全文获取类型
收费全文 | 1474篇 |
免费 | 23篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 131篇 |
综合类 | 4篇 |
化学工业 | 341篇 |
金属工艺 | 40篇 |
机械仪表 | 35篇 |
建筑科学 | 46篇 |
能源动力 | 44篇 |
轻工业 | 108篇 |
水利工程 | 6篇 |
石油天然气 | 1篇 |
无线电 | 172篇 |
一般工业技术 | 235篇 |
冶金工业 | 185篇 |
原子能技术 | 87篇 |
自动化技术 | 66篇 |
出版年
2022年 | 16篇 |
2021年 | 22篇 |
2020年 | 7篇 |
2019年 | 11篇 |
2018年 | 17篇 |
2017年 | 18篇 |
2016年 | 19篇 |
2015年 | 10篇 |
2014年 | 19篇 |
2013年 | 64篇 |
2012年 | 43篇 |
2011年 | 48篇 |
2010年 | 47篇 |
2009年 | 58篇 |
2008年 | 74篇 |
2007年 | 56篇 |
2006年 | 47篇 |
2005年 | 49篇 |
2004年 | 37篇 |
2003年 | 39篇 |
2002年 | 57篇 |
2001年 | 20篇 |
2000年 | 24篇 |
1999年 | 40篇 |
1998年 | 83篇 |
1997年 | 64篇 |
1996年 | 45篇 |
1995年 | 48篇 |
1994年 | 52篇 |
1993年 | 39篇 |
1992年 | 21篇 |
1991年 | 25篇 |
1990年 | 28篇 |
1989年 | 19篇 |
1988年 | 18篇 |
1987年 | 23篇 |
1986年 | 24篇 |
1985年 | 17篇 |
1984年 | 15篇 |
1983年 | 17篇 |
1982年 | 18篇 |
1981年 | 14篇 |
1980年 | 11篇 |
1979年 | 11篇 |
1978年 | 9篇 |
1977年 | 10篇 |
1976年 | 10篇 |
1975年 | 9篇 |
1973年 | 10篇 |
1972年 | 6篇 |
排序方式: 共有1501条查询结果,搜索用时 46 毫秒
1.
Increasing the reaction temperature of the living cationic polymerization of isobutylene is crucial for industrial production due to the cost of refrigeration. The reaction temperature increase was achieved with an accelerated reaction rate using a flow reaction system. The polymerization conditions, including the flow reactor design, were based on the results of kinetic studies. Utilizing a milli‐scale flow reactor, polyisobutylene, which has a narrow molecular weight distribution, was obtained within a considerably short residence time at a high temperature. Furthermore, it was confirmed that the value of Mw/Mn correlates with the product of the Reynolds number and the angle of collision. 相似文献
2.
3.
Vassiliou I. Vavelidis K. Georgantas T. Plevridis S. Haralabidis N. Kamoulakos G. Kapnistis C. Kavadias S. Kokolakis Y. Merakos P. Rudell J.C. Yamanaka A. Bouras S. Bouras I. 《Solid-State Circuits, IEEE Journal of》2003,38(12):2221-2231
The drive for cost reduction has led to the use of CMOS technology in the implementation of highly integrated radios. This paper presents a single-chip 5-GHz fully integrated direct conversion transceiver for IEEE 802.11a WLAN systems, manufactured in 0.18-/spl mu/m CMOS. The IC features an innovative system architecture which takes advantage of the computing resources of the digital companion chip in order to eliminate I/Q mismatch and achieve accurately matched baseband filters. The integrated voltage-controlled oscillator and synthesizer achieve an integrated phase noise of less than 0.8/spl deg/ rms. The receiver has an overall noise figure of 5.2 dB and achieves sensitivity of -75 dBm at 54-Mb/s operation, both referred to the IC input. The transmit error vector magnitude is -33 dB at -5-dBm output power from the integrated power-amplifier driver amplifier. The transceiver occupies an area of 18.5 mm/sup 2/. 相似文献
4.
