全文获取类型
收费全文 | 854篇 |
免费 | 11篇 |
国内免费 | 11篇 |
专业分类
电工技术 | 18篇 |
综合类 | 23篇 |
化学工业 | 108篇 |
金属工艺 | 116篇 |
机械仪表 | 130篇 |
建筑科学 | 29篇 |
矿业工程 | 15篇 |
能源动力 | 31篇 |
轻工业 | 41篇 |
水利工程 | 2篇 |
石油天然气 | 37篇 |
武器工业 | 2篇 |
无线电 | 94篇 |
一般工业技术 | 113篇 |
冶金工业 | 52篇 |
原子能技术 | 18篇 |
自动化技术 | 47篇 |
出版年
2023年 | 11篇 |
2022年 | 9篇 |
2021年 | 5篇 |
2020年 | 15篇 |
2019年 | 8篇 |
2018年 | 14篇 |
2017年 | 12篇 |
2016年 | 22篇 |
2015年 | 25篇 |
2014年 | 35篇 |
2013年 | 73篇 |
2012年 | 44篇 |
2011年 | 65篇 |
2010年 | 47篇 |
2009年 | 46篇 |
2008年 | 40篇 |
2007年 | 37篇 |
2006年 | 44篇 |
2005年 | 39篇 |
2004年 | 37篇 |
2003年 | 36篇 |
2002年 | 29篇 |
2001年 | 20篇 |
2000年 | 23篇 |
1999年 | 28篇 |
1998年 | 20篇 |
1997年 | 18篇 |
1996年 | 14篇 |
1995年 | 8篇 |
1994年 | 10篇 |
1993年 | 8篇 |
1992年 | 5篇 |
1991年 | 5篇 |
1990年 | 3篇 |
1989年 | 5篇 |
1988年 | 8篇 |
1987年 | 4篇 |
1986年 | 3篇 |
1985年 | 1篇 |
排序方式: 共有876条查询结果,搜索用时 15 毫秒
1.
Anh Tuan Thanh Pham Oanh Kieu Truong Le Dung Van Hoang Truong Huu Nguyen Trang Huyen Cao Pham Phuong Thanh Ngoc Vo Thang Bach Phan Vinh Cao Tran 《Journal of the European Ceramic Society》2021,41(6):3493-3500
Structure modification has been found to tune significantly the transparent-conducting performance, especially mobility and conductivity of hydrogenated Ga-doped ZnO (HGZO) films. The strong correlation between film thickness and mobility of the films is revealed. The mobility increases quickly with increasing the thickness from 350 to 900 nm, and then tends to be saturated at further thicknesses. A higher mobility than 50 cm2/Vs can be achieved, which is an extra-high value for polycrystalline ZnO films deposited by using the sputtering technique. The thickness-dependent mobility originates from scatterings on grain boundaries and dislocation-induced defects controlled by thin-film growth. Based on the Volmer-Weber model, an expansion model is built up to describe the thickness-dependent crystal growth of the HGZO films, especially at the thick films. As a result, the 800 nm-thick HGZO film obtains the highest performance with high mobility of 51.5 cm2/Vs, low resistivity of 5.3 × 10?4 Ωcm, and good transmittance of 83.3 %. 相似文献
2.
Organic devices like organic light emitting diodes (OLEDs) or organic solar cells degrade fast when exposed to ambient air. Hence, thin-films acting as permeation barriers are needed for their protection. Atomic layer deposition (ALD) is known to be one of the best technologies to reach barriers with a low defect density at gentle process conditions. As well, ALD is reported to be one of the thinnest barrier layers, with a critical thickness – defining a continuous barrier film – as low as 5–10 nm for ALD processed Al2O3. In this work, we investigate the barrier performance of Al2O3 films processed by ALD at 80 °C with trimethylaluminum and ozone as precursors. The coverage of defects in such films is investigated on a 5 nm thick Al2O3 film, i.e. below the critical thickness, on calcium using atomic force microscopy (AFM). We find for this sub-critical thickness regime that all spots giving raise to water ingress on the 20 × 20 μm2 scan range are positioned on nearly flat surface sites without the presence of particles or large substrate features. Hence below the critical thickness, ALD leaves open or at least weakly covered spots even on feature-free surface sites. The thickness dependent performance of these barrier films is investigated for thicknesses ranging from 15 to 100 nm, i.e. above the assumed critical film thickness of this system. To measure the barrier performance, electrical calcium corrosion tests are used in order to measure the water vapor transmission rate (WVTR), electrodeposition is used in order to decorate and count defects, and dark spot growth on OLEDs is used in order to confirm the results for real devices. For 15–25 nm barrier thickness, we observe an exponential decrease in defect density with barrier thickness which explains the likewise observed exponential decrease in WVTR and OLED degradation rate. Above 25 nm, a further increase in barrier thickness leads to a further exponential decrease in defect density, but an only sub-exponential decrease in WVTR and OLED degradation rate. In conclusion, the performance of the thin Al2O3 permeation barrier is dominated by its defect density. This defect density is reduced exponentially with increasing barrier thickness for alumina thicknesses of up to at least 25 nm. 相似文献
3.
