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81.
Arttu Rajantie 《Contemporary Physics》2013,54(3):195-211
One of the most basic properties of magnetism is that a magnet always has two poles, north and south, which cannot be separated into isolated poles, i.e. magnetic monopoles. There are strong theoretical arguments why magnetic monopoles should exist, but in spite of extensive searches they have never been found. This article gives an introduction to theoretical and experimental aspects of magnetic monopoles and discusses their role in our understanding of fundamental physics, both historically and today. 相似文献
82.
Carlo Alberto Bosello Roberta Nibbi 《Mathematical Methods in the Applied Sciences》2003,26(5):375-388
In this paper, we consider a non‐local electromagnetic medium for which the quadrupole term in the electric induction is not negligible. After giving an outline of the physical model, the problem of Maxwell equations for such a medium is addressed by proving existence and uniqueness of solutions and a principle of constrained minimum is shown to hold as a consequence of some thermodynamical restrictions. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
83.
归纳总结了电磁问题的测试和高效课堂模式的历程,将电磁原问题引入问答题集中,在教学实践的基础上,寻求电磁原问题与传统习题的平衡点,编制一套新的、理实交融的电磁学问答题集。根据自身教学经验和对电磁学教师的走访,对比研究中学、大学阶段物理课程教材、教法的衔接点;在大学物理电磁学课程教学过程中,取实验组和对照组,对比研究教学效果。经过实践教学的检验,该套电磁学问答题集深受学生欢迎,教学效果良好。具体地说,在结合互动答题器的基础上,该套问答题集可显著提升学生的学习兴趣;特别地能很好地培养学生的思维水平和科学素养,提高大学生分析、解决问题的能力。 相似文献
84.
The interaction between bulk and dynamic domain wall in the presence of a linear/non-linear electromagnetism make energy density, tension and pressure on the wall all variables, depending on the wall position. In Lee et al. (2009) [1] this fact seems to be ignored. 相似文献
85.
A history of variational principles is presented through theirapplications to linear models arising from the theory of electromagnetism.This historical survey is enriched by some original contribution. 相似文献
86.
J.U. Andersen E. Bonderup 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,11(3):413-434
With the aim of describing the cooling of highly excited fullerene molecules by heat radiation, we consider simple classical,
dielectric models for calculation of the electromagnetic response and show that the overall distribution of oscillator strength
for electronic transitions can be represented fairly well by such a model. The connection to a layer model for graphite is
discussed. For thermal emission of radiation from fullerenes, which depends on the oscillator strength at low frequencies
only, the classical dielectric model leads to a prediction which should be applicable at high temperatures where the fine
structure of the oscillator strength distribution is smeared out. We also estimate the emission from infrared-active vibrations,
which dominate at low temperatures but play a minor role at the high temperatures where formation and decay of fullerene molecules
take place.
Received 22 November 1999 and Received in final form 19 April 2000 相似文献
87.
M. W. Evans 《Foundations of Physics Letters》1994,7(6):591-600
The newly inferred longitudinal magnetic field of vacuum electromagnetism is given in a number of equivalent forms derived in several different ways. It is therefore overwhelmingly likely that the Evans-Vigier fieldB
(3) will be isolated experimentally through its characteristic square root power density dependence. It is the first classical field of vacuum electromagnetism to be inferred since Maxwell and as such fundamentally extends our understanding of the nature of electromagnetism and field-particle theory. 相似文献
88.
J. L. Ericksen 《Continuum Mechanics and Thermodynamics》2007,19(6):321-327
My purpose is to discuss some disagreements found in the literature on electromagnetic theory, bearing on how the fields should
be transformed under improper transformations of spatial coordinates and time reversals. I hope to encourage workers to eliminate
the disagreements. Also, I will point out logical errors made by some experts.
相似文献
89.
Summary Largely quantitative experiments by Pappas have indicated that the momentum imparted to an electrodynamic impulse pendulum
was not balanced by an equal and opposite momentum change of field energy as required by the special theory of relativity.
