全文获取类型
收费全文 | 446篇 |
免费 | 56篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 5篇 |
化学工业 | 110篇 |
金属工艺 | 10篇 |
机械仪表 | 5篇 |
建筑科学 | 6篇 |
矿业工程 | 1篇 |
能源动力 | 12篇 |
轻工业 | 13篇 |
水利工程 | 7篇 |
无线电 | 96篇 |
一般工业技术 | 104篇 |
冶金工业 | 15篇 |
原子能技术 | 3篇 |
自动化技术 | 121篇 |
出版年
2024年 | 1篇 |
2023年 | 17篇 |
2022年 | 21篇 |
2021年 | 39篇 |
2020年 | 28篇 |
2019年 | 23篇 |
2018年 | 28篇 |
2017年 | 30篇 |
2016年 | 32篇 |
2015年 | 22篇 |
2014年 | 32篇 |
2013年 | 36篇 |
2012年 | 29篇 |
2011年 | 27篇 |
2010年 | 24篇 |
2009年 | 15篇 |
2008年 | 17篇 |
2007年 | 24篇 |
2006年 | 15篇 |
2005年 | 6篇 |
2004年 | 4篇 |
2003年 | 5篇 |
2002年 | 7篇 |
2001年 | 2篇 |
2000年 | 2篇 |
1999年 | 4篇 |
1998年 | 3篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1979年 | 1篇 |
1978年 | 2篇 |
排序方式: 共有508条查询结果,搜索用时 15 毫秒
51.
Conjugated Polymers: Linking Group Influences Charge Separation and Recombination in All‐Conjugated Block Copolymer Photovoltaics (Adv. Funct. Mater. 35/2015) 下载免费PDF全文
52.
A photoelectrochemical cell based on the photochemistry of anthraquinone-2-sulfonate (D) has been set up. In the presence of formate at pH 11.0, D on illumination produces D? or D2?. In the absence of oxygen, at the platinum electrode the anodic reaction is D? → D + e, or D2? → D + 2e, and at the dark electrode the cathodic reaction is O2 + 2H2O + 4e → 4OH?. The open circuit potential of the cell is 500 mV. The short circuit current is 180 μA. The cell has been recycled at least eight times. The efficiency increases with platinized platinum electrode in the dark chamber. The steady current under illumination is 65 μA with the same open circuit voltage of 500 mV. The short circuit current is 250 μA. With a CdS electrode in the illuminated chamber the efficiency is even better. The open circuit voltage is 560 mV. After charging by illumination for 8 h a steady current of 120 μA can be drawn from the cell, with illumination off, for 40 h. The short circuit current is 450 μA. The maximum power output is 4.2 × 10?6W The cell can be recycled at least four times without any loss in efficiency. Grey deposition on the CdS electrode possibly indicates electrode decomposition. 相似文献
53.
Vander Wal RL Fujiyama-Novak JH Gaddam CK Das D Hariharan A Ward B 《Applied spectroscopy》2011,65(9):1073-1082
This paper presents a developed dielectric-barrier-discharge-based "sniffer" that offers unique characteristics not available from other techniques. It is a portable, highly specific, and sensitive detector that operates at atmospheric pressure. It provides both molecular and elemental information on organic and inorganic gases and particulate aerosols. Measurements were made to electrically characterize the plasma and calculate the energy coupled into the plasma. We created a signature database for diverse chemicals based on the atomic and diatomic emission spectrum that serves to classify the compound and ideally recognize it by composition with the optical emission intensity corresponding to concentration. For some operational regimes and species, emission from OH (A(2)Σ(+)-X(2)Π), CH (A(2)Δ-X(2)Π), and often C(2) (d(3)Π(g)-a(3)Π(u); Swan band system) diatomic radicals is produced. Limits of detection extend to parts per billion (ppb) levels for some species such as decane, 2-decanol, and nitrobenzene. Results are presented for differentiation of classes of organic compounds such as alkanes, aromatics, oxygenates, chlorinated, and nitrogen-containing organic compounds. 相似文献
54.
Xiuping Li Jianjun Gao Choi Look Law Sheel Aditya Georg Boeck 《Journal of Infrared, Millimeter and Terahertz Waves》2003,24(10):1759-1766
An improved on-wafer measurement method by using coaxial calibration instead of on-wafer calibration for PHEMT modeling is proposed in this paper. The advantage is that S-parameters of PHEMT device can be measured on wafer without impedance standard substrate (ISS) after the S-parameters of the microprobes have been determined. Excellent agreement is obtained between on-wafer calibration measurement and coaxial calibration measurements, respectively. 相似文献
55.
Jianjun Gao Choi Look Law Hong Wang Aditya S. Boeck G. 《Microwave Theory and Techniques》2003,51(10):2079-2089
A new method for determining the four noise parameters of pseudomorphic high electron-mobility transistors (pHEMTs) based on a 50-/spl Omega/ noise measurement system without a microwave tuner is presented. The noise parameters are determined based on the noise correlation matrix technique by fitting the measured noise figure of the active device. On-wafer experimental verification up to 26 GHz is presented and a comparison with a tuner-based method is given. The scaling rules for noise parameters have also been determined. Good agreement is obtained between simulated and measured results for 2/spl times/20 /spl mu/m, 2/spl times/40 /spl mu/m, and 2/spl times/60 /spl mu/m gatewidth (number of gate fingers /spl times/ unit gatewidth) 0.25-/spl mu/m double-heterojunction /spl delta/-doped pHEMTs. 相似文献
56.
