全文获取类型
收费全文 | 214篇 |
免费 | 6篇 |
专业分类
化学 | 144篇 |
晶体学 | 2篇 |
力学 | 4篇 |
数学 | 6篇 |
物理学 | 64篇 |
出版年
2022年 | 4篇 |
2021年 | 3篇 |
2020年 | 3篇 |
2019年 | 3篇 |
2018年 | 3篇 |
2017年 | 1篇 |
2016年 | 3篇 |
2015年 | 2篇 |
2014年 | 6篇 |
2013年 | 7篇 |
2012年 | 12篇 |
2011年 | 17篇 |
2010年 | 11篇 |
2009年 | 9篇 |
2008年 | 7篇 |
2007年 | 7篇 |
2006年 | 12篇 |
2005年 | 10篇 |
2004年 | 4篇 |
2003年 | 8篇 |
2002年 | 7篇 |
2001年 | 3篇 |
2000年 | 9篇 |
1999年 | 3篇 |
1998年 | 1篇 |
1997年 | 2篇 |
1996年 | 4篇 |
1995年 | 4篇 |
1994年 | 5篇 |
1993年 | 7篇 |
1992年 | 3篇 |
1991年 | 5篇 |
1990年 | 1篇 |
1989年 | 4篇 |
1988年 | 1篇 |
1987年 | 5篇 |
1986年 | 2篇 |
1985年 | 4篇 |
1984年 | 3篇 |
1982年 | 5篇 |
1980年 | 4篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1976年 | 1篇 |
排序方式: 共有220条查询结果,搜索用时 546 毫秒
131.
Nadia Grossiord Mariëlle E.L. Wouters Kangbo Lu Joachim Loos Bruno Van Mele 《European Polymer Journal》2010,46(9):1833-2438
Several series of nanocomposites were prepared using a latex-based process, the main step of which consisted of mixing an aqueous suspension of exfoliated carbon nanotubes (CNTs) and a polymer latex. In the present work, a systematic study on the electrical properties of fully amorphous (polystyrene - PS) as well as semi-crystalline (isotactic polypropylene - iPP) nanocomposites containing either single-wall (SWCNTs) or multi-wall carbon nanotubes (MWCNTs) has been conducted. Percolation thresholds as low as 0.05 wt.% or 0.1 wt.% were observed for SWCNT/iPP and MWCNT/iPP nanocomposites, respectively. The formation of a conductive percolating network at such a low CNT concentration is favored by the high intrinsic conductivity and the low viscosity of the polymer matrix. The electrical percolation threshold of the iPP-based system was found to be lower than its rheological percolation threshold. Beyond the percolation threshold, MWCNT-based nanocomposites generally exhibited higher conductivity levels than those based on SWCNTs, most probably due to the higher intrinsic conductivity of the MWCNTs as compared to that of the SWCNTs. These excellent electrical properties, associated with the strong nucleating effect of the CNTs reported earlier [1] and [2], render this type of nanocomposites extremely attractive from a technological point of view. 相似文献
132.
S. Nagao P. Mele K. Matsumoto A. Ichinose M. Mukaida Y. Yoshida S. Horii R. Kita 《Physica C: Superconductivity and its Applications》2010,470(20):1304-1307
We report the microstructure change of BaSnO3 (BSO)–YBa2Cu3O7−x (YBCO) thin film system grown on SrTiO3 single crystal substrates by pulsed laser deposition with using the “surface-modified-target” and “mixture-target” methods. Although it was confirmed that the thick BSO nanorods incorporated to YBCO films act as strong artificial pinning centers, the formation mechanism of the nanorods is still unclear. The purpose of this work is to extend the structural investigation to higher contents of BSO (up to 71 vol.%) in order to enlighten the relationship among interfacial energy, morphology and pinning performance in binary BSO–YBCO films. 相似文献
133.
P. Mele C. Artini G.A. Costa R. Masini 《Journal of Physics and Chemistry of Solids》2009,70(2):276-280
Phase relation studies in the Gd2O3-Nd2O3 system have been performed on (Gd1−xNdx)2O3 samples (0?x?1) with the purpose of performing a systematic study of the composition effects on their structural and magnetic properties. All the samples were synthesized by calcination of the related oxalates at 1200 °C in order to ensure the complete decomposition of the oxalates. Five phase regions, namely an A-type hexagonal, a B-type monoclinic, a C-type cubic solid solution and two biphasic mixtures of the former three phase fields were detected in this system. The magnetic susceptibility measurements showed the presence of antiferromagnetic interactions in all samples. The Curie-Weiss temperature shows a nonlinear dependence on concentration. Deduced effective magnetic moments are close to the free ion values. 相似文献
134.
Mele E Girardo S Pisignano D 《Langmuir : the ACS journal of surfaces and colloids》2012,28(11):5312-5317
Artificial surfaces that exhibit unidirectional water spreading and superhydrophobicity are obtained by Strelitzia reginae leaves. Both green and dried leaves are used, thus exploiting the plant senescence. We demonstrate that the natural drying process of the leaves strongly affects the surface morphology and wettability. Polymeric stamps from the green leaf show an arrangement of periodic microridges/microgrooves that favor anisotropic wetting, with a water contact angle (WCA) variation of about 21% along the two principal directions. Instead, the shrinkage of the leaf tissue, as a consequence of the natural dehydration process, induces an enhancement of the superficial corrugation. This results in the establishment of a superhydrophobic state, which shows a WCA of up to 160°, and water rolling off. S. reginae leaves are therefore easily accessible stamps suitable for controlling wettability and realizing surfaces that exhibit various wetting behaviors. 相似文献
135.
