全文获取类型
收费全文 | 91918篇 |
免费 | 10521篇 |
国内免费 | 6577篇 |
专业分类
化学 | 26211篇 |
晶体学 | 665篇 |
力学 | 5292篇 |
综合类 | 765篇 |
数学 | 12825篇 |
物理学 | 33093篇 |
无线电 | 30165篇 |
出版年
2024年 | 297篇 |
2023年 | 1170篇 |
2022年 | 2055篇 |
2021年 | 2604篇 |
2020年 | 2707篇 |
2019年 | 2155篇 |
2018年 | 1930篇 |
2017年 | 2722篇 |
2016年 | 3235篇 |
2015年 | 2897篇 |
2014年 | 4680篇 |
2013年 | 6191篇 |
2012年 | 5079篇 |
2011年 | 5266篇 |
2010年 | 4251篇 |
2009年 | 5270篇 |
2008年 | 5665篇 |
2007年 | 6207篇 |
2006年 | 5605篇 |
2005年 | 4581篇 |
2004年 | 4059篇 |
2003年 | 4062篇 |
2002年 | 4120篇 |
2001年 | 3144篇 |
2000年 | 2897篇 |
1999年 | 2350篇 |
1998年 | 2197篇 |
1997年 | 1420篇 |
1996年 | 1333篇 |
1995年 | 1151篇 |
1994年 | 1175篇 |
1993年 | 858篇 |
1992年 | 912篇 |
1991年 | 661篇 |
1990年 | 596篇 |
1989年 | 477篇 |
1988年 | 375篇 |
1987年 | 333篇 |
1986年 | 306篇 |
1985年 | 279篇 |
1984年 | 266篇 |
1983年 | 164篇 |
1982年 | 223篇 |
1981年 | 211篇 |
1980年 | 145篇 |
1979年 | 168篇 |
1978年 | 140篇 |
1977年 | 127篇 |
1976年 | 81篇 |
1973年 | 60篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
A finite element solution of the Navier-Stokes equations for steady flow under the magnetic effect through a double-branched two-dimensional section of a three-dimensional model of the canine aorta is discussed. The numerical scheme involves transforming the physical co-ordinates to a curvilinear boundary-fitted co-ordinate system. The shear stress at the wall is calculated for a Reynolds number of 1000 with the branch-to-main aortic flow rate ratio as a parameter. The results are compared with earlier works involving experimental data and found to be in reasonable qualitative agreement. The steady flow, shear stress and branch flow under the effect of a magnetic field have been discussed in detail. 相似文献
102.
Piotr Biler 《Reports on Mathematical Physics》2003,52(2):205-225
We study asymptotic properties of solutions to an extension to arbitrary dimensions of the astrophysical model proposed by Chavanis et al. to explain phenomena of gravitational collapse in clouds of self-gravitating particles. In particular, we show that in the two-dimensional case the solutions can be continued to global ones, while in three space dimensions large data of negative energy blow up in a finite time. Relations between isothermal, Streater's energy-transport and the present models are also studied. 相似文献
103.
Jilly James Chidambaram Ramalechume Asit Baran Mandal 《Journal of Polymer Science.Polymer Physics》2007,45(17):2410-2420
The shape, size, aggregation, hydration, and correlation times of water insoluble PEO‐PPO‐PEO triblock copolymer micelles with sodium dodecylsulfate (SDS) micelles were investigated using transport studies and dynamic light scattering technique. From the conductance of micellar solutions of the polymer in 25 mM SDS and 5 mM NaCl, the hydration of polymer micelles were determined using the principle of obstruction of electrolyte migration by the polymer. The asymmetry of the micellar particles of polymer and polymer‐SDS mixed micellar systems in 5 mM NaCl and their average axial ratios were calculated using intrinsic viscosity and hydration data obeying Simha–Einstein equation. Hydration number and micellar sizes were variable with temperature. The shape of the polymer micelles has been ellipsoidal rather than spherical. The micellar volume, hydrodynamic radius, radius of gyration, diffusional coefficients as well as translational, rotational and effective correlation times have been calculated from the absolute values of the axes. The partial molal volume of polymer micelles has also been determined and its comparison with the molar volume of pure polymer suggested a volume contraction due to immobilization of the water phase by the hydrophilic head groups of the polymer. The thermodynamic activation parameters for viscous flow favor a more ordered water structure around polymer micelles at higher temperatures. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2410–2420, 2007 相似文献
104.
105.
介绍了一种非接触式用于测量少子寿命的微波反射法,并与通常的光电导衰退法进行了比较。 相似文献
106.
107.
为解决高等师范院校物理专业学生的知识结构和实际能力与社会需要明显不相适应的矛盾,我们对四年制物理专业的课程结构进行了全面改革。改革后,毕业生不仅能胜任普通中学或职业中学(职业中专)的教学,而且有能力参与厂矿企业的技术工作,具有更广泛的适应性和更强的竞争力。 相似文献
108.
109.
片式阻容元件的现状和发展方向 总被引:1,自引:1,他引:0
在国外的片式元器件(SMD)中,片式阻容元件发展最快,主要表现为片式化率迅速上升,尺寸越来越小,性能越来越好,包装形式多样化和生产管理不断改进。本文综述了国外阻容元件在这些方面的进展,指出了我国的差距,提出了我国如何发展的措施。 相似文献
110.
Electric fields of the anions, cations and neutral forms of 2-aminopurine and 6-thioguanine have been mapped. Certain important
features of the maps are similar to those found earlier in the neutral and ionic forms of adenine and guanine. The computed
electric field patterns satisfactorily explain reactive sites and biological activity of the molecules. 相似文献