全文获取类型
收费全文 | 366807篇 |
免费 | 19591篇 |
国内免费 | 11282篇 |
专业分类
电工技术 | 18305篇 |
技术理论 | 4篇 |
综合类 | 14357篇 |
化学工业 | 50174篇 |
金属工艺 | 17877篇 |
机械仪表 | 16934篇 |
建筑科学 | 18304篇 |
矿业工程 | 6407篇 |
能源动力 | 9758篇 |
轻工业 | 27334篇 |
水利工程 | 5930篇 |
石油天然气 | 11183篇 |
武器工业 | 2016篇 |
无线电 | 47827篇 |
一般工业技术 | 54193篇 |
冶金工业 | 52053篇 |
原子能技术 | 5484篇 |
自动化技术 | 39540篇 |
出版年
2023年 | 3055篇 |
2022年 | 6291篇 |
2021年 | 8878篇 |
2020年 | 6664篇 |
2019年 | 5703篇 |
2018年 | 7051篇 |
2017年 | 7997篇 |
2016年 | 7239篇 |
2015年 | 9111篇 |
2014年 | 12215篇 |
2013年 | 19295篇 |
2012年 | 17711篇 |
2011年 | 19877篇 |
2010年 | 17724篇 |
2009年 | 17797篇 |
2008年 | 18015篇 |
2007年 | 17427篇 |
2006年 | 15794篇 |
2005年 | 13249篇 |
2004年 | 10783篇 |
2003年 | 9769篇 |
2002年 | 9399篇 |
2001年 | 9270篇 |
2000年 | 8074篇 |
1999年 | 7941篇 |
1998年 | 17201篇 |
1997年 | 11608篇 |
1996年 | 9133篇 |
1995年 | 6810篇 |
1994年 | 5855篇 |
1993年 | 5541篇 |
1992年 | 3806篇 |
1991年 | 3560篇 |
1990年 | 3457篇 |
1989年 | 3249篇 |
1988年 | 2929篇 |
1987年 | 2330篇 |
1986年 | 2390篇 |
1985年 | 2643篇 |
1984年 | 2348篇 |
1983年 | 2085篇 |
1982年 | 1930篇 |
1981年 | 2082篇 |
1980年 | 1828篇 |
1979年 | 1684篇 |
1978年 | 1665篇 |
1977年 | 2028篇 |
1976年 | 2712篇 |
1975年 | 1430篇 |
1974年 | 1374篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
用屏蔽暂堵技术封堵水平井裂缝性漏层 总被引:1,自引:1,他引:0
克拉玛依油田HW702水平井的大斜度段和水平段,将穿越纵向裂缝发育的二叠系佳木河组储层。为安全钻进和保护油层,用超细碳酸钙和磺化沥青复配后加入复合离子钻井液中成屏蔽暂堵的堵漏钻井液。室内用岩心试验,屏蔽暂堵后渗透率可降为0,暂堵深度小于3cm,可用酸化和射孔解堵。现场使用效果也很好,使HW702水平井顺利完钻,并获得工业油气流。 相似文献
992.
993.
After recording transiently evoked otoacoustic emissions (TEOAEs) to a click stimulus in guinea pigs by using the IL088 which was developed by Bray and Kemp (1987) for easy recording and analysis of TEOAE, the changes after intravenous administration of furosemide (30 mg/kg or 50 mg/kg) were examined. The wave of the TEOAE could be detected from 20 of 24 ears (83%). After the i.v. injection of furosemide (30 mg/kg), TEOAE powers (total echo power and highest peak power in FFT pictures) decreased quickly and showed minimum values after 5-10 min. Then they increased rapidly and recovered normally within 60 min after injection. However, no ears showed TEOAEs during the 5- to 10-min period following the injection of the 50-mg/kg dose of furosemide. They then recovered slowly as compared with the group treated with the lower dose of furosemide (30 mg/kg). These changes are similar to those of the endocochlear potential (EP) after furosemide injection. These data support the notion that the EP can contribute to the mechanism of TEOAE generation. 相似文献
994.
A. F. Lisovskii T. É. Gracheva E. S. Cherepenina I. V. Manzheleev 《Powder Metallurgy and Metal Ceramics》1988,27(6):445-449
Translated from Poroshkovaya Metallurgiya, No. 6(306), pp. 40–44, June, 1988. 相似文献
995.
996.
Vuong S.T. Lau A.C. Chan R.I. 《IEEE transactions on pattern analysis and machine intelligence》1988,14(3):384-393
The basic ideas underlying an Estelle-C compiler, which accepts an Estelle protocol specification and produces a protocol implementation in C, are presented. The implementation of the ISO (International Organization for Standardization) class-2 transparent protocol, using the semiautomatic approach, is discussed. A manual implementation of the protocol is performed and compared to the semiautomatic implementation. The semiautomatic approach to protocol implementation offers several advantages over the conventional manual one, including correctness and modularity in protocol implementation code, conformance to the specification, and reduction in implementation time. Finally, ongoing development of a new Estelle-C compiler is presented 相似文献
997.
998.
M. E. Fitzpatrick M. T. Hutchings J. E. King D. M. Knowles P. J. Withers 《Metallurgical and Materials Transactions A》1995,26(12):3191-3198
The effects of a thermal residual stress field on fatigue crack growth in a silicon carbide particle-reinforced aluminum alloy
have been measured. Stress fields were introduced into plates of material by means of a quench from a solution heat-treatment
temperature. Measurements using neutron diffraction have shown that this introduces an approximately parabolic stress field
into the plates, varying from compressive at the surfaces to tensile in the center. Long fatigue cracks were grown in specimens
cut from as-quenched plates and in specimens which were given a stress-relieving overaging heat treatment prior to testing.
Crack closure levels for these cracks were determined as a function of the position of the crack tip in the residual stress
field, and these are shown to differ between as-quenched and stress-relieved samples. By monitoring the compliance of the
specimens during fatigue cycling, the degree to which the residual stresses close the crack has been evaluated.
formerly Research Student, Department of Materials Science and Metallurgy, University of Cambridge
formerly Lecturer, Department of Materials Science and Metallurgy, University of Cambridge
This article is based on a presentation made in the symposium entitled “Creep and Fatigue in Metal Matrix Composites” at the
1994 TMS/ASM Spring meeting, held February 28–March 3, 1994, in San Francisco, California, under the auspices of the Joint
TMS-SMD/ASM-MSD Composite Materials Committee. 相似文献
999.
1000.
At strain rates greater than about 10 the deformation of polymers is an adiabatic process which can lead to the generation of very high localized temperatures. These may be well in excess of the temperatures required for thermal decomposition of the polymer to occur. It is speculated that gaseous products arising from such decomposition may act as the source of microcavities and craze initiators. Experiments are described in which the thermal decomposition reaction parameters of polyetherketone, polyetheretherketone, and polysulphone are measured using differential scanning calorimetry and thermogravimetric analysis, and the decomposition products analysed by mass spectrometry. The results indicate that the proposed mechanism could act as a source of micropores with total pore volumes amounting to several per cent of the material volume. 相似文献