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   722篇
  免费   57篇
  国内免费   4篇
电工技术   19篇
综合类   1篇
化学工业   281篇
金属工艺   19篇
机械仪表   13篇
建筑科学   17篇
能源动力   31篇
轻工业   59篇
水利工程   7篇
石油天然气   16篇
无线电   94篇
一般工业技术   128篇
冶金工业   29篇
原子能技术   3篇
自动化技术   66篇
  2023年   14篇
  2022年   21篇
  2021年   35篇
  2020年   23篇
  2019年   42篇
  2018年   62篇
  2017年   43篇
  2016年   33篇
  2015年   30篇
  2014年   37篇
  2013年   53篇
  2012年   47篇
  2011年   48篇
  2010年   37篇
  2009年   25篇
  2008年   21篇
  2007年   14篇
  2006年   13篇
  2005年   12篇
  2004年   18篇
  2003年   17篇
  2002年   17篇
  2001年   10篇
  2000年   13篇
  1999年   8篇
  1998年   11篇
  1997年   11篇
  1996年   13篇
  1995年   4篇
  1994年   3篇
  1993年   2篇
  1992年   3篇
  1991年   2篇
  1988年   2篇
  1987年   2篇
  1986年   3篇
  1985年   1篇
  1984年   3篇
  1983年   3篇
  1982年   1篇
  1981年   3篇
  1980年   1篇
  1979年   1篇
  1977年   2篇
  1976年   2篇
  1975年   4篇
  1974年   3篇
  1973年   5篇
  1972年   2篇
  1969年   1篇
排序方式: 共有783条查询结果,搜索用时 15 毫秒
11.
Continuous improvements in very-large-scale integration (VLSI) technology and design software have significantly broadened the scope of digital signal processing (DSP) applications. The use of application-specific integrated circuits (ASICs) and programmable digital signal processors for many DSP applications have changed, even though new system implementations based on reconfigurable computing are becoming more complex. Adaptable platforms that combine hardware and software programmability efficiency are rapidly maturing with discrete wavelet transformation (DWT) and sophisticated computerized design techniques, which are much needed in today’s modern world. New research and commercial efforts to sustain power optimization, cost savings, and improved runtime effectiveness have been initiated as initial reconfigurable technologies have emerged. Hence, in this paper, it is proposed that the DWT method can be implemented on a field-programmable gate array in a digital architecture (FPGA-DA). We examined the effects of quantization on DWT performance in classification problems to demonstrate its reliability concerning fixed-point math implementations. The Advanced Encryption Standard (AES) algorithm for DWT learning used in this architecture is less responsive to resampling errors than the previously proposed solution in the literature using the artificial neural networks (ANN) method. By reducing hardware area by 57%, the proposed system has a higher throughput rate of 88.72%, reliability analysis of 95.5% compared to the other standard methods.  相似文献   
12.
End-of-life disassembly has developed into a major research area within the sustainability paradigm, resulting in the emergence of several algorithms and structures proposing heuristics techniques such as Genetic Algorithm (GA), Ant Colony Optimization (ACO) and Neural Networks (NN). The performance of the proposed methodologies heavily depends on the accuracy and the flexibility of the algorithms to accommodate several factors such as preserving the precedence relationships during disassembly while obtaining near- optimal and optimal solutions. This paper improves a previously proposed Genetic Algorithm model for disassembly sequencing by utilizing a faster metaheuristic algorithm, Tabu search, to obtain the optimal solution. The objectives of the proposed algorithm are to minimize (1) the traveled distance by the robotic arm, (2) the number of disassembly method changes, and (3) the number of robotic arm travels by combining the identical-material components together and hence eliminating unnecessary disassembly operations. In addition to improving the quality of optimum sequence generation, a comprehensive statistical analysis comparing the previous Genetic Algorithm and the proposed Tabu Search Algorithm is also included  相似文献   
13.
We develop array algorithms for H filtering. These algorithms can be regarded as the Krein space generalizations of H 2 array algorithms, which are currently the preferred method fur implementing H2 filters. The array algorithms considered include two main families: square-root array algorithms, which are typically numerically more stable than conventional ones, and fast array algorithms which, when the system is time-invariant, typically offer an order of magnitude reduction in the computational effort. Both have the interesting feature that one does not need to explicitly check for the positivity conditions required for the existence of H filters, as these conditions are built into the algorithms themselves. However, since H square-root algorithms predominantly use J-unitary transformations, rather than the unitary transformations required in the H2 case, further investigation is needed to determine the numerical behavior of such algorithms  相似文献   
14.
A double‐array is a well‐known data structure to implement the trie. However, the space efficiency of the double‐array degrades with the number of key deletions because the double‐array keeps empty elements produced by the key deletion. This paper presents a fast and compact elimination method of empty elements using properties of the trie nodes that have no siblings. The present elimination method is implemented by C language. From simulation results for large sets of keys, the present elimination method is about 30–330 times faster than the conventional elimination method and maintains high space efficiency. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   
15.
