全文获取类型
收费全文 | 7202篇 |
免费 | 1736篇 |
国内免费 | 519篇 |
专业分类
化学 | 4490篇 |
晶体学 | 54篇 |
力学 | 237篇 |
综合类 | 46篇 |
数学 | 89篇 |
物理学 | 4541篇 |
出版年
2024年 | 20篇 |
2023年 | 92篇 |
2022年 | 200篇 |
2021年 | 243篇 |
2020年 | 259篇 |
2019年 | 246篇 |
2018年 | 222篇 |
2017年 | 318篇 |
2016年 | 273篇 |
2015年 | 289篇 |
2014年 | 348篇 |
2013年 | 567篇 |
2012年 | 543篇 |
2011年 | 498篇 |
2010年 | 364篇 |
2009年 | 454篇 |
2008年 | 389篇 |
2007年 | 530篇 |
2006年 | 431篇 |
2005年 | 360篇 |
2004年 | 328篇 |
2003年 | 336篇 |
2002年 | 266篇 |
2001年 | 238篇 |
2000年 | 197篇 |
1999年 | 147篇 |
1998年 | 159篇 |
1997年 | 121篇 |
1996年 | 140篇 |
1995年 | 102篇 |
1994年 | 109篇 |
1993年 | 88篇 |
1992年 | 119篇 |
1991年 | 71篇 |
1990年 | 63篇 |
1989年 | 62篇 |
1988年 | 37篇 |
1987年 | 47篇 |
1986年 | 34篇 |
1985年 | 30篇 |
1984年 | 27篇 |
1983年 | 11篇 |
1982年 | 15篇 |
1981年 | 18篇 |
1980年 | 13篇 |
1979年 | 12篇 |
1978年 | 6篇 |
1977年 | 3篇 |
1976年 | 4篇 |
1974年 | 3篇 |
排序方式: 共有9457条查询结果,搜索用时 360 毫秒
991.
纯热传导冷却产生软X射线激光 总被引:1,自引:1,他引:0
本文通过n_e=1×10~(19)cm~(-3)的热等离子体,在纯热传导冷却机制下的计算,得到了等离子体温度的时空变化,并运用碰撞-辐射模型计算了在这种条件下,类锂铝离子4f-3d,5f-3d跃迁的增益系数,计算表明:只要有合适的初始条件,用纯热传导冷却机制,也能产生软X射线激光增益. 相似文献
992.
Diagnosis of phasma in CCD damage process induced by laser 总被引:1,自引:0,他引:1
In this paper, the shapes of plasma produced by a Q-switched YAG laser acted repeatedly upon a CCD with MOS structure are used, to investigate the destroying process of the optoelectronic device. The experimental results of CCD destroyed by a 1.06μm laser beam with a pulse width of 15 ns are given. 相似文献
993.
报道计算高温高密等离子体吸收谱和发射谱(光学薄)的理论方法;该方法基于相对论原子理论,可以计算任何单元素以及多元素等离子体的谱分辨X射线吸收谱和发射谱(光学薄);应用了量子亏损理论,可以减少计算量。利用该方法计算金等离子体LTE吸收谱,计算结果与实验符合良好。本文还对金等离子体LTE的光学薄发射谱进行了研究, 这将有利于对实验进行进一步的诊断分析。该理论计算方法还可提供等离子体内各电离度能级布居等重要物理参数。因此经“标准实验”检验的该理论计算方法将是提供ICF“精密”物理辐射参数的重要基础。 相似文献
994.
We show that the temperature of plasma produced by exposure of copper-zinc alloy specimens to laser radiation changes little
(within the limits of random errors) with a change in the conditions of the laser effect and chemical composition of the specimens.
With use of electric discharges (a low-voltage spark), systematic changes in the temperature of the plasma are observed when
the chemical composition of copper-zinc alloys changes.
Institute of Molecular and Atomic Physics of the National Academy of Sciences of Belarus, 70, F. Skorina Ave., Minsk, 220072,
Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 3, pp. 319–321, May–June, 1998. 相似文献
995.
