首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   465篇
  免费   26篇
  国内免费   7篇
电工技术   12篇
综合类   4篇
化学工业   61篇
金属工艺   5篇
机械仪表   17篇
建筑科学   13篇
能源动力   7篇
轻工业   35篇
水利工程   1篇
石油天然气   5篇
无线电   88篇
一般工业技术   102篇
冶金工业   33篇
原子能技术   5篇
自动化技术   110篇
  2023年   4篇
  2022年   2篇
  2021年   15篇
  2020年   9篇
  2019年   7篇
  2018年   11篇
  2017年   14篇
  2016年   6篇
  2015年   13篇
  2014年   15篇
  2013年   25篇
  2012年   36篇
  2011年   38篇
  2010年   34篇
  2009年   46篇
  2008年   31篇
  2007年   25篇
  2006年   16篇
  2005年   17篇
  2004年   23篇
  2003年   12篇
  2002年   9篇
  2001年   10篇
  2000年   13篇
  1999年   7篇
  1998年   14篇
  1997年   8篇
  1996年   7篇
  1995年   8篇
  1994年   1篇
  1993年   2篇
  1989年   1篇
  1988年   3篇
  1987年   3篇
  1986年   1篇
  1985年   1篇
  1983年   2篇
  1982年   1篇
  1981年   1篇
  1980年   2篇
  1978年   2篇
  1976年   3篇
排序方式: 共有498条查询结果,搜索用时 31 毫秒
1.
An unexpected rapid anneal of electrically active defects in an ultrathin (15.5 nm) polar polyimide film at and below glass transition temperature (Tg) is reported. The polar polymer is the gate dielectric of a thin‐film‐transistor. Gate leakage current density (Jg) through the polymer initially increases with temperature, as expected, but decreases rapidly at Tg ? 60 °C. After ≈2 min at Tg, the leakage is reduced by nearly three orders of magnitude. A concomitant observation is that the drain current (Id)–gate voltage (Vg) hysteresis decreases with temperature, reaching zero at nearly the same temperature at which Jg collapses. As Jg drops further, the drain current hysteresis increases again but in the opposite direction. This combination strongly supports the interpretation of rapid defect annealing.  相似文献   
2.
Electrochemical CO2 reduction reaction (CO2RR) is an efficient way in the utilization of CO2. In this work, single transition-metal (TM) atom (TM = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn) anchored on two-dimensional (2D) Ti2CN2 are designed for CO2RR using density-functional-theory (DFT) calculation. We show that Ti2CN2 serves as an excellent substrate to support single atom catalysts (SACs), compared to Ti2CO2 and Ti2CF2. We find that the Sc, Ti and V supported on Ti2CN2 show high catalytic activities to produce CO with a low overpotential of 0.37, 0.27, and 0.23 eV, respectively. Differently, the Mn and Fe on Ti2CN2 are catalytically active for the production of HCOOH with a low overpotential of 0.32 and 0.43 eV, respectively. We further show that the negatively charged TM-Ti2CN2 can capture and activate CO2 more effectively, and the catalytic activity and selectivity can be significantly tuned by injecting extra electrons.  相似文献   
3.
4.
The rising production of produced water from oilfields had been proven to bring detrimental environmental effects. In this study, an efficient, recyclable, and environmental-friendly reduced graphene oxide immobilized κ-Carrageenan hydrogel composite(κCa GO) was fabricated as an alternative sorbent for crude oil-in-water demulsification. Polyethyleneimine(PEI) was employed to form a stable hydrogel composite. The conditions for the immobilization of graphene oxide(GO) on PEI-modified κ-Carrageenan(κC) beads were optimized appropriately. An immobilization yield of 77% was attained at 2% PEI, 2 h immobilization activation time, and p H6.5. Moreover, the synthesized κCa GO is capable of demulsification with an average demulsification efficiency of 70%. It was found that the demulsification efficiency increases with salinity and κCa GO dosage, and it deteriorates under alkaline condition. These phenomena can be attributed to the interfacial interactions between κCa GO and the emulsion. Furthermore, the κCa GO can be recycled to use for up to six cycles without significant leaching and degradation. As such, the synthesized κCa GO could be further developed as a potential sorbent substitute for the separation of crude oil from produced water.  相似文献   
5.
