全文获取类型
收费全文 | 3633篇 |
免费 | 430篇 |
国内免费 | 250篇 |
专业分类
化学 | 2427篇 |
晶体学 | 14篇 |
力学 | 160篇 |
综合类 | 22篇 |
数学 | 507篇 |
物理学 | 1183篇 |
出版年
2024年 | 13篇 |
2023年 | 66篇 |
2022年 | 87篇 |
2021年 | 100篇 |
2020年 | 100篇 |
2019年 | 92篇 |
2018年 | 75篇 |
2017年 | 62篇 |
2016年 | 140篇 |
2015年 | 118篇 |
2014年 | 167篇 |
2013年 | 253篇 |
2012年 | 322篇 |
2011年 | 306篇 |
2010年 | 218篇 |
2009年 | 179篇 |
2008年 | 246篇 |
2007年 | 194篇 |
2006年 | 183篇 |
2005年 | 170篇 |
2004年 | 143篇 |
2003年 | 149篇 |
2002年 | 122篇 |
2001年 | 97篇 |
2000年 | 72篇 |
1999年 | 65篇 |
1998年 | 47篇 |
1997年 | 58篇 |
1996年 | 62篇 |
1995年 | 48篇 |
1994年 | 43篇 |
1993年 | 37篇 |
1992年 | 26篇 |
1991年 | 19篇 |
1990年 | 25篇 |
1989年 | 16篇 |
1988年 | 15篇 |
1987年 | 14篇 |
1986年 | 14篇 |
1985年 | 18篇 |
1984年 | 22篇 |
1983年 | 13篇 |
1982年 | 13篇 |
1981年 | 8篇 |
1980年 | 14篇 |
1979年 | 14篇 |
1978年 | 7篇 |
1976年 | 8篇 |
1975年 | 5篇 |
1974年 | 5篇 |
排序方式: 共有4313条查询结果,搜索用时 15 毫秒
991.
992.
993.
994.
Huang Y Tang C Wang S Lu Y Shen W Yang J Chen J Lin R Cui S Xiao H Qu S Lai X Shan B 《BMC neuroscience》2012,13(1):75
ABSTRACT: BACKGROUND: Acupuncture has been applied to aid in the recovery of post-stroke patients, but its mechanism is unclear. This study aims to analyze the relationship between acupuncture and glucose metabolism in cerebral functional regions in post-stroke patients using 18 FDG PETCT techniques. Forty-three ischemic stroke patients were randomly divided into 5 groups: the Waiguan (TE5) needling group, the TE5 sham needling group, the sham point needling group, the sham point sham needling group and the non-needling group. Cerebral functional images of all patients were then acquired using PET-CT scans and processed by SPM2 software. RESULTS: Compared with the non-needling group, sham needling at TE5 and needling/sham needling at the sham point did not activate cerebral areas. However, needling at TE5 resulted in the activation of Brodmann Area (BA) 30. Needling/sham needling at TE5 and needling at the sham point did not deactivate any cerebral areas, whereas sham needling at the sham point led to deactivation in BA6. Compared with sham needling at TE5, needling at TE5 activated BA13, 19 and 47 and did not deactivate any areas. Compared with needling at the sham point, needling at TE5 had no associated activation but a deactivating effect on BA9. CONCLUSION: Needling at TE5 had a regulating effect on cerebral functional areas shown by PET-CT, and this may relate to its impact on the recovery of post-stroke patients. 相似文献
995.
996.
Rui Chen D. F. Qi Y. J. Ruan S. W. Pan S. Y. Chen Sheng Xie Cheng Li H. K. Lai H. D. Sun 《Applied Physics A: Materials Science & Processing》2012,106(1):251-255
The investigations of silicon-rich silicon nitride film grown by plasma-enhanced chemical vapor deposition and then annealed by excimer laser have been carried out systematically. The surface roughness and the crystallization of the films have significantly been improved after the excimer laser annealing. The samples demonstrate visible photoluminescence emission under optical excitation at room temperature. It is found that the emission peak energy as well as emission intensity changes with laser annealing conditions, and the relevant mechanism is discussed in detail. Our investigation exhibits the size controllability of silicon nanocrystals embedded in the silicon nitride film, which implies promising applications in optoelectronic devices such as light-emitting diodes and solar cells. 相似文献
997.
998.
999.
Conventional least‐squares finite element methods (LSFEMs) for incompressible flows conserve mass only approximately. For some problems, mass loss levels are large and result in unphysical solutions. In this paper we formulate a new, locally conservative LSFEM for the Stokes equations wherein a discrete velocity field is computed that is point‐wise divergence free on each element. The central idea is to allow discontinuous velocity approximations and then to define the velocity field on each element using a local stream‐function. The effect of the new LSFEM approach on improved local and global mass conservation is compared with a conventional LSFEM for the Stokes equations employing standard C0 Lagrangian elements. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
1000.
This paper presents a mathematical study for the Bragg scattering of water waves propagating over a series of rectangular poro-elastic submerged breakwaters. Based on the linear wave theory and the improved Biot's theory of poro-elastic media with suitable matching conditions, an analytical solution was obtained as a function of elasticity, permeability and geometry of the submerged breakwaters. Experiments were also conducted in a wave flume to verify the present analytical study. In addition, the Bragg resonances for different influence parameters were studied. Satisfactory agreement between the theoretical predictions and the laboratory observations demonstrates the applicability of the present analytical result. 相似文献