全文获取类型
收费全文 | 2984篇 |
免费 | 109篇 |
国内免费 | 19篇 |
专业分类
电工技术 | 142篇 |
综合类 | 10篇 |
化学工业 | 732篇 |
金属工艺 | 80篇 |
机械仪表 | 100篇 |
建筑科学 | 102篇 |
矿业工程 | 8篇 |
能源动力 | 108篇 |
轻工业 | 231篇 |
水利工程 | 17篇 |
石油天然气 | 15篇 |
无线电 | 261篇 |
一般工业技术 | 571篇 |
冶金工业 | 446篇 |
原子能技术 | 104篇 |
自动化技术 | 185篇 |
出版年
2024年 | 7篇 |
2023年 | 33篇 |
2022年 | 54篇 |
2021年 | 88篇 |
2020年 | 41篇 |
2019年 | 38篇 |
2018年 | 46篇 |
2017年 | 42篇 |
2016年 | 66篇 |
2015年 | 45篇 |
2014年 | 60篇 |
2013年 | 170篇 |
2012年 | 110篇 |
2011年 | 174篇 |
2010年 | 118篇 |
2009年 | 128篇 |
2008年 | 118篇 |
2007年 | 116篇 |
2006年 | 106篇 |
2005年 | 96篇 |
2004年 | 68篇 |
2003年 | 90篇 |
2002年 | 91篇 |
2001年 | 70篇 |
2000年 | 72篇 |
1999年 | 65篇 |
1998年 | 200篇 |
1997年 | 115篇 |
1996年 | 84篇 |
1995年 | 61篇 |
1994年 | 54篇 |
1993年 | 54篇 |
1992年 | 33篇 |
1991年 | 28篇 |
1990年 | 23篇 |
1989年 | 28篇 |
1988年 | 27篇 |
1987年 | 21篇 |
1986年 | 29篇 |
1985年 | 31篇 |
1984年 | 22篇 |
1983年 | 22篇 |
1982年 | 19篇 |
1981年 | 22篇 |
1980年 | 19篇 |
1979年 | 14篇 |
1978年 | 11篇 |
1977年 | 12篇 |
1976年 | 36篇 |
1975年 | 8篇 |
排序方式: 共有3112条查询结果,搜索用时 15 毫秒
271.
We propose a method of rapidly detecting radioactive cesium floating in the air for the purpose of alerting people active in the ‘difficult-to-return zone’ of Fukushima to changes in airborne radioactivity. With this purpose in mind, we set requirement specifications and created a new system concept. The targeted detection limit was 30 Bq/m3 and the mandatory level of measurement time was 48 min with a target level of 12 min, and these periods are 10 times faster than those of conventional air monitors. The system consists of a conventional gamma-spectrometer with a novel shaped shield. The targeted peak region of the measured energy spectrum is analyzed. After the basic design and confirmation of feasibility, we perform some experiments in the normal environment of Yokohama city and the difficult-to-return zone of Fukushima. Using the results, we conducted the design improvement and performance evaluation. As a result, the system performance is found to satisfy requirements. We thus conclude that this system is a promising candidate for rapid detection of airborne radioactivity in the difficult-to-return zone of Fukushima. 相似文献
272.
Jumpei Takahashi Yuji Tasaka Yuichi Murai Yasushi Takeda Takatoshi Yanagisawa 《International Journal of Heat and Mass Transfer》2010,53(7-8):1483-1490
This study determines the flow structure in a convection cell with an internally heated layer by PIV to elucidate the convection cell transition mechanisms. The vertical velocity component is determined and the cell behaviour with respect to Rayleigh number is investigated quantitatively. Cell expansion process is described as a consequence of development of the descending flow at the centre of cells. The results suggest that a spoke-like structure is stable in this system in ideal conditions and a double-cell structure is formed when there are restrictions on the system, i.e. finite lateral boundaries. 相似文献
273.
1-IntroductionSincerareearthelementshavestrongaffinitytooxygen,sulphurandotherdetrimentalelements,deoxidation,desulphurizationandremovalofdetrimentalelementscanbecarriedoutbyadditionofrareearthelementstoliquidcopper,achievingacleanliquidcopper,clea… 相似文献
274.
Abstract— By applying an energy‐recovery method to their driver circuits, the circuit power consumption of plasma displays can be reduced. However, further power reduction is necessary for large‐sized higher‐resolution displays such as used for Super HDTV. The ideal adiabatic charge method has been proven to be able to minimize circuit resistive element power consumption to 81 % of the conventional energy‐recovery‐circuit resistive‐element loss. An experimental pseudo‐adiabatic charge circuit that reduces the power consumption to about 90% of a conventional circuit has been demonstrated. The power consumption caused by both the resistance loss and the discharge loss of the switching‐element parasitic capacitances was analyzed. 相似文献
275.
Funabashi T. Otoguro H. Mizuma Y. Kai T. Takeuchi N. Akiyama S. Dube L. Ametani A. 《Power Delivery, IEEE Transactions on》1999,14(1):80-85
This paper demonstrates that the presence of multiple load taps cannot be neglected for single-phase-to-ground fault location. A new method has been developed taking this into consideration, that can be applied to correct the location error due to intermediate power sources. Then fault location methods for parallel double-circuit two-terminal transmission lines are discussed. Finally, a new fault location method is proposed for high-resistance grounded double-circuit transmission lines with three terminals 相似文献
276.
