全文获取类型
收费全文 | 485篇 |
免费 | 27篇 |
专业分类
电工技术 | 10篇 |
综合类 | 1篇 |
化学工业 | 66篇 |
金属工艺 | 18篇 |
机械仪表 | 9篇 |
建筑科学 | 5篇 |
能源动力 | 17篇 |
轻工业 | 8篇 |
水利工程 | 1篇 |
无线电 | 158篇 |
一般工业技术 | 89篇 |
冶金工业 | 17篇 |
原子能技术 | 1篇 |
自动化技术 | 112篇 |
出版年
2023年 | 2篇 |
2022年 | 1篇 |
2021年 | 5篇 |
2020年 | 2篇 |
2019年 | 8篇 |
2018年 | 4篇 |
2017年 | 8篇 |
2016年 | 16篇 |
2015年 | 11篇 |
2014年 | 19篇 |
2013年 | 59篇 |
2012年 | 40篇 |
2011年 | 37篇 |
2010年 | 23篇 |
2009年 | 42篇 |
2008年 | 26篇 |
2007年 | 19篇 |
2006年 | 25篇 |
2005年 | 17篇 |
2004年 | 11篇 |
2003年 | 11篇 |
2002年 | 5篇 |
2001年 | 21篇 |
2000年 | 7篇 |
1999年 | 14篇 |
1998年 | 13篇 |
1997年 | 8篇 |
1996年 | 13篇 |
1995年 | 4篇 |
1994年 | 10篇 |
1993年 | 5篇 |
1992年 | 4篇 |
1990年 | 5篇 |
1989年 | 4篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1978年 | 1篇 |
1973年 | 2篇 |
排序方式: 共有512条查询结果,搜索用时 0 毫秒
181.
Bo-Hung Liou Chih-Ming Chen Ray-Hua Horng Yi-Chen Chiang Dong-Sing Wuu 《Microelectronics Reliability》2012,52(5):861-865
The thermal management of high-power light-emitting-diode (LED) devices employing various die-attach materials is analyzed. Three types of die-attach materials are tested, including silver paste, Sn–3 wt.% Ag–0.5 wt.% Cu (SAC305) solder, and SAC305 solder added with a small amount of carbon nanotubes (CNTs). The analysis of thermal management is performed by comparing the temperatures of the LED chips in use and the total thermal resistances of the LED devices obtained respectively from the thermal infrared images and thermal transient analysis. Due to the high thermal conductivity of CNT, the addition of CNTs into the SAC305 solder reduces the total thermal resistance and chip temperature of the LED device, and the thermal management of the LED devices is improved accordingly. 相似文献
182.
Radio frequency identification (RFID) technology system is quickly evolved many applications to manage personnel can be more efficient for automation systems. We combine the RSA encryption and decryption algorithms to raise the safety and the information security systems. The RFID environment has been communicated to exchange data for heterogeneous wireless networks. In this paper, it is implemented the RFID-based campus system solutions to security and privacy of RFID system for wireless mesh network applications. We propose to enhance the security algorithm combined RFID devices for the antenna arrays system. This paper is also presented the integrated framework for the application and integration systems based on service oriented architecture, and given a specific application of the framework combined with campus system. 相似文献
183.
One of the most important functions in IEEE 802.11e is enhanced distributed coordination function (EDCF). EDCF is an enhanced version of IEEE 802.11 distributed coordination function (DCF) which provides a priority scheme by differentiating the inter‐frame space and the initial window size. We proposed a modified Markov chain model to study the EDCF priority scheme. We have theoretically analyzed the saturation throughput and delay by using the modified Markov chain model in non‐ideal channel scenario. We also have compared it with the Markov chain model that exists under ideal channel scenario. Simulations are also conducted to validate analytical results. Our study shows that the modified model under ideal channel scenario is better than that in channel error scenario. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
184.
185.
Jyh‐Horng Sheu Bo‐Rong Peng Lee‐Shing Fang Tsong‐Long Hwang Jui‐Hsin Su Yang‐Chang Wu Ping‐Jyun Sung 《Israel journal of chemistry》2019,59(5):403-413
The structures, names, bioactivities, and references of 75 marine diterpenoids from octocorals possessing a hydroperoxy group, including 46 cembranes, 8 eunicellins, 5 briaranes, 5 dolabellanes, 4 germacranes, 3 xenicins, 2 caryophyllanes, 1 decalin, and 1 pseudopterosin, are summarized in this review article. All the hydroperoxyditerpenoids mentioned in this review were isolated from octocorals from Alcyonacea (Briareum excavatum, Briareum polyanthes, Briareum violaceum, Briareum sp., Cespitularia sp., Cladiella tuberculosa, Cladiella sp., Clavularia inflata, Klyxum simplex, Lemnalia sp., Lobophytum crassum, Lobophytum sp., Nephthea pacifica, Sarcophyton cherbonnieri, Sarcophyton crassocaule, Sarcophyton glaucum, Sarcophyton mililatensis, Sarcophyton trocheliophorum, Sarcophyton sp., Sinularia arborea, Sinularia erecta, Sinilaria flexibilis, Sinularia gibberosa, Sinularia manaarensis, Xenia umbellata) and Gorgonacea (Astrogorgia sp., Eunicea calyculata, Eunicea pinta, Eunicea succinea, Eunicea sp., Pseudopterogorgia sp.). Among these isolates, 41 compounds exhibited potential biomedical activities, including cytotoxicity, antimalarial activity, anti‐inflammatory activity, and antibacterial activity. 相似文献
186.
