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251.
    
3D printing is recognized as a powerful tool to develop complex geometries for a variety of materials including nanocellulose. Herein, a one‐pot synthesis of 3D printable hydrogel ink containing zeolitic imidazolate frameworks (ZIF‐8) anchored on anionic 2,2,6,6‐tetramethylpiperidine‐1‐oxylradical‐mediated oxidized cellulose nanofibers (TOCNF) is presented. The synthesis approach of ZIF‐8@TOCNF (CelloZIF8) hybrid inks is simple, fast (≈30 min), environmentally friendly, takes place at room temperature, and allows easy encapsulation of guest molecules such as curcumin. Shear thinning properties of the hybrid hydrogel inks facilitate the 3D printing of porous scaffolds with excellent shape fidelity. The scaffolds show pH controlled curcumin release. The synthesis route offers a general approach for metal–organic frameworks (MOF) processing and is successfully applied to other types of MOFs such as MIL‐100 (Fe) and other guest molecules as methylene blue. This study may open new venues for MOFs processing and its large‐scale applications.  相似文献   
252.
    
Polymer based conductive and transparent thin films are an important class of functional materials at the heart of flexible organic electronic devices. These flexible films are prone to degradation and to mechanical instability leading to the formation of blisters, wrinkles, and cracks. This is detrimental to their use especially in the case of multilayer devices. Here, it is shown that a simple water or solvent drop deposited on such films gives rise to a buckling instability and the formation of several folds due to the tendency of these films to swell in contact with the solvent. A phase diagram of the instability portraying its domain of existence, and thus the means to inhibit it, is proposed. By depositing drops on such films and observing the instability, material parameters such as the elastic modulus of the thin films or their energy of adhesion to the substrate can be estimated reliably. Further, the instability can be harnessed to pattern surfaces at low cost giving rise to percolated and more conductive pathways in the conductive polymer films under scrutiny.  相似文献   
253.
    
With the increase of the number of connected vehicles on roads, the data dissemination within traditional network suffers from many limitations like high latency, a significant amount of dropped packets and network congestion. Therefore, the Internet of vehicles (IoV) has been designed as an emerging paradigm that combines the intelligent transportation system (ITS) with Internet of Things (IoT) technology. IoV allows vehicles to exchange data with its surroundings in order to enhance the traffic safety and to provide digital services to road users. In this paper, a taxonomy of data dissemination protocols proposed for IoV is surveyed according to three main categories namely, the smart control‐based category, social networks‐based category, and traditional approaches. We also review the data dissemination in IoV based on the fifth generation (5G) communications with emphasis on enabling technologies, architectures, services, and challenges. Moreover, we suggest in this study a new generic 5G‐based IoV architecture named IoVs based on fifth generation communications to enhance data dissemination by the promising and efficient transmission technologies such as fifth‐generation network properties, software‐defined network functionalities (SDN), and cloud‐fog computing services. The proposed scheme helps to meet challenges in the low latency, high reliability and security, high performance, mobility contrary to conventional architectures.  相似文献   
254.
    
Current innovative distributed architectures, proposing on-line services, involve more and more computing resources. From a provider point of view, the platform management leads to challenging problematic relating to resource allocation, which involve different kind of quality of service parameters, the provider has to focus on to keep his platform reliable and efficient. MFHS is a modular generic framework, which can be adapted to any distributed computing environment. Structured in modules, MFHS allows to discover the existing computing resources in terms of computing performance, network throughput and disk I/O speeds (Resources Discovery module) and to predict how the experiment should behave (Pi value). As the setting up of real experiments is often complex, MFHS allows: to make theoretical experimentation (based on models), to use any kind of distributed emulators, or to deploy experiments on real-experimental platforms. In this article, these three environments are used to highlight the reliability of MFHS (measured Pi=90% against 94% for the predicted Pi). Deployment and scheduling studies have also been achieved using an experimental Cloud based on OpenStack while Emulab test-bed has been used as emulator. During experiments, four QoS parameters are taken into account (Resources Monitoring module): energy consumption, cost, resource utilization, and makespan. These studies also includes a new heuristic called MMin, based on Max-Min and Min-Min algorithms. Experimentation section, proposes a detailed comparative analysis of these algorithms in terms of QoS results, while the abilities of the proposed heuristic MMin regarding the makespan metric is shown.  相似文献   
255.

Background  

In observational studies anaemia and iron deficiency are associated with cognitive deficits, suggesting that iron supplementation may improve cognitive function. However, due to the potential for confounding by socio-economic status in observational studies, this needs to be verified in data from randomised controlled trials (RCTs).  相似文献   
256.
    
