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101.
A new three-dimensional simulation procedure was developed for domain wall (grain boundary, APB, magnetic, etc.) migration in the presence of diffusing impurities. The simulation is based upon a kinetic Monte Carlo algorithm and an extended Ising model, incorporating both conserved and non-conserved dynamics. The simulations show a dependence of the domain wall velocity on driving force which is very similar to that seen in 2-d and in qualitative agreement with experiment. That is, the presence of a low mobility regime at small driving force and an abrupt transition to a high mobility regime at larger forces, under some conditions, and a continuous, non-linear dependence of the velocity on the force in others. The main qualitative difference between the 2-d and 3-d simulation results is in how the domain wall roughness depends on driving force. The velocity-driving force relation is not consistent with classic continuum models, but may be described, in the high velocity regime, by a theory based upon a discrete version of these models. 相似文献
102.
103.
我们利用单杂质Anderson模型及运动方程等理论,通过求解格林函数的方法研究了通过T型量子点结构(耦合于铁磁电极和介观环量子点结构)的自旋极化输运过程.研究结果表明,与量子点相耦合的铁磁电极中的极化强度是控制量子点电子输运的重要参数,由此可以达到自旋阀效应.另外我们还发现与量子点相耦合的介观环中的磁通会影响电子自旋向上和自旋向下近藤共振峰的分裂程度,但若加入适当的外磁场,那么这样的分裂将被抵消。 相似文献
104.
通过分析系统的杂质位与其余部分间的纠缠N1-A以及单个正常位与其余部分间的纠缠NL-A研究了匀强磁场作用下含杂质Heisenberg XX链的纠缠特性.研究表明三量子位时纠缠存在的临界温度依赖于杂质参数J1和匀强磁场B.研究发现,当量子位L为奇数时,纠缠N1-A随量子位的增加而增大,而L为偶数时则相反,并且量子位L为偶数时的纠缠大于量子位L为奇数时的纠缠;对NL-A,量子位L为奇数时,纠缠随杂质参数J1的变化与L=3类似,而L为偶数时纠缠随杂质参数|J1|的增加而增加. 相似文献
105.
讨论了在杂质电荷的电场影响下,量子环上荷负电激子X-的能-光谱及其Aharonov-Bohm振荡.当轨道总角动量不守恒的情况下,提出如何按轨道角动量分类构成基矢组并用典型的对角化方法求解体系的本征值和本征矢的方案.该方案计算简单,计算结果令人满意.还讨论了运用等效电荷变换公式和变换图,把位于三维空间的杂质简化为二维平面(或x轴上)的杂质处理,使计算变得更简单,对结果的分析也更明晰. 相似文献
106.
通过分析系统的杂质位与其余部分间的纠缠N1-A以及单个正常位与其余部分间的纠缠NL-A研究了匀强磁场作用下含杂质Heisenberg XX链的纠缠特性.研究表明三量子位时纠缠存在的临界温度依赖于杂质参数J1和匀强磁场B.研究发现,当量子位L为奇数时,纠缠N1-A随量子位的增加而增大,而L为偶数时则相反,并且量子位L为偶数时的纠缠大于量子位L为奇数时的纠缠;对NL-A, 量子位L为奇数时,纠缠随杂质参数J1的变化与L=3类似,而L为偶数时纠缠随杂质参数|J1|的增加而增加. 相似文献
107.
A comparison is given between the variational and strong perturbation techniques. It has been shown that the variational method gives, in general, better results. Also, a new formulation is presented for the strong perturbation technique that depends on a simpler equivalent form of the perturbed part of the Hamiltonian. Moreover, common expressions which are valid for both treatments have been obtained. The results are applied to calculate the binding energy for a hydrogenic impurity placed in a finite confining potential spherical quantum dot in the states (1s), (2p) and (2s). The results obtained hitherto for a central impurity by using the strong perturbation technique are deduced in a much simpler way. As regards the off-central impurity some new expressions have been derived in both treatments. The numerical results for the two states (1s) and (2p) have also been investigated. 相似文献
108.
Hideki Yoshizawa Yasuaki Oohara Yasushi Okayama Hiroki Takahashi Nobuo Môri Setsuo Mitsuda 《高压研究》2013,33(4-6):413-418
Abstract We have determined the magnetic structure of a low-carrier Kondo-lattice system CeAs, and have observed a softening of the crystalline electric field excitations. Despite the prediction of a recent magnetic polaron model in which CeAs and CeP are expected to show a stacking order of T7 and T8 layers, CeAs does not show such a stacking structure under pressure. The ordering in the intermediate phase is a regular ferromagnetic order and that of the low-temperature phase is a canted type-I AF. 相似文献
109.
M. S. Atone S. J. Dhoble S. V. Moharil S. M. Dhopte P. L. Muthal V. K. Kondawar 《辐射效应与固体损伤》2013,168(2):225-230
Abstract Photoluminescence and thermoluminescence in BaSO4:Eu is reported. In earlier works, divalent Eu has been studied in BaSO4. In the present work Eu was incorporated as in predominantly Eu3+ or Eu2+ form. It is shown that RE3+ ? RE2+ conversion or RE2+ ? RE+ conversion is not an integral part of gamma induced TL. Eu3+ ? Eu2+ conversion, on the other hand, may be important in UV induced TL. Low UV efficiency of this material is attributed to poor Eu3+ ? Eu2+ conversion. This is in quite contrast to the analogus material CaSO4: Eu. 相似文献
110.
V. Trepakov M. Savinov S. Kappahn L. Jastrabik P. Camagni L. A. Boatner 《辐射效应与固体损伤》2013,168(1-4):367-371
Abstract The highly polarizable perovskite-type oxide, KTaO3 doped simultaneously with Li+ and Nb5+ (K1?xLixTa1?yNbyO3, KLTN), reveals unexpected properties and ordering effects. Studies of the dielectric permittivity ?'(T, f) (10—300K, 100Hz-1 MHz) for x = 0.0014 and y = 0.024 show collective dipolar ordering effects with a transition from paraelectric into a mixed phase (coexisting dipole-glass-like and long-range ordered ferroelectric phases) taking place near 39 K. At 15 K another phase transition into a reentrant dipolar glass-like state is observed. Such a sequence of transitions and the existence of a reentrant glass state are unknown for electrical dipolar systems. 相似文献