Jiun-Wei Horng 《Circuits, Systems, and Signal Processing》2008,27(4):553-562
A new high input impedance voltage-mode universal biquadratic filter with three input terminals and five output terminals
is presented. The proposed circuit uses three plus-type differential difference current conveyors, two grounded resistors
and two grounded capacitors. The proposed circuit can realize all the standard filter functions: lowpass, bandpass, highpass,
notch and allpass, without component matching conditions. The proposed circuit offers the features of high input impedance,
low active and passive sensitivities and the use of only grounded resistors and capacitors. 相似文献
187.
Material removal rate and electrode wear ratio study on the powder mixed electrical discharge machining of cobalt-bonded tungsten carbide 总被引:2,自引:2,他引:0
Kuang-Yuan Kung Jenn-Tsong Horng Ko-Ta Chiang 《The International Journal of Advanced Manufacturing Technology》2009,40(1-2):95-104
In this article, a material removal rate (MRR) and electrode wear ratio (EWR) study on the powder mixed electrical discharge machining (PMEDM) of cobalt-bonded tungsten carbide (WC-Co) has been carried out. This type of cemented tungsten carbide was widely used as moulding material of metal forming, forging, squeeze casting, and high pressure die casting. In the PMEDM process, the aluminum powder particle suspended in the dielectric fluid disperses and makes the discharging energy dispersion uniform; it displays multiple discharging effects within a single input pulse. This study was made only for the finishing stages and has been carried out taking into account the four processing parameters: discharge current, pulse on time, grain size, and concentration of aluminum powder particle for the machinability evaluation of MRR and EWR. The response surface methodology (RSM) has been used to plan and analyze the experiments. The experimental plan adopts the face-centered central composite design (CCD). This study highlights the development of mathematical models for investigating the influence of processing parameters on performance characteristics. 相似文献
188.
Caffeic acid phenethyl ester upregulates N‐myc downstream regulated gene 1 via ERK pathway to inhibit human oral cancer cell growth in vitro and in vivo
下载免费PDF全文
![点击此处可从《Molecular nutrition & food research》网站下载免费的PDF全文](/ch/ext_images/free.gif)
189.
A barrier structure consisting of silicon oxide and silicon nitride films was deposited via plasma-enhanced chemical vapor deposition (PECVD) for the encapsulation of polymer solar cells (PSCs). The total concentration of the solution and the ratio of P3HT and PCBM on the performance of polymer solar cells were studied by UV-Vis absorption spectroscopy, atomic force microscopy and photocurrent measurement. Base on these measurements, there is a compromise between light absorption and phase separation with increasing blend concentration. The PSCs were annealed at 80, 100, 120 and 140 °C for 10-60 min to investigate the thermal effects and to estimate the best deposition temperature of the barrier layers. Nevertheless, the devices with the encapsulation of barrier layers had relatively low power conversion efficiencies (PCE) of 0.98% comparing to the devices heated in the PECVD system (1.57%) at the same condition of 80 °C for 45 min due to the plasma damage during the film deposition process. After inserting a 5-nm TiOx layer between Al/barrier structure and active layer against the plasma damage, the annealed devices presented an average PCE of 2.26% and demonstrated over 50% of their initial value after constant exposure to ambient atmosphere and sunlight for 1500 h. 相似文献
190.
Particulate matter characteristics during agricultural waste burning in Taichung City, Taiwan 总被引:4,自引:0,他引:4
Agricultural waste burning is performed after harvest periods in June and November in Taiwan. Typically, farmers use open burning to dispose of excess rice straw. PM(2.5) and PM(2.5-10) measurements were conducted at National Chung Hsing University in Taichung City using a dichotomous sampler. The sampling times were during straw burning periods after rice harvest during 2002-2005. Ionic species including SO(4)(2-), NO(3)(-), NH(4)(+), K(+), Ca(2+), Cl(-) and Na(+) and carbonaceous species (EC and OC) in PM(2.5) and PM(2.5-10) were analyzed. The results showed that the average PM(2.5) and PM(2.5-10) concentrations were 123.6 and 31.5 microg m(-3) during agricultural waste burning periods and 32.6 and 21.4 microg m(-3) during non-waste burning periods, respectively. The fine aerosol ionic species including Cl(-), K(+) and NO(3)(-) increased 11.0, 6.7 and 5.5 times during agricultural burning periods compared with periods when agricultural waste burning is not performed. K(+) was found mainly in the fine mode during agricultural burning. High nitrogen oxidation ratio was found during agricultural waste burning periods which might be caused by the conversion of Nitrogen dioxide (NO(2)) to NO(3)(-). It is concluded that agricultural waste burning with low dispersion often causes high PM(2.5) and gases pollutant events. 相似文献