全文获取类型
收费全文 | 974篇 |
免费 | 59篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 16篇 |
化学工业 | 301篇 |
金属工艺 | 10篇 |
机械仪表 | 29篇 |
建筑科学 | 20篇 |
能源动力 | 25篇 |
轻工业 | 85篇 |
水利工程 | 10篇 |
石油天然气 | 4篇 |
无线电 | 101篇 |
一般工业技术 | 140篇 |
冶金工业 | 98篇 |
原子能技术 | 3篇 |
自动化技术 | 193篇 |
出版年
2023年 | 11篇 |
2022年 | 69篇 |
2021年 | 66篇 |
2020年 | 35篇 |
2019年 | 17篇 |
2018年 | 44篇 |
2017年 | 30篇 |
2016年 | 26篇 |
2015年 | 27篇 |
2014年 | 44篇 |
2013年 | 68篇 |
2012年 | 64篇 |
2011年 | 63篇 |
2010年 | 37篇 |
2009年 | 29篇 |
2008年 | 40篇 |
2007年 | 38篇 |
2006年 | 36篇 |
2005年 | 19篇 |
2004年 | 22篇 |
2003年 | 16篇 |
2002年 | 15篇 |
2001年 | 14篇 |
2000年 | 9篇 |
1999年 | 22篇 |
1998年 | 24篇 |
1997年 | 16篇 |
1996年 | 20篇 |
1995年 | 5篇 |
1994年 | 8篇 |
1993年 | 17篇 |
1992年 | 8篇 |
1991年 | 7篇 |
1990年 | 3篇 |
1989年 | 7篇 |
1987年 | 6篇 |
1986年 | 2篇 |
1985年 | 7篇 |
1984年 | 4篇 |
1983年 | 5篇 |
1982年 | 2篇 |
1981年 | 4篇 |
1977年 | 8篇 |
1976年 | 2篇 |
1975年 | 3篇 |
1974年 | 2篇 |
1967年 | 1篇 |
1966年 | 2篇 |
1961年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有1035条查询结果,搜索用时 15 毫秒
1.
Salvatore Lombardo Salvatore Ugo Campisano 《Materials Science and Engineering: R: Reports》1996,17(8):739-336
We have investigated the relationship between microstructure and electrical conductivity in semi-insulating polycrystalline silicon (SIPOS) with oxygen concentrations in the 2–35 at.% range and the effect of doping with boron, phosphorus, arsenic and erbium by ion implantation. SIPOS thin films are mixtures of silicon and silicon oxide phases. The chemical and morphological evolution of these phases upon annealing is emphasized. Electrical conductivity measurements are interpreted in terms of a physical model containing few free parameters related to the material microstructure. A direct extension of this model explains also the conductivity increase in SIPOS doped with elements of the third or the fifth group. In the last part of the paper, data of electroluminescence at 1.54 μm in Er-implanted SIPOS due to intra-4f transitions of the Er3+ ion are shown and discussed. 相似文献
2.
3.
The objective, strategy, and implementation details of a new undergraduate course, Internet-based Instrumentation and Control, are presented. The course has a companion laboratory that is supported by the National Science Foundation and industry. The combination is offered to senior-level undergraduate engineering students interested in sensing, instrumentation, control, and web programming that want to learn more about the integration of these technologies for solving real-world engineering problems. The course will also be offered to gifted high school seniors with similar interests and can serve as a vehicle to attract them to engineering disciplines. Preliminary assessment of the first offering of the course is encouraging and has shown that the course has achieved success in helping students understand concepts and master basic technologies for developing Internet-based automatic systems. 相似文献
4.
5.
6.
7.
8.
Giovanni Maizza Salvatore Grasso Yoshio Sakka Tetsuji Noda Osamu Ohashi 《Science and Technology of Advanced Materials》2007,8(7-8):644
A combined experimental/numerical methodology is developed to fully consolidate pure ultrafine WC powder under a current-control mode. Three applied currents, 1900, 2100 and 2700 A, and a constant pressure of 20 MPa were employed as process conditions. The developed spark plasma sintering (SPS) finite-element model includes a moving-mesh technique to account for the contact resistance change due to sintering shrinkage and punch sliding. The effects of the heating rate on the microstructure and hardness were investigated in detail along the sample radius from both experimental and modeling points of view. The maximum hardness (2700 HV10) was achieved for a current of 1900 A at the core sample, while the maximum densification was achieved for 2100 and 2700 A. A direct relationship between the compact microstructure and both the sintering temperature and the heating rate was established. 相似文献
9.
10.
Several boron-containing organosilicon polymers were synthesized from a sodium-coupling reaction of silicon and boron halides with and without alkyl halide in hydrocarbon solvents. The B–Si preceramic polymers were characterized using techniques such as IR, UV, and NMR spectrometry, gel permeation chromatography, elemental analysis, molecular weight measurement, and thermal analyses (TGA, DSC, DTA, and TMA). The chemical structures of the preceramic polymers were postulated based on the analytical results. Black ceramic materials were obtained from the precursor polymers upon thermal degradation at temperatures above 1000°C in an inert atmosphere. The precursor polymers had a ceramic yield of up to 70%. Thermogravimetric analysis of the ceramic material in air at a flow rate of 100 mL/min showed it was stable up to 1000°C with little weight gain or loss. Several methods were used to characterize the ceramic materials: XRD, solid NMR, high-temperature DTA, elemental analysis, and acid digestion. The analyses indicated that the ceramic materials comprised a mixture of silicon carbide (SiC), silicon borides (SiB4, SiB6), and amorphous Si–B–C ceramics, with small amounts of silica and free silicon. 相似文献