Takashi Funaki Masatoshi Yanagida Nobuko Onozawa-Komatsuzaki Yuji Kawanishi Kazuyuki Kasuga Hideki Sugihara 《Solar Energy Materials & Solar Cells》2009,93(6-7):729-732
Ruthenium(II) complexes by introducing phenylene–ethynylene subunit into a tpy (tpy=2,2′:6′,2″-terpyridine) ligand were newly synthesized, and their photophysical and photochemical properties were characterized. The molar extinction coefficients of these dyes were larger than that of black dye. The photovoltaic performances of the solar cells based on these synthesizing dyes were investigated under AM 1.5 irradiation (100 mW cm?2). The conversion efficiencies of 1a and 1b were 5.7% and 2.4%, respectively. 相似文献
277.
Hideaki Araki Yuki Kubo Aya Mikaduki Kazuo Jimbo Win Shwe Maw Hironori Katagiri Makoto Yamazaki Koichiro Oishi Akiko Takeuchi 《Solar Energy Materials & Solar Cells》2009,93(6-7):996-999
Cu2ZnSnS4 (CZTS) thin films were prepared by sulfurizing precursors deposited by electroplating. The precursors (Cu/Sn/Zn stacked layers) were deposited by electroplating sequentially onto Mo-coated glass substrates. Aqueous solutions containing copper sulfate for Cu plating, tin sulfate for Sn plating and zinc sulfate for Zn plating were used as the electrolytes. The precursors were sulfurized by annealing with sulfur at temperatures of 300, 400, 500 and 600 °C in an N2 gas atmosphere. The X-ray diffraction peaks attributable to CZTS were detected in thin films sulfurized at temperatures above 400 °C. A photovoltaic cell using a CZTS thin film produced by sulfurizing an electroplated Sn-rich precursor at 600 °C exhibited an open-circuit voltage of 262 mV, a short-circuit current of 9.85 mA/cm2 and an efficiency of 0.98%. 相似文献
278.
Akage Y. Kawano K. Oku S. Iga R. Okamoto H. Miyamoto Y. Takeuchi H. 《Electronics letters》2001,37(5):299-300
A travelling-wave electrode electroabsorption modulator integrated distributed feedback laser to overcome the CR-induced bandwidth limitation is developed. A bandwidth much wider than 50 GHz is achieved. A 40 Gbit/s eye-diagram is observed. The device has a potentiality for future 100 Gbit/s transmission 相似文献
279.
Summary
New AB2 and A2B monomers, bis(4-fluorophenyl)-4'-hydroxyphenylphosphine oxide and bis(4-hydroxyphenyl)-4'-fluorophenyl-phosphine oxide were
prepared and converted to corresponding hyperbranched poly(arylene ether phosphineoxide)s with hydroxyphenyl and fluorophenyl
end functional groups. While the dihydroxy monomer gave a low molecular weight polymer, the difluoro monomer produced a high
molecular weight hyperbranched polymer. The glass transition temperature of the obtained polymers was 266°C and 230°C, and
5% weight loss temperature was 491 °C and 391 °C, respectively. The fluorophenyl-terminated hyperbranched polymer was soluble
in CHCl3, but the hydroxyphenyl-terminated polymer was not soluble in CHCl3 even though it has lower molecular weight than the fluorophenyl-terminated
polymer, indicating that properties of the hyperbranched polymers markedly depend on end functional groups as well as their
molecular weight.
Received: 23 August 2000/Revised version: 19 October 2000/Accepted: 31 October 2000 相似文献
280.
Mizuki Tsuta Yasuhiko Sasaki Ikuo Takeuchi Hideki Nakamoto Jun Ishikawa Susumu Kawasaki Junichi Sugiyama Kaori Fujita Masatoshi Yoshimura Mario Shibata Mito Kokawa 《LWT》2014
Flow cytometry (FCM) and aerobic plate count (APC) by the culture method were performed on green tea samples spiked with Escherichia coli type strain NCTC9001 (ATCC11775) solutions of different concentrations. In FCM, fluorescence signals from multiple stained bacteria and other fluorophores are detected using detector channels, and recorded as events with a voltage at each channel. FCM data were analyzed in two ways: conventional and multivariate analysis. In the former, the number of events with voltages larger than the defined threshold values was regarded as the predicted APC. In the latter, voltage histograms of all channels were obtained and merged horizontally to serve as explanatory variables. Then a partial least squares regression (PLSR) model was built to predict APC from the histogram data. The coefficient of determination (R2) and the root mean square error (RMSE) between APC by the culture method and that predicted by conventional FCM were 0.916 and 1.08 cfu/ml2. The APC values predicted by the PLSR model and those measured were in good agreement with R2 of 0.982 and RMSE of 0.417 cfu/ml, which verified the potential of the proposed method for improving APC prediction accuracy by FCM. 相似文献