全文获取类型
收费全文 | 18526篇 |
免费 | 3267篇 |
国内免费 | 2046篇 |
专业分类
化学 | 12527篇 |
晶体学 | 230篇 |
力学 | 1219篇 |
综合类 | 146篇 |
数学 | 1886篇 |
物理学 | 7831篇 |
出版年
2024年 | 64篇 |
2023年 | 420篇 |
2022年 | 651篇 |
2021年 | 651篇 |
2020年 | 738篇 |
2019年 | 714篇 |
2018年 | 621篇 |
2017年 | 570篇 |
2016年 | 915篇 |
2015年 | 886篇 |
2014年 | 1066篇 |
2013年 | 1335篇 |
2012年 | 1600篇 |
2011年 | 1595篇 |
2010年 | 1184篇 |
2009年 | 1127篇 |
2008年 | 1131篇 |
2007年 | 986篇 |
2006年 | 999篇 |
2005年 | 890篇 |
2004年 | 640篇 |
2003年 | 501篇 |
2002年 | 530篇 |
2001年 | 402篇 |
2000年 | 373篇 |
1999年 | 381篇 |
1998年 | 304篇 |
1997年 | 329篇 |
1996年 | 323篇 |
1995年 | 267篇 |
1994年 | 249篇 |
1993年 | 203篇 |
1992年 | 188篇 |
1991年 | 160篇 |
1990年 | 141篇 |
1989年 | 143篇 |
1988年 | 105篇 |
1987年 | 74篇 |
1986年 | 82篇 |
1985年 | 66篇 |
1984年 | 37篇 |
1983年 | 33篇 |
1982年 | 29篇 |
1981年 | 20篇 |
1980年 | 18篇 |
1979年 | 8篇 |
1975年 | 8篇 |
1973年 | 7篇 |
1972年 | 8篇 |
1965年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
不同激发密度下CdS晶体的光致发光和受激发射 总被引:1,自引:1,他引:0
本文主要研究在77-111K温度范围内、不同激发密度的N2激光器的337.1nm谱线激发下,激子-激子(Ex-Ex)、激子-载流子(Ex-e)的相互作用和发射一个LO声子(Ex-1LO)、两个LO声子(Ex-2LO)的自由激子的辐射复合行为.并在77K温度下观测到由Ex-Ex发射产生的受激发射. 相似文献
83.
84.
Al2O3 incorporated HfO2 films grown by atomic layer deposition (ALD) were investigated by high-resolution X-ray photoelectron spectroscopy (HRXPS). The core level energy state of a 15 Å thick film showed a shift to higher binding energy, as the result of a silicate formation and Al2O3 incorporation. The incorporation of Al2O3 into the HfO2 film had no effect on silicate formation at the interface between the film and Si, while the ionic bonding characteristics and hybridization effects were enhanced compared to a pure HfO2 film. The dissociation of the film in an ultrahigh vacuum (UHV) is effectively suppressed compared to a pure HfO2 film, indicating an enhanced thermal stability of Hf-Al-O. Any dissociated Al2O3 on the film surface was completely removed into the vacuum by vacuum annealing treatment over 850 °C, while HfO2 contributed to Hf silicide formation on the film surface. 相似文献
85.
Preparation and microwave absorption properties of electroless Co-Ni-P coated strontium ferrite powder 总被引:1,自引:0,他引:1
A new type of Co-Ni-P coated strontium ferrite nanocomposite was prepared with electroless plating enhanced by ultrasonic wave at room temperature. The plating process was studied carefully. The morphology, crystal structure and microwave absorption properties of the Co-Ni-P coated powder were studied with field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), energy dispersive analysis of X-rays (EDX) and vector network analyzer. The results show that the strontium ferrite powder was successfully coated with Co-Ni-P alloy and possesses excellent microwave absorption properties. The maximum microwave loss of the composite powder reaches −44.12 dB. The bandwidth with the loss above −10 dB exceeds 13.8 GHz. 相似文献
86.
87.
88.
89.
The generalized Mycielskians (also known as cones over graphs) are the natural generalization of the Mycielski graphs (which were first introduced by Mycielski in 1955). Given a graph G and any integer m?0, one can transform G into a new graph μm(G), the generalized Mycielskian of G. This paper investigates circular clique number, total domination number, open packing number, fractional open packing number, vertex cover number, determinant, spectrum, and biclique partition number of μm(G). 相似文献
90.
Nanometer scale Al/AlN multilayers have been prepared by dc magnetron sputtering technique with a columnar target. A set of Al/AlN multilayers with the Al layer thickness of 2.9 nm and the AlN layer thickness variation from 1.13 to 6.81 nm were determined. Low angle X-ray diffraction (LAXRD) was used to analyze the layered structure of multilayers. The phase structure of the coatings was investigated with grazing angle XRD (GAXRD). Mechanical properties of these multilayers were thoroughly studied using a nanoindentation and ball-on-disk micro-tribometer. It was found that the multilayer hardness and reduced modulus showed no strong dependence on the AlN layer thickness. Al2.9 nm/AlN1.13 nm multilayer had more excellent tribological properties than single layers and other proportion multilayers with a lowest friction coefficient of 0.15. And the tribological properties of all the multilayers are superior to the AlN single layer. 相似文献