全文获取类型
收费全文 | 318篇 |
免费 | 9篇 |
国内免费 | 13篇 |
专业分类
化学 | 38篇 |
力学 | 125篇 |
综合类 | 3篇 |
数学 | 133篇 |
物理学 | 41篇 |
出版年
2024年 | 1篇 |
2023年 | 3篇 |
2022年 | 1篇 |
2021年 | 7篇 |
2020年 | 7篇 |
2019年 | 3篇 |
2018年 | 2篇 |
2017年 | 4篇 |
2016年 | 7篇 |
2015年 | 10篇 |
2014年 | 11篇 |
2013年 | 11篇 |
2012年 | 5篇 |
2011年 | 10篇 |
2010年 | 13篇 |
2009年 | 22篇 |
2008年 | 32篇 |
2007年 | 28篇 |
2006年 | 20篇 |
2005年 | 24篇 |
2004年 | 22篇 |
2003年 | 6篇 |
2002年 | 11篇 |
2001年 | 9篇 |
2000年 | 7篇 |
1999年 | 2篇 |
1998年 | 6篇 |
1997年 | 11篇 |
1996年 | 13篇 |
1995年 | 5篇 |
1994年 | 7篇 |
1993年 | 4篇 |
1992年 | 5篇 |
1991年 | 3篇 |
1990年 | 4篇 |
1989年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1983年 | 1篇 |
排序方式: 共有340条查询结果,搜索用时 15 毫秒
101.
We study gravitational radiation reaction in the equations of motion for binary systems with spin-orbit coupling, at order
(v/c)7 beyond Newtonian gravity, or O(v/c)2 beyond the leading radiation reaction effects for non-spinning bodies. We use expressions for the energy and angular momentum
flux at infinity that include spin-orbit corrections, together with an assumption of energy and angular momentum balance,
to derive equations of motion that are valid for general orbits and for a class of coordinate gauges. We show that the equations
of motion are compatible with those derived earlier by a direct calculation. 相似文献
102.
Jan Frercks 《Physics in Perspective (PIP)》2005,7(1):35-65
Hippolyte Fizeaus research program on ether drag consisted of a sequence of optical experiments and theoretical considerations aimed at clarifying the interaction between the ether and moving matter to reveal the motion of the Earth through the ether. In addition to Fizeaus published papers, my reconstruction of his research program is based on his unpublished drafts, sketches, and experimental data.These reveal an increasingly complex interplay between his experimental setups,unexpected results, and theoretical convictions. I argue that publishing is an integral part of experimental research rather than a secondary activity undertaken after the true laboratory research has been completed. Accordingly, Fizeaus research program can best be understood as a long quest for a publishable experiment. I show that to Fizeau, to be publishable meant achieving an expected positive experimental result.This publication strategy deeply influenced the design of his experiments as well as what he and his audience regarded as successful experimental research.Jan Frercks received his Ph.D. degree in the history of physics at the Carl von Ossietzky University of Oldenburg, Germany, in 2001. He currently is a postdoctoral researcher in the Institute for History of Medicine, Science, and Technology at the Friedrich Schiller University of Jena, Germany. 相似文献
103.
H. Weisshaupt 《Acta Mathematica Hungarica》2005,107(4):329-337
Summary We generalize a result of Lehmann on the comparison of location experiments with uniform distributions on intervals. We compare a location experiment consisting of uniform distributions on parallelepipeds with a location experiment consisting of uniform distributions on convex bodies. We show that the first experiment can only be more informative than the second one if the convex bodies in the second experiment are themselves parallelepipeds. Further we show that the length of the edges of these parallelepipeds must fulfill a condition similar to the condition on the length of the intervals in Lehmanns result. 相似文献
104.
The problem of stabilizing the axis of a solid by coupled perfectly rigid bodies (PRBs) is solved. The solid executes a plane-parallel
motion. The PRBs can rotate as a single rigid body about the centroidal axis of the solid and counterrotate about its transverse
axes through equal angles. There is a particle inside the solid which causes its imbalance. It is established that the principal
state (if any) of the system—rotation about the centroidal axis—is stable, whereas the rest (unwanted) states are unstable
__________
Translated from Prikladnaya Mekhanika, Vol. 41, No. 8, pp. 122–129, August 2005. 相似文献
105.
《中国颗粒学报》2008,6(6)
We use a two-dimensional model of polygonal particles to investigate granular ratcheting. Ratcheting is a long-term response of granular materials under cyclic loading, where the same amount of permanent deformation is accumulated after each cycle. We report on ratcheting for low frequencies and extremely small loading amplitudes. The evolution of the sub-network of sliding contacts allows us to understand the micromechanics of ratcheting. We show that the contact network evolves almost periodically under cyclic loading as the sub-network of the sliding contacts reaches different stages of anisotropy in each cycle. Sliding contacts lead to a monotonic accumulation of permanent deformation per cycle in each particle. The distribution of these deformations appears to be correlated in form of vortices inside the granular assembly. 相似文献
106.
