全文获取类型
收费全文 | 64532篇 |
免费 | 7139篇 |
国内免费 | 4177篇 |
专业分类
电工技术 | 2117篇 |
技术理论 | 1篇 |
综合类 | 5235篇 |
化学工业 | 10412篇 |
金属工艺 | 6160篇 |
机械仪表 | 7276篇 |
建筑科学 | 4516篇 |
矿业工程 | 2242篇 |
能源动力 | 1675篇 |
轻工业 | 7792篇 |
水利工程 | 1717篇 |
石油天然气 | 1847篇 |
武器工业 | 594篇 |
无线电 | 5919篇 |
一般工业技术 | 8418篇 |
冶金工业 | 2238篇 |
原子能技术 | 714篇 |
自动化技术 | 6975篇 |
出版年
2024年 | 426篇 |
2023年 | 1295篇 |
2022年 | 1912篇 |
2021年 | 2297篇 |
2020年 | 2567篇 |
2019年 | 2228篇 |
2018年 | 2257篇 |
2017年 | 2663篇 |
2016年 | 2704篇 |
2015年 | 2800篇 |
2014年 | 3785篇 |
2013年 | 4487篇 |
2012年 | 4770篇 |
2011年 | 4908篇 |
2010年 | 3517篇 |
2009年 | 3535篇 |
2008年 | 3227篇 |
2007年 | 4014篇 |
2006年 | 3652篇 |
2005年 | 3010篇 |
2004年 | 2414篇 |
2003年 | 2076篇 |
2002年 | 1873篇 |
2001年 | 1476篇 |
2000年 | 1342篇 |
1999年 | 1113篇 |
1998年 | 901篇 |
1997年 | 832篇 |
1996年 | 720篇 |
1995年 | 557篇 |
1994年 | 490篇 |
1993年 | 424篇 |
1992年 | 319篇 |
1991年 | 227篇 |
1990年 | 237篇 |
1989年 | 165篇 |
1988年 | 152篇 |
1987年 | 76篇 |
1986年 | 91篇 |
1985年 | 70篇 |
1984年 | 61篇 |
1983年 | 50篇 |
1982年 | 44篇 |
1981年 | 17篇 |
1980年 | 21篇 |
1979年 | 16篇 |
1978年 | 4篇 |
1975年 | 3篇 |
1959年 | 9篇 |
1951年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
In this article, we study a linear array of bowtie nanoantennas placed between two metallic strips that can work from 800 to 1420 nm (600 nm linewidth), with an electric field enhancement factor close to 20. We study the dynamical change of the position of the electric field enhancement amongst different elements in the array and, at the same time, the effects of dispersion on the scalability of the array elements. A systematic analysis and methodology to produce an array that can operate over a large bandwidth whilst maintaining the electric field enhancement without significant variation is provided. 相似文献
33.
Edible film from water-soluble fish proteins were developed by casting film solution on leveled trays and effects of pH (9.5, 10.0 and 10.5), heating temperature (60, 70 and 80 °C), and heating time (10, 20 and 30 min) of the film solution on various film properties were determined using Response Surface Methodology (RSM). The impact of pH and heating temperature of film solution was more significant, overall, on the film's properties than heating time. Contour plots of tensile strength and elongation at break was highest at pH of 10.0 at 70 °C (2.75-3.02 MPa) but low in elongation at break (6.35-9.16%), while water vapor permeability and oxygen permeability were at their lowest (58.55-65.96 g mm/m2 d kPa and 351.33-624.18 cm3 μm/m2 d kPa). There was a direct correlation between the films’ and proteins’ solubility on one hand, and heating temperature of film solution on the other, which reversed with change in pH of film solution. Film color was darker and more yellowish with increase in the pH of film solution. 相似文献
34.
采用超高真空电子束蒸发法制备了新型高 K栅介质-非晶 ZrO2薄膜. X射线光电子能谱 (XPS) 中 Zr3d5/2 和 Zr3d3/2 对应的结合能分别为 182.1eV和 184.3eV, Zr元素的主要存在形式为 Zr4+,说明薄膜由完全氧化的 ZrO2组成 ,并且纵向分布均一.扩展电阻法( SRP)显示 ZrO2薄膜的 电阻率在 108Ω@ cm以上,通过高分辨率透射电镜( HR- XTEM)可以观察 ZrO2/Si界面陡直,没有 界面反应产物 ,证明 600℃快速退火后 ZrO2薄膜是非晶结构.原子力显微镜( AFM)表征了薄膜的 表面粗糙度,所有样品表面都很平整,其中 600℃快速退火样品 (RTA)的 RMS为 0.480nm. 相似文献
35.
36.
37.
A method and instruments based on it are proposed for the contact measurement of surface temperature when carrying out industrial experiments and when monitoring technological parameters. 相似文献
38.
J. B. Quinn G. E. Schumacher L. W. Schultheis 《Journal of Failure Analysis and Prevention》2004,4(1):41-46
Several days after heart surgery, a patient discovered his upper right canine tooth had broken at the root. Such tooth damage,
recognized post-operatively, is usually assumed to be caused by blunt mechanical force from an instrument used by the anesthesiologist
during placement of a breathing tube at the start of surgery.
In this case, the patient had saved the crown portion of the broken tooth, and it was possible to examine the root fracture
characteristics. The curvature and direction of the crack path and natural tooth situation suggested that failure could be
described through a cantilever beam model. This was confirmed when a whole extracted sample tooth was embedded and broken
by a measured force in a manner consistent with the model. The resulting fracture surface matched that of the patient’s broken
canine tooth. However, the high load and force direction necessary to fracture the root was inconsistent with forces applied
during the anesthesia procedure. The failure analysis and further investigation indicated tooth clenching on the breathing
tube during recovery was the likely cause of fracture.
This paper presents an alternate explanation for intubation-related dental injury, demonstrates the practicality of fractographic
analysis of biological materials, and introduces a methodology for simulating in vitro tooth settings for mechanical testing. 相似文献
39.
研究了红外频段非线性s偏振表面波在反铁磁晶体和电介质交界面上的频率特性,求出了非线性色散方程,揭示了非线性s偏振表面波存在一个临界频率,低于这个频率,非线性s偏振表面波的频率范围,发现功率不再是决定导波频率范围的唯一因素,两种材料的介电常数比在这里起了至关重要的作用。 相似文献
40.