Background: Silymarin (SIL) has long been utilized to treat a variety of liver illnesses, but due to its poor water solubility and low membrane permeability, it has a low oral bioavailability, limiting its therapeutic potential. Aim: Design and evaluate hepatic-targeted delivery of safe biocompatible formulated SIL-loaded chitosan nanoparticles (SCNPs) to enhance SIL’s anti-fibrotic effectiveness in rats with CCl4-induced liver fibrosis. Methods: The SCNPs and chitosan nanoparticles (CNPs) were prepared by ionotropic gelation technique and are characterized by physicochemical parameters such as particle size, morphology, zeta potential, and in vitro release studies. The therapeutic efficacy of successfully formulated SCNPs and CNPs were subjected to in vivo evaluation studies. Rats were daily administered SIL, SCNPs, and CNPs orally for 30 days. Results: The in vivo study revealed that the synthesized SCNPs demonstrated a significant antifibrotic therapeutic action against CCl4-induced hepatic injury in rats when compared to treated groups of SIL and CNPs. SCNP-treated rats had a healthy body weight, with normal values for liver weight and liver index, as well as significant improvements in liver functions, inflammatory indicators, antioxidant pathway activation, and lipid peroxidation reduction. The antifibrotic activities of SCNPs were mediated by suppressing the expression of the main fibrosis mediators TGFβR1, COL3A1, and TGFβR2 by boosting the hepatic expression of protective miRNAs; miR-22, miR-29c, and miR-219a, respectively. The anti-fibrotic effects of SCNPs were supported by histopathology and immunohistochemistry (IHC) study. Conclusions: According to the above results, SCNPs might be the best suitable carrier to target liver cells in the treatment of liver fibrosis.  相似文献   
16.
The corrosion inhibition of steel in a closed system containing sodium sulphite at room temperature has been established. Steady-state potential as well as weight loss measurements indicated that sodium sulphite did not only remove O2 from the solution but also brought complete cathodic protection. It was found also that sodium sulphite could tolerate the presence of Cl?, SO42? and S2?. In case of sulphite—sulphate or sulphite—chloride mixtures a concentration of 5 × 10?3M Na2SO3 was required to tolerate a wide range of concentration of these aggressive ions. A linear relationship was found between log sulphite concentration and log maximum tolerated concentration of sulphide.  相似文献   
17.
This study aims to predict ground surface settlement due to shallow tunneling and introduce the most affecting parameters on this phenomenon.Based on data collected from Shanghai LRT Line 2 project undertaken by TBM-EPB method,this research has considered the tunnel's geometric,strength,and operational factors as the dependent variables.At first,multiple regression(MR) method was used to propose equations based on various parameters.The results indicated the dependency of surface settlement on many parameters so that the interactions among different parameters make it impossible to use MR method as it leads to equations of poor accuracy.As such,adaptive neuro-fuzzy inference system(ANFIS),was used to evaluate its capabilities in terms of predicting surface settlement.Among generated ANFIS models,the model with all input parameters considered produced the best prediction,so as its associated R~2 in the test phase was obtained to be 0.957.The equations and models in which operational factors were taken into consideration gave better prediction results indicating larger relative effect of such factors.For sensitivity analysis of ANFIS model,cosine amplitude method(CAM) was employed; among other dependent variables,fill factor of grouting(n) and grouting pressure(P) were identified as the most affecting parameters.  相似文献   
18.
19.
20.
In this study, polyurethane (PU)-milled light bulbs glass composites were synthesized and characterized. The main interest in this study that the polyurethane derived from renewable resources and waste glass are used to form the composite constituents as an attempt towards environmental preservation. Castor oil and polymeric diphenyl methane di-isocyanates (PMDI) were used in NCO/OH ratio = 2 for polyurethane synthesis. Milled glass with average particles size less than 300 μm were prepared based on waste light bulbs. Silane A1100 (as a compatibilizer) was used in order to improve the value of recycled milled glass beads. The adhesion force between polyurethane matrix and milled glass beads was evaluated using mechanical and physical tests. Scanning electron microscopy (SEM) was used to investigate dispersion and fracture surfaces of the composites. Infrared spectrum (IR), Differential scanning calorimetry (DSC) behavior, and Thermogravimetric analysis (TGA), were employed to characterize the developed composite materials in details. Chemical resistance (weight change, thickness swelling) was measured in oil, water and dilute acetic acid media. Furthermore, tensile strength and hardness were investigated using universal materials testing machines. A slight increase in the hardness values was reported along with the increasing in particulate fillers loading up to 10% as a considerable improvement has been detected when milled glass reached 20%. The DSC analysis showed the presence of treated milled glass beads influences the thermal behavior of pure PU and composites. This can be attributed to enhancing the physical bonding between PU and silica group. Waste milled glass showed a significant effect on the thermal degradation of the composites in the presence of coupling agent. Further analysis on the tensile strength of the composites indicated that such improved mechanical properties may be attributed to the presence of coupling agent.  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