全文获取类型
收费全文 | 99625篇 |
免费 | 3788篇 |
国内免费 | 2824篇 |
专业分类
化学 | 39671篇 |
晶体学 | 1053篇 |
力学 | 7969篇 |
综合类 | 188篇 |
数学 | 34036篇 |
物理学 | 23320篇 |
出版年
2024年 | 68篇 |
2023年 | 429篇 |
2022年 | 743篇 |
2021年 | 824篇 |
2020年 | 865篇 |
2019年 | 838篇 |
2018年 | 10974篇 |
2017年 | 10810篇 |
2016年 | 6976篇 |
2015年 | 1863篇 |
2014年 | 1460篇 |
2013年 | 1912篇 |
2012年 | 5584篇 |
2011年 | 12354篇 |
2010年 | 6847篇 |
2009年 | 7246篇 |
2008年 | 7968篇 |
2007年 | 10004篇 |
2006年 | 1431篇 |
2005年 | 2252篇 |
2004年 | 2282篇 |
2003年 | 2600篇 |
2002年 | 1616篇 |
2001年 | 709篇 |
2000年 | 743篇 |
1999年 | 637篇 |
1998年 | 613篇 |
1997年 | 568篇 |
1996年 | 659篇 |
1995年 | 481篇 |
1994年 | 457篇 |
1993年 | 365篇 |
1992年 | 306篇 |
1991年 | 296篇 |
1990年 | 214篇 |
1989年 | 187篇 |
1988年 | 175篇 |
1987年 | 154篇 |
1986年 | 152篇 |
1985年 | 131篇 |
1984年 | 100篇 |
1983年 | 85篇 |
1982年 | 79篇 |
1981年 | 66篇 |
1980年 | 77篇 |
1979年 | 62篇 |
1978年 | 44篇 |
1914年 | 45篇 |
1909年 | 41篇 |
1908年 | 40篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
He Haidong Yang Haifeng Zhou Longpeng Chen Tianchi 《Journal of Russian Laser Research》2015,36(3):292-299
Ni–Co alloys have a wide range of applications in various fields owning to their excellent physical, chemical, and mechanical properties. In this paper, we prepare Ni–Co alloy coatings on 316L stain steel surfaces by electroplating. We present a novel approach utilizing a nanosecond laser to induce microtextures on Ni–Co alloy coatings. We study experimentally the effects of laser power and scanning rate on the surface morphologies of Ni–Co alloy coatings. The results indicate that the shape and size of induced microtextures can be controlled by the laser power and scanning rate. The size of grains increases with increase in the work current of the laser (WCL) at a certain scanning rate. With the WCL constant, the size of grains decreases with increase in scanning rate while their average height increases. It is a simple and easily-controlled method for the fabrication of microstructures on Ni–Co alloy coatings, which has promising applications in investigations of the properties of microtextured surfaces, such as friction, adhesion, and wetting. 相似文献
12.
13.
14.
15.
16.
17.
18.
Understanding and control of the surface properties such as molecular orientations are of great importance in numerous applications of ionic liquids. However, there remain discrepancies among the previous experimental and theoretical studies on the surface orientation and structures of room temperature ionic liquids(RTIL) systems. In this article, the orientation of 1-butyl-3-methylimidazolium([bmin]) cation at the air/liquid interface of a characteristic RTIL, 1-butyl-3-methylimidazolium hexafluorophosphate([bmim][PF6]), was investigated by the sum frequency generation vibrational spectroscopy(SFG-VS). Detailed polarization and experimental configuration analyses of the SFG-VS spectra showed the possibility of a small spectral splitting in the CH3 symmetric stretching region, which can be further attributed to the probable existence of multiple orientations for the interfacial [bmim] cations. In addition, the(N)–CH3 vibrations were absent, ruling out the prediction by several recent molecular dynamics simulations which state that portions of the [bmim] cations orient with a standing-up(N)–CH3 group at the ionic liquid surface. Hence, new realistic theoretical models have to be developed to reflect the complex nature of the ionic liquid surface. 相似文献
19.
A rapid method had been used for comparative study on Artemisia halodendron Turcz. and its two related plants by gas phase-mass spectrometry (GC-MS). The comparison of the volatile oils obtained in three plants by GC-MS were similar in 20 compositions. However, n-Hexadecanoic acid (10.40%), Biphenyl (7.867%) and 9,12-Octadecadienoic acid (7.25%) were the predominant in the volatile oils of A. halodendron Turcz., whereas these constituents did not exist in the other two plants. And the study investigated the effect of three plants against CCl4-induced hepatotoxicity in mice. 70% ethanol extracts of A. halodendron Turcz. showed weaker protective effect than the other two plants. It suggested that they provide a basis for the identification of the A. halodendron Turcz. from the other two plants and the ethanol extract from three plants exerted a protecting effect against hepatotoxicity. 相似文献
20.