全文获取类型
收费全文 | 206773篇 |
免费 | 11603篇 |
国内免费 | 6897篇 |
专业分类
电工技术 | 9117篇 |
技术理论 | 9篇 |
综合类 | 9474篇 |
化学工业 | 26729篇 |
金属工艺 | 11418篇 |
机械仪表 | 9824篇 |
建筑科学 | 10132篇 |
矿业工程 | 2979篇 |
能源动力 | 5825篇 |
轻工业 | 16740篇 |
水利工程 | 2805篇 |
石油天然气 | 5895篇 |
武器工业 | 1041篇 |
无线电 | 27019篇 |
一般工业技术 | 32597篇 |
冶金工业 | 29058篇 |
原子能技术 | 2499篇 |
自动化技术 | 22112篇 |
出版年
2024年 | 550篇 |
2023年 | 1993篇 |
2022年 | 3956篇 |
2021年 | 5205篇 |
2020年 | 3960篇 |
2019年 | 3365篇 |
2018年 | 4050篇 |
2017年 | 4535篇 |
2016年 | 4153篇 |
2015年 | 5362篇 |
2014年 | 7152篇 |
2013年 | 11130篇 |
2012年 | 10216篇 |
2011年 | 12158篇 |
2010年 | 10583篇 |
2009年 | 10792篇 |
2008年 | 10935篇 |
2007年 | 10653篇 |
2006年 | 9955篇 |
2005年 | 8312篇 |
2004年 | 6705篇 |
2003年 | 6004篇 |
2002年 | 5704篇 |
2001年 | 5525篇 |
2000年 | 4839篇 |
1999年 | 4915篇 |
1998年 | 10757篇 |
1997年 | 7158篇 |
1996年 | 5650篇 |
1995年 | 3831篇 |
1994年 | 3333篇 |
1993年 | 3100篇 |
1992年 | 1950篇 |
1991年 | 1832篇 |
1990年 | 1681篇 |
1989年 | 1461篇 |
1988年 | 1259篇 |
1987年 | 934篇 |
1986年 | 944篇 |
1985年 | 945篇 |
1984年 | 820篇 |
1983年 | 718篇 |
1982年 | 723篇 |
1981年 | 705篇 |
1980年 | 597篇 |
1979年 | 485篇 |
1978年 | 416篇 |
1977年 | 534篇 |
1976年 | 960篇 |
1975年 | 299篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
环境试验与可靠性试验的关系 总被引:1,自引:1,他引:0
从环境试验和可靠性试验的相关标准入手,详细论述了两者之间的相互关系与区别:互为补充,互为依存,共同发展,共同为保障产品的环境适应性和使用可靠性发挥作用。最后阐述了加强自然环境试验的重要性,它是检验实验结果的基本标准。 相似文献
992.
993.
A high-speed bilevel reproduction algorithm, called modified error diffusion (MED) algorithm, has been developed to provide high-quality halftoning images for continuous tone images and has been implemented in a CMOS LSI chip. The chip has been designed with standard-cell 1.5-μm CMOS technology using an optimum layout design. The chip has achieved a maximum processing speed of 60 ns/pixel 相似文献
994.
Trapping of net positive charge at low gate stress voltage, and of net negative charge at high gate stress voltage, is observed through changes in the gate-to-drain capacitance of the stressed junction. These observations can be explained in terms of electron trapping, hole trapping, and generation of acceptor-like interface states located in the upper half of the bandgap. Channel shortening is also observed and found to exhibit a logarithmic time dependence 相似文献
995.
The effect of different amounts (5, 10 and 15%) of compressive deformation of austenite on the isothermal transformation of acicular ferrite in an alloy-steel weld metal has been investigated. It was found that prior deformation of austenite significantly enhanced acicular ferrite transformation. At the same isothermal transformation temperature, as a higher amount of prior deformation was applied, a greater quantity of acicular ferrite could be obtained and the size of acicular ferrite plates became much finer. These results implied that the effective nucleation sites of acicular ferrite increased with increasing amount of prior deformation. The other results also emphasized that the accumulated strain (due to prior deformation of austenite) could trigger acicular ferrite to nucleate on inclusions at high temperatures, where undeformed austenite remained stable. The acicular ferrite start temperature was found to be raised continuously by increasing the amount of prior deformation of austenite. Further evidence suggests that the application of deformation can boost the driving force for acicular ferrite formation. This phenomenon is similar to the case in which martensite forms under the influence of deformation. 相似文献
996.
997.
Ishiguro A. Furuhashi T. Okuma S. Uchikawa Y. 《Industrial Electronics, IEEE Transactions on》1992,39(6):565-570
A neural network controller for trajectory control of robotic manipulators that is used not to internalize the inverse dynamic model of the controlled object but to compensate only the uncertainties of the robotic manipulator is presented. Its performance is compared with that of the conventional adaptive scheme. The results show the ability of the neural network controller to adapt to unstructured effects. A learning method for the neural network compensator with true teaching signals is shown. The tracking error of the robotic manipulator was greatly reduced when this controller was used 相似文献
998.
J Valla A Leguerrier H Corbineau B Sevray T Langanay H Le Couls M Sellin C Rioux Y Logeais 《Canadian Metallurgical Quarterly》1995,49(9):816-823
From 1978 to 1992, 121 cases of postinfarction left ventricular aneurysm (99 males, 22 females, mean age 60 years) were operated on. The authors insist on a high rate of clinical arhythmogenicity (31.4%) and associated mechanical complications (21%). 76% of patients were in functional NYHA class III or IV. Resection was performed in 90% of patients, plication in 10%. 58% underwent coronary artery bypass grafting (1.7 graft/patient), 16% encircling ventriculotomy, 8% mitral valve replacement and 13% closure of ventricular septal defect. Operative mortality was 14.9% (10% when other mechanical complications where excluded). 5-year survival is 67.9%. Late cardiac deaths are as follow: left ventricular failure (1.8% A/P), Sudden death (1.4% A/P), Myocardial infarction (0.6% A/P). 82% of survivals are in functional NYHA class I or II. Only functional class NYHA III or IV is predictive of late death. We conclude that postinfarction left ventricular aneurysm remains a high risk complication especially when associated with other mechanical complications. When arhythmogenicity is present we suggest rhythmologic surgery and in all cases, complete revascularization. 相似文献
999.
Morphology of thin anatase coatings prepared from alkoxide solutions containing organic polymer,affecting the photocatalytic decomposition of aqueous acetic acid 总被引:13,自引:0,他引:13
K. Kato A. Tsuzuki Y. Torii H. Taoda T. Kato Y. Butsugan 《Journal of Materials Science》1995,30(3):837-841
Porous anatase coatings were prepared from alkoxide solutions containing organic polymer by a dip-coating technique. The morphology of the coatings, such as pore size, pore distribution and thickness, was controlled. The effects of the morphology of the porous anatase coatings on the photocatalytic activity for the photocatalytic decomposition of aqueous acetic acid were examined. 相似文献
1000.