全文获取类型
收费全文 | 226650篇 |
免费 | 5087篇 |
国内免费 | 2003篇 |
专业分类
电工技术 | 5197篇 |
技术理论 | 1篇 |
综合类 | 2124篇 |
化学工业 | 33366篇 |
金属工艺 | 9485篇 |
机械仪表 | 7848篇 |
建筑科学 | 6953篇 |
矿业工程 | 2200篇 |
能源动力 | 5890篇 |
轻工业 | 19530篇 |
水利工程 | 2830篇 |
石油天然气 | 5773篇 |
武器工业 | 214篇 |
无线电 | 25813篇 |
一般工业技术 | 42900篇 |
冶金工业 | 38482篇 |
原子能技术 | 5401篇 |
自动化技术 | 19733篇 |
出版年
2022年 | 1625篇 |
2021年 | 2772篇 |
2020年 | 2004篇 |
2019年 | 2293篇 |
2018年 | 3394篇 |
2017年 | 3536篇 |
2016年 | 3574篇 |
2015年 | 2872篇 |
2014年 | 4531篇 |
2013年 | 10705篇 |
2012年 | 6907篇 |
2011年 | 9157篇 |
2010年 | 7411篇 |
2009年 | 8109篇 |
2008年 | 8223篇 |
2007年 | 8118篇 |
2006年 | 7111篇 |
2005年 | 6601篇 |
2004年 | 5919篇 |
2003年 | 5640篇 |
2002年 | 5234篇 |
2001年 | 5280篇 |
2000年 | 5187篇 |
1999年 | 5301篇 |
1998年 | 11813篇 |
1997年 | 8529篇 |
1996年 | 6755篇 |
1995年 | 4951篇 |
1994年 | 4517篇 |
1993年 | 4234篇 |
1992年 | 3365篇 |
1991年 | 3157篇 |
1990年 | 2933篇 |
1989年 | 2984篇 |
1988年 | 2869篇 |
1987年 | 2424篇 |
1986年 | 2322篇 |
1985年 | 2721篇 |
1984年 | 2515篇 |
1983年 | 2351篇 |
1982年 | 2098篇 |
1981年 | 2210篇 |
1980年 | 2034篇 |
1979年 | 2126篇 |
1978年 | 2120篇 |
1977年 | 2366篇 |
1976年 | 3188篇 |
1975年 | 1833篇 |
1974年 | 1761篇 |
1973年 | 1772篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
An explicit extraction of the retinal vessel is a standout amongst the most significant errands in the field of medical imaging to analyze both the ophthalmological infections, for example, Glaucoma, Diabetic Retinopathy (DR), Retinopathy of Prematurity (ROP), Age-Related Macular Degeneration (AMD) as well as non retinal sickness such as stroke, hypertension and cardiovascular diseases. The state of the retinal vasculature is a significant indicative element in the field of ophthalmology. Retinal vessel extraction in fundus imaging is a difficult task because of varying size vessels, moderately low distinction, and presence of pathologies such as hemorrhages, microaneurysms etc. Manual vessel extraction is a challenging task due to the complicated nature of the retinal vessel structure, which also needs strong skill set and training. In this paper, a supervised technique for blood vessel extraction in retinal images using Modified Adaboost Extreme Learning Machine (MAD-ELM) is proposed. Firstly, the fundus image preprocessing is done for contrast enhancement and in-homogeneity correction. Then, a set of core features is extracted, and the best features are selected using “minimal Redundancy-maximum Relevance (mRmR).” Later, using MAD-ELM method vessels and non vessels are classified. DRIVE and DR-HAGIS datasets are used for the evaluation of the proposed method. The algorithm’s performance is assessed based on accuracy, sensitivity and specificity. The proposed technique attains accuracy of 0.9619 on the DRIVE database and 0.9519 on DR-HAGIS database, which contains pathological images. Our results show that, in addition to healthy retinal images, the proposed method performs well in extracting blood vessels from pathological images and is therefore comparable with state of the art methods. 相似文献
82.
设计了一种以STM32F103微控制器为控制核心,基于24位高精度模数转换器的钻孔深度测量仪器。利用弹性波回波测距原理,通过测量出钻孔中钻杆的长度,实现钻孔深度的快速、无损、准确的测量,主要用于井下瓦斯抽放钻孔、探放水钻孔等煤矿通防工作的施工验收。仪器小巧轻便,操作简单,单人即可完成测量工作,节约下井的人力物力,提高生产效率,最长测量长度可达250米,误差不超过1米。 相似文献
83.
84.
85.
86.
87.
88.
The design of a microstrip‐fed annular‐ring slot antenna (ARSA) with circular polarization (CP) radiation is initially studied. To obtain CP radiation with broad 3‐dB axial ratio (AR) bandwidth that can cover the WiMAX 2.3 GHz (2305–2320 MHz, 2345–2360 MHz) and WLAN 2.4 GHz (2400–2480 MHz) bands, a novel technique of extending an inverted L‐shaped slot from the bottom section of the annular‐ring is proposed. To suppress the harmonic modes induced by the CP ARSA, the technique of integrating a defected ground structure into the annular‐ring slot is further introduced. From the measured results, 10‐dB impedance bandwidth and 3‐dB AR bandwidth of 44.86 and 9.68% were achieved by the proposed harmonic suppressed CP ARSA. Furthermore, average gain and radiation efficiency of ~4.7 dBic and 71%, respectively, were also exhibited across the bands of interest. © 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:337–345, 2015. 相似文献
89.
90.
Parsania P. H. Sankhavara Dharmesh B. Chopda Jalpa Patel Jignesh P. 《Polymer Bulletin》2020,77(6):3111-3128
Polymer Bulletin - Jute and glass composites of epoxy resin of (2E, 6E)-bis(4-hydroxybenzylidene)cyclohexanone (EBHBC) were prepared by compressing molding technique using three different hardeners... 相似文献