全文获取类型
收费全文 | 150篇 |
免费 | 0篇 |
专业分类
化学 | 23篇 |
晶体学 | 6篇 |
数学 | 3篇 |
物理学 | 118篇 |
出版年
2022年 | 1篇 |
2014年 | 1篇 |
2013年 | 6篇 |
2012年 | 2篇 |
2011年 | 4篇 |
2010年 | 3篇 |
2009年 | 3篇 |
2008年 | 2篇 |
2007年 | 6篇 |
2006年 | 8篇 |
2005年 | 7篇 |
2004年 | 6篇 |
2003年 | 6篇 |
2002年 | 4篇 |
2001年 | 2篇 |
2000年 | 5篇 |
1999年 | 4篇 |
1998年 | 1篇 |
1995年 | 1篇 |
1994年 | 7篇 |
1993年 | 17篇 |
1992年 | 22篇 |
1990年 | 1篇 |
1988年 | 1篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 6篇 |
1981年 | 5篇 |
1980年 | 3篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1976年 | 3篇 |
1975年 | 2篇 |
排序方式: 共有150条查询结果,搜索用时 502 毫秒
91.
92.
93.
94.
95.
Relaxation of toroidal discharges is described by the principle of minimum energy dissipation together with the constraint
of conserved global helicity. The resulting Euler-Lagrange equation is solved in toroidal coordinates for an axisymmetric
torus by expressing the solutions in terms of Chandrasekhar-Kendall (C-K) eigenfunctions analytically continued in the complex
domain. The C-K eigenfunctions are obtained as hypergeometric functions that are solutions of scalar Helmholtz equation in
toroidal coordinates in the large aspect-ratio approximation. Equilibria are constructed by assuming the current to vanish
at the edge of plasma. For the m=0, n=0 (m and n are the poloidal and toroidal mode numbers respectively) relaxed states, the magnetic field, current, q (safety factor) and pressure profiles are calculated for a given value of aspect-ratio of the torus and for different values
of the eigenvalue λ
r
0. The new feature of the present model is that solutions allow for both tokamak as well as RFP-like behaviour with increase
in the values of λ
r
0, which is related directly to volt-sec in the experiment. 相似文献
96.
Matthew Rogers Steven Barcelo Xiaobo Chen Thomas J. Richardson Vincent Berube Gang Chen Mildred S. Dresselhaus Costas P. Grigoropoulos Samuel S. Mao 《Applied Physics A: Materials Science & Processing》2009,96(2):349-352
Free-standing magnesium–nickel (Mg–Ni) films with extensive nanoscale grain structures were fabricated using a combination
of pulsed laser deposition and film delaminating processes. Hydrogen sorption and desorption properties of the films, free
from the influence of substrates, were investigated. Oxidation of the material was reduced through the use of a sandwiched
free-standing film structure in which the top and bottom layers consist of nanometer-thick Pd layers, which also acted as
a catalyst to promote hydrogen uptake and release. Hydrogen storage characteristics were studied at three temperatures, 296,
232, and 180°C, where multiple sorption/desorption cycles were measured gravimetrically. An improvement in hydrogen storage
capacity over the bulk Mg–Ni target material was found for the free-standing films. As shown from a Van’t Hoff plot, the thermodynamic
stability of the nanograined films is similar to that of Mg2Ni. These results suggest that free-standing films, of which better control of material compositions and microstructures can
be realized than is possible for conventional ball-milled powders, represent a useful materials platform for solid-state hydrogen
storage research. 相似文献
97.
Gustavo M. do Nascimento Tilana B. Silva Paola Corio Mildred S. Dresselhaus 《Journal of Raman spectroscopy : JRS》2010,41(12):1587-1593
Highly dispersed nanocomposites of polyaniline(PANI) and oxidized single wall carbon nanotubes(SWNTs) have been prepared using dodecylbenzenesulfonic acid as dispersant. The materials were characterized via resonance Raman and electronic absorption spectroscopies. The behavior of the composites as a function of the applied potential was also investigated using in situ Raman electrochemical measurements. The results obtained at Elaser = 1.17 eV suggest that a charge‐transfer process occur between PANI and semiconducting nanotubes for samples where the metallic tubes are previously oxidized. The spectroelectrochemical data show that the presence of SWNTs prevents the oxidation of PANI rings. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
98.
