全文获取类型
收费全文 | 147095篇 |
免费 | 1472篇 |
国内免费 | 394篇 |
专业分类
化学 | 80371篇 |
晶体学 | 2391篇 |
力学 | 6067篇 |
综合类 | 3篇 |
数学 | 13609篇 |
物理学 | 46520篇 |
出版年
2021年 | 1036篇 |
2020年 | 1188篇 |
2019年 | 1256篇 |
2018年 | 1642篇 |
2017年 | 1695篇 |
2016年 | 2544篇 |
2015年 | 1568篇 |
2014年 | 2356篇 |
2013年 | 6046篇 |
2012年 | 4853篇 |
2011年 | 5952篇 |
2010年 | 4189篇 |
2009年 | 4214篇 |
2008年 | 5734篇 |
2007年 | 5518篇 |
2006年 | 5390篇 |
2005年 | 4953篇 |
2004年 | 4459篇 |
2003年 | 4120篇 |
2002年 | 4016篇 |
2001年 | 5548篇 |
2000年 | 3974篇 |
1999年 | 3076篇 |
1998年 | 2112篇 |
1997年 | 2208篇 |
1996年 | 2073篇 |
1995年 | 1918篇 |
1994年 | 1915篇 |
1993年 | 1729篇 |
1992年 | 2216篇 |
1991年 | 2301篇 |
1990年 | 2139篇 |
1989年 | 2104篇 |
1988年 | 2080篇 |
1987年 | 2089篇 |
1986年 | 1913篇 |
1985年 | 2377篇 |
1984年 | 2392篇 |
1983年 | 1915篇 |
1982年 | 1918篇 |
1981年 | 1752篇 |
1980年 | 1738篇 |
1979年 | 2028篇 |
1978年 | 2103篇 |
1977年 | 2047篇 |
1976年 | 1977篇 |
1975年 | 1859篇 |
1974年 | 1843篇 |
1973年 | 1876篇 |
1972年 | 1235篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
This study addresses the problem of the automatic flow regime identification in two-phase flows in pipes. A novel wavelet transform-based approach is proposed and validated using time series of differential pressure fluctuations. The experimental data on the differential pressure measured in a vertically installed Venturi meter for air-water flow were analyzed and found to be appropriate for flow regime identification. The wavelet spectrum of the measured signal is shown to characterize the flow patterns completely, and the vector of the wavelet variances is proposed as the characteristic vector for use in an on-line flow regime identification system. 相似文献
102.
103.
P Vincent A BrioudeC Journet S RabasteS.T Purcell J Le BrusqJ.C Plenet 《Journal of Non》2002,311(2):130-137
We report here the successful inclusion of carbon nanotubes (CNs) into a TiO2 matrix prepared by a sol-gel method. The presence of CNs in the sol-gel matrix and the structure of the film were analyzed principally by transmission electron microscopy. Complementary information about the behavior of embedded carbon nanotubes versus heat treatment and ion irradiation were obtained by X-ray photoelectron spectroscopy. The elaboration of an inorganic matrix containing embedded carbon nanotubes leads to a new nanocomposite. The possible applications of this nanocomposite are discussed. 相似文献
104.
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
105.
Richard T. Hammond 《General Relativity and Gravitation》1991,23(9):973-980
It is shown that torsion can be built from two independent vector fields, and that these vector fields obey, for the Lagrangian chosen, the equations of electromagnetism with magnetic charge from the two photon formalism. The equation of motion follows from the Bianchi identity ofU
4 spacetime, and finally the interpretation of these fields is discussed. 相似文献
106.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 51, No. 2, pp. 212–217, August, 1989. 相似文献
107.
Palle E. T. Jorgensen 《Mathematische Zeitschrift》1989,201(4):455-476
Work supported in part by the NSF 相似文献
108.
The Cauchy Problem for the relativistic Vlasov-Maxwell equations is studied in three space dimensions. It is assumed that the initial data satisfy the required constraints and have compact support. If in addition the data have sufficiently smallC
2 norm, then a uniqueC
1 solution to this system is shown to exist on all of spacetime.Research supported in part by NSF DMS 85-20662 and NSF DMS 84-20957 相似文献
109.
T. Kumita Y. Kamiya M. Babzien I. Ben-Zvi K. Kusche I. V. Pavlishin I. V. Pogorelsky D. P. Siddons V. Yakimenko T. Hirose T. Omori J. Urakawa K. Yokoya D. Cline F. Zhou 《Laser Physics》2006,16(2):267-271
Thomson scattering of high-power laser and electron beams is a good test of electrodynamics in the high-field region. We demonstrated production of high-intensity X-rays in the head-on collision of a CO2 laser and 60-MeV electron beams at Brookhaven National Laboratory, Accelerator Test Facility. The energy of an X-ray photon was limited at 6.5 keV in the linear (lowest order) Thomson scattering, but the nonlinear (higher order) process produces higher energy X-rays. We measured the angular distribution of the high-energy X-rays and confirmed that it agrees with theoretical predictions. 相似文献
110.
General coordinate invariance and conformal invariance in nonrelativistic physics: Unitary Fermi gas
D.T. Son 《Annals of Physics》2006,321(1):197-224
We show that the Lagrangian for interacting nonrelativistic particles can be coupled to an external gauge field and metric tensor in a way that exhibits a nonrelativistic version of general coordinate invariance. We explore the consequences of this invariance on the example of the degenerate Fermi gas at infinite scattering length, where conformal invariance also plays an important role. We find the most general effective Lagrangian consistent with both general coordinate and conformal invariance to leading and next-to-leading orders in the momentum expansion. At the leading order the Lagrangian contains one phenomenological constant and reproduces the results of the Thomas-Fermi theory and superfluid hydrodynamics. At the next-to-leading order there are two additional constants. We express various physical quantities through these constants. 相似文献