全文获取类型
收费全文 | 4644篇 |
免费 | 312篇 |
国内免费 | 94篇 |
专业分类
电工技术 | 209篇 |
综合类 | 210篇 |
化学工业 | 960篇 |
金属工艺 | 187篇 |
机械仪表 | 204篇 |
建筑科学 | 311篇 |
矿业工程 | 90篇 |
能源动力 | 165篇 |
轻工业 | 339篇 |
水利工程 | 52篇 |
石油天然气 | 253篇 |
武器工业 | 41篇 |
无线电 | 449篇 |
一般工业技术 | 678篇 |
冶金工业 | 288篇 |
原子能技术 | 54篇 |
自动化技术 | 560篇 |
出版年
2024年 | 17篇 |
2023年 | 69篇 |
2022年 | 116篇 |
2021年 | 138篇 |
2020年 | 110篇 |
2019年 | 72篇 |
2018年 | 107篇 |
2017年 | 140篇 |
2016年 | 103篇 |
2015年 | 133篇 |
2014年 | 199篇 |
2013年 | 282篇 |
2012年 | 236篇 |
2011年 | 298篇 |
2010年 | 231篇 |
2009年 | 249篇 |
2008年 | 234篇 |
2007年 | 251篇 |
2006年 | 249篇 |
2005年 | 225篇 |
2004年 | 155篇 |
2003年 | 139篇 |
2002年 | 130篇 |
2001年 | 124篇 |
2000年 | 135篇 |
1999年 | 139篇 |
1998年 | 125篇 |
1997年 | 96篇 |
1996年 | 95篇 |
1995年 | 77篇 |
1994年 | 73篇 |
1993年 | 67篇 |
1992年 | 50篇 |
1991年 | 25篇 |
1990年 | 23篇 |
1989年 | 23篇 |
1988年 | 14篇 |
1987年 | 23篇 |
1986年 | 15篇 |
1985年 | 10篇 |
1984年 | 7篇 |
1983年 | 3篇 |
1982年 | 8篇 |
1981年 | 7篇 |
1980年 | 10篇 |
1979年 | 2篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1975年 | 4篇 |
1970年 | 4篇 |
排序方式: 共有5050条查询结果,搜索用时 15 毫秒
71.
研究了高氯氯化聚乙烯(HCPE)对氯丁橡胶与甲基丙烯酸甲酯接枝共聚及其反应产物的影响。结果表明,HCPE能加快聚合速率,提高转化率、接枝效率和接枝度。含HCPE的产物,含有较高分子量的级份,分子量分布较宽,树脂相的分布比较均匀,并具有较好的机械性能和较高的粘接强度。 相似文献
72.
Diamond-like carbon (DLC) thin films are extensively utilized in the semiconductor, electric and cutting machine industries owing to their high hardness, high elastic modulus, low friction coefficients and high chemical stability. DLC films are prepared by ion beam-assisted deposition (BAD), sputter deposition, plasma-enhanced chemical vapor deposition (PECVD), cathodic arc evaporation (CAE), and filter arc deposition (FAD). The major drawbacks of these methods are the degraded hardness associated with the low sp3/sp2 bonding ratio, the rough surface and poor adhesion caused by the presence of particles. In this study, a self-developed filter arc deposition (FAD) system was employed to prepare metal-containing DLC films with a low particle density. The relationships between the DLC film properties, such as film structure, surface morphology and mechanical behavior, with variation of substrate bias and target current, are examined. Experimental results demonstrate that FAD-DLC films have a lower ratio, suggesting that FAD-DLC films have a greater sp3 bonding than the CAE-DLC films. FAD-DLC films also exhibit a low friction coefficient of 0.14 and half of the number of surface particles as in the CAE-DLC films. Introducing a CrN interfacial layer between the substrate and the DLC films enables the magnetic field strength of the filter to be controlled to improve the adhesion and effectively eliminate the contaminating particles. Accordingly, the FAD system improves the tribological properties of the DLC films. 相似文献
73.
74.
Nornikman Hassan Zahriladha Zakaria Weng Yik Sam Izyan Nazihan Mohd Hanapiah A. Nasoruddin Mohamad Ameer Farhan Roslan Badrul Hisham Ahmad Mohd Khairy Ismail Mohamad Zoinol Abidin Abd Aziz 《国际射频与微波计算机辅助工程杂志》2019,29(1)
This work focusing on the dual‐band antenna design with rectifying circuit for energy transfer system technology for enhancement gain performance. The air gap technique is applied on this microstrip antenna design work to enhance the antenna gain. The work begins with designing and analyzing the antenna via the CST Microwave Studio software. After validation on acceptable performance in simulation side is obtained, the return loss, S11 of the antenna is measured using vector network analyzer equipment. The rectifier circuit is used to convert the captured signal to DC voltage. This projected dual‐band antenna has successfully accomplished the target on return loss of ?44.707 dB and ?32.163 dB at dual resonant frequencies for 1.8 GHz and 2.4 GHz, respectively. This proposed antenna design benefits in low cost fabrication and has achieved high gain of 6.31 dBi and 7.82 dBi for dual‐band functioning frequencies. 相似文献
75.
76.
77.
A successful product family design method should achieve an optimal tradeoff among a set of conflicting objectives, which
involves maximizing commonality across the family of products with the prerequisite of satisfying customers’ performance requirements.
Optimization based methods are experiencing new found use in product family design to resolve the inherent tradeoff between
commonality and distinctiveness that exists within a product family. This paper presents and develops a 2-level chromosome
structured genetic algorithm (2LCGA) to simultaneously determine the optimal settings for the product platform and corresponding
family of products, by automatically varying the amount of platform commonality within the product family during a single
optimization process. The single-stage approach can yield improvements in the overall performance of the product family compared
with two-stage approaches, in which the first stage involves determining the best settings for the platform variables and
values of unique variables are found for each product in the second stage. The augmented scope of 2LCGA allows multiple platforms
to be considered during product family optimization, offering opportunities for superior overall design by more efficacious
tradeoffs between commonality and performance. The effectiveness of the proposed approach is demonstrated through the design
of a family of universal electric motors and comparison against previous work. 相似文献
78.
79.
在舞台排练系统中,经常有上百盏不同式样的灯同时照亮场景的情况发生,但是目前图形处理器硬件只支持8盏灯同时点亮,而且大多数渲染引擎只提供点光源、聚光源和方向光源三种灯光模型.为了实时模拟真实的效果,使用了一个称为超级椭圆的光源模型,它可以把各种不同形状的灯的式样预先计算出并保存在纹理贴图中,这样后期计算光强度时只要从纹理中获得即可.此外,还提出如何进行光照优化,减少不必要计算,使所有灯都能发挥作用的方法.通过测试,系统达到了令人满意的实时帧数和效果. 相似文献
80.
根据CTL发布的DSH 0743决议,归纳了LED节能灯测试标准中的要求,主要包含对灯头、防触电、灯头温升、绝缘材料、异常状态、结构的考核,以及灯的光生物学安全考核。 相似文献