全文获取类型
收费全文 | 401123篇 |
免费 | 2476篇 |
国内免费 | 819篇 |
专业分类
化学 | 192849篇 |
晶体学 | 6265篇 |
力学 | 21625篇 |
综合类 | 13篇 |
数学 | 55994篇 |
物理学 | 127672篇 |
出版年
2021年 | 2777篇 |
2020年 | 2929篇 |
2019年 | 3513篇 |
2018年 | 11687篇 |
2017年 | 12242篇 |
2016年 | 9992篇 |
2015年 | 4191篇 |
2014年 | 6257篇 |
2013年 | 13790篇 |
2012年 | 14265篇 |
2011年 | 22884篇 |
2010年 | 15431篇 |
2009年 | 15685篇 |
2008年 | 20719篇 |
2007年 | 23347篇 |
2006年 | 11266篇 |
2005年 | 15000篇 |
2004年 | 11887篇 |
2003年 | 11326篇 |
2002年 | 9624篇 |
2001年 | 10281篇 |
2000年 | 7788篇 |
1999年 | 5729篇 |
1998年 | 4520篇 |
1997年 | 4614篇 |
1996年 | 4438篇 |
1995年 | 3941篇 |
1994年 | 4028篇 |
1993年 | 3754篇 |
1992年 | 4438篇 |
1991年 | 4650篇 |
1990年 | 4387篇 |
1989年 | 4442篇 |
1988年 | 4313篇 |
1987年 | 4327篇 |
1986年 | 4044篇 |
1985年 | 5092篇 |
1984年 | 5203篇 |
1983年 | 4279篇 |
1982年 | 4241篇 |
1981年 | 4069篇 |
1980年 | 3884篇 |
1979年 | 4484篇 |
1978年 | 4558篇 |
1977年 | 4597篇 |
1976年 | 4536篇 |
1975年 | 4252篇 |
1974年 | 4202篇 |
1973年 | 4341篇 |
1972年 | 3131篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
981.
982.
The equation of sound propagation in an unstable medium produced by the presence of supersaturated water vapor in it, which
can appear in a hurricane area, is derived. This equation takes into account the effects of sound velocity dispersion, amplification,
damping, and nonlinear effects. Some solutions to this equation are presented, illustrating the specific features of sound
propagation in an unstable medium.
Published in Akusticheskiĭ Zhurnal, 2007, Vol. 53, No. 3, pp. 477–480. 相似文献
983.
H. Maekawa K. Tsubakihara A. Ohnishi 《The European Physical Journal A - Hadrons and Nuclei》2007,33(3):269-272
We study the hyperon-nucleus potential with distorted-wave impulse wave approximation (DWIA) using the Green's function method.
In order to include the nucleon and hyperon potential effects in Fermi averaging, we introduce the local optimal momentum
approximation of target nucleons. We can describe the quasi-free Λ , Σ and Ξ production spectra in a better way than in the
standard Fermi-averaged t -matrix treatments. 相似文献
984.
985.
A new method of using time-averaged digital speckle pattern interferometry for the quantitative measurement of vibration amplitude was developed. Signal processing techniques especially the Hilbert transformation for quantitative evaluation of the Bessel fringes obtained in time-averaged digital speckle pattern interferometry were explored. The quadrature signal after Hilbert transformation is equivalent to a 90° phase-shifted interferogram for a monotonically increasing or decreasing phase function. An algorithm was developed for Bessel fringe contrast enhancement and phase extraction. The techniques were tested numerically and experimentally. Sub-fringe quantification of the time-averaged vibration fringes is realised with the proposed method. Compared with the commonly used phase shift method which requires a minimum of two images for image processing, this method requires only one fringe pattern for data extraction. 相似文献
986.
Polycarbonates and copolycarbonates based on BPSi and BPA were easily made using the standard interfacial technique. Molecular weight and NMR data indicate that up to 4 mol % of the BPSi decomposes during polymerization via a base-catalyzed rearrangement of BPSi to arylsiloxanes. Oxygen index studies show an increased flame resistance with increasing BPSi monomer content. DSC measurements show a decrease in glass transition with BPSi monomer concentration while TGA shows an increase in char residue with BPSi monomer content. In addition, TGA indicates no change in either thermal or thermooxidative stability with the relative BPSi/BPA concentrations. Outdoor weathering of BPSi PC and BPA PC films indicates that BPSi PC is ca. 5 times more weathering resistant than BPA PC. This latter result can be attributed to a combination of BPSi PC's lower UV absorptivity, higher water repellency, and lower likelihood for side chain photooxidation. © 1993 John Wiley & Sons, Inc. 相似文献
987.
Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, p. 2899, December, 1991. 相似文献
988.
989.
P. Schuurmans J. Wouters P. De Moor N. Severijns W. Vanderpoorten J. Vanhaverbeke L. Vanneste 《Hyperfine Interactions》1992,75(1-4):423-430
Anisotropic α-emission from nuclei in the decay chain from223Ra to207Tl has been observed using low temperature nuclear orientation in combination with high resolution α-detection at 4.2 K. Information
on partial wave amplitudes as well as hyperfine interactions has been extracted. 相似文献
990.
It is shown that the dephasing which suppresses the weak localization correction to the conductivity has the same physical origin than pair-breaking in superconductors and thus-following de Gennes-may be expressed in terms of the correlation function of the operator for time reversal. 相似文献