全文获取类型
收费全文 | 1035篇 |
免费 | 41篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 16篇 |
综合类 | 3篇 |
化学工业 | 237篇 |
金属工艺 | 22篇 |
机械仪表 | 40篇 |
建筑科学 | 28篇 |
能源动力 | 44篇 |
轻工业 | 93篇 |
水利工程 | 4篇 |
石油天然气 | 19篇 |
无线电 | 110篇 |
一般工业技术 | 221篇 |
冶金工业 | 37篇 |
原子能技术 | 2篇 |
自动化技术 | 203篇 |
出版年
2024年 | 6篇 |
2023年 | 15篇 |
2022年 | 46篇 |
2021年 | 56篇 |
2020年 | 35篇 |
2019年 | 40篇 |
2018年 | 35篇 |
2017年 | 38篇 |
2016年 | 30篇 |
2015年 | 34篇 |
2014年 | 29篇 |
2013年 | 78篇 |
2012年 | 57篇 |
2011年 | 82篇 |
2010年 | 54篇 |
2009年 | 56篇 |
2008年 | 46篇 |
2007年 | 31篇 |
2006年 | 38篇 |
2005年 | 23篇 |
2004年 | 30篇 |
2003年 | 18篇 |
2002年 | 15篇 |
2001年 | 13篇 |
2000年 | 12篇 |
1999年 | 8篇 |
1998年 | 17篇 |
1997年 | 15篇 |
1996年 | 10篇 |
1995年 | 9篇 |
1994年 | 8篇 |
1993年 | 10篇 |
1992年 | 8篇 |
1991年 | 8篇 |
1990年 | 3篇 |
1989年 | 15篇 |
1988年 | 8篇 |
1987年 | 5篇 |
1986年 | 6篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 5篇 |
1979年 | 2篇 |
1976年 | 3篇 |
1974年 | 3篇 |
1972年 | 2篇 |
1969年 | 1篇 |
1968年 | 1篇 |
排序方式: 共有1079条查询结果,搜索用时 15 毫秒
81.
Abdelwahhab KHATIR Roberto CAPOZUCCA Samir KHATIR Erica MAGAGNINI 《Frontiers of Structural and Civil Engineering》2022,16(8):976
Vibration-based damage detection methods have become widely used because of their advantages over traditional methods. This paper presents a new approach to identify the crack depth in steel beam structures based on vibration analysis using the Finite Element Method (FEM) and Artificial Neural Network (ANN) combined with Butterfly Optimization Algorithm (BOA). ANN is quite successful in such identification issues, but it has some limitations, such as reduction of error after system training is complete, which means the output does not provide optimal results. This paper improves ANN training after introducing BOA as a hybrid model (BOA-ANN). Natural frequencies are used as input parameters and crack depth as output. The data are collected from improved FEM using simulation tools (ABAQUS) based on different crack depths and locations as the first stage. Next, data are collected from experimental analysis of cracked beams based on different crack depths and locations to test the reliability of the presented technique. The proposed approach, compared to other methods, can predict crack depth with improved accuracy. 相似文献
82.
Trong NGHIA-NGUYEN Mamoru KIKUMOTO Samir KHATIR Salisa CHAIYAPUT H. NGUYEN-XUAN Thanh CUONG-LE 《Frontiers of Structural and Civil Engineering》2021,15(3):696
Currently, the vertical drain consolidation problem is solved by numerous analytical solutions, such as time-dependent solutions and linear or parabolic radial drainage in the smear zone, and no artificial intelligence (AI) approach has been applied. Thus, in this study, a new hybrid model based on deep neural networks (DNNs), particle swarm optimization (PSO), and genetic algorithms (GAs) is proposed to solve this problem. The DNN can effectively simulate any sophisticated equation, and the PSO and GA can optimize the selected DNN and improve the performance of the prediction model. In the present study, analytical solutions to vertical drains in the literature are incorporated into the DNN–PSO and DNN–GA prediction models with three different radial drainage patterns in the smear zone under time-dependent loading. The verification performed with analytical solutions and measurements from three full-scale embankment tests revealed promising applications of the proposed approach. 相似文献
83.
