全文获取类型
收费全文 | 237篇 |
免费 | 5篇 |
专业分类
化学 | 91篇 |
晶体学 | 1篇 |
力学 | 1篇 |
数学 | 3篇 |
物理学 | 146篇 |
出版年
2022年 | 1篇 |
2021年 | 2篇 |
2020年 | 4篇 |
2019年 | 3篇 |
2018年 | 1篇 |
2017年 | 3篇 |
2016年 | 8篇 |
2015年 | 3篇 |
2014年 | 12篇 |
2013年 | 10篇 |
2012年 | 15篇 |
2011年 | 14篇 |
2010年 | 12篇 |
2009年 | 8篇 |
2008年 | 4篇 |
2007年 | 13篇 |
2006年 | 12篇 |
2005年 | 12篇 |
2004年 | 6篇 |
2003年 | 8篇 |
2002年 | 8篇 |
2001年 | 5篇 |
2000年 | 10篇 |
1999年 | 8篇 |
1998年 | 4篇 |
1997年 | 3篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1994年 | 9篇 |
1993年 | 3篇 |
1992年 | 8篇 |
1991年 | 5篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1984年 | 1篇 |
1981年 | 1篇 |
1976年 | 1篇 |
1932年 | 1篇 |
1913年 | 1篇 |
1906年 | 2篇 |
1899年 | 1篇 |
1894年 | 2篇 |
排序方式: 共有242条查询结果,搜索用时 10 毫秒
1.
2.
J. C. Fabris S. V. B. Gonçalves P. E. de Souza 《General Relativity and Gravitation》2002,34(12):2111-2126
The mass power spectrum for a Universe dominated by the Chaplygin gas is evaluated numerically from scales of the order of the Hubble horizon to 100 Mpc. The results are compared with a pure baryonic Universe and a cosmological constant model. In all three cases, the spectrum increases with k, the wavenumber of the perturbations. The slope of the spectrum is higher for the baryonic model and smaller for the cosmological constant model, the Chaplygin gas interpolating these two models. The results are analyzed in terms of the sound velocity of the Chaplygin gas and the moment the Universe begins to accelerate. 相似文献
3.
Ilda Abe Rafael E. de Ges Jos L. Fabris Hypolito J. Kalinowski Mrcia Müller Meire C. Fugihara Rosane Falate Barbara W. Diesel Ricardo C. Kamikawachi Carmen L. Barbosa 《Optics and Lasers in Engineering》2003,39(5-6):537-548
In this work, we report production and modelling of both Bragg gratings and rocking filters in high birefringence fibre optics. Bragg gratings are produced by UV (257.0 nm) external interferometric exposition of a frequency-doubled Ar+ ion laser, whereas for rocking filters formation the visible Ar+ ion laser lines in 488.0 and 514.5 nm are used in an internal method. The spectral characteristics due to the birefringence properties are studied through numerical methods and experimental techniques. The spectral responsivity of the structures under temperature changes and stress application is presented. 相似文献
4.
5.
LoSecco JM Bionta RM Biewitt G Bratton CB Casper D Chrysicopoulou P Claus R Cortez BG Errede S Foster GW Gajewski W Ganezer KS Goldhaber M Haines TJ Jones TW Kielczewska D Kropp WR Learned JG Lehmann E Park HS Reines F Schultz J Seidel S Shumard E Sinclair D Sobel HW Stone JL Sulak L Svoboda R van der Velde JC Wuest C 《Physical review letters》1985,54(21):2299-2301
6.