Charlotte Martin Edith Oyen Yannick Van Wanseele Tanila Ben Haddou Helmut Schmidhammer Jessica Andrade Lynne Waddington Ann Van Eeckhaut Bruno Van Mele James Gardiner Richard Hoogenboom Annemieke Madder Mariana Spetea Steven Ballet 《Materials Today Chemistry》2017
To overcome drawbacks related to repeated opioid administration during the treatment of chronic pain, several controlled-drug delivery systems of opioids have been designed. In order to address some of the limitations of the existing systems, injectable peptide-based hydrogels represent a promising alternative. This work reports on the design and synthesis of short amphipathic peptide-based hydrogels as controlled-drug delivery systems for opioids. Based on the lead sequence H-FEFQFK-NH2, a new set of peptide hydrogelators was designed including β-homo and d-amino acids, mainly aiming at enhancing proteolytic resistance of the peptides, and which hypothetically allows an extension of the drug release period. After self-assembly in aqueous media, the resulting hydrogels were characterized by dynamic rheometry, cryogenic transmission electronic microscopy and their cytotoxicity was assessed. The cryoTEM images of drug loaded hydrogels show the association of microcrystals of the loaded drug along the axes of the fibres, suggesting that the peptide fibres play a key-role as nucleating site for the drug crystals. Hydrogelators devoid of cytotoxicity were considered for further in vivo evaluation. Upon encapsulation of morphine and 14-methoxymetopon, two opioid analgesics, the applicability of the peptide hydrogels as controlled-drug delivery platforms was validated in vivo using the mouse tail-flick test. A sustained antinociceptive effect was observed after subcutaneous injection of the drug loaded gels and, in comparison with the lead sequence H-FEFQFK-NH2, novel sequences revealed extension of the in vivo antinociception up to 72–96 h post injection. 相似文献
136.
2-[(18)F]Fluoro-L-phenylalanine and 2-[(18)F]fluoro-L-tyrosine have been developed as promising radiopharmaceuticals for molecular imaging using positron emission tomography (PET). However, the lack of a convenient radiosynthetic pathway has limited their practical use. In this work a new three-step nucleophilic synthesis of these compounds starting from [(18)F]fluoride is described. Corresponding precursors (1a and 1b) were (18)F-fluorinated by isotopic exchange, followed by the removal of an activating formyl group with Rh(PPh(3))(3)Cl and subsequent hydrolysis of protecting groups in acidic medium. All reactions were carried out using both conventional and microwave heating. Conventional heated reactions yielded the desired products 2-[(18)F]Fphe and 2-[(18)F]Ftyr in 43% and 49% whereas radiochemical yields of 34% and 43%, respectively, were obtained when they were heated by microwaves. Under optimized conditions the enantiomeric purity was ≥94% for both radiopharmaceuticals. 相似文献
137.
Christophe Block Nick Watzeels Hubert Rahier Bruno Van Mele Guy Van Assche 《Journal of Thermal Analysis and Calorimetry》2011,105(2):731-736
In this study, a methodology is developed for the quantitative characterisation of the nanofiller network in polymer nanocomposites
via dynamic rheometry. Nanoclay-reinforced poly(ε-caprolactone) (PCL) nanocomposites were prepared by melt mixing. Frequency
sweep experiments in the melt state display at low frequencies a solid-like elastic response that can be attributed to the
formation of a physical nanofiller network. Combining a semi empirical model and the time–temperature superposition principle
permits a reliable determination of the zero shear modulus that characterises the solid-like response of nanocomposites at
low frequency, and which is related to the nanofiller dispersion. 相似文献
138.
Vasapollo G Mele G Sole RD Pio I Li J Mazzetto SE 《Molecules (Basel, Switzerland)》2011,16(7):5769-5784
Cardanol, a well known hazardous byproduct of the cashew industry, has been used as starting material for the synthesis of useful differently substituted "cardanol-based" porphyrins and their zinc(II), copper(II), cobalt(II) and Fe(III) complexes. Novel composites prepared by impregnation of polycrystalline TiO? powder with an opportune amount of "cardanol-based" porphyrins, which act as sensitizers for the improvement of the photo-catalytic activity of the bare TiO?, have been used in the photodegradation in water of 4-nitrophenol (4-NP), which is a toxic and bio-refractory pollutant, dangerous for ecosystems and human health. 相似文献
139.
V. Crupi A. Fontana D. Majolino A. Mele L. Melone C. Punta B. Rossi F. Rossi F. Trotta V. Venuti 《Journal of inclusion phenomena and macrocyclic chemistry》2014,80(1-2):69-75
Cyclodextrin nanosponges (CDNS) are a very promising class of cross-linked polymers, made up of cyclodextrins. CDNS swollen in aqueous solution give rise to cyclodextrin-based hydrogel in different states—gel or liquid suspension—depending on the hydration level of the system. Here we present a thorough inspection of the vibrational dynamics of these hydrogel by Raman scattering experiments, with the aim of clarifying the role played by the hydrogen-bond dynamics of water molecules confined into the nano-sized pores of nanosponges in determining the rigidity of the hydrogel network and their maximum water-holding capacity. Changes occurring in the spectral shape of the OH stretching band of water were interpreted by accounting the connectivity pattern of water molecules concurring to the gelation process. Spectral deconvolution analysis gives evidence of the existence of a characteristic cross-over hydration level associated to the rearrangement of water molecules in more cooperative, bulk-like networks as a consequence of saturation sites of water confinement of nanosponges. This interpretation is further confirmed by the inspection of the estimated collective intensities. These findings also support the existence of a specific phase diagram of the cyclodextrin nanosponges hydrogel, where the molecular structure of the cross-linking agent used during the synthesis of nanosponge plays a fundamental role in defining the nano- and microscopic properties of the system. 相似文献
140.