全文获取类型
收费全文 | 35016篇 |
免费 | 2349篇 |
国内免费 | 2561篇 |
专业分类
电工技术 | 1063篇 |
综合类 | 2018篇 |
化学工业 | 6643篇 |
金属工艺 | 4136篇 |
机械仪表 | 2328篇 |
建筑科学 | 757篇 |
矿业工程 | 755篇 |
能源动力 | 1482篇 |
轻工业 | 1978篇 |
水利工程 | 183篇 |
石油天然气 | 864篇 |
武器工业 | 154篇 |
无线电 | 5848篇 |
一般工业技术 | 8936篇 |
冶金工业 | 1340篇 |
原子能技术 | 450篇 |
自动化技术 | 991篇 |
出版年
2024年 | 137篇 |
2023年 | 411篇 |
2022年 | 603篇 |
2021年 | 765篇 |
2020年 | 886篇 |
2019年 | 731篇 |
2018年 | 776篇 |
2017年 | 1051篇 |
2016年 | 1022篇 |
2015年 | 1024篇 |
2014年 | 1570篇 |
2013年 | 1948篇 |
2012年 | 2200篇 |
2011年 | 2763篇 |
2010年 | 1973篇 |
2009年 | 2137篇 |
2008年 | 1991篇 |
2007年 | 2448篇 |
2006年 | 2313篇 |
2005年 | 1918篇 |
2004年 | 1717篇 |
2003年 | 1471篇 |
2002年 | 1301篇 |
2001年 | 1168篇 |
2000年 | 1017篇 |
1999年 | 817篇 |
1998年 | 697篇 |
1997年 | 575篇 |
1996年 | 474篇 |
1995年 | 446篇 |
1994年 | 374篇 |
1993年 | 316篇 |
1992年 | 233篇 |
1991年 | 171篇 |
1990年 | 118篇 |
1989年 | 101篇 |
1988年 | 68篇 |
1987年 | 43篇 |
1986年 | 23篇 |
1985年 | 20篇 |
1984年 | 19篇 |
1983年 | 10篇 |
1982年 | 14篇 |
1981年 | 10篇 |
1980年 | 5篇 |
1979年 | 11篇 |
1978年 | 5篇 |
1976年 | 7篇 |
1974年 | 7篇 |
1959年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
71.
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
72.
73.
Toshiharu Makino Hiromitsu Kato Sung-Gi Ri Yigang Chen Hideyo Okushi 《Diamond and Related Materials》2005,14(11-12):1995
Electrical properties of homoepitaxial diamond p–n+ junction of boron (B)-doped p-type layer and phosphorus-doped n-type layer on Ib (111) diamond single crystal have been characterized. Current–voltage characteristics show a clear rectifying property with rectification ratio of over 105 at ± 10 V. From capacitance–voltage characteristics, it is found that a spatial distribution of space-charge density Ni of the p–n+ junction is not uniform and Ni at a middle region of the space-charge layer formed at zero bias voltage is higher than that of other region of the space-charge layer. This peculiar characteristic can be explained by superposition of two effects; one is the deep dopant effect due to B atoms in the p-type layer, which makes to reduce Ni at around the edge of the space-charge layer formed at zero bias voltage. The other is the compensation of B acceptors by impurity atoms diffusing during the p–n+ interface and incorporating during the growth of p-type layer, which makes to reduce Ni at the vicinity of the p–n+ interface. 相似文献
74.
The fabrication process of a low-temperature poly-Si thin-film transistor (TFT) with a storage capacitor was studied. The atmospheric-pressure chemical-vapour deposited SiO2 protected the buried indium tin oxide (ITO) from reduction by a pure H2 plasma treatment that was essential for the effective improvement of the poly-Si TFT characteristics. Thus, a storage capacitor with an ITO (picture electrode)-SiO2-ITO (buried common electrode) structure was successfully fabricated. The poly-Si TFT with a channel width/length W/L ratio of 5 drove a 3 pF storage capacitor in 2 μs, and it showed superior driverability for LCD use. The TFT also had good hold characteristics under illumination for the realization of grey-scale representation. 相似文献
75.
田长乐 《粉末冶金材料科学与工程》2003,8(4):363-366
从毛坯厚度差、装舟方式、冷却速度、舟皿涂料等方面分析了YG8和J12硬质合金长条薄片的弯曲变形原因,提出了几种抑制弯曲变形的措施。 相似文献
76.
本文综术了集成电路工艺的Cu布线中Cu薄膜化学气相沉积(CVD)的研究背景,详细介绍了CVD生长Cu金属薄膜的国内外研究进展及CVD对前趋物的要求,并对前趋物的一些物理、化学性质进行了总结,最后,对薄膜沉积的计算机摸拟作了简要介绍。 相似文献
77.
对唐钢薄板坯连铸机生产的SS400钢的生产工艺进行了分析,认为薄板坯连铸机生产的SS400钢,在采取了精炼站在线定氧,将钢水全氧控制在25×10~(-6)左右,同时连铸采取保护浇注和轻压下等技术后,能够确保薄板坯连铸SS400钢的顺利浇注,轧制的板带材表面质量良好,机械性能符合要求。 相似文献
78.
In this paper, we examine, both experimentally and theoretically, the kinetics of formation and microstructure of product
phases in thin film reactions, using the Nb/Al and Ti/Al systems as our prototypes. The results of calorimetry and microscopy
studies are interpreted using simple kinetic and morphology models. In particular, the kinetic models employed here focus
on the nucleation and growth components of the phase formation process and the morphology models provide a starting point
for the classification of product grain structures.
An erratum to this article is available at . 相似文献
79.
提出了溅射-气体-聚集共沉积制备金属/金属(介质)复合团簇镶嵌薄膜的新方法,并利用该方法成功地在方华膜衬底上制备了系列Fe/Ag及CaF2复合团簇镶嵌薄膜样品。透射电镜分析结果表明,样品中Fe(Cu)团簇都较好地镶嵌于Ag(CaF2)基质中,其结构为两种材料的多晶共存形态。进一步分析发现,与块材相比,Fe/Ag样品中Fe团簇晶格常数呈现出不同程度的收缩,而Cu/CaF2样品中Cu团簇晶格常数则呈现出不同程度的膨胀。运用附加压力的模型对该现象进行了解释。 相似文献
80.