The characteristics of radio-frequency (RF) plasma sheaths have been topics of much scientific study for decades, and have
also been of great importance in the manufacture of integrated circuits and fabricating microelectromechanical systems (MEMS),
as well as in the study of physical phenomena in dusty plasmas. The sheaths behave special properties under various situations
where they can be treated as collisionless or collisional, single-or dual-RF, one-or two-dimensional (1D or 2D) sheaths, etc.
This paper reviews our recent progress on the dynamics of RF plasma sheaths using a fluid method that includes the fluid equations
and Poission’s equation coupled with an equivalent circuit model and a hybrid method in which the fluid model is combined
with the Monte-Carlo (MC) method. The structures of RF sheaths behave differently in various situations and plasma parameters
such as the ion density, electron temperature, as well as the external parameters such as the applied frequency, power, gas
pressure, magnetic field, are crucial for determining the characteristics of plasma sheaths. 相似文献
996.
In this contribution the plasma of an arc discharge in a mixture of helium and argon is studied. The gas mixture is introduced uniformly along the arc column between each of the stabilizing plates. From the measured lateral distribution of radiation (HeI, HI, ArI, ArII, NI, FI line intensity and width measurements), after Abel inversion, the radial temperature distributions were obtained at various positions of the arc column. Beside the expected radial temperature gradients, a distinct temperature gradient along the arc column was found. 相似文献
997.
Yan Peng Robert Hugon Christophe Brosset 《Journal of Quantitative Spectroscopy & Radiative Transfer》2008,109(9):1549-1562
This present paper deals with the spectral characterization of dusty plasmas such as those produced during ITER fusion experiments. Such plasma formed in a small radio frequency plasma reactor with acetylene was characterized using in situ Fourier transform infrared (FTIR) absorption spectroscopy and laser scattering, and ex situ transmission electron microscopy (TEM). The plasma absorbance spectra thus obtained in the visible and infrared wavelengths exhibit special features associated with the dust particle growth which absorbs and scatters IR light. This experimental absorbance behavior is reproduced using a dedicated radiation modeling based on the Mie theory and the Monte Carlo simulation. The bimodal distribution assumed for particle sizes brings the model-determined optical properties closer to the experimental dust absorbance than the normal and uniform distributions. Dust formation mechanism is further discussed comparing the experimental and simulated absorbance. 相似文献
998.
D. Gold C. Bonet G. Chauvin A. C. Mathieu G. Geirnaert J. Millet 《Plasma Chemistry and Plasma Processing》1981,1(2):161-178
A 100-kW three-phase ac plasma furnace with sheathed copper electrodes (sheathing gas: air) is presented. It is used for spheroidizing chamotte (refractory-fired clay) particles having a smooth, pore-free surface. A simple, one-dimensional numerical model for the heat transfer to the particles explains the maximum processing rate and the detrimental influence of an inhomogeneous particle size distribution. 相似文献
999.
S Chakrabarty 《Pramana》1985,25(6):673-683
Transport coefficients of quark-gluon plasma are discussed in the framework of relativistic kinetic theory with the relaxation
time approximation of Boltzmann transport equation. The expressions for the coefficients of shear and volume viscosities and
heat conductivity are derived assuming quark-gluon plasma to be a non-reactive mixture of quarks, anti-quarks and gluons.
A lowest order in deviations from local thermal equilibrium and in plasma phase, lowest order in coupling constant are assumed.
Entropy production due to irreversible processes is discussed. 相似文献
1000.
A method is described for the determination of 10–100 nmole of methanal and 20–150 nmole of ethanal and propanal. The method is based on the oxidation of aldehydes to the corresponding acids by mercuric ion which in turn is reduced to elemental mercury, followed by cold-vapour atomic absorption spectrometry. Calibration plots were constructed between the concentration of each aldehyde and absorbance, while the calibration from the conventional cold vapour procedure was used for total aldehydes determination. The method is selective and can be used for aldehyde determination in the presence of ketones, acetals, alcohols, acids, esters, ethers, organic chlorides and epoxides. This simple method is characterised by 98–102% recoveries and standard deviations of 3%. 相似文献