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171.
A. Banerjee M.K. Harbola 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,5(2):201-206
Employing a near exact Hylleraas wavefunction we calculate various third-order nonlinear optical properties for the helium
atom within the time-dependent Kohn-Sham theory. In our calculations we employ the adiabatic local-density approximation (ALDA)
for the exchange and correlation kernels fxc and gxc, and compare the numbers obtained by us with the available accurate theoretical as well as experimental results. Our results
demonstrate the accuracy of ALDA for the calculation of nonlinear optical properties of many electron systems.
Received: 22 June 1998 / Accepted: 15 October 1998 相似文献
172.
APOLLONOV V V 《中国光学》2011,4(1):9-20
对低频共振情况下激光引擎的基本特性与其理论预测值做了比较,并研究了实现这些技术的重要步骤,认为基于不同学科与工业组织之间的合作,不久的将来会实现利用累计势能来驱动微型汽车。 相似文献
173.
About 40 years ago, Helfrich introduced an elastic model to explain shapes and shape transitions of cells (Z Naturforsch C, 1973; 28:693). This seminal article stimulated numerous theoretical as well as experimental investigations and created new research fields. In particular, the predictive power of his approach was demonstrated in a large variety of lipid model system. Here in this review, we focus on the development with respect to planar lipid membranes in external electric fields. Stimulated by the early work of Helfrich on electric field forces acting on liposomes, we extended his early approach to understand the kinetics of lipid membrane rupture. First, we revisit the main forces determining the kinetics of membrane rupture followed by an overview on various experiments. Knowledge on the kinetics of defect formation may help to design stable membranes or serve for novel mechanism for controlled release. 相似文献
174.
Tieyan Si Xian Zou Zhiguang Wu Tianlong Li Xin Wang Krasnyuk Ivan Ivanovich Qiang He 《化学:亚洲杂志》2019,14(14):2460-2464
We report the bubble dragged microrocket consisting of functionalized multilayer polymer covered asymmetrically by platinum nanoparticles. The microrocket is pushed back during bubble growth over a small step and dragged forward over a big step during bubble explosion. Each bubble explosion induced a shock wave of gas which propagates in water at ultrafast speed. The bubble dragged microrocket can move along an approximate straight line instead of a fluctuating circle which is the trajectory of a bubble‐pushed microrocket in most cases, which makes it a promising candidate for drug delivery and simulating rod‐shaped bacteria. 相似文献
175.
M. Genkin E. Lindroth 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,51(2):205-212
Solar magnetic structures are often observed in the form of flux tubes composed of a number of smaller elements called fibres
or threads, although theoretically such concentrations should not appear but should be flattened by magnetic diffusivity into
a uniform, low intensity field. In this paper we describe a mechanism which may be responsible for the fibrillation and also
for the very large diffusivity which dissipates magnetic flux tubes in hours instead of years. Firstly, the electric current
associated with magnetic field gradients usually increases the local electron temperature and reduces the resistivity, so
that the current becomes concentrated into sheets or streamers. Secondly, the magnetic field gradients continue to increase
until the current magnitude reaches its limit, which is determined by the electron-ion streaming instability. Then with appropriate
temperature and number densities, the Larmor radius of the ions overlaps the near discontinuity in Bz and generates a sharply peaked fluid motion at the edge that is close to the thermal speed. Finally, the resulting vorticity
generates an axial magnetic field opposing Bz in the term , and if this is sufficient to change the sign of this term, the very unstable backward heat equation results. This instability
repeatedly switches on and off and maintains the magnetic structure in the fibrillated form. Such structures are eventually
eliminated by magnetic diffusivity in the usual way, but because of the fluctuations in Bz, this occurs at a vastly increased rate. We show that this phenomenon increases the magnetic diffusivity, D, by a factor
~ 108 in agreement with some observations of plasma loops and supergranules. 相似文献
176.
R. Plasil I. Korolov T. Kotrik P. Dohnal G. Bano Z. Donko J. Glosik 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,54(2):391-398
Experimental studies of the electron energy distribution function “EEDF” under well defined conditions in flowing afterglow
plasma, using a Langmuir probe are reported. The EEDF is measured in He2
+ and Ar+ dominated plasmas and in XeH+ and XeD+ dominated recombining plasmas. He is used as a buffer gas at medium pressures in all experiments (1600 Pa, 250 K). The deviation
of the measured EEDF from Maxwellian distribution is shown to depend on plasma composition and on the processes governing
the plasma decay. The influence of energetic electrons produced during the plasma decay on the body and tail of the EEDF is
observed. The mechanism of energy balance in afterglow plasma is discussed. 相似文献
177.
