全文获取类型
收费全文 | 7599篇 |
免费 | 1709篇 |
国内免费 | 511篇 |
专业分类
化学 | 4399篇 |
晶体学 | 52篇 |
力学 | 264篇 |
综合类 | 44篇 |
数学 | 71篇 |
物理学 | 4989篇 |
出版年
2024年 | 23篇 |
2023年 | 89篇 |
2022年 | 221篇 |
2021年 | 260篇 |
2020年 | 265篇 |
2019年 | 250篇 |
2018年 | 233篇 |
2017年 | 319篇 |
2016年 | 270篇 |
2015年 | 309篇 |
2014年 | 360篇 |
2013年 | 571篇 |
2012年 | 542篇 |
2011年 | 519篇 |
2010年 | 386篇 |
2009年 | 452篇 |
2008年 | 387篇 |
2007年 | 549篇 |
2006年 | 440篇 |
2005年 | 364篇 |
2004年 | 336篇 |
2003年 | 351篇 |
2002年 | 278篇 |
2001年 | 246篇 |
2000年 | 222篇 |
1999年 | 176篇 |
1998年 | 164篇 |
1997年 | 139篇 |
1996年 | 157篇 |
1995年 | 105篇 |
1994年 | 108篇 |
1993年 | 88篇 |
1992年 | 116篇 |
1991年 | 69篇 |
1990年 | 66篇 |
1989年 | 70篇 |
1988年 | 39篇 |
1987年 | 53篇 |
1986年 | 37篇 |
1985年 | 33篇 |
1984年 | 28篇 |
1983年 | 10篇 |
1982年 | 16篇 |
1981年 | 23篇 |
1980年 | 17篇 |
1979年 | 16篇 |
1978年 | 9篇 |
1977年 | 8篇 |
1976年 | 7篇 |
1974年 | 6篇 |
排序方式: 共有9819条查询结果,搜索用时 15 毫秒
971.
972.
The dust screening and dust attraction in plasmas is considered for the constant ionization source. Both limits of linear and nonlinear screening are considered. It is shown that the non‐linear screening changes substantially the collective dust screening and collective dust attraction. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
973.
974.
975.
A correlation reflectometer in 8-mm wavelength range has been constructed and installed on CASTOR tokamak. The reflectometer can operate on three fixed frequencies (29, 33, and 35 GHz). This is universal correlation sine-cosine reflectometer, which can work in poloidal or toroidal correlation regime and in ordinary mode (O-mode) and/or extraordinary mode (X-mode). A computational method of a direct evaluation of the phase fluctuations as well as absolute value of the phase from sine-cosine data has been developed. Using this method the relative plasma density fluctuations in the CASTOR core plasma has been determined in the range of few percent under assumption of parabolic density distribution. 相似文献
976.
理论研究和数值模拟发现入射光和反射光在低密度等离子体中形成的干涉场可以产生深度的等离子体密度调制. 对于中等强度的入射光,譬如1015W/cm2 ,产生密度调制的时间尺度在几十个光周期的范围. 这样的等离子体密度调制可以起类似布拉格反射镜的 作用,使得后面的入射光在临界面以下的区域产生相位反射. 因为密度调制的周期是光在等 离子体中波长的一半,其产生的反射率可以接近100%. 相位反射也可以在不均匀的低密度 等离子体中产生,它可以极大地减少等离子体对光的吸收,因此在惯性约束核聚变中需要考 虑到它的影响.
关键词:
相位反射
密度调制
激光等离子体
粒子模拟 相似文献
977.
报道了0.53μm高功率激光辐照金盘靶产生的受激拉曼散射光光谱和散射光谱能量角分布,由散射光角分布计算的散射光能量与实验通过打靶透镜测得的受激拉曼散射能量不符,而且角的分布的实验结果与受激布里渊散射理论也不符。 相似文献
978.
Nanopowders are produced in a low temperature, non-equilibrium plasma jet (APPJ), which produces a glow discharge at atmospheric pressure, for the first time. Amorphous carbon and iron nanoparticles have been synthesized from Acetylene and Ferrocene/H2, respectively. High generation rates are achieved from the glow discharge at near-ambient temperature (40–80°C), and rise with increasing plasma power and precursor concentration. Fairly narrow particle size distributions are measured with a differential mobility analyzer (DMA) and an aerosol electrometer (AEM), and are centered around 30–35 nm for carbon and 20–25 nm for iron. Particle characteristics analyzed by TEM and EDX reveal amorphous carbon and iron nanoparticles. The Fe particles are highly oxidized on exposure to air. Comparison of the mobility and micrograph diameters reveal that the particles are hardly agglomerated or unagglomerated. This is ascribed to the unipolar charge on particles in the plasma. The generated particle distributions are examined as a function of process parameters. 相似文献
979.
Nobuki Kashihara Heru Setyawan Manabu Shimada Yutaka Hayashi Chan Soo Kim Kikuo Okuyama Sugeng Winardi 《Journal of nanoparticle research》2006,8(3-4):395-403
Sine-wave modulated rf plasma has been used to control particle generation and growth in a plasma-enhanced chemical vapor deposition of silicon dioxide thin films using TEOS/O2. The density and the size of particles generated in the plasma are greatly reduced when the plasma is modulated with sine-wave modulation at low modulation frequency (<1000 Hz). In addition, particle contamination on the films is significantly reduced also for nanoparticles, and the film growth rates at the range of modulation frequencies where particle generation are greatly reduced do not decrease appreciably. Compared to its counterpart pulse-wave modulation plasma, the sine-wave modulation plasma has demonstrated a better performance in terms of reduction of particle generation and film contamination, and of film growth rate. Thus, the sine-wave modulation plasma has shown as a promising method to be applied in the production of thin film with a high deposition rate and a low particle contamination. 相似文献
980.
In this study, cyclic olefin copolymer (COC)/layered silicate nanocomposites (CLSNs) were prepared by the intercalation of COC polymer into organically‐modified layered silicate through the solution mixing process. Both X‐ray diffraction data and transmission electron microscopy images of CLSNs indicate most of the swellable silicate layers were disorderedly intercalated into the COC matrix. The effect of layered silicate on the mechanical and barrier properties of the fabricated nanocomposites shows significant improvements in the storage modulus and water permeability when compared with that of neat COC matrix. Surfaces of COC and CLSN films were modified by a mixture of oxygen (O2) and nitrogen (N2) plasmas with various treated times, system pressures, and radio frequency (RF) powers. The surfaces of plasma‐modified COC and CLSN were investigated using scanning probe microscopy and contact‐angle measurements. The exposure of the COC and CLSN film to the plasmas led to the combination of etching reactions of polymer surface initiated by plasma and the following addition reactions of new functional groups onto polymer surfaces to change the topology of COC film surfaces. The surface roughness was closely related to how high and how long the RF power was input into the system. The plasmas also led to changes in the surface properties of the CLSN surfaces from hydrophobic to hydrophilic; and the contact angle of water on the surface decreases. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2745–2753, 2005 相似文献