全文获取类型
收费全文 | 329678篇 |
免费 | 3441篇 |
国内免费 | 932篇 |
专业分类
化学 | 164826篇 |
晶体学 | 5374篇 |
力学 | 15535篇 |
综合类 | 8篇 |
数学 | 38472篇 |
物理学 | 109836篇 |
出版年
2021年 | 3129篇 |
2020年 | 3330篇 |
2019年 | 3763篇 |
2018年 | 5198篇 |
2017年 | 5439篇 |
2016年 | 7371篇 |
2015年 | 4139篇 |
2014年 | 7030篇 |
2013年 | 15907篇 |
2012年 | 12380篇 |
2011年 | 14828篇 |
2010年 | 11015篇 |
2009年 | 10921篇 |
2008年 | 13235篇 |
2007年 | 13198篇 |
2006年 | 12140篇 |
2005年 | 10522篇 |
2004年 | 9836篇 |
2003年 | 8693篇 |
2002年 | 8673篇 |
2001年 | 10396篇 |
2000年 | 7657篇 |
1999年 | 5973篇 |
1998年 | 4979篇 |
1997年 | 4813篇 |
1996年 | 4484篇 |
1995年 | 3866篇 |
1994年 | 3825篇 |
1993年 | 3704篇 |
1992年 | 4096篇 |
1991年 | 4310篇 |
1990年 | 4098篇 |
1989年 | 4010篇 |
1988年 | 3781篇 |
1987年 | 3920篇 |
1986年 | 3684篇 |
1985年 | 4631篇 |
1984年 | 4688篇 |
1983年 | 3885篇 |
1982年 | 3978篇 |
1981年 | 3698篇 |
1980年 | 3649篇 |
1979年 | 3914篇 |
1978年 | 3903篇 |
1977年 | 3911篇 |
1976年 | 3883篇 |
1975年 | 3679篇 |
1974年 | 3623篇 |
1973年 | 3654篇 |
1972年 | 2605篇 |
排序方式: 共有10000条查询结果,搜索用时 14 毫秒
911.
912.
S. A. Salem 《Journal of Applied Mathematics and Computing》2006,21(1-2):331-355
We study a model procedure to solve the incompressible Navier-Stokes equations on the flow inside contraction geometry. The governing equations are expressed in the primitive variable formulation. A rectangular computational plane is arises by elliptic grid generation technique. The numerical solution is based on a technique of automatic numerical generation of a curvilinear coordinate system. By transformed the governing equation into computational plane. The time dependent momentum equations are solved explicitly for the velocity field using the explicit marching procedure, the continuity equation is applied at each grid point in the solution of pressure equation, while the successive over relaxation (SOR) method is used for the Neumann problem for pressure. We will apply the technique on several irregular-shape. 相似文献
913.
Y. Qu J.X. Zhang A. Uddin C.Y. Liu S. Yuan M.C.Y. Chan B. Bo G. Liu H. Jiang 《Applied Physics A: Materials Science & Processing》2006,82(2):305-308
Ridge-waveguide InGaAsN triple-quantum-well strain-compensated lasers grown by metal organic chemical vapor deposition were fabricated with pulsed anodic oxidation. The laser’s output power reached 145 mW in continuous-wave mode at room temperature for a 4-?m -stripe-width laser. Continuous-wave single longitudinal mode operation was maintained at a high injection current level with a wavelength of 1287.3 nm at room temperature. Single longitudinal mode operation at 1317.2 nm was achieved at twice the threshold current at 100 °C. The band gap of InGaAsN in the quantum wells at different temperatures was calculated and compared to the measured temperature-dependent laser wavelength. 相似文献
914.
S. P. Popov 《Computational Mathematics and Mathematical Physics》2006,46(6):983-994
Numerical solutions to three systems of integrable evolutionary equations from the Toda lattice hierarchy are analyzed. These are the classical Toda lattice, the second local dispersive flow, and the second extended dispersive flow. Special attention is given to the properties of soliton solutions. For the equations of the second local flow, two types of solitons interacting in a special manner are found. Solutions corresponding to various initial data are qualitatively outlined. 相似文献
915.
S. V. Ivanov V. V. Trachevskii O. S. Titova L. A. Zozulya 《Russian Journal of Applied Chemistry》2006,79(10):1712-1714
Experimental data demonstrate that a study of accelerated aging can enable prognostication of the working capacity and storage life of polymeric formulations used in aircraft components on the basis of changes in thermogravimetric constants of these polymeric formulations. 相似文献
916.
A. A. Lamberov E. V. Dement’eva Kh. Kh. Gil’manov S. R. Egorova N. V. Romanova 《Russian Journal of Applied Chemistry》2006,79(9):1453-1457
The effect of the paste molding pressure on the physicomechanical and texture characteristics of catalysts was studied. An indirect criterion is suggested to evaluate the molding pressure in industrial extruders, whose optimal value ensures good physicomechanical properties of the catalysts and kinetic control over the catalyzed reaction. The results obtained were verified in paste molding on various industrial extruders, and this enabled the optimal choice of the molding equipment. 相似文献
917.
918.
Sherif Yehia C. Mitros Sanjeev Kumar S. Jha Glenn M. Julian R. A. Dunlap 《Hyperfine Interactions》1987,34(1-4):415-418
The systematics of hyperfine magnetic fields at sp impurities on the Z-sites in Co based Heusler alloys are investigated. New TDPAC measurements of Cd hyperfine fields are reported. 相似文献
919.
A high-performance liquid chromatographic procedure was developed for the quantitation of homoharringtonine in plasma. Harringtonine was used as an internal standard, and 1 ml of sample was required. The single-step extraction with dichloromethane resulted in almost 100% recovery for homoharringtonine and harringtonine. Analysis was performed on a reversed-phase CN column with amperometric detection. Chromatography was completed in 12 min. At an oxidation potential of +1.0 V, the detection limit was 1 ng/ml at a signal-to-noise ratio of 2. The mean analytical recovery for homoharringtonine was 99.5%. The within-run precision and between-run precision were both less than 11%. The method is equally applicable for plasma or serum, and it has been demonstrated to be applicable for study of the pharmacokinetics of homoharringtonine in patients suffering from acute non-lymphocytic leukaemia. 相似文献
920.