Yi Pang Lu-Tai Tien Hobart Zhu Juying Shen Camilla F. Wright Tembra K. Jones Samir A. Mamoon Abhay J. Bhatt Zhengwei Cai Lir-Wan Fan 《International journal of molecular sciences》2015,16(4):8635-8654
Our previous study showed that a single lipopolysaccharide (LPS) treatment to neonatal rats could induce a long-lasting neuroinflammatory response and dopaminergic system injury late in life. This is evidenced by a sustained activation of microglia and elevated interleukin-1β (IL-1β) levels, as well as reduced tyrosine hydroxylase (TH) expression in the substantia nigra (SN) of P70 rat brain. The object of the current study was to test whether co-administration of IL-1 receptor antagonist (IL-1ra) protects against LPS-induced neurological dysfunction later in life. LPS (1 mg/kg) with or without IL-1ra (0.1 mg/kg), or sterile saline was injected intracerebrally into postnatal day 5 (P5) Sprague-Dawley male rat pups. Motor behavioral tests were carried out from P7 to P70 with subsequent examination of brain injury. Our results showed that neonatal administration of IL-1ra significantly attenuated LPS-induced motor behavioral deficits, loss of TH immunoreactive neurons, as well as microglia activation in the SN of P70 rats. These data suggest that IL-1β may play a pivotal role in mediating a chronic neuroinflammation status by a single LPS exposure in early postnatal life, and blockading IL-1β might be a novel approach to protect the dopaminergic system against perinatal infection/inflammation exposure. 相似文献
84.
Nanduri V. Sudarsan Samir K. Das Smita D. Naik 《Propellants, Explosives, Pyrotechnics》2016,41(5):844-849
Determination of propellant formulation by ballistic requirement is an important area of research in recent times. In this study, a theoretical method for the design of gun propellant formulation using primary data of ingredients and necessary thermochemical properties of the resultant propellant was established. The employed method is based on a mathematical model of thermochemical properties of the propellant by optimizing the heat of explosion of the propellant using the fmincon tool in MATLAB. A graphical user interface (GUI) based code was generated and developed for the formulation design of solid gun propellants. The designed code was verified by available data in the literature. Such code will be useful to the researchers working in the area of high energy materials for the design of unknown propellant compositions. Further, it can be extended to redesign the existing propellant formulation in order to enhance the ballistic performance. 相似文献
85.
We propose a novel protection approach for the design of link-protection schemes in survivable Wavelength Division Multiplexing
mesh networks by merging the well-known p-cycle- and p-tree-protection structures. So doing, we aim at gathering the advantages of p-cycles in terms of protection capabilities, and of p-trees in terms of protection flexibilities (local re-routing, scalability) in a single protection scheme. As opposed to existing
protection schemes based on protection structures with a pre-defined shape, the building blocks of the new scheme are protection
structures with unrestricted shapes. Thus, they allow more flexibility in provisioning spare capacity, and provide higher
capacity efficiency when compared to the shaped-protection schemes that have been proposed so far. In order to cope with the
size of the solution space which includes all the possible protection structures, we propose an efficient and scalable optimization
technique in large-scale systems named column generation (CG). In our CG-based optimization approach, the shape of a candidate
protection structure is dynamically decided during the optimization process according to a link spare capacity budget. Experimental
results on different network instances show that the protection plan resulting from the merging of p-cycle and p-tree structures is, on average, ~15% less capacity redundant and ~15% more reliable than the pure p-cycle one. It also requires, on average, ~30% less protection structures. In addition, those structures provide backup paths
~30% smaller than those of the p-cycle-based scheme. 相似文献
86.
This paper is concerned with palladium–(La0.75Sr0.25)0.97Cr0.5Mn0.5O3 (LSCM) composite current collectors for solid oxide fuel cells (SOFCs); the composites, which are in a 2D configuration (thickness of about 8–10 µm), are deposited upon an LSCM electrode layer on top of an yttria zirconia electrolyte substrate. The influence of the LSCM particle size on the adhesion between palladium and LSCM are reported and discussed. Compositions using four different LSCM particle sizes (0.21, 0.49, 0.64, and 0.81 µm) with sintered Pd particle sizes approaching 10 µm are investigated. The best bonding is obtained when smaller particles are used. The electrical dc conductivity of the composite is reported as a function of the palladium volume fraction for all used LSCM particle sizes. The measured experimental values present typical insulating–conductive percolation. However, the transition occurs at ~33% of the conductive phase, that is, a lower percentage than for 2D ideal systems and a higher percentage than for 3D ideal systems. This is consistent with lower‐dimension percolation for a system of large‐grained conductors and small‐grained insulators. The general effective media (GEM) equation is used to fit the experimental data, and the two main parameters (the threshold point ?c and the exponent t) are defined. 相似文献
87.
