全文获取类型
收费全文 | 171351篇 |
免费 | 1552篇 |
国内免费 | 507篇 |
专业分类
化学 | 88258篇 |
晶体学 | 3039篇 |
力学 | 7154篇 |
综合类 | 3篇 |
数学 | 19515篇 |
物理学 | 55441篇 |
出版年
2020年 | 1398篇 |
2019年 | 1552篇 |
2018年 | 1980篇 |
2017年 | 2065篇 |
2016年 | 3184篇 |
2015年 | 1890篇 |
2014年 | 3112篇 |
2013年 | 7660篇 |
2012年 | 5749篇 |
2011年 | 6880篇 |
2010年 | 5022篇 |
2009年 | 5004篇 |
2008年 | 6536篇 |
2007年 | 6431篇 |
2006年 | 6077篇 |
2005年 | 5503篇 |
2004年 | 5092篇 |
2003年 | 4593篇 |
2002年 | 4450篇 |
2001年 | 5218篇 |
2000年 | 3861篇 |
1999年 | 2967篇 |
1998年 | 2481篇 |
1997年 | 2385篇 |
1996年 | 2241篇 |
1995年 | 2116篇 |
1994年 | 2093篇 |
1993年 | 2001篇 |
1992年 | 2306篇 |
1991年 | 2245篇 |
1990年 | 2194篇 |
1989年 | 2121篇 |
1988年 | 2119篇 |
1987年 | 2124篇 |
1986年 | 2019篇 |
1985年 | 2630篇 |
1984年 | 2683篇 |
1983年 | 2381篇 |
1982年 | 2492篇 |
1981年 | 2307篇 |
1980年 | 2284篇 |
1979年 | 2426篇 |
1978年 | 2462篇 |
1977年 | 2388篇 |
1976年 | 2436篇 |
1975年 | 2360篇 |
1974年 | 2327篇 |
1973年 | 2504篇 |
1972年 | 1623篇 |
1971年 | 1337篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
M. V. Kartikeyan G. Singh E. Borie B. Piosczyk M. Thumm 《International Journal of Infrared and Millimeter Waves》2006,27(5):657-670
The feasibility of an 84 GHz, 500 kW, CW gyrotron for ECRH on an experimental tokamak will be presented in this paper. Mode
competition and mode selection procedures are carefully investigated by considering various candidate modes and the TE10,4 mode is chosen as the operating mode. A conventional cylindrical cavity resonator with weak input and output tapers and parabolic
roundings is considered for interaction studies. Self-consistent, both single mode and time-dependent, calculations are carried
out and power and efficiencies are computed for a typical set of beam parameters. The results show that an output power of
well over 500 kW, CW and efficiency around 40% can be reached without a depressed collector. 相似文献
12.
J. C. Fabris S. V. B. Gonçalves P. E. de Souza 《General Relativity and Gravitation》2002,34(12):2111-2126
The mass power spectrum for a Universe dominated by the Chaplygin gas is evaluated numerically from scales of the order of the Hubble horizon to 100 Mpc. The results are compared with a pure baryonic Universe and a cosmological constant model. In all three cases, the spectrum increases with k, the wavenumber of the perturbations. The slope of the spectrum is higher for the baryonic model and smaller for the cosmological constant model, the Chaplygin gas interpolating these two models. The results are analyzed in terms of the sound velocity of the Chaplygin gas and the moment the Universe begins to accelerate. 相似文献
13.
A. L. Apanasenko A. V. Kuznichenko Yu. B. Govyadovskii V. G. Yakunin 《Journal of Applied Spectroscopy》1991,54(3):271-276
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 54, No. 3, pp. 438–444, March, 1991. 相似文献
14.
Yu. K. Voron'ko A. B. Kudryavtsev V. V. Osiko E. V. Sorokin 《Journal of Applied Spectroscopy》1991,55(4):953-957
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 55, No. 4, pp. 535–540, October, 1991. 相似文献
15.
A. R. Volkov B. V. Shul'gin T. I. Polupanova V. N. Lebedev A. A. Nagornyi V. L. Petrov Yu. F. Kargin 《Journal of Applied Spectroscopy》1991,54(6):585-590
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 54, No. 6, pp. 970–975, June, 1991. 相似文献
16.
17.
18.
B. Dubrulle F. Hersant 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,26(3):379-386
We generalize an analogy between rotating and stratified shear flows. This analogy is summarized in Table 1. We use this analogy
in the unstable case (centrifugally unstable flow vs. convection) to compute the torque in Taylor-Couette configuration, as a function of the Reynolds number. At low Reynolds
numbers, when most of the dissipation comes from the mean flow, we predict that the non-dimensional torque G = T/ν2
L, where L is the cylinder length, scales with Reynolds number R and gap width η, G = 1.46η3/2(1 - η)-7/4
R
3/2. At larger Reynolds number, velocity fluctuations become non-negligible in the dissipation. In these regimes, there is no
exact power law dependence the torque versus Reynolds. Instead, we obtain logarithmic corrections to the classical ultra-hard (exponent 2) regimes: G = 0.50
. These predictions are found to be in excellent agreement with avail-able experimental data. Predictions for scaling of velocity
fluctuations are also provided.
Received 7 June 2001 and Received in final form 7 December 2001 相似文献
19.
Electrical resistivity of U3Tein4, U2Te3 (cubic) and UTe3 has been measured over temperature range 4.2–300 K. The two former compounds appear to be semimetallic conductors while the last one has semiconducting character. The results are discussed in the terms of available magnetic data. 相似文献
20.