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81.
Anisotropic Sm-Fe-N bulk magnets were produced by the compression shearing method using a hardened steel plate and a tungsten-carbide (WC) plate. It was found that the magnets retained the original Sm2Fe17N3 phase structure without any appreciable decomposition of the Sm2Fe17N3 phase. The anisotropic Sm-Fe-N bulk magnet produced using a WC plate had a higher density and higher crystallographic alignment of the Sm2Fe17N3 phase than that produced using a hardened steel plate, and exhibited high maximum energy products of 228 kJ/m3 with a high coercivity of 0.88 MA/m. 相似文献
82.
The theoretical predictions that UGa3 and CeFe2 should be regarded as itinerant magnets stimulated new investigations. In this paper we focus on Mössbauer measurements aimed to characterize their magnetic properties. We show that the analysis of the transferred hyperfine interactions at the 119Sn nuclei in U(Ga0.98Sn0.02)3, a type II antiferromagnet, provides direct information on the f-p hybridization and allows to determine the orientation of the U moments. The study of CeFe2 demonstrates that the intrinsic ferromagnetism coexists with short range antiferromagnetic correlations. The instability of the ferromagnetic state is illustrated by doping CeFe2 with a small amount of Co and by application of pressure on pure CeFe2. Our results will be discussed in connection with neutron and synchrotron experiments. 相似文献
83.
The aim of this study is to characterize the non-isothermal crystallization of polyamide 6 bonded highly filled ferrites which were prepared by the melt extrusion. Especially, the effect of ferrite concentration and its surface property on the non-isothermal crystallization were investigated by means of differential scanning calorimetry. The highly filled ferrite particles acting as obstacles could severely hinder the motion of surrounding chain segments, which were irrespective of surface nature. The ferrite could be modified by silane and obtain a visually enhanced interaction with polymer matrix which evoked the heterogeneous nucleation. Increasing this enhanced interfacial area between polymer-particle can promote the heterogeneous nucleation. However, a strong interaction can slow the motion of surrounding chain segments of particles, thereby producing a competitive effect on the crystallization rate and crystallinity. The plot of crystallization activation energy against concentration also can evaluate dispersion performance of hydrophilic fillers within hydrophobic polymer. 相似文献
84.
José Bento Borba da Silva Maria Bert?lia Oss Giacomelli Ivan Gonçalves de Souza Adilson José Curtius 《Microchemical Journal》1998,60(3):249-257
Performance of graphite platforms coated with Ir, Rh, and a mixture of both, as permanent modifiers for Ag, As, Bi, Cd, and Sb, was evaluated. The coating process is very simple: a solution containing Ir, Rh, or a mixture of both is pipetted on the platform inserted in a graphite tube, and this is submitted to a temperature program. High pyrolysis temperatures are allowed, especially for As and Bi, 1400°C, in the Ir + Rh-coated platform. The sensitivity remains about the same for all analytes with different coatings, except for As in the Ir-coated platform, for which a remarkable gain was obtained in comparison to the other coatings. The lifetimes of the treated tubes were in the range 50 to more than 1000 cycles, being especially long for Sb and Ag in the Rh-coated platform, more than 600 and 1000 cycles, respectively. The Rh coating could not be used for Bi and Cd. Analysis of a certified reference water and of acid oyster tissue digests showed the absence of interference and good precision. Advantages of the permanent coatings are the possibility of low blanks byin situcleaning of the modifier and shorter analysis time. 相似文献
85.
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
86.
87.
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
88.
稀土永磁薄膜材料 总被引:1,自引:0,他引:1
简要地介绍在纳米复合稀土永磁薄膜材料、各向异性稀土永磁薄膜材料方面的进展。在纳米复合稀土永磁薄膜材料中实现磁性交换耦合和剩磁增强效应,系统地研究了其结构与磁性的关系。制备成功高磁能积的各向异性稀土永磁薄膜材料,比较了Ti或Mo缓冲层对Nd-Fe-B薄膜的表面形貌、磁畴结构和磁性能的影响。发现薄膜的表面形貌强烈地依赖于缓冲层的厚度。由于它极大地影响薄膜的成分,溅射速率被证明是控制薄膜的显微结构、表面形貌和磁性能的一个重要因素。在微磁学模型的基础上,通过分析从5到300K的矫顽力温度依赖关系。研究了各向异性Pr-Fe-B薄膜的矫顽力机制。在晶粒表面,由于磁各向异性的降低和局域退磁场的提高导致的反转畴的形核被确定为控制各向异性Pr-Fe—B薄膜的磁化反转过程的首要机制。 相似文献
89.
爆炸荷载下矩形板的塑性动力响应 总被引:8,自引:1,他引:8
本文采用Jones-Sawczuk控制方程,导出了脉冲荷载下矩形板最大残余挠度的简单理论计算公式,并应用该公式和动态屈服条件,计算了固支方板在爆炸荷载下的最大残余挠度值,与试验结果比较,取得了令人满意的结果。 相似文献
90.