全文获取类型
收费全文 | 91篇 |
免费 | 1篇 |
专业分类
化学 | 44篇 |
数学 | 23篇 |
物理学 | 25篇 |
出版年
2024年 | 1篇 |
2023年 | 1篇 |
2021年 | 3篇 |
2020年 | 2篇 |
2018年 | 1篇 |
2016年 | 3篇 |
2015年 | 1篇 |
2014年 | 2篇 |
2013年 | 2篇 |
2012年 | 4篇 |
2011年 | 16篇 |
2010年 | 8篇 |
2009年 | 4篇 |
2008年 | 4篇 |
2007年 | 2篇 |
2006年 | 4篇 |
2005年 | 5篇 |
2004年 | 1篇 |
2003年 | 2篇 |
2001年 | 1篇 |
1997年 | 2篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1975年 | 4篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有92条查询结果,搜索用时 31 毫秒
21.
The C2H2 isothermal dissociation rate on Ni(111) was measured by following, with HREEL spectroscopy, the intensity of the CH stretching peak as a function of time. By repeating the experiment at several different temperatures we have obtained an activation energy of 1.2 ± 0.1 eV/molecule and a pre-exponential factor of 1014±1 s−1 for the first step of the C2H2 dissociation reaction. 相似文献
22.
Stefano DUGHERI Nicola MUCCI Ilenia POMPILIO Giovanni CAPPELLI Costanza BOSSI Alessandro BONARI Giulio ARCANGELI 《色谱》2018,36(12):1311-1322
Long-term indoor-air limit for formaldehyde stipulated by the European Commission is 1 μg/m3,while the World Health Organization has set a threshold of 100 μg/m3 that should not be exceeded for more than 30 min. To date,however,only a few analytical techniques have been developed that can be used to detect formaldehyde at these very restrictive limits. Thus,there is a need to develop for comprehensive methods for analyzing airborne formaldehyde and other carbonyl pollutants in the ambient environment. The aim of this study is to develop a highly sensitive online automated preconcentration gas chromatographic method using large-volume injection with a programmed temperature vaporization injector for the analysis of airborne formaldehyde and ten other carbonyl compounds. The influence of several parameters,such as the maximum volume injected,programmed temperature vaporization transfer time and temperature,carrier gas flow rate,and type of packing material was investigated. After optimization,highly satisfactory results in terms of the absolute and methodological detection limits were achieved,i. e. as low as the μg/m3 level for all the carbonyl pollutants studied. A commercially available sampler,originally designed for active sampling,was evaluated as a passive sampling device;this optimized technique was applied to monitor the concentrations of carbonyl pollutants in the indoor air of ten public buildings in Florence. The strength of this methodology lies both in the low detection limits reached in the simultaneous analysis of a wide group of 2,4-dinitrophenylhydrazine derivatives,and the potential adaptability of this method to other gas chromatographic applications to achieve lower sensitivity. 相似文献
23.
A general affine combination of B-spline subdivision masks is here considered with the aim of generating new subdivision schemes
with enhanced properties. This will be done using either stationary or non-stationary coefficients combining both B-splines
and their non-stationary counterparts. 相似文献
24.
25.
John R. Costanza Joseph A. Vona 《Journal of polymer science. Part A, Polymer chemistry》1966,4(10):2659-2666
Polymers of 3-methoxybutyl acrylate (3-MBA) were prepared by máss, solution, and emulsion polymerization techniques. The 3-MBA polymers could be converted from soft, rubbery, soluble, thermoplastic films to hard, glossy, flexible, crosslinked films when exposed to air and/or transition metal catalysts at elevated temperatures. The crosslinked polymers are resistant to common organic solvents and to mineral acids. Strong alkalis degraded the crosslinked polymers. The second-order transition temperature of poly-3-MBA is ?56°C. as determined by volume dilatometry. A comparison of the crosslinking properties of poly-3-MBA and other alkyl and alkoxyalkyl polymers is discussed. An autoxidative mechanism is proposed for the crosslinking of 3-MBA polymers. 相似文献
26.
In this paper we develop adaptive numerical solvers for certain nonlinear variational problems. The discretization of the
variational problems is done by a suitable frame decomposition of the solution, i.e., a complete, stable, and redundant expansion.
The discretization yields an equivalent nonlinear problem on the space of frame coefficients. The discrete problem is then
adaptively solved using approximated nested fixed point and Richardson type iterations. We investigate the convergence, stability,
and optimal complexity of the scheme. A theoretical advantage, for example, with respect to adaptive finite element schemes
is that convergence and complexity results for the latter are usually hard to prove. The use of frames is further motivated
by their redundancy, which, at least numerically, has been shown to improve the conditioning of the discretization matrices.
Also frames are usually easier to construct than Riesz bases. We present a construction of divergence-free wavelet frames
suitable for applications in fluid dynamics and magnetohydrodynamics.
M. Fornasier acknowledges the financial support provided through the Intra-European Individual Marie Curie Fellowship Programme,
under contract MOIF-CT-2006-039438. All of the authors acknowledge the hospitality of Dipartimento di Metodi e Modelli Matematici
per le Scienze Applicate, Università di Roma “La Sapienza”, Italy, during the early preparation of this work. The authors
want to thank Daniele Boffi, Dorina Mitrea, and Karsten Urban for the helpful and fruitful discussions on divergence-free
function spaces. 相似文献
27.
G. Costanza 《Physica A》2003,330(3-4):421-441
The analytical continuous equations for the Tang and Leschhorn (Phys. Rev. A 45 (1992) R8309) and the Buldyrev et al. (Phys. Rev. A 45 (1992) R8313) models are derived from the microscopic rules using a regularization procedure. As was shown in a previous paper (Phys. Rev. E 62 (2000) 6970) the continuous equation for the Tang and Leschhorn model is formally different to the Kardar–Parisi–Zhang equation (Phys. Rev. Lett. 56 (1986) 889) with quenched noise (QKPZ). Nevertheless, after expanding the multiplicative noise, it is shown that we recover the usual QKPZ, demonstrating analytically that both equations belong to the same universality class. 相似文献
28.
Ghulinyan M Oton CJ Gaburro Z Pavesi L Toninelli C Wiersma DS 《Physical review letters》2005,94(12):127401
We report on the observation of Zener tunneling of light waves in spectral and time-resolved transmission measurements, performed on an optical superlattice made of porous silicon. The structure was designed to have two photonic minibands, spaced by a narrow frequency gap. A gradient in the refractive index was introduced to create two optical Wannier-Stark ladders and, at a critical value of the optical gradient, tunneling between energy bands was observed in the form of an enhanced transmission peak and a characteristic time dependence of the transmission. 相似文献
29.
30.
G. Bendiscioli T. Bressani S. Costanza P. Salvini 《The European Physical Journal A - Hadrons and Nuclei》2011,47(6):82
New data on the pion spectra measured in selected channels following the antiproton annihilation at rest on 4He are presented and discussed in the light of statistical models. 相似文献