Measurement Method of the Thickness Uniformity for Polymer Films 总被引:1,自引:0,他引:1
YANGHong-liang RENQuan FANYun-zheng 《半导体光子学与技术》2003,9(2):128-132
Several methods for investigating the thickness uniformity of polymer thin films are presented as well their measurement principles.A comparison of these experimental methods is given.The cylindrical lightwave feflection method is found to can obtain the thickness distribution along a certain direction.It is simple and suitable method to evaluate the film thickness uniformity. 相似文献
4.
The breakdown processes of oil films under quasi-static loading have been investigated by using a newly developed steel-oil-mercury system. The relationship between the thickness and breakdown ratio of a hexadecane film is represented by a single master curve independently of the indentation speed, indentation load, and temperature. The master curve shows that the breakdown process of hexadecane includes two stages; one is the decrement of the thickness without breakdown and the other is the decrement of the thickness with a drastic progress of breakdown. By solving a small amount of fatty acid in hexadecane, the thickness increases and the breakdown ratio decreases noticeably; a multilayer residual film supporting normal load is formed between two metal surfaces. Experiments at different temperatures reveal a negative relationship between the temperature and thickness of residual film, which indicates that the residual film is organized by physical interaction rather than chemical interaction. At least under a lower concentration, the residual film appears to consist of not only fatty acid molecules but also hexadecane molecules. 相似文献
5.
River ice jams are a common occurrence on northern rivers, and their formation can present a severe flood risk to nearby communities. As more and more river regulation projects are developed to provide an alternative to fossil fuels for electrical power-generating capacity, our need to understand the mechanisms associated with ice jam formation under variable flow conditions becomes more vital. This is because, at present, hydropeaking operations are often severely curtailed during the ice-affected seasons due to concerns that sudden flow fluctuations might instigate ice jams and associated flooding. Here, an experimental investigation explores the effects of rapid increases in discharge on ice jam formation and evolution. It is found that the thickness of ice jams formed under highly dynamic flow conditions tend to be slightly thinner than those formed during steady carrier flows for comparable discharges. Also, despite the highly dynamic nature of these consolidation events, the resulting ice thicknesses appear reasonably well approximated by steady flow theory. 相似文献
6.
椭球反射镜膜厚均匀性 总被引:2,自引:1,他引:1
本文分析了椭球反射镜膜层厚度均匀性对反射率的影响,从理论上得到膜厚计算公式。根据计算的膜厚分布设计了遮蔽板,获得较好的反射特性。 相似文献
7.
双旋Y切石英振子厚度模式的频温特性的研究 总被引:1,自引:0,他引:1
本文利用描述固体中弹性声波的克里斯托费尔方程,建立了双旋Y切石英振子厚度模式的频温特性分析方法,并编制了相应的计算机程序。该程序可给出双旋Y切石英振子在任意切角(ф_3ф_1)下的厚度模(a、b、c模)的频率温度特性曲线。文中给出了单旋AT切、BT切(b模)、双旋SC切(b、c模)、FC切、IT切、LC切、NL_1切、NL_2切、AK切等各已知切型的频温特性曲线。对石英谐振器的切角灵敏度和切角误差进行了分析。 相似文献
8.
S.F. Lee P. Lovenitti M.K. Lam S.H. Masood 《The International Journal of Advanced Manufacturing Technology》2002,20(3):180-189
This paper describes the design and development of a precision calliper system to measure the surface profile of an outboard
marine engine propeller blade. Several instruments that are commonly used for measuring the surface profile of a propeller
blade are reviewed in this paper. These include the pitch meter, the profilometer and the computer numerical control coordinate-measuring
machine (CNC-CMM). However, the operating practices and availability of different facilities in industry necessitate a more
cost-effective approach. An alternative method using a precision calliper system is therefore proposed. Details of the design
criteria, principles of operation and the testing and verification of the system are presented. The paper concludes that the
precision calliper system is a cost-effective method for measuring the surface profile of a propeller. 相似文献
9.
10.