全文获取类型
收费全文 | 169474篇 |
免费 | 14790篇 |
国内免费 | 7468篇 |
学科分类
工业技术 | 191732篇 |
出版年
2024年 | 794篇 |
2023年 | 2900篇 |
2022年 | 5089篇 |
2021年 | 7038篇 |
2020年 | 5382篇 |
2019年 | 4562篇 |
2018年 | 4992篇 |
2017年 | 5646篇 |
2016年 | 4922篇 |
2015年 | 6865篇 |
2014年 | 8455篇 |
2013年 | 9941篇 |
2012年 | 11086篇 |
2011年 | 11841篇 |
2010年 | 10354篇 |
2009年 | 9886篇 |
2008年 | 9502篇 |
2007年 | 8956篇 |
2006年 | 9076篇 |
2005年 | 7792篇 |
2004年 | 5476篇 |
2003年 | 4851篇 |
2002年 | 4729篇 |
2001年 | 4247篇 |
2000年 | 4089篇 |
1999年 | 4270篇 |
1998年 | 3416篇 |
1997年 | 2879篇 |
1996年 | 2652篇 |
1995年 | 2315篇 |
1994年 | 1827篇 |
1993年 | 1354篇 |
1992年 | 1092篇 |
1991年 | 843篇 |
1990年 | 624篇 |
1989年 | 519篇 |
1988年 | 451篇 |
1987年 | 292篇 |
1986年 | 222篇 |
1985年 | 124篇 |
1984年 | 89篇 |
1983年 | 64篇 |
1982年 | 76篇 |
1981年 | 46篇 |
1980年 | 41篇 |
1979年 | 20篇 |
1978年 | 5篇 |
1977年 | 7篇 |
1975年 | 5篇 |
1970年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Shuang Shao Yong Liu Chun-Shui Xu Ying-Xuan Xu Bin Wu Xiao-Shu Zeng Xian-Feng Lu Xiang-Jie Yang 《金属学报(英文版)》2015,(1):7-14
The microstructure and mechanical properties of Mg–6Zn–1Y and Mg–6Zn–3Y(wt%) alloys under different cooling rates were investigated. The results show that the second dendrite arm spacing(SDAS) of Mg–6Zn–1Y and Mg–6Zn–3Y is reduced by 32 and 30% with increasing cooling rates(Rc) from 10.2 to 23 K/s, which can be predicted using a empirical model of SDAS=68 R 0:45:45cand SDAS=73 R 0c, respectively. The compressive strength of both alloys increases with increasing the cooling rate, which is attributed to the increase of volume fraction(Vf) of secondary phases under high cooling rate. The interaction of the cooling rate and component with SDAS has been theoretically analyzed using interdependence theory. 相似文献
22.
为了提高注入剖面测井的准确性,研制了一种新型注入剖面组合测井仪。该仪器由流量处理单元、伽马处理单元、井温处理单元、磁性定位处理单元、调制式传输、电源电路六部分组成。一次下井可同时测取流量、伽马、井温、磁性定位四组参数。具有测取资料精度高、单芯电缆传输、流量可单点测量也可连续测量以厦现场监测和维修方便等特点。 相似文献
23.
24.
A multi-level attention framework for tracking and segmentation of humans and objects under complex occlusions is investigated,
featuring an effective probabilistic appearance-based technique for pixel reclassification during object grouping and splitting.
A novel ’spatial-depth affinity metric’ is introduced in the conventional likelihood function, utilising information of both
spatial locations of pixels and dynamic depth ordering of the component objects in grouping. Depth ordering estimation is
achieved through a combination of top-down and bottom-up approach. Experiments on some realworld difficult scenarios of low
quality and highly compressed videos demonstrate the very promising results achieved. 相似文献
25.
26.
27.
28.
主要对各国3G许可证与使用技术标准的抽绑政策.各国对2G/3G网络漫游的管制规定。以及3G网络之间共享的种类及实施方式等方面做了详尽的讲解,并进行比较和分析。 相似文献
29.
The structure and properties of high density polyethylene (HDPE) functionalized by ultraviolet irradiation at different light intensities in air were studied by electron analysis, FTIR spectroscopy, contact angle with water, differential scanning calorimetry and mechanical properties measurement. The results show that oxygen‐containing groups such as C?O, C—O and C(?O)O were introduced onto the molecular chain of HDPE following irradiation, and the rate and efficiency of HDPE functionalization increased with enhancement of irradiation intensity. After irradiation, the melting temperature, contact angle with water and notched impact strength of HDPE decreased, the degree of crystallinity increased, and their variation amplitude increased with irradiation intensity. Compared with HDPE, the yield strength of HDPE irradiated at lower light intensity (32 W m?2 and 45 W m?2) increases monotonically with irradiation time, and the yield strength of HDPE irradiated at higher light intensity (78 W m?2) increases up to 48 h and then decreased with further increase in irradiation time. The irradiated HDPE behaved as a compatibilizer in HDPE/polycarbonate (PC) blends, and the interface bonding between HDPE and PC was ameliorated. After adding 20 wt% HDPE irradiated at 78 W m?2 irradiation intensity for 24 h to HDPE/PC blends, the tensile yield strength and notched Izod impact strength of the blend were increased from 26.3 MPa and 51 J m?1 to 30.2 MPa and 158 J m?1, respectively. Copyright © 2003 Society of Chemical Industry 相似文献
30.
随着我国经济的高速发展,业主要求提交资料的时间越来越短。为了提高工作效率,保质保量地完成工作,本文介绍了一些AutoCAD 2000及其以上版本的比较实用的技巧。灵活掌握了以下技巧后,绘图速度大约能提高50%。 相似文献