全文获取类型
收费全文 | 2143篇 |
免费 | 118篇 |
国内免费 | 12篇 |
专业分类
电工技术 | 37篇 |
综合类 | 2篇 |
化学工业 | 466篇 |
金属工艺 | 81篇 |
机械仪表 | 62篇 |
建筑科学 | 47篇 |
能源动力 | 68篇 |
轻工业 | 103篇 |
水利工程 | 1篇 |
石油天然气 | 4篇 |
无线电 | 394篇 |
一般工业技术 | 435篇 |
冶金工业 | 228篇 |
原子能技术 | 28篇 |
自动化技术 | 317篇 |
出版年
2023年 | 7篇 |
2022年 | 20篇 |
2021年 | 21篇 |
2020年 | 25篇 |
2019年 | 25篇 |
2018年 | 48篇 |
2017年 | 46篇 |
2016年 | 46篇 |
2015年 | 50篇 |
2014年 | 69篇 |
2013年 | 183篇 |
2012年 | 99篇 |
2011年 | 130篇 |
2010年 | 118篇 |
2009年 | 119篇 |
2008年 | 126篇 |
2007年 | 106篇 |
2006年 | 75篇 |
2005年 | 68篇 |
2004年 | 62篇 |
2003年 | 71篇 |
2002年 | 47篇 |
2001年 | 46篇 |
2000年 | 55篇 |
1999年 | 68篇 |
1998年 | 102篇 |
1997年 | 51篇 |
1996年 | 45篇 |
1995年 | 43篇 |
1994年 | 37篇 |
1993年 | 30篇 |
1992年 | 17篇 |
1991年 | 24篇 |
1990年 | 13篇 |
1989年 | 24篇 |
1988年 | 18篇 |
1987年 | 20篇 |
1986年 | 14篇 |
1985年 | 16篇 |
1984年 | 6篇 |
1983年 | 13篇 |
1982年 | 6篇 |
1981年 | 11篇 |
1980年 | 5篇 |
1978年 | 7篇 |
1977年 | 9篇 |
1976年 | 9篇 |
1975年 | 8篇 |
1974年 | 4篇 |
1973年 | 3篇 |
排序方式: 共有2273条查询结果,搜索用时 15 毫秒
41.
Jau-Der Shih 《Information Processing Letters》2003,88(6):271-278
In this paper, we present a fault-tolerant routing algorithm for torus networks by using only 4 virtual channels. The proposed algorithm is based on the solid fault model, which includes rectangular faults and many practical nonconvex faults. Previous works need at least 6 virtual channels to achieve the same fault-tolerant ability. 相似文献
42.
Design, optimization, and performance analysis of new photodiode structures for CMOS active-pixel-sensor (APS) imager applications 总被引:5,自引:0,他引:5
Chung-Yu Wu Yu-Chuan Shih Jeng-Feng Lan Chih-Cheng Hsieh Chien-Chang Huang Jr-Houng Lu 《IEEE sensors journal》2004,4(1):135-144
The dark current in the active-pixel-sensor (APS) cell of a CMOS imager is known to be mainly generated in the regions of bird's beak after the local oxidation of silicon process as well as the surface damage caused by the implantation of high doping concentration. Furthermore, shallow and deep pn-junctions can improve the photo-sensitivity for light of short and long wavelengths, respectively. In this paper, two new photodiode structures using p-substrate and lightly-doped sensor implant SN- as pn-junction photodiode with the regions of bird's beak embraced by SN- and p-field implants, respectively, are proposed and analyzed to reduce dark current and enhance the overall spectral response. 5 /spl mu/m/spl times/5 /spl mu/m APS cells fabricated in a 0.35-/spl mu/m single-poly-triple-metal (1P3M) 3.3-V CMOS process are designed by using the proposed photodiode structures. As shown from the experimental results, the two proposed photodiode structures of 5 /spl mu/m/spl times/5 /spl mu/m APS cells have lower dark currents of 30.6 mV/s and 35.2 mV/s at the reverse-biased voltage of 2 V and higher spectral response, as compared to the conventional structure and other photodiode structures. Thus, the two proposed new photodiode structures can be applied to CMOS imager systems with small pixel size, high resolution, and high quality. 相似文献
43.
In this paper, both numerical simulation and experiment were performed to investigate the mixing process within mixing chambers of the planar micromixer with three baffles at varied baffle height. The presence of three baffles causes the flow to separate and creates the recirculation and back flow within mixing chambers. The fluid mixing was greatly influenced by the baffle height and Reynolds number (Re) related to the size of recirculation zone. Larger baffle height or Re produces larger recirculation zone and convective mixing. The micromixer with 350 μm high baffles in 400 μm wide channel results in over 95% mixing at Re = 80 from the simulation results. The experiment results confirm the above simulation results qualitatively. This planar micromixer has the merits of simple design and easy fabrication as compared to the three-dimensional passive micromixers. 相似文献
44.