Vaddiraju S Mohite A Chin A Meyyappan M Sumanasekera G Alphenaar BW Sunkara MK 《Nano letters》2005,5(8):1625-1631
Indium nitride (InN) nanowire synthesis using indium (In) vapor transport in a dissociated ammonia environment (reactive vapor transport) is studied in detail to understand the nucleation and growth mechanisms involved with the so-called "self-catalysis" schemes. The results show that the nucleation of InN crystal occurs first on the substrate. Later, In droplets are formed on top of the InN crystals because of selective wetting of In onto InN crystals. Further growth via liquid-phase epitaxy through In droplets leads the growth in one dimension (1D), resulting in the formation of InN nanowires. The details about the nucleation and growth aspects within these self-catalysis schemes are rationalized further by demonstrating the growth of heteroepitaxially oriented nanowire arrays on single-crystal substrates and "tree-like" morphologies on a variety of substrates. However, the direct nitridation of In droplets using dissociated ammonia results in the spontaneous nucleation and basal growth of nanowires directly from the In melt surface, which is quite different from the above-mentioned nucleation mechanism with the reactive vapor transport case. The InN nanowires exhibit a band gap of 0.8 eV, whereas the mixed phase of InN and In(2)O(3) nanowires exhibit a peak at approximately 1.9 eV in addition to that at 0.8 eV. 相似文献
57.
Aditya Kumar Ying Yang Chee C. Wong Vaidhyanathan Kripesh Zhong Chen 《Journal of Electronic Materials》2009,38(1):78-87
The effect of moderate electric current density (1 × 103 to 3 × 103 A/cm2) on the mechanical properties of Ni-P/Sn-3.5Ag/Ni-P and Ni/Sn-3.5Ag/Ni solder joints was investigated using a microtensile
test. Thermal aging was carried out at 160°C for 100 h while the current was passed. The interfacial microstructure and intermetallic
compound (IMC) growth were analyzed. It was found that, at these levels of current density, there were no observable voids
or hillocks. Samples aged at 160°C without current stressing failed mostly inside the bulk solder with significant prior plastic
deformation. The passage of current was found to cause brittle failure of the solder joints and this tendency for brittle
failure increased with increasing current density. Fractographic analysis showed that, in most of the electrically stressed
samples, fracture occurred at the interface region between the solder and the joining metals. The critical current density
that caused brittle fracture was about 2 × 103 A/cm2. Once brittle fracture occurred, the tensile toughness, defined as the energy per unit fractured area, was usually lower
than ~5 kJ/m2, compared with the case of ductile fracture where this value was typically greater than ~9 kJ/m2. When comparing the two types of joint, the brittle failure was found to be more severe with the Ni than with the Ni-P joint.
This work also found that the passage of electric current affects the IMC growth rate more significantly in the Ni than in
the Ni-P joint. In the case of the Ni joint, the Ni3Sn4 IMC at the anode side was appreciably thicker than that formed at the cathode side. However, in the case of electroless Ni-P
metallization, this difference was much smaller. 相似文献
58.
ABSTRACTIn India, of late, micro-irrigation has received considerable policy focus. However, as of 2017, only about 10% of the potential area is under micro-irrigation. The present study analyzes the pattern and equity issues of distribution of micro-irrigation in India and identifies the potential correlates. The regression analysis reveals that the stage of groundwater development and agro-climatic differences significantly influence the spread of micro-irrigation. The relatively low spread of micro-irrigation in states with over-exploited groundwater needs attention. Overall, the study points to the need to revamp the current micro-irrigation development programmes, which focus excessively on subsidy. 相似文献
59.
Ahmad Khusro Mohammad S. Hashmi Abdul Quaiyum Ansari Aditya Mishra Mohammad Tarique 《International Journal of Circuit Theory and Applications》2019,47(6):941-953
In this paper, development of a small signal model for 2 × 200 μm GaN HEMT based on the conventional 20-element model is presented. The proposed model presents a direct parameter extraction algorithm, instead of the hybrid optimization approach, that provides simplification, accuracy, and less computational complexity. The extrinsic elements are extracted using a modified cold pinch-off condition while discarding the unwanted forward biasing of the gate. The negative drain to source capacitance Cds is also observed in the ohmic region (for smaller VDS). An excellent agreement found between the measured and modeled data for a wide range of frequencies and bias values shows the effectiveness of the proposed approach. The proposed modeling technique is validated with a good agreement between the achieved bias dependency of intrinsic parameter values and the respective theoretical parameter values. 相似文献
60.
Melanie H. Bowler Aditya Mishra Austen C. Adams Corinne L.‐D. Blangy Jason D. Slinker 《Advanced functional materials》2020,30(33)
Light‐emitting electrochemical cells (LECs) are devices that utilize efficient ion redistribution to produce high‐efficiency electroluminescence in a simple device architecture. Prototypical polymer LECs utilize three components in the active layer: a luminescent conducting polymer, a salt, and an electrolyte. Similarly, many small‐molecule LECs also utilize an electrolyte to disperse salts. In these systems, the electrolyte is incorporated to efficiently conduct ions and to maintain phase compatibility between all components. However, certain LEC approaches and materials systems enable device operation without a dedicated electrolyte. This review describes the general methods and materials used to circumvent the use of a dedicated electrolyte in LECs. The techniques of synthetically coupling electrolytes, incorporating ionic liquids, and introducing inorganic salts are presented in view of research efforts to date. The use of these techniques in emerging classes of light‐emitting electrochemical cells is also discussed. These approaches have yielded some of the most efficient, long‐lasting, and commercially applicable LECs to date. 相似文献