全文获取类型
收费全文 | 389篇 |
免费 | 47篇 |
国内免费 | 16篇 |
专业分类
化学 | 62篇 |
晶体学 | 12篇 |
综合类 | 1篇 |
物理学 | 377篇 |
出版年
2023年 | 2篇 |
2021年 | 3篇 |
2020年 | 2篇 |
2019年 | 4篇 |
2018年 | 1篇 |
2017年 | 4篇 |
2016年 | 3篇 |
2015年 | 3篇 |
2014年 | 11篇 |
2013年 | 6篇 |
2012年 | 7篇 |
2011年 | 10篇 |
2010年 | 10篇 |
2009年 | 72篇 |
2008年 | 64篇 |
2007年 | 51篇 |
2006年 | 30篇 |
2005年 | 8篇 |
2004年 | 8篇 |
2003年 | 22篇 |
2002年 | 26篇 |
2001年 | 18篇 |
2000年 | 17篇 |
1999年 | 19篇 |
1998年 | 19篇 |
1997年 | 7篇 |
1996年 | 1篇 |
1995年 | 5篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1990年 | 4篇 |
1985年 | 1篇 |
1981年 | 2篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1972年 | 1篇 |
排序方式: 共有452条查询结果,搜索用时 31 毫秒
71.
D. S. L. Pontes E. Longo F. M. Pontes M. S. Galhiane L. S. Santos Marcelo A. Pereira-da-Silva J. H. D. da Silva A. J. Chiquito P. S. Pizani 《Applied Physics A: Materials Science & Processing》2009,96(3):731-740
Ferroelectric Pb1−x−y
Ca
x
Sr
y
TiO3 thin films (denoted by PCST90, PCST70, and PCST30) were deposited on the Pt/Ti/SiO2/Si substrates by a chemical solution deposition method. Their properties were investigated from the viewpoint of crystal
structure, microstructure, dielectric, and ferroelectric properties. X-ray diffraction patterns revealed the formation of
PCST90, PCST70, and PCST30 thin films without any secondary phases. Infrared and Raman spectroscopy results show that a gradual
phase transition from tetragonal to pseudocubic or cubic perovskite structure may occur in PCST thin films with the simultaneous
increase of Ca2+ and Sr2+ contents. Both substitution of isovalent Ca2+ and Sr2+ at Pb2+-site enhanced the dielectric constant and reduced the remnant polarization. In addition, ferroelectric test analyses show
that the PCST thin films undergo a ferroelectric-to-paraelectric phase transformation with an amount of Pb2+, Ca2+, and Sr2+ at 30%, 35%, and 35% mol, respectively. Hence, the absence of ferroelectric property may be attributed to a decreasing of
the octahedron distortion in the perovskite structure accompanied by a weakening of long-range ferroelectric order. 相似文献
72.
J. J. Camacho M. Santos L. Díaz J. M. L. Poyato 《Applied Physics A: Materials Science & Processing》2009,94(2):373-380
We have used ferrocene and paraffin wax as novel precursor and solvent for the growth of iron oxide nanoparticles. The proposed
method of growth has several advantages over existing methods of growth using iron pentacarbonyl a precursor. Highly crystalline
and monodispersed particles are obtained which assemble in two- and three-dimensional hexagonal closed packed superlattices.
Growth kinetics has been studied by varying concentration of the precursor and time of growth. A phenomenological model has
been proposed to explain the growth kinetics. 相似文献
73.
S. Senthilkumaar R. Thamiz Selvi 《Applied Physics A: Materials Science & Processing》2009,94(1):123-129
Zinc sulfide nanorods with good photoluminescence have been successfully fabricated using a simple sol-gel process via ultrasonication,
with mercaptoethanol as capping agent. The formation of ZnS nucleation, followed by subsequent growth, is significant in obtaining
highly oriented ZnS nanorods. Temperature, time, and capping agent also proved to be significant factors in the growth of
ZnS nanorods and greatly affect their photo luminescent properties. X-ray diffraction (XRD) analysis, low and high-resolution
transmission electron microscopy (TEM & HRTEM), selected-area electron diffraction (SAED) pattern, and scanning electron microscopy
(SEM) indicated that the ZnS nanorods were single crystal in nature and that they had grown up preferentially along the [0001]
direction. This simple method of nucleation, followed by their successive growth, resulted in the development of an effective
and low-cost fabrication process for high-quality ZnS nanorods with good photo luminescent properties that can be applied
to luminescent sensors and optoelectronic devices. 相似文献
74.
V. L. Gayou B. Salazar-Hernandez G. Zavala P. Santiago J. A. Ascencio 《Applied Physics A: Materials Science & Processing》2009,94(4):735-738
In this work, we report the synthesis of ZnS nanostructures by a simple and eco-friendly method that makes possible producing
nanoflakes at room temperature. Scanning electron microscopy and transmission electron microscopy methods (mainly bright-field,
high resolution and high angle annular dark-field) were used to identify and study the obtained nanostructures. The structure
of these nanoflakes consists of nanosized crystalline particles around 1.5 to 3 nm. Domains with different contrast of nanometer-size
diameters are formed in the self-assembled nanoflakes as a result of a noncompact arrangement of nanocrystallites during agglomeration
and differences in the presence of the organic passivation agent. Agglomeration can be attributed to the amount of crystallites
generated at the beginning of the reaction or to an anisotropic interaction between phosphate ions and the surfaces of ZnS
clusters, and consequently a bottom-up synthesis is considered, which opens a simple route for the production of nanomaterials
with the inclusion of extra elements by a simple way. 相似文献
75.