We use a two-dimensional model of polygonal particles to investigate granular ratcheting. Ratcheting is a long-term response of granular materials under cyclic loading, where the same amount of permanent deformation is accumulated after each cycle. We report on ratcheting for low frequencies and extremely small loading amplitudes. The evolution of the sub-network of sliding contacts allows us to understand the micromechanics of ratcheting. We show that the contact network evolves almost periodically under cyclic loading as the sub-network of the sliding contacts reaches different stages of anisotropy in each cycle. Sliding contacts lead to a monotonic accumulation of permanent deformation per cycle in each particle. The distribution of these deformations appears to be correlated in form of vortices inside the granular assembly. 相似文献
107.
From the knotted pictures this article gives a possible quantitative measure
of the degree of entanglement. We suggest to use the area ratio to measure
the degree of entanglement, moreover, from the two parts of the
non-overlapping area we can also know vividly and pictorially the phase
difference between the two variable coefficients
α and β. 相似文献
108.
Antoine Ducoin Jacques Andr Astolfi Franois Deniset Jean-Franois Sigrist 《European Journal of Mechanics - B/Fluids》2009,28(6):728-743
The present study is developed within the framework of marine structure design operating in transient regimes. It deals with an experimental and numerical investigation of the time–space distribution of the wall-pressure field on a NACA66 hydrofoil undergoing a transient up-and-down pitching motion from 0° to 15° at four pitching velocities and a Reynolds number Re = 0.75 × 106. The experimental investigation is performed using an array of wall-pressure transducers located on the suction side and by means of time–frequency analysis and Empirical Modal Decomposition method. The numerical study is conducted for the same flow conditions. It is based on a 2D RANS code including mesh reconstruction and an ALE formulation in order to take into account the foil rotation and the tunnel walls. Due to the moderate Reynolds number, a laminar to turbulent transition model was also activated. For the operating flow conditions of the study, experimental and numerical flow analysis revealed that the flow experiences complex boundary layer events as leading-edge laminar separation bubble, laminar to turbulent transition, trailing-edge separation and flow detachment at stall. Although the flow is relatively complex, the calculated wall pressure shows a quite good agreement with the experiment provided that the mesh resolution and the temporal discretization are carefully selected depending on the pitching velocity. It is particularly shown that the general trend of the wall pressure (low frequency) is rather well predicted for the four pitching velocities with for instance a net inflection of the wall pressure when transition occurs. The inflection zone is reduced as the pitching velocity increases and tends to disappear for the highest pitching velocity. Conversely, high frequency wall-pressure fluctuations observed experimentally are not captured by the RANS model. Based on the good agreement with experiment, the model is then used to investigate the effects of the pitching velocity on boundary layer events and on hydrodynamic loadings. It is shown that increasing the pitching velocity tends to delay the laminar-to-turbulence transition and even to suppress it for the highest pitching velocity during the pitch-up motion. It induces also an increase of the stall angle (compared to quasi-static one) and an increase of the hysteresis effect during pitch-down motion resulting to a significant increase of the hydrodynamic loading. 相似文献
109.
G. E. Savchenko E. A. Klyuchareva I. I. Denev A. P. Stupak 《Journal of Applied Spectroscopy》2000,67(3):473-481
The fluorescence parameters of pyrene and pyrenedecanoic acid in lipid micelles and native membranes of etioplasts whose basic
lipid components are mono- and digalactosyldiacylglycerol (MGDG and DGDG) have been investigated. The vibrational structure
of the emission spectra of pyrene (λexc = 337 nm) in the 370–400-nm range points to the hydrophilic microsurrounding of pyrene molecules in all types of the investigated
membranes. The absence of MGDG from liposomes leads to a decrease in the degree of excimerization of a probe. In native membranes,
this parameter increases with increasing content of pigments. Pyrene covalently bound to decanoic acid is found in the membranes
of prolamellar bodies and in artificial monolayer micellae in an even more hydrophilic microsurrounding than the molecules
of a free probe, and a decrease in the degree of eximerization is observed thereby. The specific features of localization
of the investigated probes in plastid membranes are discussed.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 67, No. 3, pp. 344–349, May–June, 2000. 相似文献
110.
One‐step refolding and purification of recombinant human tumor necrosis factor‐α (rhTNF‐α) using ion‐exchange chromatography 下载免费PDF全文
Yan Wang Wenxuan Ren Dong Gao Lili Wang Ying Yang Quan Bai 《Biomedical chromatography : BMC》2015,29(2):305-311
Protein refolding is a key step for the production of recombinant proteins, especially at large scales, and usually their yields are very low. Chromatographic‐based protein refolding techniques have proven to be superior to conventional dilution refolding methods. High refolding yield can be achieved using these methods compared with dilution refolding of proteins. In this work, recombinant human tumor necrosis factor‐α (rhTNF‐α) from inclusion bodies expressed in Escherichia coli was renatured with simultaneous purification by ion exchange chromatography with a DEAE Sepharose FF column. Several chromatographic parameters influencing the refolding yield of the denatured/reduced rhTNF‐α, such as the urea concentration, pH value and concentration ratio of glutathione/oxidized glutathione in the mobile phase, were investigated in detail. Under optimal conditions, rhTNF‐α can be renatured and purified simultaneously within 30 min by one step. Specific bioactivity of 2.18 × 108 IU/mg, purity of 95.2% and mass recovery of 76.8% of refolded rhTNF‐α were achieved. Compared with the usual dilution method, the ion exchange chromatography method developed here is simple and more effective for rhTNF‐α refolding in terms of specific bioactivity and mass recovery. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献