全文获取类型
收费全文 | 2807篇 |
免费 | 613篇 |
国内免费 | 183篇 |
专业分类
化学 | 541篇 |
晶体学 | 9篇 |
力学 | 300篇 |
综合类 | 62篇 |
数学 | 918篇 |
物理学 | 1773篇 |
出版年
2024年 | 4篇 |
2023年 | 21篇 |
2022年 | 58篇 |
2021年 | 50篇 |
2020年 | 51篇 |
2019年 | 54篇 |
2018年 | 72篇 |
2017年 | 112篇 |
2016年 | 120篇 |
2015年 | 87篇 |
2014年 | 179篇 |
2013年 | 197篇 |
2012年 | 183篇 |
2011年 | 204篇 |
2010年 | 167篇 |
2009年 | 199篇 |
2008年 | 202篇 |
2007年 | 183篇 |
2006年 | 164篇 |
2005年 | 146篇 |
2004年 | 150篇 |
2003年 | 121篇 |
2002年 | 120篇 |
2001年 | 109篇 |
2000年 | 99篇 |
1999年 | 81篇 |
1998年 | 94篇 |
1997年 | 63篇 |
1996年 | 63篇 |
1995年 | 47篇 |
1994年 | 22篇 |
1993年 | 30篇 |
1992年 | 23篇 |
1991年 | 21篇 |
1990年 | 14篇 |
1989年 | 15篇 |
1988年 | 13篇 |
1987年 | 9篇 |
1986年 | 9篇 |
1985年 | 6篇 |
1984年 | 7篇 |
1983年 | 4篇 |
1982年 | 6篇 |
1981年 | 6篇 |
1980年 | 5篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1973年 | 1篇 |
1971年 | 2篇 |
排序方式: 共有3603条查询结果,搜索用时 125 毫秒
191.
A new class of distributions for the microcanonical ensemble, which are shown to be stable laws, are derived by applying the central limit theorem to the canonical ensemble. This opens up a whole new host of phenomena that can be treated from a unified thermodynamic point of view. Pressure broadening of line shapes is used as an illustration.1. Work supported, in part, by contributions from the Consiglio Nazionale di Ricerche and the Ministero dell'Università e della Ricerca Scientifica e Tecnologica.2. The interaction parameterC is proportional to the mean square dipole moment. As an order of magnitude of the dipole moment, we can take it as the product of the electric charge and a typical atomic radius for a moderately excited state, which is several times the Bohr radius. Multiplication by the fine structure constant converts the Bohr radius into the Compton wavelength, thereby reducing the magnitude of the interaction by 1/137. 相似文献
192.
用修正的RELIEF方法测量高速空气流瞬时速度的理论研究 总被引:3,自引:1,他引:2
修正了拉曼激发激光感应电子荧光(RamanExciationpulseLaser-inducedElectronicFluorescence简称RELIEF)方法,以实现对亚音速和超音速空气流多点时速度的测量,测量精度优于2%。 相似文献
193.
The collisional broadening and shift of four spectral lines of neon (747.2, 748.8, 753.5, 754.4 nm) arising from 2p5 3p - 2p5 3d transitions, emitted from a low-pressure glow discharge in pure neon and neon-helium mixtures have been measured using a Fabry-Perot interferometer. The values of pressure broadening and shift coefficients are determined and analyzed in terms of the impact theory. 相似文献
194.
本文提出了一种用线阵CCD非接触实时测量塑料导线直径的仪器,它有如下特点:(1)采用了对被测目标所发出的烟雾不敏感的光学系统,提高了测量精度;(2)采用工作于脉冲方式的大功率近红外LED做照明光源,其寿命比采用白炽灯作为光源大为增长,同时缩小了体积并有利于抑制可见光的干扰;(3)对电信号采用了两级滤波、直流恢复、自适应阈值二值化等处理技术;(4)采用定标的方法来消除目标位置移动的影响,提高了测量精度,降低了加工装配精度要求。现场使用证明,它能长期可靠地工作,总的测量误差小于±0.02mm。 相似文献
195.
196.
The method of angular line (MAL) is presented for calculating the resonant frequency of microstrip antenna, which is available in other literature and originally used to analyze various waveguide structure. The results obtained by using this method are in conformity with those reported elsewhere. 相似文献
197.
THE VARIATION OF INVARIANT LINES AND LIMIT CYCLES FOR A QUADRATIC DIFFERENTIAL SYSTEM 总被引:1,自引:0,他引:1
1IntroductionConsidertherealquadraticdiferentialsystemx=-y+δx-4x2+3xy+13y2y=x(1-13x-y).(1)First,forconvenience,wedenotethetwo... 相似文献
198.
Z.?Simic M.?S.?DimitrijevicEmail author L.?C.?Popovic M.?D.?Dacic 《Journal of Applied Spectroscopy》2005,72(3):443-446
Using a semiclassical approach, we have considered electron-, proton-, and ionized helium-impact line widths and shifts for
the F III 2p3
4So-3s 4P resonant line. Moreover, for 10 F III multiplets where the full semiclassical perturbation approach is not applicable in
an adequate way due to the lack of reliable atomic data, electron-impact line widths have been calculated within the modified
semiempirical approach. Results are obtained as a function of temperature for perturber density of 1017 cm−3. The theoretical data obtained have been used to consider the influence of Stark broadening for A-type star atmosphere conditions.
__________
Published in Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 3, pp. 412–415, May–June, 2005. 相似文献
199.
The conditions for realization of the regime of self-oscillations of the intensity of a continuously pumped solid-state laser have been qualitatively analyzed using a system of kinetic equations. It has been established that, in the case where a thin semiconductor layer absorbing light at frequencies close to the lasing frequency is placed into the cavity of such a laser, self-oscillations of its radiation intensity arise as a result of the amplitude-phase self-modulation of the laser light field.__________Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 1, pp. 136–139, January–February, 2005. 相似文献
200.
David Jacquemart Robert Gamache 《Journal of Quantitative Spectroscopy & Radiative Transfer》2005,96(2):205-239
This paper describes a semi-empirical calculation of the air-broadened half-widths and the air pressure-induced frequency shifts for the H216O isotopologue. This semi-empirical calculation is based on fits of several recent high-quality measurements and theoretical calculations to the first-order terms in the expansion of the complex Robert-Bonamy (CRB) equations, which yields a second- and first-order polynomial function of the differences in the upper- and lower-state vibrational quantum numbers for the half-width and line shift, respectively. The aim of this work was to obtain a complete set of air-broadened half-widths and air pressure-induced frequency shifts for transitions of H216O present in the HITRAN database from microwave to the visible in order to supplement the observed and calculated values. For around 700 sets of rotational quantum numbers (), semi-empirical coefficients describing the vibrational dependence of the air-broadened half-widths and the air pressure-induced frequency shifts have been obtained directly from the fit of experimental and/or theoretical data. The accuracy of the parameters deduced from this calculation is estimated to be between 5% and 10% for the air-broadened half-widths and between 0.001 and for the air pressure-induced frequency shifts. For sets of rotational quantum numbers for which either none or insufficient experimental/theoretical data were available to deduce a vibrational dependence, further approximations have been used to obtain a complete set of semi-empirical coefficients. 相似文献