全文获取类型
收费全文 | 517842篇 |
免费 | 8761篇 |
国内免费 | 3541篇 |
专业分类
电工技术 | 10071篇 |
技术理论 | 2篇 |
综合类 | 2890篇 |
化学工业 | 77252篇 |
金属工艺 | 19765篇 |
机械仪表 | 16275篇 |
建筑科学 | 14590篇 |
矿业工程 | 3093篇 |
能源动力 | 13746篇 |
轻工业 | 47414篇 |
水利工程 | 5245篇 |
石油天然气 | 9154篇 |
武器工业 | 276篇 |
无线电 | 63869篇 |
一般工业技术 | 97797篇 |
冶金工业 | 91212篇 |
原子能技术 | 10473篇 |
自动化技术 | 47020篇 |
出版年
2022年 | 3171篇 |
2021年 | 4988篇 |
2020年 | 3828篇 |
2019年 | 4296篇 |
2018年 | 6692篇 |
2017年 | 6913篇 |
2016年 | 7173篇 |
2015年 | 5520篇 |
2014年 | 8872篇 |
2013年 | 23935篇 |
2012年 | 14480篇 |
2011年 | 19759篇 |
2010年 | 15513篇 |
2009年 | 17265篇 |
2008年 | 18006篇 |
2007年 | 17916篇 |
2006年 | 16294篇 |
2005年 | 14927篇 |
2004年 | 14003篇 |
2003年 | 13522篇 |
2002年 | 12823篇 |
2001年 | 13088篇 |
2000年 | 12273篇 |
1999年 | 13118篇 |
1998年 | 30204篇 |
1997年 | 21452篇 |
1996年 | 16579篇 |
1995年 | 12673篇 |
1994年 | 11082篇 |
1993年 | 10933篇 |
1992年 | 7904篇 |
1991年 | 7460篇 |
1990年 | 7191篇 |
1989年 | 6960篇 |
1988年 | 6595篇 |
1987年 | 5656篇 |
1986年 | 5555篇 |
1985年 | 6440篇 |
1984年 | 5872篇 |
1983年 | 5401篇 |
1982年 | 5066篇 |
1981年 | 5077篇 |
1980年 | 4899篇 |
1979年 | 4583篇 |
1978年 | 4484篇 |
1977年 | 5048篇 |
1976年 | 6462篇 |
1975年 | 3807篇 |
1974年 | 3674篇 |
1973年 | 3752篇 |
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
41.
This paper provides an overview of the main aspects of modern fluorescence microscopy. It covers the principles of fluorescence and highlights the key discoveries in the history of fluorescence microscopy. The paper also discusses the optics of fluorescence microscopes and examines the various types of detectors. It also discusses the signal and image processing challenges in fluorescence microscopy and highlights some of the present developments and future trends in the field. 相似文献
42.
43.
In this paper a digital filter is proposed for the generation of smooth set points for motion control systems. The proposed nonlinear filter produces profiles with bounded velocity and acceleration starting from rough reference signals (steps and ramps). An actual implementation of the filter for a tile printing machine is presented and experimental results are reported. 相似文献
44.
45.
Managing sewerage systems is a highly complex task due to the dynamic nature of the facilities. Their performance strongly depends on the know-how applied by the operators. In order to define optimal operational settings, two decision support tools based on mathematical models have been developed. Moreover, easy-to-use interfaces have been created as well, aiding operators who presumably do not have the necessary skills to use modelling software. The two developed programs simulate the behaviour of both wastewater treatment plants (WWTP) and sewer network systems, respectively. They have essentially the same structure, including raw data management and statistical analysis, a simulation layer using the application programming interface of the applied software and a layer responsible for the representation of the obtained results. Four user modes are provided in the two software including the simulation of historical data using the applied and novel operational settings, as well as modes concerning prediction of possible operation periods and updates. Concerning the WWTP software, it was successfully installed in Nantes (France) in June 2004. Moreover, the one managing sewer networks has been deployed in Saint-Malo (France) in January 2005. This paper presents the structure of the developed software and the first results obtained during the commissioning phase. 相似文献
46.
Demiguel S. Giraudet L. Joulaud L. Decobert J. Blache F. Coupe V. Jorge F. Pagnod-Rossiaux P. Boucherez E. Achouche M. Devaux F. 《Lightwave Technology, Journal of》2002,20(12):2004-2014
The design, fabrication, and performance of double-stage taper photodiodes (DSTPs) are reported. The objective of this work is to develop devices compatible with 40-Gb/s applications. Such devices require high efficiency, ultrawide band, high optical power handling capability, and compatibility with low-cost module fabrication. The integration of mode size converters improves both the coupling efficiency and the responsivity with a large fiber mode diameter. Responsivity of 0.6 A/W and 0.45 A/W are achieved with a 6-/spl mu/m fiber mode diameter and cleaved fiber, respectively, providing relaxed alignment tolerances (/spl plusmn/1.6 /spl mu/m and /spl plusmn/2 /spl mu/m, respectively), compatible with cost-effective packaging techniques. DSTPs also offer a wide bandwidth greater than 40 GHz and transverse-electric/transverse-magnetic polarization dependence lower than 0.2 dB. Furthermore, a DSTP saturation current as high as 11 mA results in optical power handling greater than +10 dBm and a high output voltage of 0.8 V. These capabilities allow the photodiode to drive the decision circuit without the need of a broad-band electrical amplifier. The DSTP devices presented here demonstrate higher responsivities with large fiber mode diameter and better optical power handling capabilities and are compared with classical side-illuminated photodiodes. 相似文献
47.
Presents the Satellite Communications Network Expert (SaNE), a knowledge-based aid designed to provide engineering support for fault diagnosis. The SaNE is composed of two elements: a satcom network model, which simulates the structure and functionality of a system based loosely upon a large military satcom network, and a diagnostic component, which uses knowledge- and model-based reasoning techniques to analyse system anomalies and diagnose possible causes for the alarms such networks generate. The development cycle is described, emphasising lessons learnt during development and testing and the advantages and disadvantages of the techniques applied. The goal of the SaNE project is primarily commercial acceptance rather than innovation. The authors illustrate how novel concepts can be implemented in a practical system without compromising this goal 相似文献
48.
49.
The thermal expansion of tellurides of germanium, bismuth, and intermetallic compounds is investigated over the temperature range 293-973 K.Belarusian Agricultural Technical University, Minsk. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 66, No. 5, pp. 612–616, May 1994. 相似文献
50.
P Rutgeerts 《Canadian Metallurgical Quarterly》1996,19(1):44-46
Absorbable and nonabsorbable buried sutures were studied in primary cleft lip repair. Group 1 (N = 56) consisted of patients repaired with buried nonabsorbable material (monofilament nylon). Group 2 (N = 47) consisted of patients repaired with absorbable materials (polyglyconate, polydioxanone). All patients were monitored for 12 months. There were stitch abscesses in Group 1 (14%). There were no abscesses in Group 2. This difference was significant (p = 0.007). Abscesses were located in the suture line with no identifiable distribution. There was no significant difference in the cosmetic appearance of the scars in Groups 1 and 2. These results support the view that absorbable sutures are preferable to nonabsorbable sutures for primary cleft lip repair. 相似文献