全文获取类型
收费全文 | 1387篇 |
免费 | 147篇 |
国内免费 | 87篇 |
专业分类
化学 | 385篇 |
晶体学 | 8篇 |
力学 | 383篇 |
综合类 | 17篇 |
数学 | 297篇 |
物理学 | 531篇 |
出版年
2024年 | 4篇 |
2023年 | 11篇 |
2022年 | 14篇 |
2021年 | 25篇 |
2020年 | 29篇 |
2019年 | 19篇 |
2018年 | 36篇 |
2017年 | 38篇 |
2016年 | 67篇 |
2015年 | 47篇 |
2014年 | 57篇 |
2013年 | 105篇 |
2012年 | 85篇 |
2011年 | 61篇 |
2010年 | 48篇 |
2009年 | 70篇 |
2008年 | 73篇 |
2007年 | 87篇 |
2006年 | 75篇 |
2005年 | 70篇 |
2004年 | 51篇 |
2003年 | 56篇 |
2002年 | 54篇 |
2001年 | 52篇 |
2000年 | 53篇 |
1999年 | 36篇 |
1998年 | 40篇 |
1997年 | 30篇 |
1996年 | 23篇 |
1995年 | 21篇 |
1994年 | 20篇 |
1993年 | 10篇 |
1992年 | 15篇 |
1991年 | 11篇 |
1990年 | 21篇 |
1989年 | 14篇 |
1988年 | 7篇 |
1987年 | 9篇 |
1986年 | 12篇 |
1985年 | 7篇 |
1984年 | 15篇 |
1983年 | 6篇 |
1982年 | 5篇 |
1981年 | 9篇 |
1980年 | 5篇 |
1979年 | 3篇 |
1977年 | 4篇 |
1976年 | 2篇 |
1974年 | 2篇 |
1973年 | 2篇 |
排序方式: 共有1621条查询结果,搜索用时 15 毫秒
1.
2.
We consider a quark model based on QCD scale anomaly in which the quarks move in the field of an effective glueball field.
Hadrons correspond to solitonic bags of higher energy density in a nonperturbative sea of condensed gluons. We calculate the
static properties of nucleon in this model and find that the nucleon mass is far too large (2.4–4 GeV) and the proton charge
radius (0.37–0.54 fm) is low. The proton gyromagnetic ratio and gA/gv are in reasonable agreement with the experimental numbers. 相似文献
3.
W. Hufenbach R. Böhm A. Langkamp L. Kroll T. Ritschel 《Mechanics of Composite Materials》2006,42(2):151-162
The basic damage and failure models of multiaxially reinforced composites with a thermoplastic matrix are presented and verified.
Within the framework of continuum damage mechanics, a phenomenological model is introduced, where the damage is defined as
a change in the elasticity tensor. For damage identification, a specific ultrasonic device was developed. A combination of
an immersion set-up and a contact coupling device formed a system for an efficient determination of stiffness-tensor components
from convenient sets of velocity measurements. Linked to a tensile machine, it allowed us to measure the anisotropic damage
of the new materials group caused by tensile loading.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 42, No. 2, pp. 221–234, March–April, 2006. 相似文献
4.
Two tests for multivariate conditional heteroscedastic models are proposed. One is based on the cross-correlations of standardized squared residuals and the other is a score (Lagrange multiplier) test. The cross-correlations test can be used to detect the presence of multivariate conditional heteroscedasticity whereas the other test can be used for diagnostic checking. Simulation studies on the size and power of the test statistics are reported. The application of the tests is illustrated by an example using the S & P 500 and Sydney All Ordinary Indexes. 相似文献
5.
6.
Summary We discuss a null experiment to search for the fifth force at ranges around 10 km. It is proposed to use a three-axis gravity
gradiometer to measure the trace of the Earth gravity tensor from a freely falling elevator dropped by a balloon. The main
error sources are considered to some extent.
Paper presented at the V Cosmic Physics National Conference, S. Miniato, November 27–30, 1990. 相似文献
7.
F. Herfurth K. Blaum S. Eliseev O. Kester H.-J. Kluge S. Koszudowski C. Kozhuharov G. Maero D. Neidherr W. Quint S. Schwarz S. Stahl G. Vorobjev 《Hyperfine Interactions》2006,173(1-3):93-101
A decelerator will be installed at GSI in order to provide and study heavy nuclei without or with only few electrons at very
low energies or even at rest. Highly-charged ions will be produced by stripping at relativistic energies. After electron cooling
and deceleration in the Experimental Storage Ring (ESR) the ions are ejected out of the storage ring at 4 MeV/u and further
decelerated in a combination of linear accelerator structures operated in reverse. Finally, they are injected into a Penning
trap where the ions are cooled to 4 K by electron cooling in combination with resistive cooling. From here, the ions can be
transferred in a quasi DC or in a pulsed mode to different experimental setups. This article describes the technical concepts
of this project focused on the Penning trap.
相似文献
8.
Richard P. Fischer Arne W. Fliflet 《International Journal of Infrared and Millimeter Waves》2002,23(9):1297-1313
This paper presents the design and test of asymmetric quasioptical resonators for gyrotron applications, where most of the diffraction output coupling comes from the smaller of two mirrors. A computer code based on scalar diffraction theory is used to calculate the resonator losses and the electric field near the mirrors. Resonators with mirror separations approaching confocal have reduced side lobes in the diffraction patterns, which should allow for better power transmission and focusing. Cold tests have been performed at 94 and 141 GHz to measure the quality factor of the asymmetric resonators as a function of mirror separation and mirror misalignment. Typical resonator parameters include 65 cm mirror separation, 1-3% output coupling and 85% of the losses from the small mirror. A half-symmetric resonator with one flat and one curved mirror has also been investigated. The calculated values of Q are in reasonably good agreement with the cold test measurements. 相似文献
9.
由Q-Nd:YAG脉冲激光(波长1.06μm,脉宽10 ns)烧蚀Al靶产生等离子体.观测了在低气压和直流电场条件下的Al等离子体发射光谱.研究了激光功率密度和直流电场对各谱线强度的影响,分析了谱线半高全宽与外加电压,等离子体电子温度与激光能量的变化规律.结果表明,直流电场对铝原子谱线强度有显著的增强,铝原子谱线的半高全宽与直流电场的外加电压基本上呈线性关系. 相似文献
10.
The asymptotic null distribution of the likelihood ratio test for two cases of ordered hypotheses in a particular genetic model is considered. A simple iterative process is proposed in order to get the restricted estimates. It is shown that both tests have asymptotically a chi-bar squared distribution and the same size. A simulation study is also conducted in order to compare the usual unrestricted test with the corresponding one of ordered hypotheses. Finally, the results are extended to some special cases. 相似文献