A low threshold current density of ~100 A/cm2 has been obtained at 1.55 μm using a graded-index separate-confinement-heterostructure strained InGaAsP single-quantum-well laser. The design of the laser structure is based on results calculated from the viewpoint of effective carrier injection into the well 相似文献
5.
Yamanaka N. Kawano R. Oki E. Yasukawa S. Okazaki K. 《Advanced Packaging, IEEE Transactions on》2002,25(1):65-72
A 640-Gb/s high-speed ATM switching system that is based on the technologies of advanced MCM-C, 0.25-μm CMOS, and optical wavelength-division-multiplexing (WDM) interconnection is fabricated for future broadband backbone networks. A 40-layer, 160×114 mm ceramic MCM forms the basic ATM switch module with 80-Gb/s throughput. It consists of 8 advanced 0.25-μm CMOS LSIs and 32 I/O bipolar LSIs. The MCM has a 7-layer high-speed signal line structure having 50-Ω strip lines, high-speed signal lines, and 33 power supply layers formed using 50-μm thick ceramic layers to achieve high capacity. A uniquely structured closed-loop-type liquid cooling system for the MCM is used to cope with its high power dissipation of 230 W. A three-stage ATM switch is made using the optical WDM interconnection between high-performance MCMs. For WDM interconnection, newly developed compact 10-Gb/s, 8-WDM optical transmitter and receiver modules are used. These modules are each only 80×120×20 mm and dissipate 9.65 W and 22.5 W, respectively. They have a special chassis for cooling, which contains high-performance heat-conductive plates and micro-fans. An optical WDM router based on an arrayed waveguide router is used for mesh interconnection of boards. The optical WDM interconnect has 640-Gb/s throughput and simple interconnection 相似文献
6.
7.
In recent years, computer technology has made remarkable progress and a computer has become an indispensable tool for both engineers and scientists. In this article, utilization of computers in welding research is briefly summarized. Their use in numerical analysis is particularly discussed and applied to physical phenomena in molten pool, hydrogen diffusion and residual stresses due to welding. A comparison is made between theoretical and experimental results. 相似文献
8.
Masato Miyauchi Atsuko Miyake Yukio Nakanishi Yasuyuki Sagara 《Drying Technology》1995,13(8):1741-1761
An experimental study has been carried out on the characteristics of binary adsorption isotherms of water and volatile flavor for typical materials used in a box of a tobacco product or cigarettes. Ethyl acetate chosen as a model for water-soluble volatile flavor. Binary adsorption isotherms for the tobacco, papers, filters, and activated carbons were measured with a flow-type multi-component adsorption system under the canstant conditions of temperature a t 303 K and vapor pressure of water a t 2.5 kPain the vapor pressure range of ethyl acetate from 0 to 4.2 kPa. A linear equation was applied to express the binary adsorption isotherms for the tobacco, papers and filters, while a Dubinin-Astakhov equation was applied for the activated carbons. The binary adsorption was characterized into three groups, depending on the selectivity as well as the mechanism of adsorption; i.e.(l) for tobacco and papers, water was adsorbed much greater rather than ethyl acetate, (2) for filters, ethyl acetate was adsorbed on the surface as great as water, (3) for activated carbons, ethyl acetate was adsorbed much greater onto their micropores rather than water. The results showed that ethyl 相似文献
9.
E Kobayashi Y Yoshida A Fujimura T Yamanaka H Endo T Hamamoto Y Kagawa 《Canadian Metallurgical Quarterly》1997,24(12):1775-1777
We studied the in vivo gene transfusion using a gene gun, formerly used in plants and culture cells. The hand-held type gene gun (Helios Gene Gun System) is simple and convenient for effective gene transfection in living animals. This method has some advantages in that there is no need for use of viral vector, independence on the cell cycle and local inducement of plural genes. There is a great possibility for application to local-regional cancer. 相似文献
10.
Yukio Tateishi 《Tribology International》1994,27(1)
In this paper improvement in fuel economy by reducing piston ring friction is studied and reduction of piston ring tension and the use of two-ring packages are found to be effective. However, these can be accompanied by adverse effects such as excessive wear and increasing oil consumption, and measures to overcome these problems are studied in detail. 相似文献