Xuefei Sun Dan Li Adam T. Woolley Paul B. Farnsworth H. Dennis Tolley Karl F. Warnick Milton L. Lee 《Journal of chromatography. A》2009,1216(37):6532-6538
Electric field gradient focusing (EFGF) uses an electric field gradient and a hydrodynamic counter flow to simultaneously separate and focus charged analytes in a channel. Previously, most EFGF devices were designed to form a linear field gradient in the channel. However, the peak capacity obtained using a linear gradient is not much better than what can be obtained using conventional CE. Dynamic improvement of peak capacity in EFGF can be achieved by using a nonlinear gradient. Numerical simulation results indicate that the peak capacity in a 4-cm long channel can be increased from 20 to 150 when changing from a linear to convex bilinear gradient. To demonstrate the increased capacity experimentally, an EFGF device with convex bilinear gradient was fabricated from poly(ethylene glycol) (PEG)-functionalized acrylic copolymers. The desired gradient profile was confirmed by measuring the focusing positions of a standard protein for different counter flow rates at constant voltage. Dynamically controlled elution of analytes was demonstrated using a monolith-filled bilinear EFGF channel. By increasing the flow rate, stacked proteins that were ordered but not resolved after focusing in the steep gradient segment were moved into the shallow gradient segment, where the analyte peak resolution increased significantly. In this way, the nonlinear field gradient was used to realize a dynamic increase in the peak capacity of the EFGF method. 相似文献
178.
J.C. Caillon 《Physics letters. A》2018,382(46):3307-3312
We have considered electric charge as the fourth component of the particle momentum in five-dimensional space–time. The fifth dimension has been compactified on a circle with an extremely small radius determined from the fundamental physics constants. First, we have given equations in the framework of five-dimensional special relativity and determined the corresponding reduction to four-dimensional space–time. Then, in order to obtain an appropriate charge-to-mass ratio and to avoid the Fourier modes problem, we have considered the propagation of an off-mass shell particle in the five-dimensional space–time which can be interpreted as the motion of an on-mass shell particle in the four-dimensional world we experience. As an example, we have discussed the five-dimensional kinematic equations associated with the electron-positron annihilation process into two photons. Finally, the consequences on the gravitational interaction between two elementary charged particles has been studied. As a main result, we have obtained a unification of Newton's gravitational and Coulomb's electrostatic forces. 相似文献
179.
基于导体的尖端效应原理提出一种静电纺丝法, 将探针阵列有序嵌入并垂直于聚合物溶液槽底部, 保持针头与液面高度相近, 当给溶液施加高电压时, 会在针头附近区域形成峰值电场, 由于流体在电场中具有不稳定性, 射流能够在溶液表面的峰值电场处自发形成, 进而拉伸细化、 劈裂成丝, 固化在收集板上. 但有序排列的探针阵列之间也存在电场相互干扰问题. 为了得到最佳的纺丝电场环境, 需对工作电场进行模拟及优化. 利用COMSOL Multiphysics 5.0建立几何模型, 分析嵌入探针的长短、 数量、 针间距及几何排布方式对溶液表面场强峰值的影响. 当溶液槽中嵌入一排探针时, 凸弧形的几何排布方式能提高中间区域的场强峰值; 对于两排探针, 交错的排布方式有利于改善溶液表面电场的均匀性, 而并列排布和对角线排布对均衡场强的效果不显著. 相似文献
180.
Fuel-optimal trajectory design using solar electric propulsion under power constraints and performance degradation 总被引:1,自引:0,他引:1
The fuel-optimal transfer trajectories using solar electric propulsion are designed considering the power constraints and solar array performance degradation.Three different performance degradation models including linear,positive and negative exponential degradations are used in the analysis of three typical rendezvous missions including Apophis,Venus and Ceres,respectively.The optimal control problem is formulated using the calculus of variations and Pontryagin’s maximum principle,which leads to a bang-bang control that is solved by indirect method combined with a homotopic technique.In demonstrating the effects of the power constraints and solar array performance degradation on the power budget and fuel consumption,the time histories of the power profile and the fuel consumptions are compared for the three missions.This study indicates that it is necessary to consider the power constraints and solar array performance degradation for the SEP-based low-thrust trajectory design,espacially for long-duration outbound flights. 相似文献