全文获取类型
收费全文 | 8040篇 |
免费 | 1131篇 |
国内免费 | 645篇 |
专业分类
化学 | 5616篇 |
晶体学 | 52篇 |
力学 | 423篇 |
综合类 | 24篇 |
数学 | 1035篇 |
物理学 | 2666篇 |
出版年
2024年 | 23篇 |
2023年 | 173篇 |
2022年 | 265篇 |
2021年 | 310篇 |
2020年 | 335篇 |
2019年 | 288篇 |
2018年 | 269篇 |
2017年 | 223篇 |
2016年 | 360篇 |
2015年 | 335篇 |
2014年 | 439篇 |
2013年 | 540篇 |
2012年 | 675篇 |
2011年 | 717篇 |
2010年 | 479篇 |
2009年 | 402篇 |
2008年 | 487篇 |
2007年 | 429篇 |
2006年 | 411篇 |
2005年 | 321篇 |
2004年 | 236篇 |
2003年 | 182篇 |
2002年 | 148篇 |
2001年 | 145篇 |
2000年 | 146篇 |
1999年 | 150篇 |
1998年 | 121篇 |
1997年 | 105篇 |
1996年 | 142篇 |
1995年 | 126篇 |
1994年 | 81篇 |
1993年 | 79篇 |
1992年 | 88篇 |
1991年 | 75篇 |
1990年 | 83篇 |
1989年 | 58篇 |
1988年 | 38篇 |
1987年 | 34篇 |
1986年 | 30篇 |
1985年 | 26篇 |
1984年 | 21篇 |
1983年 | 24篇 |
1982年 | 22篇 |
1981年 | 15篇 |
1979年 | 22篇 |
1978年 | 23篇 |
1977年 | 20篇 |
1976年 | 16篇 |
1975年 | 15篇 |
1973年 | 18篇 |
排序方式: 共有9816条查询结果,搜索用时 0 毫秒
51.
Alignment carbon nanotubes (ACNTs) were synthesized on silicon substrate coated with Ni catalyst film and Ta buffer layer by plasma-enhanced hot filament chemical vapor deposition using CH4, NH3, and H2 as the reaction gas, and they were investigated by scanning electron microscopy and transmission electron microscopy. It is found that the diameter of the bamboo-structured ACNTs is increased from 62 to 177 nm when the substrate temperature was changed from 626 to 756 °C. Their growth rate is enhanced by the substrate temperature in a range of 626-683 °C and it is reversely reduced with the substrate temperature after the substrate temperature is over 683 °C. Beginning with wetting phenomenon, the effects of the substrate temperature on the structure and growth rate of the ACNTs are analyzed. 相似文献
52.
Liu Yuren Lu Yanxin Xie Yali Wang Yonghai Du Youling Tan Jin Meng Bonian R. S. Seymour 《Journal of Radioanalytical and Nuclear Chemistry》1991,151(1):83-93
This paper introduces the principles, instrumentation, implementation, and industrial applications of an on-line thermal neutron prompt-gamma element analysis system (using a252Cf neutron source, Am–Be neutron source, or neutron generator). The energy resolution of the system at the H prompt-gamma full-energy photopeak (2.22325 MeV) is 3.6 keV. The concentration measurement error of Al2O3, FeO3, CaO, and SiO2 is ±0.3%, ±0.1%, ±0.4%, and ±0.4%, respectively. The system has been tested on-site at both the Shandong and the Zhengzhou Aluminium Works. Our preliminary on-site measurements confirm that the stability, reliability, measurement range, and accuracy of the system can meet the requirements of the aluminium production process. Facilitation of this measurement at aluminium plants is expected to reduce plant costs by over 3 million dollars annually through reduced energy consumption, more rapid qualification of pulps being mixed during the production process, and in reduced labor costs.Other participants of Shandong and Zhenghou Aluminium Works are: Wang Aili, Zengshen, Dei Jianguo and Lu Jinnan, Wang Deyu, Jin Hequan. 相似文献
53.
54.
55.
I. Tsiaoussis N. Frangis C. Manolikas T.A. Nguyen Tan 《Journal of Crystal Growth》2007,300(2):368-373
Pd thin films, grown on Si-rich 6H-SiC(0 0 0 1) substrates, were studied by atomic force microscopy, electron diffraction and high-resolution transmission electron microscopy. It is concluded that the growth is successful only when all the growth process takes place at room temperature. Under these conditions a very good epitaxial growth of Pd is achieved, despite the large misfit (about 8.6%) between Pd and the substrate and the existence of a semi-amorphous layer between the thin film and the substrate. A large number of twins appear in these films. 相似文献
56.
Summary Some stability and convergence theorems of the modified Ishikawa iterative sequences with errors for asymptotically nonexpansive
mapping in the intermediate sense and asymptotically pseudo contractive and uniformly Lipschitzian mappings in Banach spaces
are obtained. 相似文献
57.
58.
59.
60.