全文获取类型
收费全文 | 162篇 |
免费 | 4篇 |
国内免费 | 2篇 |
专业分类
化学 | 108篇 |
数学 | 36篇 |
物理学 | 24篇 |
出版年
2023年 | 1篇 |
2022年 | 3篇 |
2021年 | 2篇 |
2020年 | 3篇 |
2019年 | 2篇 |
2018年 | 4篇 |
2016年 | 7篇 |
2015年 | 4篇 |
2014年 | 3篇 |
2013年 | 7篇 |
2012年 | 15篇 |
2011年 | 11篇 |
2010年 | 9篇 |
2009年 | 7篇 |
2008年 | 9篇 |
2007年 | 13篇 |
2006年 | 11篇 |
2005年 | 13篇 |
2004年 | 6篇 |
2003年 | 10篇 |
2002年 | 5篇 |
2001年 | 2篇 |
2000年 | 2篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1997年 | 3篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1990年 | 2篇 |
1988年 | 2篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1978年 | 2篇 |
排序方式: 共有168条查询结果,搜索用时 15 毫秒
81.
The electrooxidation of benzylic alcohol derivative in acidic aqueous solution shows an oxidation pre-peak in the cyclic voltammogram, which means that the reaction is proceeding via an ECE mechanism where the second electron transfer occurs at a less positive potential. From the result of the rotating ring-disk electrode voltammetry, the initial oxidation response of the electrode reaction can be extracted. 相似文献
82.
Takane Imaoka Reiko Tanaka Kimihisa Yamamoto 《Journal of polymer science. Part A, Polymer chemistry》2006,44(17):5229-5236
Phenylazomethine dendrimers bearing a cobalt porphyrin core act as catalysts for CO2 reduction in the presence of a strong Lewis acid such as lanthanide trifluoromethanesulfonate (Ln(OTf)3). We investigated the catalytic activity using electrochemical measurements (cyclic voltammetry) on a glassy carbon electrode in a DMF solution. Dissolving CO2 gas into the solution, the cyclic voltammograms displayed an irreversible increase of the cathodic current. This result suggests the catalytic reduction of CO2. The redox potential (–1.3 V versus Fc/Fc+) at which the catalytic behavior was observed is 1.1 V higher than that catalyzed by cobalt tetraphenylporphyrin (CoTPP). The generation number (n) dependence of the dendrimer catalysts showed the maximum activity at n = 3. A significant decrease of the activity for the largest dendrimer (n = 4) indicates a steric effect, which prevents transmission of the substrate (CO2 molecule) and electrons to the catalytic center (cobalt porphyrin core). For more efficient catalysis, a novel open-shell dendrimer having a pocket on one side of the molecule was designed and synthesized. Because the accessibility to the core in the opened shell improved, this dendrimer exhibited the highest catalytic activity. These results suggest that tuning of the local domain around the cobalt porphyrin center would lead to a decisive solution for further activation of the CO2 molecule. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5229–5236, 2006 相似文献
83.
Yoshio Takane Yongge Tian Haruo Yanai 《Annals of the Institute of Statistical Mathematics》2007,59(4):807-820
A matrix G is called a generalized inverse (g-invserse) of matrix A if AGA = A and is denoted by G = A
−. Constrained g-inverses of A are defined through some matrix expressions like E(AE)−, (FA)−
F and E(FAE)−
F. In this paper, we derive a variety of properties of these constrained g-inverses by making use of the matrix rank method. As applications, we give some results on g-inverses of block matrices, and weighted least-squares estimators for the general linear model. 相似文献
84.
85.
Novel hybrid polymer hydrogels were prepared in a facile manner by simple mixing of a water-soluble copolymer having trimethoxysilyl side chains with silica nanoparticles used as multiple crosslinkers. 相似文献
86.
Several decompositions of the orthogonal projector PX = X(X′X)−X′ are proposed with a prospect of their use in constrained principal component analysis (CPCA). In CPCA, the main data matrix X is first decomposed into several additive components by the row side and/or column side predictor variables G and H. The decomposed components are then subjected to singular value decomposition (SVD) to explore structures within the components. Unlike the previous proposal, the current proposal ensures that the decomposed parts are columnwise orthogonal and stay inside the column space of X. Mathematical properties of the decompositions and their data analytic implications are investigated. Extensions to regularized PCA are also envisaged, considering analogous decompositions of ridge operators. 相似文献
87.
Shin-ya Matsushita Wataru Takahashi 《Nonlinear Analysis: Theory, Methods & Applications》2010,73(6):1466-6030
Let C be a nonempty, closed and convex subset of a uniformly convex and smooth Banach space and let {Tn} be a family of mappings of C into itself such that the set of all common fixed points of {Tn} is nonempty. We consider a sequence {xn} generated by the hybrid method by generalized projection in mathematical programming. We give conditions on {Tn} under which {xn} converges strongly to a common fixed point of {Tn} and generalize the results given in [12], [14], [13] and [11]. 相似文献
88.
ABSTRACTDue to the photobiology of the flavoproteins DNA photolyase and cryptochrome, electron transfer reactions between flavins and tryptophan are of significant biological relevance. In addition, electron transfer across vesicle membranes has also seen much attention. In this work, we study the electron transfer reaction between flavins and tryptophan across lipid bilayer membranes in 1,2-dipalmitoyl-sn-glycero-3-phosphocholine small unilamellar vesicles using time-resolved optical absorption microspectroscopy and magnetically affected reaction yield spectroscopy. We demonstrate that riboflavin tetrabutyrate is embedded in the vesicle bilayer and can undergo electron transfer with tryptophan molecules in either the inner water pool or the bulk solution. Remarkably, flavin mononucleotide encapsulated in the inner water pool can undergo electron transfer across the vesicle bilayer to generate a magnetically sensitive radical pair with tryptophan molecules located in the bulk solution. The observed kinetics suggest that back electron transfer occurs between radical pairs generated by diffusive reencounter, either in the vesicle surface water or via electron hopping through degenerate electron exchange. 相似文献
89.
We report the anomalous phase evolution in ferroelectric single crystals Ba1-xCaxTiO3 (0.02相似文献
90.