全文获取类型
收费全文 | 19449篇 |
免费 | 1833篇 |
国内免费 | 533篇 |
学科分类
工业技术 | 21815篇 |
出版年
2024年 | 80篇 |
2023年 | 195篇 |
2022年 | 392篇 |
2021年 | 574篇 |
2020年 | 538篇 |
2019年 | 312篇 |
2018年 | 378篇 |
2017年 | 479篇 |
2016年 | 550篇 |
2015年 | 641篇 |
2014年 | 1285篇 |
2013年 | 1131篇 |
2012年 | 1512篇 |
2011年 | 1443篇 |
2010年 | 1133篇 |
2009年 | 1185篇 |
2008年 | 993篇 |
2007年 | 1221篇 |
2006年 | 1154篇 |
2005年 | 1071篇 |
2004年 | 848篇 |
2003年 | 862篇 |
2002年 | 698篇 |
2001年 | 623篇 |
2000年 | 523篇 |
1999年 | 384篇 |
1998年 | 318篇 |
1997年 | 233篇 |
1996年 | 244篇 |
1995年 | 177篇 |
1994年 | 153篇 |
1993年 | 100篇 |
1992年 | 95篇 |
1991年 | 78篇 |
1990年 | 58篇 |
1989年 | 48篇 |
1988年 | 19篇 |
1987年 | 14篇 |
1986年 | 9篇 |
1985年 | 25篇 |
1984年 | 15篇 |
1983年 | 9篇 |
1982年 | 9篇 |
1981年 | 1篇 |
1980年 | 4篇 |
1978年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
Uma Maheswar Rao S. S. M. S. Abdul Majeed C. Venkataseshaiah R. Sarathi 《Bulletin of Materials Science》2002,25(6):473-475
In the present work, tracking phenomena has been studied with silicone rubber material under the a.c. and d.c. voltages following
IEC-587 standards. The surface condition of the tracked zone was analysed using wide angle X-ray diffraction (WAXD) and thermogravimetric
differential thermal analysis (TG-DTA) studies. The tracking time was different for a.c. and d.c. voltages. 相似文献
33.
本文详细系统地介绍了我国有线是视发展历史和现状,及其经营和管理方法。重点介绍了北美的CATV技术发展动向。最后,指出我国CATV事业发展中的应用重视的问题。 相似文献
34.
Fracture toughness and fatigue crack propagation (FCP) of plain and modified anhydride-cured epoxy resin (EP) were studied at ambient temperature. Liquid carboxyl-terminated acrylonitrile-butadiene (CTBN) and silicon (SI) rubber dispersions were used as tougheners for the EP. The morphology of the modified EP was characterized by dynamic mechanical analysis (DMA) and by scanning electron microscopy (SEM). The fracture toughness, Kc, of the compositions decreased with increasing deformation rate. Kc of the EP was slightly improved by CTBN addition and practically unaffected by incorporation of the SI dispersion when tests were performed at low cross-head speed, v. Both modifiers improved Kc at high v, and also the resistance to FCP, by shifting the curves to higher stress intensity factor ranges, ΔK, by comparison with the plain EP. It was established that both fracture and fatigue performance rely on the compliance, JR, at the rubbery plateau, and thus on the apparent molecular mass between crosslinks, Mc. The failure mechanisms were less dependent upon the loading mode (fracture, fatigue), but differed basically for the various modifiers. Rubber-induced cavitation and shear yielding of the EP were dominant for CTBN, whereas crack bifurcation and branching controlled the cracking in SI-modified EP. The simultaneous use of both modifiers resulted in a synergistic effect for both the fracture toughness at high deformation rate and the FCP behavior. 相似文献
35.
36.
介绍了ADSS光缆的力学计算,给出了光缆弧垂、张力、应变和悬长等计算公式,并对普遍采用的“悬链线”和“抛物线”两种计算方法加以比较。 相似文献
37.
38.
ATH在无卤阻燃聚乙烯电缆料中的应用研究 总被引:12,自引:0,他引:12
何云南 《高分子材料科学与工程》1992,8(6):126-130
以EVA改性LDPE,以偶联剂改性ATH,通过一系列配方的研究和性能测定,认为可以设计出适合于电缆料用的无卤阻燃聚乙烯的配方。 相似文献
39.
Naoki Takinami Takashi Chino Shotaro Yoshida Isao Miura Kazuo Watanabe Kazuo Amano 《Electrical Engineering in Japan》1994,114(6):1-12
When ground-fault problems occur on a cable line, immediate fault location and restoration are required. Therefore, various new methods to locate the fault point instantaneously have been investigated to replace such conventional methods as the Murray loop method and the pulse radar method [1]. These methods require a long time to locate the fault point. One possible fault location method is to sense the temperature rise following a ground fault using a fiber optic distributed temperature sensor. Application of this method was found feasible through sensing the temperature rise at a ground-fault test using a thermocouple as a temperature sensor with test cables [4]. A power/optical composite cable was prepared experimentally and after verifying its thermal mechanical performance, the temperature rise at an incidence of a fault was determined and the anticipated performance was demonstrated in a ground-fault test. This article describes the outline of the test. 相似文献
40.