Hung-Pin D. Yang Chih-Tsung Shih Su-Mei Yang Tsin-Dong Lee 《Microelectronics Reliability》2010,50(5):722-725
High-power broad-area InGaNAs/GaAs quantum-well (QW) edge-emitting lasers on GaAs substrates in the 1200 nm range are reported. The epitaxial layers of the InGaNAs/GaAs QW laser wafers were grown on n+-GaAs substrates by using metal-organic chemical vapor deposition (MOCVD). The thickness of the InGaNAs/GaAs QW layers is 70 Å/1200 Å. The indium content (x) of the InxGa1−xNyAs1−y QW layers is estimated to be 0.35-0.36, while the nitrogen content (y) is estimated to be 0.006-0.009. More indium content (In) and nitrogen content (N) in the InGaNAs QW layer enables the laser emission up to 1300 nm range. The epitaxial layer quality, however, is limited by the strain in the grown layer. The devices were made with different ridge widths from 5 to 50 μm. A very low threshold current density (Jth) of 80 A/cm2 has been obtained for the 50 μm × 500 μm LD. A number of InGaNAs/GaAs epi-wafers were made into broad-area LDs. A maximum output power of 95 mW was measured for the broad-area InGaNAs/GaAs QW LDs. The variations in the output powers of the broad-area LDs are mainly due to strain-induced defects the InGaNAs QW layers. 相似文献
45.
Sensors: 6‐Mercaptopurine‐Induced Fluorescence Quenching of Monolayer MoS2 Nanodots: Applications to Glutathione Sensing,Cellular Imaging,and Glutathione‐Stimulated Drug Delivery (Adv. Funct. Mater. 41/2017) 下载免费PDF全文
46.
47.
The sleep behavior of drosophila is analyzed under different temperatures. The activity per minute of the flies is recorded automatically. Sleep for a fruit fly is defined as the periods without any activity and longer than 5 minutes. Several parameters such as total sleep time, circadian sleep profile, quality of sleep are analyzed. The sleep behaviors are significantly different for flies at different temperature. Interestingly, the durations of daytime sleep periods show a common scale-free power law distribution. We propose a stochastic model to simulate the activities of the population of neurons which regulate the dynamics of sleep–wake process to explain the distribution of daytime sleep. 相似文献
48.
Self‐Crack‐Filled Graphene Films by Metallic Nanoparticles for High‐Performance Graphene Heterojunction Solar Cells 下载免费PDF全文
49.
Antioxidant activities of aqueous extracts of selected plants 总被引:1,自引:0,他引:1
The antioxidant properties of 25 edible tropical plants, expressed as Trolox equivalent antioxidant capacity (TEAC), were studied using DPPH (1,1-diphenyl-2-picrylhydrazyl free radical) scavenging and reducing ferric ion antioxidant potential (FRAP) assays. Their cupric ion chelating activities (CCA) and total polyphenol contents (TPC) were also determined. A strong correlation between TEAC values obtained for the DPPH assay (TEACDPPH) and those for the FRAP assay (TEACFRAP) implied that compounds in the extracts were capable of scavenging the DPPH free radical and reducing ferric ions. A satisfactory correlation of TPC with TEACDPPH and TEACFRAP suggested that polyphenols in the extracts were partly responsible for the antioxidant activities while its correlation with CCA was poor, indicating that polyphenols might not be the main cupric ion chelators. Principal component analysis (PCA) indicated that TEACDPPH, TEACFRAP and TPC contributed to the total variation in the antioxidant activities of the plants. 相似文献
50.
Modularization strategy for syngas generation in chemical looping methane reforming systems with CO2 as feedstock 下载免费PDF全文
Peter Sandvik Fanhe Kong Yitao Zhang Abbey Empfield Liang‐Shih Fan 《American Institute of Chemical Engineers》2017,63(8):3343-3360
This study considers a CO2 feedstock in conventional methane reforming processes and metal oxide lattice oxygen based chemical looping reforming. Lattice oxygen from iron‐titanium composite metal oxide provides the most efficient co‐utilization of CO2 with CH4. A modularization chemical looping strategy is developed to further improve process efficiencies using a thermodynamic rationale. Modularization leverages the ability of two or more reactors operating in parallel to produce a higher quality syngas than a single reactor operating alone while offering a direct solution to scale up of multiple parallel reactor processes. Experiments conducted validate the thermodynamic simulation results. Simulation and experimental results ascertain that a cocurrent moving bed in a modularization system can operate under CO2 neutral or negative conditions. The results for a modularization process system for 7950 m3 per day (50,000 barrels per day) of liquid fuel indicate a ~23% reduction of natural gas usage over baseline‐case. © 2017 American Institute of Chemical Engineers AIChE J, 63: 3343–3360, 2017 相似文献