全文获取类型
收费全文 | 371篇 |
免费 | 19篇 |
国内免费 | 5篇 |
专业分类
化学 | 277篇 |
晶体学 | 1篇 |
力学 | 15篇 |
数学 | 40篇 |
物理学 | 62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 | 19篇 |
2015年 | 11篇 |
2014年 | 14篇 |
2013年 | 27篇 |
2012年 | 21篇 |
2011年 | 22篇 |
2010年 | 16篇 |
2009年 | 8篇 |
2008年 | 25篇 |
2007年 | 20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 | 6篇 |
1994年 | 5篇 |
1993年 | 2篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 3篇 |
1984年 | 8篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1981年 | 4篇 |
1978年 | 1篇 |
1974年 | 1篇 |
1972年 | 3篇 |
1971年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有395条查询结果,搜索用时 15 毫秒
31.
We study the problem of asset and liability management of participating insurance policies with guarantees. We develop a scenario optimization model for integrative asset and liability management, analyze the tradeoffs in structuring such policies, and study alternative choices in funding them. The nonlinearly constrained optimization model can be linearized through closed form solutions of the dynamic equations. Thus large-scale problems are solved with standard methods. We report on an empirical analysis of policies offered by Italian insurers. The optimized model results are in general agreement with current industry practices. However, some inefficiencies are identified and potential improvements are highlighted. 相似文献
32.
33.
Flavio S. Damos Rita C.S. Luz Auro A. Tanaka Lauro T. Kubota 《Analytica chimica acta》2010,664(2):144-10063
The development of a simple, efficient and sensitive sensor for dissolved oxygen is proposed using the host-guest binding of a supramolecular complex at a host surface by combining a self-assembled monolayer (SAM) of mono-(6-deoxy-6-mercapto)-β-cyclodextrin (βCDSH), iron (III) tetra-(N-methyl-4-pyridyl)-porphyrin (FeTMPyP) and cyclodextrin-functionalized gold nanoparticles (CDAuNP). The supramolecular modified electrode showed excellent catalytic activity for oxygen reduction. The reduction potential of oxygen was shifted about 200 mV toward less negative values with this modified electrode, presenting a peak current much higher than those observed on a bare gold electrode. Cyclic voltammetry and rotating disk electrode (RDE) experiments indicated that the oxygen reduction reaction involves probably 4-electrons with a rate constant (kobs) of 7 × 104 mol−1 L s−1. A linear response range from 0.2 up to 6.5 mg L−1, with a sensitivity of 5.5 μA L mg−1 (or 77.5 μA cm−2 L mg−1) and a detection limit of 0.02 mg L−1 was obtained with this sensor. The repeatability of the proposed sensor, evaluated in terms of relative standard deviation was 3.0% for 10 measurements of a solution of 6.5 mg L−1 oxygen. 相似文献
34.
Flavio Ceretta Alessandro Zaggia Lino Conte Bruno Ameduri 《Journal of polymer science. Part A, Polymer chemistry》2013,51(15):3202-3212
4′‐Nonafluorobutylstyrene (3) was synthesized and polymerized by conventional and controlled radical polymerization (iodine transfer polymerization (ITP)). Such an aromatic fluoromonomer was prepared from Ullmann coupling between 1‐iodoperfluorobutane and 4‐bromoacetophenone followed by a reduction and a dehydration in 50% overall yield. Two radical polymerizations of (3) were initiated by AIBN either under conventional or controlled conditions, with 1‐iodoperfluorohexane in 84% monomer conversion and in 50% yield. ITP of (3) featured a fast monomer conversion and a linear evolution of the ln([M]0/[M]) versus time. The kinetics of radical homopolymerization of (3) enabled one to assess its square of the propagation rate to the termination rate (kp2/kt) in ITP conditions (36.2·10?2 l·mol?2·sec?2 at 80 °C) from the Tobolsky's kinetic law. Polydispersity index (?) of the fluoropolymer achieved by conventional polymerization was 1.30 while it worthed 1.15 when synthesized by ITP. Thermal stabilities of these oligomers were satisfactory (10% weight loss under air occurred from 305 °C) whereas the melting point was 47 °C. Contact angles and surface energies assessed from spin‐coated poly(3) films obtained by conventional (hysteresis = 18°, surface energy 18 mN.m?1) and ITP (hysteresis = 47°, surface energy 15 mN.m?1) evidenced ? values' influence onto surface properties of the synthesized polymers. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 3202–3212 相似文献
35.
