both CC and HQ can generate a pair of quasi‐reversible and well‐defined redox peaks. Under optimized experimental and operational conditions, the cathodic peak currents were linear over the range 1–600 µmol L?1 for both CC and HQ, with limits of detection of 0.095 and 0.041 µmol L?1, respectively. The anodic peak currents were also linear over the range 1–600 µmol L?1 for both CC and HQ, with limits of detection of 0.096 and 0.048 µmol L?1, respectively. The proposed method was effectively applied for the simultaneous detection of hydroquinone and catechol in water samples and the results were in agreement with those obtained by a comparative method described in the literature. 相似文献
257.
In this paper we study the semigroups of matrices over a commutative semiring. We prove that a semigroup of matrices over a tropical semiring satisfies a combinatorial property called weak permutation property. We consider an application of this result to the Burnside problem for groups. 相似文献
258.
The statistical mechanical theory of adsorption is presented as an expansion about the two-dimensional approximation. Two corrections to the latter are additive in the perturbation limit. One contribution, arising from the lateral variation of the substrate potential, has been previously evaluated. The second correction term is due to the particles' mutual interaction when their separation vector is not parallel to the surface. The latter is expressed in terms of the radial distribution function. Its contribution to the deviation from two-dimensionality is shown to be comparable to the first term for the case of a Lennard-Jones model. 相似文献
259.
Ricardo Vessecchi Flavio S. Emery Sérgio E. Galembeck Norberto P. Lopes 《Rapid communications in mass spectrometry : RCM》2010,24(14):2101-2108
Electrospray ionization mass spectrometric analysis of lapachol (2‐hydroxy‐3‐(3‐methyl‐2‐butenyl)‐1,4‐naphthoquinone) was accomplished in order to elucidate the gas‐phase dissociation reactions of this important biologically active natural product. The occurrence of protonated and cationized species in the positive mode and of deprotonated species in the negative mode was explored by means of collision‐induced dissociation (CID) experiments. For the protonated molecule, the H2O and C4H8 losses occur by two competitive channels. For the deprotonated molecule, the even‐electron rule is not conserved, and the radicalar species are eliminated by formation of distonic anions. The fragmentation mechanism for each ion was suggested on the basis of computational thermochemistry. Atomic charges, relative energies, and frontier orbitals were employed aiming at a better understanding of the gas‐phase reactivity of lapachol. Potential energy surfaces for fragmentation reactions were obtained by the B3LYP/6‐31+G(d,p) model. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
260.
[4+2] Cycloaddition of singlet oxygen to suitably substituted furans followed by reduction of the corresponding endoperoxides afforded functionalized enediones which quickly cyclized into the titled spiroketals. The reported method represents a green synthetic one-pot procedure for novel [6,6]-, [5,6]-, and [5,5]-spiroketals of sugars. 相似文献