全文获取类型
收费全文 | 8354篇 |
免费 | 2613篇 |
国内免费 | 614篇 |
专业分类
化学 | 1089篇 |
晶体学 | 168篇 |
力学 | 1288篇 |
综合类 | 90篇 |
数学 | 644篇 |
物理学 | 8302篇 |
出版年
2024年 | 17篇 |
2023年 | 82篇 |
2022年 | 182篇 |
2021年 | 174篇 |
2020年 | 248篇 |
2019年 | 210篇 |
2018年 | 221篇 |
2017年 | 297篇 |
2016年 | 332篇 |
2015年 | 341篇 |
2014年 | 634篇 |
2013年 | 707篇 |
2012年 | 533篇 |
2011年 | 750篇 |
2010年 | 597篇 |
2009年 | 639篇 |
2008年 | 641篇 |
2007年 | 637篇 |
2006年 | 590篇 |
2005年 | 519篇 |
2004年 | 454篇 |
2003年 | 394篇 |
2002年 | 354篇 |
2001年 | 337篇 |
2000年 | 316篇 |
1999年 | 222篇 |
1998年 | 224篇 |
1997年 | 179篇 |
1996年 | 144篇 |
1995年 | 121篇 |
1994年 | 84篇 |
1993年 | 78篇 |
1992年 | 67篇 |
1991年 | 56篇 |
1990年 | 41篇 |
1989年 | 36篇 |
1988年 | 23篇 |
1987年 | 21篇 |
1986年 | 14篇 |
1985年 | 15篇 |
1984年 | 14篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1981年 | 6篇 |
1980年 | 5篇 |
1979年 | 5篇 |
1978年 | 2篇 |
1976年 | 4篇 |
1974年 | 2篇 |
1971年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Surface reconstructions of InGaAs alloys 总被引:1,自引:0,他引:1
The surface reconstructions of InxGa1−xAs alloys grown by molecular beam epitaxy on the (0 0 1) surfaces of GaAs and InAs have been studied by reflection high-energy electron diffraction and scanning tunnelling microscopy. A surface phase diagram is presented for the nominally strain-free alloy as a function of substrate temperature and alloy composition, and structural models for the commonly observed 3× reconstructions are discussed. Two new, electronically stable structural models are described that account for the transition of the InxGa1−xAs surface alloy from a c(4 × 4) to an asymmetric 3× reconstruction and that are fully consistent with all current experimental evidence. 相似文献
102.
A. Pompei 《Applied Acoustics》2006,67(5):420-431
In the present paper, we simulate focused wave fields generated by a system of plane transducers used in an immersion ultrasonic technique. The ultrasonic beam penetrates into the elastic medium through the fluid-solid boundary. A real-time computer algorithm is proposed to calculate stress components in the solid medium. It is shown that a good focusing wave structure can be provided by a pair of plane rectangular transducers, inclined with respect to each other and to the beam acoustic axis. 相似文献
103.
104.
105.
106.
《Surface and interface analysis : SIA》2006,38(3):150-157
The role of water‐soluble corrosion products on galvanized wires was examined. The samples used were industrial hot‐dip galvanized wires, which were exposed to the open air under all weather conditions for a relatively short time (6 and 12 months), in an urban environment close to the sea. The samples were studied by different methods, i.e. scanning electron microscopy (SEM), transmission electron microscopy (TEM), X‐ray diffraction (XRD) and optical microscopy (OM). Several phases were detected because of the galvanization procedure and the steel substrate. Furthermore, phases which were formed as a result of the reaction of zinc with the atmosphere were also detected. These were oxides like ZnO, carbonates like ZnCO3 and hydrated Zn and Fe sulfates. Their presence influences the corrosion resistance of the wires, which finally, strongly depends on the solubility of the wires in water. The SO42? compounds especially are very soluble and consequently are easily removed from the coating surface, leading to its degradation by the formation of cavities. In any case, their presence, even after a short period of exposure, implies that the coating is highly affected by the atmosphere of the modern city. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
107.
Based on scalar diffraction theory, 8-phase-level 256×256 elements diffractive microlens array with element dimension of 50×33 μm2 have been fabricated on the back-side of PtSi(3~5 μm) infrared CCD. The measurement results indicated that the ratio of the signal-to-noise of the infrared CCD with microlens was increased by a factor of 2.8. 相似文献
108.
109.
110.