The numerous benefits offered by diesel engines, compared to gasoline ones, are balanced by a drawback of increasing concern, namely soot emissions. Nowadays, soot emissions can be reduced by physically trapping the particles within on-board diesel particulate filters (DPF). The filter gets progressively loaded by filtering the soot laden flue gases, thus causing an increasing pressure drop, until regeneration takes place. The aim of this work is to develop a fully predictive three-dimensional mathematical model able to accurately describe the soot deposition process into the filter, the consequent gradual modification of the properties of the filter itself (i.e. permeability and porosity), the formation of a soot filtration cake, and the final regeneration step. The commercial computational fluid dynamics (CFD) code Fluent 6.2.16, based on a finite-volume numerical scheme, is used to simulate the gas and particulate flow fields in the DPF, whereas particle filtration sub-models and regeneration kinetics are implemented through user-defined-subroutines (UDS).Model predictions highlight uneven soot deposition profiles in the first steps of the filtration process; however, the very high resistance to the gas flow of the readily formed cake layer determines the evolution into an almost constant layer of soot particles. The ignition of the loaded soot was simulated under different operating conditions, and two regeneration strategies were investigated: a “mild regeneration” at low temperature and oxygen concentration, that operated a spatially homogeneous ignition of the deposited soot, and a “fast regeneration”, with an uneven soot combustion along the axial coordinate of the filter, due to strong temperature gradients inside the filter itself. These findings are supported by comparison and validation with experimental data. 相似文献
88.
Samir Messaoudi Jean‐Daniel Brion Moud Alami 《Advanced Synthesis \u0026amp; Catalysis》2010,352(10):1677-1687
An efficient copper‐catalyzed in situ C(sp2) NH2 bond formation to provide a range of 3‐aminoquinolin‐2(1H)‐ones and 3‐aminocoumarins from 3‐bromoquinolinones and 3‐bromocoumarins, respectively, has been achieved. The reaction conditions involve the use of copper powder as the catalyst, eco‐friendly ethanol as the solvent in the presence of pipecolinic acid as the ligand and ascorbic acid as the additive. The efficiency of this practical method was demonstrated in the synthesis of various anilines. 相似文献
89.
A comprehensive model based on a new approach was developed to simulate the duckweed growth under controlled conditions. Contrary to other approaches which use the specific growth rate, this approach uses the intrinsic growth rate which permits to differentiate the effect of duckweed mat density from that of temperature, photoperiod and phosphorus-nitrogen concentrations. The model was calibrated using data from laboratory experiments carried out during the present study and validated using other data from two literature sources. In both cases, the results demonstrated that the model was capable of predicting duckweed growth with a reliability of 95%. 相似文献
90.
Arturo Di Fraia Edoardo Miliotti Andrea Maria Rizzo Giulia Zoppi Giuseppe Pipitone Raffaele Pirone Luca Rosi David Chiaramonti Samir Bensaid 《American Institute of Chemical Engineers》2023,69(1):e17652
Lignin-rich stream from lignocellulosic ethanol production was converted into biocrude by continuous hydrothermal liquefaction (HTL) while hydrogen was produced by aqueous phase reforming (APR) of the HTL aqueous by-product. The effects of Na2CO3 and NaOH were investigated both in terms of processability of the feedstock as well as yield and composition of the obtained products. A maximum biocrude yield of 27 wt% was reached in the NaOH-catalyzed runs. A relevant amount of dissolved phenolics were detected in the co-produced aqueous phase (AP), and removed by liquid–liquid extraction using butyl acetate or diethyl ether, preserving the APR catalyst stability and reaching an hydrogen yield up to 146 mmol H2 L−1 AP. Preliminary mass balances integrating HTL and APR showed that the hydrogen provided by APR may account for up to 46% of the hydrogen amount theoretically required for upgrading the HTL biocrude, thus significantly improving the process performance and sustainability. 相似文献