全文获取类型
收费全文 | 100057篇 |
免费 | 2081篇 |
国内免费 | 1190篇 |
专业分类
化学 | 39752篇 |
晶体学 | 950篇 |
力学 | 7568篇 |
综合类 | 44篇 |
数学 | 35083篇 |
物理学 | 19931篇 |
出版年
2023年 | 181篇 |
2022年 | 217篇 |
2021年 | 391篇 |
2020年 | 557篇 |
2019年 | 450篇 |
2018年 | 10728篇 |
2017年 | 10512篇 |
2016年 | 6618篇 |
2015年 | 1446篇 |
2014年 | 970篇 |
2013年 | 1559篇 |
2012年 | 5120篇 |
2011年 | 12106篇 |
2010年 | 6507篇 |
2009年 | 6810篇 |
2008年 | 7800篇 |
2007年 | 9936篇 |
2006年 | 1523篇 |
2005年 | 2416篇 |
2004年 | 2532篇 |
2003年 | 2816篇 |
2002年 | 1853篇 |
2001年 | 584篇 |
2000年 | 614篇 |
1999年 | 453篇 |
1998年 | 504篇 |
1997年 | 480篇 |
1996年 | 550篇 |
1995年 | 405篇 |
1994年 | 357篇 |
1993年 | 337篇 |
1992年 | 270篇 |
1991年 | 272篇 |
1990年 | 233篇 |
1989年 | 202篇 |
1988年 | 235篇 |
1987年 | 228篇 |
1986年 | 175篇 |
1985年 | 280篇 |
1984年 | 281篇 |
1983年 | 209篇 |
1982年 | 280篇 |
1981年 | 262篇 |
1980年 | 269篇 |
1979年 | 249篇 |
1978年 | 230篇 |
1977年 | 199篇 |
1976年 | 198篇 |
1974年 | 173篇 |
1973年 | 179篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
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
22.
23.
Nonlinear Dynamics - In the present article, a combination of numerical and experimental studies is undertaken to comprehend the influence of noise on the responses of continuous-time dynamical... 相似文献
24.
25.
26.
27.
Zenon Moszner 《Aequationes Mathematicae》2018,92(4):617-625
We give the form of the output function in Ginsburg’s machine in which the input and output dictionaries are abelian groups and the transition function is of a special form. 相似文献
28.
29.
Susana Estopiñá-Durán Liam J. Donnelly Euan B. Mclean Bryony M. Hockin Prof. Alexandra M. Z. Slawin Dr. James E. Taylor 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(15):3950-3956
A combination of pentafluorophenylboronic acid and oxalic acid catalyses the dehydrative substitution of benzylic alcohols with a second alcohol to form new C−O bonds. This method has been applied to the intermolecular substitution of benzylic alcohols to form symmetrical ethers, intramolecular cyclisations of diols to form aryl-substituted tetrahydrofuran and tetrahydropyran derivatives, and intermolecular crossed-etherification reactions between two different alcohols. Mechanistic control experiments have identified a potential catalytic intermediate formed between the aryl boronic acid and oxalic acid. 相似文献
30.
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