全文获取类型
收费全文 | 3927篇 |
免费 | 373篇 |
国内免费 | 347篇 |
专业分类
电工技术 | 249篇 |
综合类 | 441篇 |
化学工业 | 297篇 |
金属工艺 | 534篇 |
机械仪表 | 304篇 |
建筑科学 | 302篇 |
矿业工程 | 113篇 |
能源动力 | 187篇 |
轻工业 | 21篇 |
水利工程 | 1094篇 |
石油天然气 | 229篇 |
武器工业 | 57篇 |
无线电 | 58篇 |
一般工业技术 | 327篇 |
冶金工业 | 260篇 |
原子能技术 | 44篇 |
自动化技术 | 130篇 |
出版年
2024年 | 25篇 |
2023年 | 70篇 |
2022年 | 135篇 |
2021年 | 129篇 |
2020年 | 156篇 |
2019年 | 138篇 |
2018年 | 123篇 |
2017年 | 162篇 |
2016年 | 159篇 |
2015年 | 152篇 |
2014年 | 200篇 |
2013年 | 204篇 |
2012年 | 238篇 |
2011年 | 256篇 |
2010年 | 165篇 |
2009年 | 205篇 |
2008年 | 205篇 |
2007年 | 248篇 |
2006年 | 235篇 |
2005年 | 233篇 |
2004年 | 198篇 |
2003年 | 155篇 |
2002年 | 159篇 |
2001年 | 140篇 |
2000年 | 104篇 |
1999年 | 87篇 |
1998年 | 52篇 |
1997年 | 75篇 |
1996年 | 46篇 |
1995年 | 49篇 |
1994年 | 35篇 |
1993年 | 25篇 |
1992年 | 20篇 |
1991年 | 14篇 |
1990年 | 8篇 |
1989年 | 12篇 |
1988年 | 6篇 |
1987年 | 6篇 |
1986年 | 3篇 |
1985年 | 5篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1979年 | 1篇 |
排序方式: 共有4647条查询结果,搜索用时 15 毫秒
1.
2.
Abrasive water jet technology can be used for micro-milling using recently developed miniaturized nozzles. Abrasive water jet (AWJ) machining is often used with both the nozzle tip and workpiece submerged in water to reduce noise and contain debris. This paper compares the performance of submerged and unsubmerged abrasive water jet micro-milling of channels in 316L stainless steel and 6061-T6 aluminum at various nozzle angles and standoff distances. The effect of submergence on the diameter and effective footprint of AWJ erosion footprints was measured and compared. It was found that the centerline erosion rate decreased with channel depth due to the spreading of the jet as the effective standoff distance increased, and because of the growing effect of stagnation as the channel became deeper. The erosive jet spread over a larger effective footprint in air than in water, since particles on the jet periphery were slowed much more quickly in water due to increased drag. As a result, the width of a channel machined in air was wider than that in water. Moreover, it was observed that the instantaneous erosion rate decreased with channel depth, and that this decrease was a function only of the channel cross-sectional geometry, being independent of the type of metal, the jet angle, the standoff distance, and regardless of whether the jet was submerged or in air, in either the forward or backward directions. It is shown that submerged AWJM results in narrower features than those produced while machining in air, without a decrease in centerline etch rate. 相似文献
3.
Shengyue Gu Shouyang Zhang Fei Liu Wei Li 《Journal of the European Ceramic Society》2018,38(15):5082-5091
Y2Hf2O7 possesses low thermal conductivity and high melting point, which make it promising for a new anti-ablation material. For evaluating the thermal stability and the potential applications of Y2Hf2O7 on anti-ablation protection of C/C composites, Y2Hf2O7 ceramic powder was synthesized by solution combustion method and Y2Hf2O7 coating was prepared on the surface of SiC coated C/C composites using SAPS. Results shown that the coating exhibits good ablation resistance under the heat flux of 2.4?MW/m2 with the linear and mass ablation rates are 0.16?μm?s?1 and ?0.028?mg?s?1, respectively, after ablation for 40?s. With the prolonging of the ablation time, the increasing thermal stress causes the increase of cracks. Moreover, the chemical erosion from SiO2 and the physical volatilization of low temperature molten products aggravate failure of the Y2Hf2O7 coating. 相似文献
4.
5.
李静 《水利水电科技进展》2006,26(3):15-17
总结了20世纪80年代前珠江三角洲网河河床演变特征,并采用80年代和90年代末的河道地形图,通过对比珠江三角洲各主要河道的深泓线、平均河底高程以及河道容积、河床断面宽深比的变化,分析珠江三角洲80年代后的河床演变特征。对比分析结果表明珠江三角洲在不同时期呈现出不同的河床演变规律——20世纪80年代前以淤积为主,80年代至90年代末转变为以冲刷为主。 相似文献
6.
The feature scale planarization of the copper chemical mechanical planarization (CMP) process has been characterized for two
copper processes using Hitachi 430-TU/Hitachi T605 and Cabot 5001/Arch Cu10K consumables. The first process is an example
of an abrasive-free polish with a high-selectivity barrier slurry, while the second is an example of a conventional abrasive
slurry with a low-selectivity barrier slurry. Copper fill planarization has been characterized for structures with conformal
deposition as well as with bumps resulting from bottom-up fill. Dishing and erosion were characterized for several structures
after clearing. The abrasive-free polish resulted in low sensitivity to overpolish and low saturation levels for dishing and
erosion. Consequently, this demonstrated superior performance when compared to the International Technology Roadmap for Semiconductors
(ITRS) 2000 roadmap targets for planarization. While the conventional slurry could achieve the 0.13-μm technology node requirements,
the abrasive-free polish met the planarization requirements beyond the 0.10-μm technology node. 相似文献
7.
8.
采用遥感技术与地面调查相结合的方法,组织多学科综合调查研究,对云南滇池流域水土流失状况及程度进行了调查分析。初步查明了引起水土流失灾害的原因并提出相应的防止对策。 相似文献
9.
10.
苏金华 《石油化工腐蚀与防护》2002,19(3):33-34
对换热站容积式加热器管束失效原因进行了分析 ,指出主要是由于汽蚀和电化学腐蚀所致。从操作工艺和采用 12Cr2AlMoV材质两方面进行改进 ,可使管束的使用寿命由 4个月延长到 2年 相似文献