Kassab K Fabris C Defilippis MP Dei D Fantetti L Roncucci G Reddi E Jori G 《Journal of photochemistry and photobiology. B, Biology》2000,55(2-3):128-137
A Zn-phthalocyanine derivative bearing four 4-oxy-N-methyl-piperidinyl peripheral substituents has been formulated in an azone-containing gel for topical administration and its potential as a photodynamic therapy agent has been investigated. The phthalocyanine displays an intense absorbance in the 680 nm range and shows a high photosensitizing activity toward a model biological substrate (N-acetyl-L-tryptophanamide). Upon administration of 20 microg cm(-2) onto the dorsal skin of Balb/c mice, maximal phthalocyanine concentrations (ca. 64.2 ng mg(-1) of skin) are reached at 1 h after the deposition. The photosensitizer appears to be localized in the epidermal layers, since (a) no detectable amounts of phthalocyanine are recovered from the mouse blood and liver; and (b) upon photoactivation with a diode laser at 675 nm, only the epidermis is heavily damaged, as shown by histological and ultrastructural analysis. The photodamage is largely of inflammatory nature and an essentially complete healing of the damaged skin is observed at 72 h after the end of the phototreatment. The minimal phototoxic dose for 20 microg cm(-2) photosensitizer and 675 nm irradiation is found to be (150 mW cm(-2)-120 J cm(-2)) or (180 mW cm(-2)-100 J cm(-2)). 相似文献
7.
Andrea Paesano Jr. Alexandre Christófaro Silva Flávio Francisco Ivashita Carla Fabiana Cerqueira Machado-Flavio Sives Flávio Sives Roberto Carlos Mercader José Domingos Fabris 《Hyperfine Interactions》2014,226(1-3):585-592
A peatland in Pinheiro, Diamantina City, Minas Gerais State - Brazil, was sampled at different depths of two profiles with diverse vegetation coverings (grassland field and bush) in order to collect materials that might reflect changes in the chemical states of iron over the peat formation coming from original minerals such as hematitic phyllite surrounding the boggy pedon. Samples collected were chemically, structurally and magnetically characterized. The results show that both series of peats are composed of organic matter and minerals such as quartz, kaolinite, gibbsite, rutile and muscovite. Deeper layers present only quartz. Mössbauer spectroscopy shows that iron is present in both electron states, Fe2+ and Fe3+, under both vegetations, each valence appearing in the spectra in the form of a discrete doublet. No hyperfine magnetic splitting was observed in any spectrum at room temperature. The Mössbauer subspectral area of Fe2+ tended to increase from the upper to deeper layers. Magnetic measurements reveal that the magnetic response of the surface samples is the highest, displaying a sharp decrease below 15 cm and that the magnetic signal is a superposition of (super)paramagnetic and ferrimagnetic contributions. Samples from the grassland field also show a diamagnetic component for the deeper layers. 相似文献
8.
Murat Güney Selçuk Eşsiz Arif Daştan Metin Balci Ottorino De Lucchi Ertan Şahin Fabrizio Fabris 《Helvetica chimica acta》2013,96(5):941-950
Stereoisomerically pure endo‐ and exo‐7‐halo‐7‐(trimethylstannyl)benzonorcar‐3‐enes (=endo‐ and exo‐(1‐halo‐1a,2,7,7a‐tetrahydro‐1H‐cyclopropa[b]naphthalen‐1‐yl)trimethylstannane) 4 and 6 were selectively obtained by lithium? tin or magnesium? tin transmetalation in good yields (Scheme 2 and 3). The reaction of these compounds with copper(I) thiophene‐2‐carboxylate (CuTC) produced in both cases the corresponding CS‐symmetric bicyclopropylidene (=cyclopropylidenecyclopropane) syn‐ 1 , a single diastereoisomer (Schemes 5 and 6). The structure of syn‐ 1 was undoubtedly elucidated by X‐ray single crystal diffraction. The coupling mechanism of the carbenoid cyclopropane is discussed (Scheme 7). 相似文献
9.
10.
F. G. Alvarenga J. C. Fabris N. A. Lemos G. A. Monerat 《General Relativity and Gravitation》2002,34(5):651-663
Perfect fluid Friedmann-Robertson-Walker quantum cosmological models for an arbitrary barotropic equation of state p = are constructed using Schutz's variational formalism. In this approach the notion of time can be recovered. By superposition of stationary states, finite-norm wave-packet solutions to the Wheeler-DeWitt equation are found. The behaviour of the scale factor is studied by applying the many-worlds and the ontological interpretations of quantum mechanics. Singularity-free models are obtained for < 1. Accelerated expansion at present requires –1/3 > > – 1. 相似文献