全文获取类型
收费全文 | 1596篇 |
免费 | 387篇 |
国内免费 | 322篇 |
专业分类
化学 | 520篇 |
晶体学 | 6篇 |
力学 | 588篇 |
综合类 | 25篇 |
数学 | 275篇 |
物理学 | 891篇 |
出版年
2024年 | 10篇 |
2023年 | 38篇 |
2022年 | 50篇 |
2021年 | 53篇 |
2020年 | 36篇 |
2019年 | 36篇 |
2018年 | 29篇 |
2017年 | 39篇 |
2016年 | 49篇 |
2015年 | 39篇 |
2014年 | 111篇 |
2013年 | 75篇 |
2012年 | 124篇 |
2011年 | 99篇 |
2010年 | 109篇 |
2009年 | 116篇 |
2008年 | 117篇 |
2007年 | 121篇 |
2006年 | 103篇 |
2005年 | 109篇 |
2004年 | 131篇 |
2003年 | 104篇 |
2002年 | 64篇 |
2001年 | 66篇 |
2000年 | 45篇 |
1999年 | 49篇 |
1998年 | 54篇 |
1997年 | 48篇 |
1996年 | 54篇 |
1995年 | 36篇 |
1994年 | 39篇 |
1993年 | 29篇 |
1992年 | 29篇 |
1991年 | 29篇 |
1990年 | 36篇 |
1989年 | 11篇 |
1988年 | 6篇 |
1987年 | 9篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1982年 | 1篇 |
排序方式: 共有2305条查询结果,搜索用时 15 毫秒
1.
超临界流体色谱流程设计及其应用 总被引:1,自引:1,他引:0
本文设计了多功能超临界流体色谱流程,流程中包括毛细管/微填充柱SFC,GC,计算机控制温度、压力、密度及信号采集、处理,配置有超临界流体萃取池,解决了超临界流体色谱分流口易堵问题。利用该流程,将石腊、DC-200气相色谱固定相、黄油、蜂蜡、救心油、红花油等样品进行超临界流体色谱分离。 相似文献
2.
Second-order random wave solutions for interfacial internal waves in N-layer density-stratified fluid 下载免费PDF全文
This paper studies the random internal wave equations describing the density interface displacements and the velocity potentials of N-layer stratified fluid contained between two rigid walls at the top and bottom. The density interface displacements and the velocity potentials were solved to the second-order by an expansion approach used by Longuet-Higgins (1963) and Dean (1979) in the study of random surface waves and by Song (2004) in the study of second- order random wave solutions for internal waves in a two-layer fluid. The obtained results indicate that the first-order solutions are a linear superposition of many wave components with different amplitudes, wave numbers and frequencies, and that the amplitudes of first-order wave components with the same wave numbers and frequencies between the adjacent density interfaces are modulated by each other. They also show that the second-order solutions consist of two parts: the first one is the first-order solutions, and the second one is the solutions of the second-order asymptotic equations, which describe the second-order nonlinear modification and the second-order wave-wave interactions not only among the wave components on same density interfaces but also among the wave components between the adjacent density interfaces. Both the first-order and second-order solutions depend on the density and depth of each layer. It is also deduced that the results of the present work include those derived by Song (2004) for second-order random wave solutions for internal waves in a two-layer fluid as a particular case. 相似文献
3.
4.
5.
Hydrodynamic Properties of Fe3O4 Kerosene-Based Ferrofluids with Narrow Particle Size Distribution 下载免费PDF全文
We investigate the hydrodynamic properties of Fe3O4 kerosene-based ferrofluids with narrow particle size distribution. The ferrofluids are synthesized by improving chemical coprecipitation technique. A narrow distribution of 8.6-10.8nm particle sizes is obtained from the magnetization curve with the free-form model based on the Bayesian inference theory. The fitting result is consistent with average particle size obtained from x-ray diffraction. With the increase of applied magnetic field and magnetic particle concentration, apparent viscosity of ferrofluids increases. At concentration 4.04%, the type of flow for the ferrofluid transforms from Newtonian to Bingham plastic fluid as the applied magnetic field increases. 相似文献
6.
本文改进实验方法,在0.0001—1.23GPa流体静高压下测量了整片非晶锂离子导体B2O3-0.7Li2O-0.7LiCl-xAl2O3(x=0.05;0.15)及其粉末压片的离子电导率及激活体积。发现粉末压片电导率峰值是由非晶微粒间的接触电导及非晶微粒体电导两者叠加;对整片非晶电导率的压力效应用离子迁移通道的物理图象给出初步的微观解释。此外,还观测到氧化铝组分减少使电导率的压力转变点明显降低;测量出不同温度热处理以及300℃等温热处理4—20h后离子电导率-压力曲线的变化规律,仍可归因于非晶态相分离及两种非晶相的先后晶化。
关键词: 相似文献
8.
对边界层等离子体中常见的物理问题,从两点模型到二维流体描述。从原子分子物理过程到杂质的输运和辐射等进行了系统的归纳和总结,特别是对等离子体不同参数运行区如鞘层限制参数区、传导限制参数区以及脱靶参数区等的一维流体描述,在参阅相关文献的基础上使用一定的假设条件进行了简单推导。分别阐述了它们的特点。 相似文献
9.
To describe pulsar spin-down,we present a simple combined torque model that takes into account both the standard magnetic dipole radiation and the electromagnetic radiation from the 3P2 superluid vortex neutrons inside neutron star.Using an ordinary exponential model for the magnetic field decay,we derive an analytical formulae for pulsar evolution tracks,The pulsar evolution on the P-P diagram is quite different from that of the standard magnetic dipole radiation model,especially when the superfluid torque or field decay becomes dominant. 相似文献
10.