全文获取类型
收费全文 | 457199篇 |
免费 | 5256篇 |
国内免费 | 1074篇 |
专业分类
化学 | 247113篇 |
晶体学 | 7268篇 |
力学 | 19480篇 |
综合类 | 19篇 |
数学 | 51662篇 |
物理学 | 137987篇 |
出版年
2020年 | 3854篇 |
2019年 | 4112篇 |
2018年 | 5254篇 |
2017年 | 5294篇 |
2016年 | 8076篇 |
2015年 | 5081篇 |
2014年 | 7855篇 |
2013年 | 19825篇 |
2012年 | 14559篇 |
2011年 | 17799篇 |
2010年 | 12435篇 |
2009年 | 12134篇 |
2008年 | 16434篇 |
2007年 | 16435篇 |
2006年 | 15316篇 |
2005年 | 13793篇 |
2004年 | 12594篇 |
2003年 | 11473篇 |
2002年 | 11133篇 |
2001年 | 12685篇 |
2000年 | 9836篇 |
1999年 | 7530篇 |
1998年 | 6329篇 |
1997年 | 6267篇 |
1996年 | 6032篇 |
1995年 | 5632篇 |
1994年 | 5703篇 |
1993年 | 5370篇 |
1992年 | 6312篇 |
1991年 | 6124篇 |
1990年 | 6036篇 |
1989年 | 5867篇 |
1988年 | 6038篇 |
1987年 | 5911篇 |
1986年 | 5587篇 |
1985年 | 7393篇 |
1984年 | 7606篇 |
1983年 | 6265篇 |
1982年 | 6440篇 |
1981年 | 6443篇 |
1980年 | 6226篇 |
1979年 | 6444篇 |
1978年 | 6771篇 |
1977年 | 6730篇 |
1976年 | 6618篇 |
1975年 | 6091篇 |
1974年 | 6079篇 |
1973年 | 6204篇 |
1972年 | 4316篇 |
1968年 | 3667篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
971.
We propose an effective method of numerical determination of the gradient vector and the Hessian matrix of a quadratic quality
criterion in parametric optimization of continuous-discrete stochastic dynamic control systems based on the application of
adjoint equations.
Translated fromDinamicheskie Sistemy, No. 13, 1994, pp. 20–25. 相似文献
972.
G. Carelli N. Ioli A. Messina A. Moretti S. Schepis F. Strumia 《International Journal of Infrared and Millimeter Waves》1998,19(9):1191-1199
We measured the dependence of the reflectivity of InSb crystals upon temperature in the submillimeter region using monochromatic radiation from an optically pumped far infrared (FIR) laser. The measures allowed us to determine the value of the electron effective mass at low temperatures with radiations of different frequencies. Our measurements extend the results obtained recently on pure crystals with magneto-optical methods to the low temperatures region where only old measures were available. 相似文献
973.
T Akamatsu D Wang K Nakamura K Wang 《The Journal of the Acoustical Society of America》1998,104(4):2511-2516
The interclick intervals of captive dolphins are known to be longer than the two-way transit time between the dolphin and a target. In the present study, the interclick intervals of free-ranging baiji, finless porpoises, and bottlenose dolphins in the wild and in captivity were compared. The click intervals in open waters ranged up to 100-200 ms, whereas the click intervals in captivity were in the order of 4-28 ms. Echolocation of free-ranging dolphins appears to adapt to various distance in navigation or ranging, sometimes up to 140 m. Additionally, the difference of waveform characteristics of clicks between species was recognized in the frequency of maximum energy and the click duration. 相似文献
974.
DAndrea A. Tomassini N. Ferrari L. Righini M. Selci S. Bruni M. R. Simeoni G. 《Il Nuovo Cimento D》1995,17(11):1423-1427
Il Nuovo Cimento D - Normalized reflection spectra in GaInAs/GaAs quantum wells are shown for two sets of samples with different alloy concentration (x=9% and 18.5%) and well thickness ranging from... 相似文献
975.
976.
977.
V. G. Osmolovski 《Journal of Mathematical Sciences》1997,84(1):898-910
An existence theorem for the variational problem for the two-phase medium energy functional is proved. Dependence of the solution
on the surface tension coefficient and on the temperature is investigated. Bibliography: 7 titles.
Dedicated to V. A. Solonnikov on his sixtieth anniversary
Translated fromZapiski Nauchnykh Seminarov POMI, Vol. 213, 1994, pp. 131–150.
Translated by S. Yu. Pilyugin. 相似文献
978.
An iterative method from the class of completely implicit methods (CIM) is proposed for solving the equation of the velocity
potential of elliptical-hyperbolic type. The advantage of the proposed method compared to other CIM schemes is demonstrated
in application to mixed perfect gas flows in a nozzle of a given shape. Accuracy issues, rate of convergence, and various
techniques of ensuring stability in the hyperbolic region are discussed.
Translated from Chislennye Metody v Matematicheskoi Fizike, Published by Moscow University, Moscow, 1996, pp. 39–51. 相似文献
979.
980.