全文获取类型
收费全文 | 754篇 |
免费 | 17篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 7篇 |
综合类 | 1篇 |
化学工业 | 108篇 |
金属工艺 | 16篇 |
机械仪表 | 12篇 |
建筑科学 | 30篇 |
矿业工程 | 1篇 |
能源动力 | 18篇 |
轻工业 | 57篇 |
水利工程 | 13篇 |
石油天然气 | 4篇 |
无线电 | 68篇 |
一般工业技术 | 112篇 |
冶金工业 | 263篇 |
原子能技术 | 6篇 |
自动化技术 | 57篇 |
出版年
2023年 | 5篇 |
2021年 | 9篇 |
2020年 | 4篇 |
2019年 | 5篇 |
2018年 | 7篇 |
2017年 | 10篇 |
2016年 | 6篇 |
2015年 | 7篇 |
2014年 | 13篇 |
2013年 | 28篇 |
2012年 | 17篇 |
2011年 | 21篇 |
2010年 | 19篇 |
2009年 | 23篇 |
2008年 | 12篇 |
2007年 | 15篇 |
2006年 | 23篇 |
2005年 | 30篇 |
2004年 | 18篇 |
2003年 | 26篇 |
2002年 | 20篇 |
2001年 | 17篇 |
2000年 | 13篇 |
1999年 | 22篇 |
1998年 | 71篇 |
1997年 | 36篇 |
1996年 | 35篇 |
1995年 | 20篇 |
1994年 | 23篇 |
1993年 | 21篇 |
1992年 | 11篇 |
1991年 | 14篇 |
1990年 | 15篇 |
1989年 | 16篇 |
1988年 | 6篇 |
1987年 | 7篇 |
1986年 | 10篇 |
1985年 | 15篇 |
1984年 | 11篇 |
1983年 | 12篇 |
1982年 | 3篇 |
1981年 | 10篇 |
1980年 | 6篇 |
1979年 | 9篇 |
1978年 | 4篇 |
1977年 | 10篇 |
1976年 | 15篇 |
1974年 | 5篇 |
1973年 | 3篇 |
1968年 | 3篇 |
排序方式: 共有773条查询结果,搜索用时 10 毫秒
1.
2.
3.
A. Goyal E. D. Specht Z. L. Wang D. M. Kroeger J. A. Sutliff J. E. Tkaczyk J. A. Deluca L. Masur G. N. Riley 《Journal of Electronic Materials》1994,23(11):1191-1197
Microstructural origins for reduced weak-link behavior in high-Jc melt-processed YBCO, spray pyrolyzed thick films of Tl-1223, metallic precursor Y-124 polycrystalline powder-in-tube (PIT)
wires and PIT Bi-2212/2223 are discussed. Since the materials studied are the highest Jc, polycrystalline, high-Tc superconductors fabricated worldwide, the results provide important guidelines for further improvements in superconducting
properties, thereby enabling practical applications of these materials. It is found that strongly linked current flow within
domains of melt-processed 123 occurs effectively through a single crystal path. In c-axis oriented, polycrystalline Tl-1223
thick films, local in-plane texture has been found to play a crucial role in the reduced weak-link behavior. Formation of
“colonies” of grains with a common c-axis and modest in-plane misorientation was observed. Furthermore, a colony boundary
in general has a varying misorientation along the boundary. Large regions comprised primarily of low angle boundaries were
observed. Percolative transport through a network of such small angle boundaries appears to provide the nonweak-linked current
path. Although powder-in-tube BSCCO 2212 and 2223 also appear to have a “colony” microstructure, there are some important
differences. Colonies in BSCCO consist of stacks of grains with similar c-axis orientation in contrast to colonies in Tl-1223
films where few grains are stacked on top of one another. Furthermore, most grains within a colony in BSCCO have the same
lateral dimensions as that of the colony, resulting largely largely in “twist” boundaries. Further microstructural characterization
of high-Jc PIT 2212 and 2223 is currently underway. In the case of Y-124 wires, weak macroscopic in-plane texture is found. Additional
measurements are underway to determine if a sharper, local in-plane texture also exists. It is found that in three of the
four types of superconductors studied, reduced weak-link behavior can be ascribed to some degree of biaxial alignment between
grains, either on a “local” or a “global” scale. 相似文献
4.
5.
6.
7.
The characteristics of SF6/He plasmas which are used to etch Si3N4 have been examined with experimental design and modeled empirically by response-surface methodology using a Lam Research Autoetch 480 single-wafer system. The effects of variations of process gas flow rate (20-380 sccm), reactor pressure (300-900 mtorr). RF power (50-450 W at 13.56 MHz), and interelectrode spacing (8-25 mm) on the etch rates of LPCVD (low-pressure chemical vapor deposition) Si3N4, thermal SiO2, and photoresist were examined at 22±2°C. Whereas the etch rate of photoresist increases with interelectrode spacing between 8 and 19 mm and then declines between 19 and 25 mm, the etch rate of Si3N 4 increases smoothly from 8 to 25 mm, while the etch rate of thermal SiO2 shows no dependence on spacing between 8 and 25 mm. The etch rates of all three films decrease with increasing reactor pressure. Contour plots of the response surfaces for etch rate and etch uniformity of Si3N4 as a function of spacing and flow rate at constant RF power (250 W) display complex behavior at fixed reactor pressures. A satisfactory balance of etch rate and etch uniformity for Si3N4 is predicted at low reactor pressure (~300 mtorr), large electrode spacing (12-25 mm), and moderate process gas flow rates (20-250 sccm) 相似文献
8.
9.
10.
The eighth sentences shpuld read as follows. rFosLZGSTweakly associates beyond a dimer (Ka 4x104 M1)and rJunLZGST associates indefinitely (Ka 4x105M1), consistent with an isodesmic model of association. 相似文献