全文获取类型
收费全文 | 140篇 |
免费 | 5篇 |
国内免费 | 1篇 |
专业分类
化学 | 108篇 |
晶体学 | 2篇 |
数学 | 11篇 |
物理学 | 25篇 |
出版年
2023年 | 3篇 |
2022年 | 2篇 |
2021年 | 5篇 |
2020年 | 1篇 |
2019年 | 7篇 |
2018年 | 1篇 |
2017年 | 1篇 |
2016年 | 10篇 |
2015年 | 1篇 |
2014年 | 12篇 |
2013年 | 5篇 |
2012年 | 5篇 |
2011年 | 14篇 |
2010年 | 7篇 |
2009年 | 6篇 |
2008年 | 9篇 |
2007年 | 9篇 |
2006年 | 9篇 |
2005年 | 7篇 |
2004年 | 2篇 |
2003年 | 5篇 |
2002年 | 3篇 |
1999年 | 2篇 |
1996年 | 3篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1986年 | 3篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1974年 | 1篇 |
排序方式: 共有146条查询结果,搜索用时 15 毫秒
131.
Guzmán-Ramírez G Robles J Vega A Aguilera-Granja F 《The Journal of chemical physics》2011,134(5):054101
We report a theoretical investigation of free-standing Fe(x)Co(y)Ni(z) ternary clusters with x + y + z = 5 and 6. Our study is performed within density functional theory as implemented in the GAUSSIAN 03 set of programs and with the BPW91/SDD level of theory. We analyze the geometries, chemical order, local and total magnetic moments, binding energies, excess energies, and second difference in the energy in the whole range of composition, from which structural, magnetic, and stability phase diagrams are predicted for these cluster sizes. We determine the optimal stoichiometries for these clusters as regards the maximum total magnetic moment and stability. 相似文献
132.
Estévez RE Oller-López JL Robles R Melgarejo CR Gansäuer A Cuerva JM Oltra JE 《Organic letters》2006,8(24):5433-5436
In the presence of water, titanocene(III) complexes promote a stereoselective C-C bond-forming reaction that provides gamma-lactols by radical coupling between aldehydes and conjugated alkenals. The method is useful for both intermolecular reactions and cyclizations. The relative stereochemistry of the products can be predicted with confidence with the aid of model Ti-coordinated intermediates. The procedure can be carried out enantioselectively using chiral titanocene catalysts. [reaction: see text]. 相似文献
133.
J.Y. Vlez-Cerrada J. Robles N. Castro-Gonzlez 《Applied mathematics and computation》2009,215(6):2154-2161
This paper studies the Drazin inverse for perturbed matrices. For that, given a square matrix A, we consider and characterize the class of matrices B with index s such that , and , where and denote the null space and the range space of a matrix A, respectively, and AD denote the Drazin inverse of A. Then, we provide explicit representations for BD and BBD, and upper bounds for the relative error BD-AD/AD and the error BBD-AAD. A numerical example illustrates that the obtained bounds are better than others given in the literature. 相似文献
134.
135.
136.
137.
J. A. Jaén I. M. Barrios S. E. Robles 《Journal of Radioanalytical and Nuclear Chemistry》1988,128(2):139-146
Fe/OOCH/2.2HCOOH obtained by solvolytic reaction of FeCl2.4H2O in formic acid was studied by Mössbauer spectroscopy. It displays two quadrupole doublets. Upon air contact it easily transforms to a high-spin octahedral iron/III/ complex, whereas Fe/OOCH/2.2H2O undergoes a very slow oxidation. The formate complex coordinated with pyridine could not be prepared, instead we obtained the anhydrous phase Fe/OOCH/2. 相似文献
138.
Syntheses of the protected amino- and guanidino-G-clamp PNA monomers, 9a and 9b, respectively, have been accomplished in eight steps from 5-bromouracil. Enhanced stacking interactions and additional hydrogen bonds with guanine should increase the affinity of PNAs incorporating these cytosine analogues for their complementary strands. [reaction: see text] 相似文献
139.
A procedure for the determination of beryllium in natural waters is proposed. A solvent extraction step was performed in order to overcome interferences and isolate beryllium before it was atomized by direct nebulization of the organic phase in a dinitrogen oxide-acetylene flame. N-Benzoyl-N-phenylhydroxylamine was used as the extractant whilst isobutyl methyl ketone was the organic solvent. The effects of pH, amine concentration in the organic phase, shaking time, stability of the complex and nature of the extracted species were studied. The detection limit and linear response range are 2 ng ml-1 and 0-1.0 microgram ml-1, respectively. The result obtained for a standard reference material compared well with the quoted value. 相似文献
140.
In this paper, we present a system developed to identify metal nanoparticles at different orientations, using digital image processing and analysis. The correct identification is important in nanotechnology, where it is possible to build structures for different purposes at the nanometric level. The recognition system computes automatically different characteristics such as: nanoparticle area, polygons, symmetry and molecular arrays (twins) in order to recognize different nanostructures. All these characteristics are obtained through the use of morphological, texture (co-occurrence matrix) and region analysis. Complexity issues, advantages, and results are presented and discussed. 相似文献