全文获取类型
收费全文 | 95篇 |
免费 | 6篇 |
国内免费 | 9篇 |
专业分类
化学 | 34篇 |
晶体学 | 1篇 |
力学 | 9篇 |
数学 | 16篇 |
物理学 | 50篇 |
出版年
2024年 | 1篇 |
2023年 | 2篇 |
2021年 | 1篇 |
2020年 | 2篇 |
2019年 | 1篇 |
2018年 | 2篇 |
2017年 | 1篇 |
2016年 | 1篇 |
2015年 | 1篇 |
2014年 | 2篇 |
2013年 | 5篇 |
2012年 | 4篇 |
2011年 | 9篇 |
2010年 | 9篇 |
2009年 | 9篇 |
2008年 | 10篇 |
2007年 | 10篇 |
2006年 | 6篇 |
2005年 | 6篇 |
2004年 | 3篇 |
2003年 | 5篇 |
2002年 | 5篇 |
2001年 | 3篇 |
2000年 | 2篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1996年 | 2篇 |
1992年 | 2篇 |
1990年 | 1篇 |
1988年 | 1篇 |
1985年 | 1篇 |
1981年 | 1篇 |
排序方式: 共有110条查询结果,搜索用时 0 毫秒
1.
The major goal of this paper is to examine the hypothesis that stock returns and return volatility are asymmetric, threshold nonlinear, functions of change in trading volume. A minor goal is to examine whether return spillover effects also display such asymmetry. Employing a double-threshold GARCH model with trading volume as a threshold variable, we find strong evidence supporting this hypothesis in five international market return series. Asymmetric causality tests lend further support to our trading volume threshold model and conclusions. Specifically, an increase in volume is positively associated, while decreasing volume is negatively associated, with the major price index in four of the five markets. The volatility of each series also displays an asymmetric reaction, four of the markets display higher volatility following increases in trading volume. Using posterior odds ratio, the proposed threshold model is strongly favored in three of the five markets, compared to a US news double threshold GARCH model and a symmetric GARCH model. We also find significant nonlinear asymmetric return spillover effects from the US market. 相似文献
2.
An effect of Berry’s phase on the NQR spectrum of the rotating powder sample is described and applied for the determination of the electric field gradient asymmetry. The proposed method involves the analysis of the frequency singularities in the NQR powder patterns of the rotating samples. The Berry’s phases for the eigenstates, associated with an adiabatically changing quadrupole hamiltonian, are calculated for nuclei with a spin I = 3/2 and I = 1 as a function of the asymmetry parameter. 相似文献
3.
The shock structure problem is one of the classical problems of fluid mechanics and at least for non-reacting dilute gases it has been considered essentially solved. Here we present a few recent findings, to show that this is not the case. There are still new physical effects to be discovered provided that the numerical technique is general enough to not rule them out a priori. While the results have been obtained for dense fluids, some of the effects might also be observable for shocks in dilute gases. 相似文献
4.
Enantioselective addition of aryllithium reagents to aromatic imines mediated by 1,2-diamine ligands
A variety of optically enriched amines have been obtained by addition of aryllithium reagents to aromatic imines using N,N′-tetramethylcyclohexane-1,2-diamine as chiral ligands. Enantiomeric excesses up to 90% could be obtained. 相似文献
5.
Brain asymmetry is a phenomenon well known for handedness and has been studied in motor cortices. However, few quantitative studies on asymmetrical cortical activity in motor areas have been conducted. In this study, we systematically investigated asymmetrical cortical activity in motor areas during sequential finger movement by quantitatively analyzing functional magnetic resonance imaging (fMRI) blood oxygenation level-dependent (BOLD) responses. The norm of BOLD signal percentage of change was introduced to quantitatively measure the BOLD signal intensity change difference between the left and right motor areas. The results of the data collected from six subjects show that the norm of BOLD signal percentage of change in the right motor area is higher than that in the left motor area for two-hand movement (P=.0059) and single-hand movement (P=.0279) with right-handedness. These results from fMRI show the asymmetry of motor areas and may suggest that the left hemisphere motor area comes into being as an adaptation system that needs few neuron cells only to finish any movement task for right-handedness. The activation intensity in the left motor area is reduced with normal right finger movement. The activation intensity in the right motor area is obviously higher than that in the left motor area. 相似文献
6.
Devendra Adhikari 《Physica B: Condensed Matter》2011,406(3):445-448
The concentration dependent asymmetry in mixing properties of MgPb liquid alloys at 973 K has been investigated on the basis of regular associated solution model. The analysis suggests that heterocoordination leading to the formation of chemical complex Mg2Pb is likely to exist in the melt. 相似文献
7.
This paper investigates possible asymmetries in the monetary policy reaction function of the Central Bank of Republic of Turkey over the business cycles. It is found that the bank reacted more aggressively towards output stabilisation during recessions than expansions. The empirical evidence suggests that the inflation targeting policy of the Turkish Central Bank was accommodative rather than stabilising. Furthermore, it is found that although the Central Bank of Republic of Turkey responded to foreign reserves, real exchange rates and short-term capital inflows both in expansion and recession periods, the bank targeted money growth, budget deficits, and net foreign assets only in expansion periods. 相似文献
8.
Resonant multi-modal dynamics due to planar 2:1 internal resonances in the non-linear, finite-amplitude, free vibrations of
horizontal/inclined cables are parametrically investigated based on the second-order multiple scales solution in Part I [1]
(in press). The already validated kinematically non-condensed cable model accounts for the effects of both non-linear dynamic
extensibility and system asymmetry due to inclined sagged configurations. Actual activation of 2:1 resonances is discussed, enlightening on a remarkable qualitative difference of horizontal/inclined cables as regards
non-linear orthogonality properties of normal modes. Based on the analysis of modal contribution and solution convergence
of various resonant cables, hints are obtained on proper reduced-order model selections from the asymptotic solution accounting for higher-order effects of quadratic nonlinearities. The dependence of
resonant dynamics on coupled vibration amplitudes, and the significant effects of cable sag, inclination and extensibility
on system non-linear behavior are highlighted, along with meaningful contributions of longitudinal dynamics. The spatio-temporal
variation of non-linear dynamic configurations and dynamic tensions associated with 2:1 resonant non-linear normal modes is illustrated. Overall, the analytical predictions are validated by finite difference-based numerical investigations of
the original partial-differential equations of motion. 相似文献
9.
The environment of Eu3+ in zinc-thallium-tellurite glass of the molar composition 60TeO2-30TlO0.5-9.9ZnO-0.1Eu2O3 was investigated by laser-induced fluorescence line narrowing (FLN) techniques using Eu3+ as a local site probe. From the site selective luminescence spectra of Eu3+ at 7 K, the energies of the Stark components of the 7F1 and 7F2 states were recorded and then the crystal field parameters Bnm were calculated assuming a C2v site symmetry. The ratios B22/B20 and B44/B40 for each excitation energy within 7F0-5D0 transition were obtained and compared with the values calculated for Eu3+ in other types of glasses. 相似文献
10.