S. Gleyzes A. El Amili R. A. Cornelussen P. Lalanne C. I. Westbrook A. Aspect J. Estève G. Moreau A. Martinez X. Lafosse L. Ferlazzo J. C. Harmand D. Mailly A. Ramdane 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,53(1):107-111
We study a Fabry-Perot cavity formed from a ridge waveguide on a AlGaAs substrate. We experimentally determined the propagation
losses in the waveguide at 780 nm, the wavelength of Rb atoms. We have also made a numerical and analytical estimate of the
losses induced by the presence of the gap which would allow the interaction of cold atoms with the cavity field. We found
that the intrinsic finesse of the gapped cavity can be on the order of F∼30, which, when one takes into account the losses
due to mirror transmission, corresponds to a cooperativity parameter for our system C∼1. 相似文献
76.
M. Abe N. Nishio N. Hanyu M. Tada A. Sandhu H. Handa 《Journal of magnetism and magnetic materials》2009,321(7):645-649
Ferrite nanobeads were synthesized from an aqueous solution utilizing Fe2+ to Fe3+ oxidation for use as magnetic carriers in bioscreening, bio-molecular recognition and anti-cancer diagnosis and therapy. The beads had a crystal structure that was intermediate between Fe3O4 and γ-Fe2O3. Functional biomolecules were strongly conjugated onto the surfaces of the ferrite beads via COOH and SH groups. The addition of ferrite seed crystals (3-8 nm in size) together with a disaccharide enabled the synthesis of monodisperse, spherical ferrite beads with average diameters (d¯) between 50 and 150 nm and relative deviation Δd/d¯=9-16%. Hollow ferrite nano-spheres (d¯=150-450 nm, Δd/d¯≈10%) were prepared using silica spheres as templates, which were dissolved in NaOH solution. Ferrite beads 40 nm in size were encapsulated in polymer spheres of styrene and polymerized glycidyl methacrylate (poly-GMA), 184±9 nm in diameter. They were used for high throughput bioscreening system for affinity purification of target proteins which make specific bindings to anti-cancer drugs, porphyrins, environment hormones, etc. 相似文献
77.
Zn1 − xFexS (x=0.0, 0.1, 0.2, 0.4 and 0.6) nanocrystals have been obtained by chemical co-precipitation from homogeneous solutions of zinc and iron salt compounds, with S2− as precipitating anion formed by decomposition of thiophenol. The TEM micrographs show a spherical shape for ZnS nanocrystals and their average size is around 7 nm. The optical absorption spectra indicate a blue shift of the absorption edge with increasing Fe-content. The luminescence of nanoparticles excite at about 370 nm with an emission peak at around 490 nm. At room temperature, ESR signal characteristic of Fe3+ was observed in samples of all concentrations. 相似文献
78.
Intense infrared-to-visible up-conversion (UC) emissions were obtained in hexagonal Yb3+-Tm3+ co-doped NaYF4 nanorods under excitation at 980 nm. Especially, luminescent switching between different UC emission wavelengths at 800, 480 and 450 nm were observed by adjusting excitation powers. Based on power-dependent spectral analyses, it was found that the cooperative energy transfer between Yb3+-Yb3+ pairs and Tm3+ ions play a key role on the luminescent switching besides the saturation effect of Yb3+2F5/2 and Tm3+1G4 excited states. Our results indicate that hexagonal NaYF4 nanostructures have potential applications in miniaturized solid-state laser, optical processing sensors and fluorescent biolabels. 相似文献
79.
80.
Li ZR Wang FF Wu D Li Y Chen W Sun XY Gu FL Aoki Y 《Journal of computational chemistry》2006,27(8):986-993
The structure and aromaticity of a royal crown-shaped molecule Li(3)-N(3)-Be are studied at the CCSD(T)/aug-cc-pVDZ level. This molecule is a charge-separated system and can be denoted as Li(3) (2+)N(3) (3-)Be(+). It is found that the Li(3) (2+) ring exhibits aromaticity mainly because the Li(3) (2+) ring can share the pi-electron with the N(3) (-3) ring. The 4n+2 electron counter rule can be satisfied for the Li(3) (2+) subunit if the shared pi valence electron of N(3) (3-) subunit is also taken into account. This new knowledge on aromaticity of a ring from the interactions between subunits is revealed first time in this paper. Li(3)-N(3)-Be can be also regarded as a molecule containing two superatoms (Li(3) and N(3)), which may be named as a "superomolecule." Li(3)-N(3)-Be is a new metal-nonmetal-metal type sandwich complex. The N(3) (3-) trianion in the middle repulses the electron clouds of the two metal subunits (mainly to the Li(3) superatom) to generate an excess electron, and thus Li(3)-N(3)-Be is also an electride. This phenomenon of the repulsion results in: (a) the HOMO energy level increased, (b) the electron cloud in HOMO distended, (c) the area of the negative NICS value extended, and (d) the VIE value lowered. So the superomolecule Li(3)-N(3)-Be is not only a new metal-nonmetal-metal type sandwich complex but also a new type electride, which comes from the interaction between the alkali superatom (Li(3)) and the nonmetal superatom (N(3)). 相似文献