Gustavo M. Do Nascimento Paola Corio Richard W. Novickis Marcia L. A. Temperini Mildred S. Dresselhaus 《Journal of polymer science. Part A, Polymer chemistry》2005,43(4):815-822
Nanocomposites of polyaniline (PANI) and single‐wall carbon nanotubes (SWNTs) were prepared and characterized via resonance Raman and electronic absorption spectroscopy (ultraviolet–visible/near‐infrared). The chemical synthesis of PANI was performed in the presence of SWNTs in concentrations ranging from 10 to 50 wt % (SWNT/PANI). The obtained materials were hydrophilic, homogeneous composite compounds. The chemical interaction between PANI (in the conducting emeraldine salt form and in the insulating emeraldine base form) and metallic and semiconducting nanotubes was investigated. The emeraldine salt form of the polymer was significantly stabilized in the composite in comparison with plain PANI. A selective electronic interaction process between PANI and metallic SWNTs was found. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 815–822, 2005 相似文献
99.
Huang JY Chen S Ren ZF Wang Z Kempa K Naughton MJ Chen G Dresselhaus MS 《Physical review letters》2007,98(18):185501
We report exceptional ductile behavior in individual double-walled and triple-walled carbon nanotubes at temperatures above 2000 degrees C, with tensile elongation of 190% and diameter reduction of 90%, during in situ tensile-loading experiments conducted inside a high-resolution transmission electron microscope. Concurrent atomic-scale microstructure observations reveal that the superelongation is attributed to a high temperature creep deformation mechanism mediated by atom or vacancy diffusion, dislocation climb, and kink motion at high temperatures. The superelongation in double-walled and triple-walled carbon nanotubes, the creep deformation mechanism, and dislocation climb in carbon nanotubes are reported here for the first time. 相似文献
100.
Iron-doped carbon aerogels: novel porous substrates for direct growth of carbon nanotubes 总被引:2,自引:0,他引:2
Steiner SA Baumann TF Kong J Satcher JH Dresselhaus MS 《Langmuir : the ACS journal of surfaces and colloids》2007,23(9):5161-5166
We present the synthesis and characterization of Fe-doped carbon aerogels (CAs) and demonstrate the ability to grow carbon nanotubes directly on monoliths of these materials to afford novel carbon aerogel-carbon nanotube composites. Preparation of the Fe-doped CAs begins with the sol-gel polymerization of the potassium salt of 2,4-dihydroxybenzoic acid with formaldehyde, affording K+-doped gels that can then be converted to Fe2+- or Fe3+-doped gels through an ion exchange process, dried with supercritical CO2, and subsequently carbonized under an inert atmosphere. Analysis of the Fe-doped CAs by TEM, XRD, and XPS revealed that the doped iron species are reduced during carbonization to form metallic iron and iron carbide nanoparticles. The sizes and chemical composition of the reduced Fe species were related to pyrolysis temperature as well as the type of iron salt used in the ion exchange process. Raman spectroscopy and XRD analysis further reveal that, despite the presence of the Fe species, the CA framework is not significantly graphitized during pyrolysis. The Fe-doped CAs were subsequently placed in a thermal CVD reactor and exposed to a mixture of CH4 (1000 sccm), H2 (500 sccm), and C2H4 (20 sccm) at temperatures ranging from 600 to 800 degrees C for 10 min, resulting in direct growth of carbon nanotubes on the aerogel monoliths. Carbon nanotubes grown by this method appear to be multiwalled (approximately 25 nm in diameter and up to 4 microm long) and grow through a tip-growth mechanism that pushes catalytic iron particles out of the aerogel framework. The highest yield of CNTs was grown on Fe-doped CAs pyrolyzed at 800 degrees C treated at CVD temperatures of 700 degrees C. 相似文献