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131.
用熔体快淬法制备了纳米复合永磁样品Pr9Fe74Co12B5 与Pr9Fe74Co12B5Sn0.5,分析了样品的起始磁化、反磁化过程,测得样品的总磁化率、可逆磁化率以及样品的磁黏滞性.结果表明,两样品在室温下均表现为单一硬磁相磁化行为,在低温下表现为双相行为,且由于添加Sn后使晶粒均匀化从而导致样品低温下的双相行为更加明显.添加Sn后引起样品中软磁相含量和软磁相晶粒尺寸的增加,使磁化反转中可逆磁化部分增多,且使反磁化形核场降低.磁黏滞性研究表明,热激活体积与软磁相晶粒的大小有关.
关键词:
纳米复合永磁
磁化反转
磁粘滞 相似文献
132.
133.
S. R. Mishra G. J. Long F. Grandjean R. P. Hermann S. Roy N. Ali A. Viano 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):93-96
The structural and magnetic properties of the granular
iron nitride-alumina composite materials,
(FexN)0.2(Al2O3)0.8
and
(FexN)0.6(Al2O3)0.4,
fabricated using high-energy ball milling have been determined
by using X-ray diffraction, Mössbauer spectroscopy, and
magnetization measurements. The Mössbauer spectra, fit with a
distribution of hyperfine fields between zero and 40 T, indicate
that the weighted average field decreases with increasing
milling time. The isomer shift increases with milling time
because of a reduced iron 4s-electron density at the grain
boundaries. Coercive fields as high as 325 and 110 Oe are
obtained for
(FexN)0.2(Al2O3)0.8
at 5 and 300 K, respectively; the increase in the coercive field
upon cooling indicates the presence of superparamagnetic
particles. The coercive field increases with milling time
because of the reduced particle size. The decrease in the
magnetization results from the increase in both the
superparamagnetic fraction and the concentration of surface
defects with increased milling time. 相似文献
134.
DISTORTION OF CRYSTAL LATTICE IN NANOCRYSTALLINE Fe_2O_3 总被引:1,自引:1,他引:0
Ye Xisheng Sha Jian Jiao Zhengkuan Department of Physics Zhejiang University Hangzhou Zhang Lide Institute of Solid State Physics CAS Hefei 《原子与分子物理学报》1997,(4)
DISTORTIONOFCRYSTALLATTICEINNANOCRYSTALLINEFe2O3YeXishengShaJianJiaoZhengkuanDepartmentofPhysics,ZhejiangUniversityHangzhou3... 相似文献
135.
N. G. Fytas A. Malakis 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,50(1-2):39-43
The three-dimensional bimodal random-field Ising model is studied
via a new finite temperature numerical approach. The methods of
Wang-Landau sampling and broad histogram are implemented in a
unified algorithm by using the N-fold version of the Wang-Landau
algorithm. The simulations are performed in dominant energy
subspaces, determined by the recently developed critical minimum
energy subspace technique. The random-fields are obtained from a
bimodal distribution, that is we consider the discrete
(±Δ) case and the model is studied on cubic lattices with
sizes 4≤L ≤20. In order to extract information for the
relevant probability distributions of the specific heat and
susceptibility peaks, large samples of random-field realizations
are generated. The general aspects of the model's scaling behavior
are discussed and the process of averaging finite-size anomalies
in random systems is re-examined under the prism of the lack of
self-averaging of the specific heat and susceptibility of the
model. 相似文献
136.
Hole-drilling method is one of the most convenient methods for engineering residual stress measurement. Combined with moiré
interferometry to obtain the relaxed whole-field displacement data, hole-drilling technique can be used to solve non-uniform
residual stress problems, both in-depth and in-plane. In this paper, the theory of moiré interferometry and incremental hole-drilling
(MIIHD) for non-uniform residual stress measurement is introduced. Three dimensional finite element model is constructed by
ABAQUS to obtain the coefficients for the residual stress calculation. An experimental system including real-time measurement,
automatic data processing and residual stresses calculation is established. Two applications for non-uniform in-depth residual
stress of surface nanocrystalline material and non-uniform in-plane residual stress of friction stir welding are presented.
Experimental results show that MIIHD is effective for both non-uniform in-depth and in-plane residual stress measurements.
The project supported by the FRAMATOME ANP 相似文献
137.
Self‐Assembly of a Giant Tetrahedral 3 d–4 f Single‐Molecule Magnet within a Polyoxometalate System 下载免费PDF全文
Dr. Masooma Ibrahim Dr. Valeriu Mereacre Dr. Nicolas Leblanc Prof. Wolfgang Wernsdorfer Dr. Christopher E. Anson Prof. Annie K. Powell 《Angewandte Chemie (International ed. in English)》2015,54(51):15574-15578
A giant tetrahedral heterometallic polyoxometalate (POM) [Dy30Co8Ge12W108O408(OH)42(OH2)30]56?, which shows single‐molecule magnet (SMM) behavior, is described. This hybrid contains the largest number of 4f ions of any polyoxometalate (POM) reported to date and is the first to incorporate two different 3d–4f and 4f coordination cluster assemblies within same POM framework. 相似文献
138.
Methane as a Selectivity Booster in the Arc‐Discharge Synthesis of Endohedral Fullerenes: Selective Synthesis of the Single‐Molecule Magnet Dy2TiC@C80 and Its Congener Dy2TiC2@C80 下载免费PDF全文
Katrin Junghans Christin Schlesier Aram Kostanyan Nataliya A. Samoylova Qingming Deng Marco Rosenkranz Sandra Schiemenz Dr. Rasmus Westerström Prof. Dr. Thomas Greber Prof. Dr. Bernd Büchner Dr. Alexey A. Popov 《Angewandte Chemie (International ed. in English)》2015,54(45):13411-13415
The use of methane as a reactive gas dramatically increases the selectivity of the arc‐discharge synthesis of M‐Ti‐carbide clusterfullerenes (M=Y, Nd, Gd, Dy, Er, Lu). Optimization of the process parameters allows the synthesis of Dy2TiC@C80‐I and its facile isolation in a single chromatographic step. A new type of cluster with an endohedral acetylide unit, M2TiC2@C80, is discovered along with the second isomer of M2TiC@C80. Dy2TiC@C80‐(I,II) and Dy2TiC2@C80‐I are shown to be single‐molecule magnets (SMM), but the presence of the second carbon atom in the cluster Dy2TiC2@C80 leads to substantially poorer SMM properties. 相似文献
139.
A spray‐based technique, originally developed for the production of semiconductor nanocrystals, is utilized for the preparation of high‐quality nanocrystalline thin films, as demonstrated with manganese sulfide. The films are formed by the use of pneumatic‐assisted thermospray or pneumatic nebulizers. Our simple, low‐cost, and low‐temperature process results in a dense and phase‐pure grain structure. The concepts and benefits of this technique are described and discussed. The film characteristics show dependence on the experimental parameters, in particular the rate of solvent vaporization. Three alternative film formation mechanisms are suggested for cases with varied experimental conditions. 相似文献
140.
Three unprecedented nitronyl nitroxide radical‐bridged 3d–4f clusters, [Ln2Cu2(hfac)10(NIT‐3py)2(H2O)2](LnIII=Y, Gd, Dy), have been obtained from the self‐assembly of Ln(hfac)3, Cu(hfac)2, and the radical ligand. The Dy complex shows a slow relaxation of magnetization, representing the first nitronyl nitroxide radical‐based 3d–4f cluster with single‐molecule magnet behavior. 相似文献