全文获取类型
收费全文 | 235720篇 |
免费 | 2712篇 |
国内免费 | 847篇 |
专业分类
化学 | 124159篇 |
晶体学 | 3581篇 |
力学 | 9922篇 |
综合类 | 6篇 |
数学 | 28242篇 |
物理学 | 73369篇 |
出版年
2021年 | 2040篇 |
2020年 | 2353篇 |
2019年 | 2562篇 |
2018年 | 3078篇 |
2017年 | 2954篇 |
2016年 | 4630篇 |
2015年 | 3056篇 |
2014年 | 4548篇 |
2013年 | 10663篇 |
2012年 | 9177篇 |
2011年 | 10904篇 |
2010年 | 7252篇 |
2009年 | 6992篇 |
2008年 | 9948篇 |
2007年 | 9903篇 |
2006年 | 9573篇 |
2005年 | 8642篇 |
2004年 | 7892篇 |
2003年 | 6889篇 |
2002年 | 6660篇 |
2001年 | 6867篇 |
2000年 | 5380篇 |
1999年 | 4168篇 |
1998年 | 3405篇 |
1997年 | 3425篇 |
1996年 | 3195篇 |
1995年 | 2901篇 |
1994年 | 2794篇 |
1993年 | 2646篇 |
1992年 | 2972篇 |
1991年 | 2935篇 |
1990年 | 2834篇 |
1989年 | 2592篇 |
1988年 | 2651篇 |
1987年 | 2655篇 |
1986年 | 2449篇 |
1985年 | 3304篇 |
1984年 | 3522篇 |
1983年 | 2897篇 |
1982年 | 3119篇 |
1981年 | 3038篇 |
1980年 | 2900篇 |
1979年 | 2953篇 |
1978年 | 3037篇 |
1977年 | 3026篇 |
1976年 | 3083篇 |
1975年 | 2845篇 |
1974年 | 2787篇 |
1973年 | 2890篇 |
1972年 | 1844篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Summary We present the preliminary results of a time-dependent simulation, with the Smoothed-Particle Hydrodynamics tecnique, of the
accretion of gas onto Schwartzschild black holes. The flow should exibit a stable shock for the parameters chosen. In the
case of 1D axisymmetric simulations, we find that the predicted inner shock position is unstable. For 2D axisymmetric simulations,
in the light of the first runs, we argue that in this case shocks may be a more common result. 相似文献
992.
M. I. Dykman D. G. Luchinsky R. Mannella P. V. E. McClintock N. D. Stein N. G. Stocks 《Il Nuovo Cimento D》1995,17(7-8):661-683
Summary We outline the historical development of stochastic resonance (SR), a phenomenon in which the signal and/or the signal-to-noise
ratio in a nonlinear system increase with increasing intensity of noise. We discuss basic theoretical ideas explaining and
describing SR, and we review some revealing experimental data that place SR within the wider context of statistical physics.
We emphasize the close relationship of SR to some effects that are well known in condensed-matter physics.
Paper presented at the International Workshop ?Fluctuations in Physics and Biology: Stochastic Resonance, Signal Processing
and Related Phenomena?, Elba, 5–10 June 1994. 相似文献
993.
L. D. Olivier W. A. Richter J. A. Stander J. W. Koen 《Zeitschrift für Physik A Hadrons and Nuclei》1993,347(2):99-108
Levels up to 9.3 MeV excitation in22Ne were studied with the19 F(α, pγ) 22Ne reaction atE α = 12 MeV. Level energies, branching ratios, mean lifetimes, spins and mixing ratios were obtained for a number of levels. Relevant results are compared with many-particle shell-model calculations. 相似文献
994.
Prof. Ing. A. Sopková D.Sc. 《Journal of Thermal Analysis and Calorimetry》1996,46(2):335-336
995.
996.
An analogue of the differential calculus associated with a unitary solution of the quantum Young-Baxter equation is constructed.
An example of a ring sheaf is considered in which local solutions of the Young-Baxter quantum equation are defined but there
is no global section. Bibliography: 13 titles.
Translated fromZapiski Nauchnykh Seminarov POMI, Vol. 199, 1992, pp. 51–70.
Translated by I. A. Izergina. 相似文献
997.
998.
A. L'Esprance J. Nicolas D.K. Wilson D.W. Thomson Y. Gabillet G. Daigle 《Applied Acoustics》1993,40(4)
This paper presents a set of acoustical and meteorological data from an outdoor sound propagation experiment. This experiment was done in a farm field near Rock Springs, Pennsylvania, on 7 July 1990. Meteorological and acoustical measurements were recorded simultaneously during six different times in the day. The meteorological measurements permitted determination of the sound speed profiles during each of the measurement sessions, using a method based on surface-layer similarity scaling. The acoustical measurements allowed precise determination of the relative sound pressure levels for a frequency range up to 3150 Hz at six different distances (66, 88, 125, 175, 250 and 350 m). The results show atmospheric conditions have an important effect on sound propagation. At medium and high frequencies, variations of the relative SPL have been measured at distances as short as 62 m. These effects increased with the distances so that variations as great as 30 dB have been measured during that day. Comparisons with the fast field program predictions are also presented, and amply demonstrate the accuracies of this model, especially for the downward refraction cases. 相似文献
999.
Electromagnetic fields are often used industrially to controlthe flow of liquid metal, and in particular this review is concernedwth applications of alternating fields. An alternating fieldinduces eddy currents in liquid metal which interact with thefield to give a Lorentz body force which is generally rotationaland which must therefore drive fluid motion. We derive generalexpressions for the Lorentz force, showing that it consistsof both steady and oscillatory components. The flow in a circularcylinder due to a rotating field is discussed in detail, sincethis problem is simple to analyse and illustrates several importantgeneral principles. In the high-frequency limit, the field isconfined to a narrow layer on the surface of the conductor,and we derive approximate methods for calculating the surfacemagnetic pressure andthe induced flow. We also examine the otherextreme of slowly alternating fields. As each problem is studied,we discuss practical applications. 相似文献
1000.
P. Tekely V. G rardy P. Palmas D. Canet A. Retournard 《Solid state nuclear magnetic resonance》1995,4(6):361-367
A simple modification of the standard cross-polarization method designed for quenching the proton T1ρ dependence when studying polarization transfer is presented. It is demonstrated that by using this simple procedure, new and subtle details of cross-polarization dynamics, previously hidden by the T1ρ(1H) effect, can be observed in dipolar-coupled spin systems. 相似文献