The authors repeated Pappas' experiment using discharge currents from a capacitor bank which contained a known amount of stored
energy. It turned out that, for momentum conservation, the magnetic-field energy required would have been 1000 to 2000 times
as large as the energy that was actually stored in the capacitors. In the second part of the paper the pendulum experiments
are interpreted in terms of Ampère's force law. It is shown that the Ampère force exerted on the pendulum is almost exactly
the same as the lorentz force, but it arises in different parts of the pendulum conductor. Furthermore, the Ampère reaction
force does not reside in the field but in the stationary part of the circuit which supplies current to the pendulum. Hence
in the Ampère electrodynamics the momentum is definitely conserved. The experimental and analytical findings confirm the work
by Pappas. A new and important experimental fact emerged from the present investigation. The momentum imparted to the pendulum
was found to be significantly smaller than the calculated mechanical impulse given by the Lorentz and Ampère force laws. The
Ampère force distribution offers an explanation of this observation in terms of the elastic distortion of the pendulum structure.
The Lorentz force distribution could not produce this distortion.
Riassunto Esperimenti ampiamente quantitativi di Pappas hanno indicato che l'impulso assegnato ad un pendolo ad impulso elettrodinamico non è bilanciato da un cambio d'impulso uguale e opposto dell'energia del campo come richiesto dalla teoria speciale della relatività. Gli autori ahnno ripetuto l'esperimento di Pappas usando correnti di scarico da una riserva di capacitori che contiene una quantità nota di energia immagazzinata. Risulta che, per la conservazione del momento, l'energia del campo magnetico richiesta sarebbe da 1000 a 2000 volte grande come l'energia che è in realtà immagazzinata nei capacitori. Nella seconda parte del lavoro gli esperimenti cel pendolo sono interpretati sulle basi delle leggi di forza di Ampère. Si mostra che la forza di Ampère esercitata sul pendolo è quasi esattamente uguale alla forza di Lorentz, ma essa si verifica in parti differenti del conduttore del pendolo. Inoltre, la forza di reazione di Ampère non sta nel campo, ma nella parte stazionaria del circuito che fornisce corrente al pendolo. Quindi nell'elettrodinamica di Ampère l'impulso è conservato in maniera definita. I risultati sperimentali e dell'analisi confermano il lavoro di Pappas. Da questo studio è emerso un nuovo ed importante fatto sperimentale. Il momento impartito al pendolo appare essere specificativamente piú piccolo dell'impulso meccanico calcolato fornito dalla leggi di forza di Lorentz ed Ampère. La distribuzione di forze di Ampère offre una spiegazione di questa osservazione in termini di distorsione elastica della struttura del pendolo. La distribuzione di forze di Lorentz potrebbe non produrre questa distorsione.
Резюме Количественные эксперименты Паппаса показывают, что импульс, переданный электромагнитному импульсному маятнику, не компенсируется равным и противоположным изменением импульса поля, как это следует из специальной теории относительности. Авторы повторили эксперимент Паппаса, используя разряд батареи конденсаторов, которая содержит известное количество запасенной энергии. Оказывается, что для охранения импульса требуемая энергия магнитного поля должна в 1000–2000 раз превосходить энергию, фактическн запасенную в конденсаторах. Во второй части статьи эксперименты с маятником интерпретируются в терминах закона для силы Ампера. Показывается, что сипа Ампера, действующая на мятник, оказывается точно такои же, как сила Лоренца, но возникает в разных частях прводника маятника. Кроме того, сила реакции Ампера принадлежит не полю, а стационарной части контура, который подводит ток к маятнику. Следовательно, электродинамический импульс Ампера сохраняется. Экспериментальные и теоретические результаты подтверкдают работу Паппаса. Из проведенных исследований получен новый и важный зкспериментальный результат. Обнаружено, что импульс, переданный маятинку, оказывается знапительно меньше, чем вычесленный механический импульс, определяемый законами для сил Ампера и Лоренца. Распеделение силы Ампера предлагает объяснение этого факта с помощью упругой деформации структуры маятника. Распределение силы Лоренца не может создавать такой деформации.相似文献
90.
The resonances of parametric vibration with forced vibration is analyzed, the bifurcation equation of the system is obtained
and the singularity analysis is made. Some of the laws and phenomena are revealed. The transition variety and bifurcation
diagram of the physical parametric plane are given. The results can be used in engineering.
Supported by National Natural Science Foundation and Doctoral Programme Foundation of Institution of Higher Education of China. 相似文献