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31.
Leveraging online communities in fostering adaptive schools 总被引:1,自引:0,他引:1
David Hung Kenneth Y. T. Lim Der-Thanq Victor Chen Thiam Seng Koh 《International Journal of Computer-Supported Collaborative Learning》2008,3(4):373-386
There has long been a call for schools to prepare students for the twenty-first century where skills and dispositions differ
significantly from much of what has historically characterized formal education. The knowledge based economy calls for policy
and pedagogical efforts that would transform schools. Schools are to foster communities of learners. This paper suggests that
para-communities may be points of leverage in the fostering of adaptive schools. A critical analysis is done on the differences
between para-communities (such as online communities) and schools; and an argument is made that they each serve differing
goals and should be left distinct because they achieve different societal and economic demands. 相似文献
32.
In recent years, educators and students are increasingly employing online collaboration applications such as Google Docs™ and PBWorks™ for group projects and assignments. Yet, the effectiveness of these emerging technologies has not been rigorously examined. Anchoring upon and informed by the existing literature, two design characteristics – sociability and visibility, and two human characteristics – gender and age, are focused on, which are salient in online collaboration applications. A field experiment was conducted to examine the direct and moderating effects of design and human characteristics on learning outcomes. The research found that sociability improved process satisfaction and positive social environment while visibility enhanced academic performance and solution satisfaction of learners. Males had higher solution satisfaction while older learners had higher academic performance. Moderating effects were also found. Both theoretical and practical implications are drawn. In particular, a rubric for online collaboration application selection for academic performance is conceived. This study provides empirical support for online collaboration application effectiveness in education which will augur well for future adoption, use and evolution. 相似文献
33.
王洪梅 KIM Jae-hyung LEE Sang-hyuk KIM Hyung-jung KIM Jin-up KOH Jong-seog 《中南工业大学学报(英文版)》2012,19(2):408-416
The problem of designing a digital frontend (DFE) was considered which can dynamically access or sense dual bands in any radio
frequency (RF) regions without requiring hardware changes. In particular, second-order bandpass sampling (BPS) as a technique
that enables to realize the multiband reception function was discussed. In a second-order BPS system, digital reconstruction
filters were utilized to eliminate the interferences generated while down converting arbitrarily positioned RF-band signals
by using the direct digitization method. However, the inaccuracy in the phase shift or the amplitude mismatch between the
two sample streams may cause insufficient rejection of interference. Practical problems were studied, such as performance
degradation in signal-to-interference ratio (SIR) and compensation methods to overcome them. In order to demonstrate the second-order
BPS as a flexible DFE suitable for software-defined radio (SDR) or cognitive radio (CR), a DFE testbed with a reconfigurable
structure was implemented. Moreover, with a view to further demonstrate the proposed compensation algorithms, experimental
results show that dual bands are received simultaneously. 相似文献
34.
Undoped (IO) and Sn-doped In2O3 (ITO) films have been deposited on glass and polymer substrates by an advanced ion beam technologies including ion-assisted deposition (IAD), hybrid ion beam, ion beam sputter deposition (IBSD), and ion-assisted reaction (IAR). Physical and chemical properties of the oxide films and adhesion between films and substrates were improved significantly by these technologies. By using the IAD method, non-stoichiometry and microstructure of the films were controlled by changing assisted oxygen ion energy and arrival ratio of assisted oxygen ion to evaporated atoms. Relationships between structural and electrical properties in ITO films on glass substrates were intensively investigated by using the IBSD method with changing ion energy, reactive gas environment, and substrate temperature. Smooth-surface ITO films (Rrms ≤ 1 nm and Rp-v ≤ 10 nm) for organic light-emitting diodes were developed with a combination of deposition conditions with controlling microstructure of a seed layer on glass. IAR surface treatment enormously enhanced the adhesion of oxide films to polymer substrate. The different dependence of IO and ITO films' properties on the experimental parameters, such as ion energy and oxygen gas environment, will be intensively discussed. 相似文献
35.
Jung-Hyuk Koh Mun-Su Ha Soon-Jong Jeong Jae-Sung Song Tae-geun Kim Sang-Mo Koo Jae-geun Ha 《Journal of Electroceramics》2006,16(4):403-406
The solid solution of Pb(Mg,Nb)O3-Pb(Zr,TiO) O3 materials have high piezoelectric constant of 600 ∼650 pC/N and electromechanical coupling coefficient k
p of 0.65. Due to such high piezoelectric constant and electromechanical coupling coefficient, Pb(Mg,Nb)O3-Pb(Zr,TiO)O3 materials have been attracted attentions for the applications of multilayer ceramic actuators. Actuators can be produced
by staking piezoelectric ceramic materials and inner electrodes, alternatively. However, it is difficult to fabricate huge
ceramic actuators without any serious problems during the process conditions. Because ceramic are easily cracked during the
sintering process, due to strikingly different shrinkage rate between the ceramic materials and metal electrodes. In this
research, new jointing methods will be proposed for huge ceramic actuators, and then their electrical properties were investigated.
Time dependent leakage current and impedance spectroscopy were employed to expect device performances. 相似文献
36.