6.
The effectiveness of Monte Carlo simulation relative to intelligent search strategies for solving block layout problems is investigated. For testing purposes, 810 block layout problems are constructed to span a wide range of problem sizes, material flow variation levels, work centre space requirements distributions, and work centre shape distributions. Contrary to preliminary results reported in earlier studies, greedy search and simulated annealing consistently outperform Monte Carlo Simulation across the full range of test problems and sample sizes. This divergence is explained through a comparison based on probabilistic derivations between the proportion of good solutions sampled by the Monte Carlo method and those found by the heuristic search methods. Conditions for the superiority of either method are identified. Therefore, the current study complements earlier studies by providing analytical arguments and additional experimental evidence for the effectiveness of simple Monte Carlo method and intelligent search heuristics on solving layout problems.  相似文献   
7.
Microfluidic systems provide a total solution of biological and chemical analysis from the sample application to the display of the analysis results. A lot of developments on the point-of-care diagnostic applications have been reported and the commercial possibility is shown. To achieve sensitive and specific biological sensing, nanoparticles may provide a promising tool because they have similar length scale with the biomolecules. The nano-sensing technology suggests a molecular level detection of the biomolecules to pursue higher performance. In this review, recent developments and patents on the biological sensing using nanoparticles in microfluidic systems are discussed. An updated, systematic and rapid reference in the field of nano-biological sensing is provided.  相似文献   
8.
We conducted a feasibility study for producing a high-purity medical radioisotope 64Cu from natural zinc with accelerator-based neutrons. 64Cu isotopes were produced via the 64Zn(n,p) reaction. The accelerator-based neutrons were generated via the C(d,n) reaction using low-energy deuterons of 9 and 12 MeV on a 1-mm-thick carbon target. First, the production purity was estimated using the evaluated nuclear data library JENDL-4.0 and our previously measured thick target neutron yield. We found that even when natural zinc was used as the starting material, significantly high-purity 64Cu could be obtained. Next, irradiation experiments for producing 64Cu using natural zinc were conducted at Kyushu University Tandem Laboratory, with the amounts of 64Cu isotopes and other gamma-emission nuclides measured by a high-purity germanium detector. As a result, high-purity 64Cu isotopes of 1.11(49) × 100 and 3.70 (17) × 100 Bq/g/μC were produced with incident deuteron energies of 9 and 12 MeV, respectively.  相似文献   
9.
A dynamic meta-learning rate-based model for gold market forecasting   总被引:1,自引:0,他引:1  
In this paper, an improved EMD meta-learning rate-based model for gold price forecasting is proposed. First, we adopt the EMD method to divide the time series data into different subsets. Second, a back-propagation neural network model (BPNN) is used to function as the prediction model in our system. We update the online learning rate of BPNN instantly as well as the weight matrix. Finally, a rating method is used to identify the most suitable BPNN model for further prediction. The experiment results show that our system has a good forecasting performance.  相似文献   
10.
Sin ML  Liu T  Pyne JD  Gau V  Liao JC  Wong PK 《Analytical chemistry》2012,84(6):2702-2707
This study reports a multifunctional electrode approach which directly implements electrokinetic enhancement on a self-assembled-monolayer-based electrochemical sensor for point-of-care diagnostics. Using urinary tract infections as a model system, we demonstrate that electrokinetic enhancement, which involves in situ stirring and heating, can enhance the sensitivity of the strain specific 16S rRNA hybridization assay for 1 order of magnitude and accelerate the time-limiting incubation step with a 6-fold reduction in the incubation time. Since the same electrode platform is used for both electrochemical signal enhancement and electrochemical sensing, the multifunctional electrode approach provides a highly effective strategy toward fully integrated lab-on-a-chip systems for various biomedical applications.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号