全文获取类型
收费全文 | 612篇 |
免费 | 35篇 |
国内免费 | 7篇 |
专业分类
化学 | 383篇 |
晶体学 | 3篇 |
力学 | 71篇 |
数学 | 69篇 |
物理学 | 128篇 |
出版年
2024年 | 1篇 |
2023年 | 5篇 |
2022年 | 17篇 |
2021年 | 32篇 |
2020年 | 36篇 |
2019年 | 27篇 |
2018年 | 40篇 |
2017年 | 27篇 |
2016年 | 41篇 |
2015年 | 26篇 |
2014年 | 42篇 |
2013年 | 78篇 |
2012年 | 57篇 |
2011年 | 58篇 |
2010年 | 25篇 |
2009年 | 21篇 |
2008年 | 13篇 |
2007年 | 13篇 |
2006年 | 10篇 |
2005年 | 2篇 |
2004年 | 3篇 |
2003年 | 6篇 |
2002年 | 6篇 |
2001年 | 3篇 |
2000年 | 7篇 |
1999年 | 2篇 |
1998年 | 4篇 |
1997年 | 4篇 |
1996年 | 5篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1993年 | 9篇 |
1992年 | 1篇 |
1991年 | 4篇 |
1990年 | 2篇 |
1989年 | 3篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1977年 | 1篇 |
1953年 | 1篇 |
排序方式: 共有654条查询结果,搜索用时 31 毫秒
651.
Mahmoud R. Mahmoud Wael S.I. Abou‐Elmagd Hamed A. Derbala Mohamed H. Hekal 《中国化学》2011,29(7):1446-1450
Dimethyl homophthalate condensed with isatin to give the unexpected five membered lactone 3 rather than the half ester 1 and the δ‐lactone 2 . Treatment of compound 3 with excess hydrazine hydrate afforded phthalazinone carbohydrazide 4 which represents a novel method for the synthesis of phthalazinone derivatives. The carbohydrazide 4 upon treatment with carbon disulphide afforded 1,3,4‐oxadiazole derivative 5 , which reacted with ethylchloroacetate to give the S‐alkylated product 6 . The structure of compound 3 compared with 2 was discussed using hyperchem professional (7) AM1 calculations, X‐ray single crystal structure and complete spectral data. 相似文献
652.
The nonlinear dynamical characteristics of a doubly curved shallow microshell are investigated thoroughly. A consistent nonlinear model for the microshell is developed on the basis of the modified couple stress theory (MCST) in an orthogonal curvilinear coordinate system. In particular, based on Donnell’s nonlinear theory, the expressions for the strain and the symmetric rotation gradient tensors are obtained in the framework of MCST, which are then used to derive the potential energy of the microshell. The analytical geometrically nonlinear equations of motion of the doubly microshell are obtained for in-plane displacements as well as the out-of-plane one. These equations of partial differential type are reduced to a large set of ordinary differential equations making use of a two-dimensional Galerkin scheme. Extensive numerical simulations are conducted to obtain the nonlinear resonant response of the system for various principal radii of curvature and to examine the effect of modal interactions and the length-scale parameter. 相似文献
653.
The effect of different doses of γ‐rays on the behavior of the critical current density, Jc in an YBa2Cu3O7 polycrystalline sample has been investigated at high temperatures. The samples were irradiated at room temperature by a 60Co γ‐ray source at a dose rate of 0.5 MR/h. Jc was found to increase significantly with after irradiation dose of 10 MR. Further irradiation dose of 50 MR produced a slight and field dependent enhancement of Jc above its values at 10 MR. The most interesting result is that the relative change in the critical current density was found to have a non‐monotonic behavior with the applied magnetic field. These results are discussed in terms of the roles of several mechanisms created by γ‐rays in the regions of the grain boundaries combined with the effect of the magnetic field on these mechanisms. (© 2007 WILEY ‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
654.
In this work, CuO/n-Si and AuNPs-decorated CuO/n-Si heterojunction photodetectors were fabricated by deposition of CuO nanoplatelets and Au nanoparticles NPs decorated CuO nanoplatelets on silicon substrates by laser ablation in methanol. Atomic force microscope AFM, scanning electron microscope SEM and transmission electron microscope TEM were used to study the structural and surface morphology of CuO and AuNPs–CuO. The electrical properties showed that the CuO/Si and AuNPs decorated-CuO/Si showed rectifying behavior. The maximum values of quantum efficiency were about 41 and 78% at 700 nm for CuO/Si and AuNPs–CuO/Si photodetectors, respectively. The I–V characteristics of the photodetectors were measured under UV light. 相似文献