Abraham F. Jalbout Flavio F. Contreras‐Torres Aned De Leon 《International journal of quantum chemistry》2008,108(3):598-606
In this work we present a methodology for the synthesis of simple molecules from basic formaldehyde (H2CO) precursors. We have approached this challenging problem by considering a basic dimerization scheme that eventually leads to diose and methyl formate, using an HCO+ proton source. This species was chosen due to its ample abundance in the atmosphere. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2008 相似文献
36.
37.
High Sensitive Microsensor Based on Organic‐Inorganic Composite for Two‐Dimensional Mapping of H2O2 by SECM
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)
Danielle Diniz Justino Isabel Lourenço Torres Rita de Cássia Silva Luz Flavio Santos Damos 《Electroanalysis》2015,27(5):1202-1209
The present work describes the development of a selective, sensitive and stable sensing microsensor for scanning electrochemical microscopy (SECM) to measure H2O2 during electrochemical reduction of oxygen. The microsensor is based on graphene and Poly(3,4‐ethylenedioxythiophene) composite as support to iron (III) hexacyanoferrate (II) (PEDOT/graphene/FeIII4[FeII(CN)6]3 microsensor). The electrochemical properties of the PEDOT/graphene/FeIII4[FeII(CN)6]3 microsensor were investigated by cyclic voltammetry (CV) and scanning electrochemical microscopy (SECM). The PEDOT/graphene/FeIII4[FeII(CN)6]3 microsensor showed an excellent electrocatalytic activity toward hydrogen peroxide (H2O2) reduction with a diminution of the overpotential of about 500 mV in comparison to the process at a bare gold microelectrode. The microsensor presented excellent performance for two dimensional mapping of H2O2 by SECM in 0.1 mol L?1 phosphate buffer solution (pH 7.0). Under optimized conditions, a linear response range from 1 up to 1000 µmol L?1 was obtained with a sensitivity of 0.08 nA L µmol?1 and limit of detection of 0.5 µmol L?1. 相似文献
38.
Lorenzo Rovigatti Petr Šulc István Z. Reguly Flavio Romano 《Journal of computational chemistry》2015,36(1):1-8
We test the relative performances of two different approaches to the computation of forces for molecular dynamics simulations on graphics processing units. A “vertex‐based” approach, where a computing thread is started per particle, is compared to an “edge‐based” approach, where a thread is started per each potentially non‐zero interaction. We find that the former is more efficient for systems with many simple interactions per particle while the latter is more efficient if the system has more complicated interactions or fewer of them. By comparing computation times on more and less recent graphics processing unit technology, we predict that, if the current trend of increasing the number of processing cores—as opposed to their computing power—remains, the “edge‐based” approach will gradually become the most efficient choice in an increasing number of cases. © 2014 Wiley Periodicals, Inc. 相似文献
39.
Marco Bee Giuseppe Espa Diego Giuliani Flavio Santi 《Journal of computational and graphical statistics》2017,26(3):695-708
In this article, we use the cross-entropy method for noisy optimization for fitting generalized linear multilevel models through maximum likelihood. We propose specifications of the instrumental distributions for positive and bounded parameters that improve the computational performance. We also introduce a new stopping criterion, which has the advantage of being problem-independent. In a second step we find, by means of extensive Monte Carlo experiments, the most suitable values of the input parameters of the algorithm. Finally, we compare the method to the benchmark estimation technique based on numerical integration. The cross-entropy approach turns out to be preferable from both the statistical and the computational point of view. In the last part of the article, the method is used to model the probability of firm exits in the healthcare industry in Italy. Supplemental materials are available online. 相似文献
40.