Wong E. H. Koh S. W. Lee K. H. Lim K.-M. Lim T. B. Mai Y.-W. 《Advanced Packaging, IEEE Transactions on》2006,29(4):751-759
Two advanced techniques have been developed for modeling vapor pressure within the plastic IC packages during solder reflow. The first involves the extension of the "wetness" technique to delamination along multimaterial interface and during dynamic solder reflow. Despite its simplicity, this technique is capable of offering reliable and accurate prediction for packages with high flexural rigidity. For packages with low flexural rigidity, the new "decoupling" technique that integrates thermodynamics, moisture diffusion, and structural analysis into a unified procedure has been shown to be more useful. The rigorous technique has been validated on both leadframe-based as well as laminate-based packages. With high accuracy and computational efficiency, these dynamic modeling tools will be valuable for optimization of package construction, materials, and solder reflow profile against popcorn cracking for both SnPb and Pb-free solders 相似文献
37.
Indium tin oxide (ITO) films with a smooth surface (root-mean-square roughness; Rrms=0.40 nm) were made using a combination of the deposition conditions in the ion beam-sputtering method. Sheet resistance was 13.8 Ω/sq for a 150-nm-thick film grown at 150 °C. Oxygen was fed into the growth chamber during film growth up to 15 nm, after which, the oxygen was turned off throughout the rest of the deposition. The surface of the films became smooth with the addition of ambient oxygen but electrical resistance increased. In films grown at 150 °C with no oxygen present, a rough surface (Rrms=2.1 nm) and low sheet resistance (14.4 Ω/sq) were observed. A flat surface (Rrms=0.5 nm) with high sheet resistance (41 Ω/sq) was obtained in the films grown with ambient oxygen throughout the film growth. Surface morphology and microstructure of the films were determined by the deposition conditions at the beginning of the growth. Therefore, fabrication of ITO films with a smooth surface and high electrical conductivity was possible by combining experimental conditions. 相似文献
38.
Bone morphogenic protein-2 (BMP-2) loaded hybrid coating on porous hydroxyapatite scaffolds for bone tissue engineering 总被引:1,自引:0,他引:1
Shin-Hee Jun Eun-Jung Lee Tae-Sik Jang Hyoun-Ee Kim Jun-Hyeog Jang Young-Hag Koh 《Journal of materials science. Materials in medicine》2013,24(3):773-782
In this study, a silica xerogel-chitosan hybrid is utilized as a coating material to incorporate bone morphogenic protein-2 (BMP-2) on a porous hydroxyapatite (HA) scaffold for bone tissue engineering. BMP-2 is known as a therapeutic agent for improving bone regeneration and repair. Silica xerogel-chitosan hybrids have been used for the delivery of a growth factor as well as osteoconductive coatings. The biological properties of the hybrid coating incorporated with BMP-2 were evaluated in terms of the BMP-2 release behavior, osteoblastic cellular responses and in vivo performance. BMP-2 was continuously released from the hybrid coating layer on the porous HA scaffold for up to 6 weeks. The hybrid coating containing BMP-2 showed significantly enhanced osteoblastic cell responses in comparison with the hybrid coating and HA substrate. Consequently, new bone formation was significantly increased within the hybrid coating containing BMP-2. These results reveal that the hybrid coating containing BMP-2 has the potential to be used as a bone implant, whose osteogenic properties are promoted by the release of BMP-2 in a controlled manner for a prolonged period of time. 相似文献
39.
Eugene Wai Keong Koh Cheng Hsin Chiu Yao Kun Lim Yong-Wei Zhang Hui Pan 《International Journal of Hydrogen Energy》2012
We investigate the hydrogen adsorption on and diffusion through the MoS2 monolayer based on density-functional theory. We show that the hydrogen atom prefers to bond to the S atom at the monolayer, leading to enhanced conductivity. The hydrogen atom can also adsorb at the middle of the hexagon ring by overcoming an energy barrier of 0.57 eV at a strain of 8%. Also, we show that the MoS2 monolayer is flexible and any mechanical deformation of the monolayer is reversible because the extension of the Mo–S bond is much smaller than the applied strain. The monolayer can block the diffusion of hydrogen molecule from one side to the other due to a high energy barrier (6.56 eV). However, the barrier can be reduced to 1.38 eV at a strain of 30% and even totally removed by creating S vacancies and applying a strain of 15%. The MoS2 monolayer may find applications in sensors to detect hydrogen, and as mechanical valve to control the concentration of hydrogen gas. 相似文献
40.
Commercial process for mass production of synthetic natural gas through the adiabatic reactors: operational characteristics of a 50‐kW pilot‐plant,influence of steam,and CO2
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Suk‐Hwan Kang Jin‐Ho Kim Ki‐Jin Jung Young‐Don Yoo Kwang‐Jun Kim Dong‐Jun Koh Jae‐Hong Ryu 《国际能源研究杂志》2017,41(3):353-364
In synthetic natural gas (SNG) reaction process, the water gas shift (WGS) reaction and methanation reaction take place simultaneously, and an insufficient supply of steam might deactivate the catalyst. In this study, the characteristics of the methanation reaction with a commercial catalyst and using a low [H2]/[CO] mole ratio in SNG synthesis are evaluated. The reaction characteristics at various possible process parameters are evaluated varying different process parameters such as the [H2O]/[CO] mole ratio, [H2]/[CO] mole ratio, flow of different % CO2, and reaction temperature. Temperature profiles on catalyst bed are monitored as a function of the [H2O]/[CO] mole ratio, [H2]/[CO] mole ratio, and flow of different % CO2. Through a lab‐scale optimization process, suitable optimum conditions are selected and in the same condition a 50‐kW pilot‐scale SNG production process through adiabatic reactors is carried out. The pilot scale SNG reaction is stable through overnight and the CO conversion efficiency and CH4 selectivity are 100% and 97.3%, respectively, while the maximum CH4 productivity is 0.654 m3/kgcat · h. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献