Wind power is one of the sustainable ways to generate renewable energy. In recent years, some countries have set renewables to meet future energy needs, with the primary goal of reducing emissions and promoting sustainable growth, primarily the use of wind and solar power. To achieve the prediction of wind power generation, several deep and machine learning models are constructed in this article as base models. These regression models are Deep neural network (DNN), k-nearest neighbor (KNN) regressor, long short-term memory (LSTM), averaging model, random forest (RF) regressor, bagging regressor, and gradient boosting (GB) regressor. In addition, data cleaning and data preprocessing were performed to the data. The dataset used in this study includes 4 features and 50530 instances. To accurately predict the wind power values, we propose in this paper a new optimization technique based on stochastic fractal search and particle swarm optimization (SFS-PSO) to optimize the parameters of LSTM network. Five evaluation criteria were utilized to estimate the efficiency of the regression models, namely, mean absolute error (MAE), Nash Sutcliffe Efficiency (NSE), mean square error (MSE), coefficient of determination (R2), root mean squared error (RMSE). The experimental results illustrated that the proposed optimization of LSTM using SFS-PSO model achieved the best results with R2 equals 99.99% in predicting the wind power values.  相似文献   
257.
Titanium-substituted large pore SSZ-42 zeolite was synthesized for the first time using the corresponding borosilicate as starting material. Substitution of boron by titanium took place via either high temperature treatment with TiCl4 vapor or by treatment with Ti(OiPr)4 in dry toluene at 120°C. Both deboronated and boron-containing samples were found to be suitable for post-synthesis incorporation of titanium in the zeolite framework. The obtained materials were characterized by FTIR, UV-visible and XPS. Titanium-modified SSZ-42 was found to be active for phenol hydroxylation and cyclohexene epoxidation.  相似文献   
258.
A series of Fe–BEA catalysts, differing in the amount of iron have been characterized by XRD, BET surface area, UV–vis spectroscopy and chemical analysis. The zeolite samples have been tested as heterogeneous catalysts for the wet hydrogen peroxide oxidation of crude olive mill wastewaters (OMW) under very mild conditions (at 28 °C and atmospheric pressure). All experiments were performed on a laboratory scale set-up.BSE-1/3 catalyst with a moderate Fe content (Fe/Al = 1.19) showed the best results in terms of catalytic activity and loss of active species into the aqueous solutions. The stability of Fe species has been shown to be strongly dependent on the Fe environment into the zeolite framework.Over the selected catalyst, application of catalytic procedure on diluted OMW solution permitted high removal efficiencies of pollutants. The process produces a removal capacity of 28% of total organic carbon (TOC), 40% of total phenols, 30% of chemical oxygen demand (COD) and 59% of colour, just after 12 h. 5-Day biochemical oxygen demand (BOD5), and toxicity towards the bioluminescent bacteria Vibrio fischeri were selected to follow the performance of this process in terms of reducing the ecotoxicity of OMW. Results showed an increase in the biodegradability of the treated sample and a decrease of the microtoxicity from 100% to 70% load towards V. fischeri.Occurrence of small catalyst deactivation by carbonaeous during the oxidation reaction was observed through scanning electron microscopy (SEM) and elemental analysis.  相似文献   
259.
Protection of Metals and Physical Chemistry of Surfaces - The inhibition effect of cyclohexylphosphonic acid (CHPA) on the corrosion of structural steel (EN 10027) in 3.5% sodium chloride solution...  相似文献   
260.
With the rise of VOD (Video-on-Demand) services provisioning as a successful service on the Internet and managed networks, we are witnessing a drive towards cost-efficiency and economies of scale. Many broadband operators around the world are experimenting with P2P (Peer-to-Peer) systems centered on STBs (Set-Top-Boxes) to increase the competitiveness of their VOD services offering. By leveraging the storage and uplink bandwidth capacities available at a certain number of STBs operated by the broadband operator, the savings in terms of backend streaming capacities will represent sizable and decisive gains in cost. In these systems, video contents are usually fragmented into a number of complementary content fragments, called sub-streams, which are randomly injected in the network of STBs, and the VOD service is essentially provisioned through multisource streaming sessions from neighboring STBs to the requesting STB. One of the main challenges in such peer-assisted streaming systems remains the maximization of the utilization of STB resources utility for a given content popularity pattern. In this paper, we specifically focus on the content injection strategy and how the different content fragments should be dispatched in the network to achieve the highest performance in the VOD services provisioning epoch. We demonstrate that the random injection strategy is not appropriate for maximizing the number of simultaneous VOD streaming sessions in the network. Our objective is to first gain a better understanding of the factors driving P2P-based VOD streaming systems and provide guidelines to better operate such systems and ultimately give service operators the tools to achieve different performance objectives and/or fit specific network configurations. Further, we propose a new content dispatching strategy that maximizes the number of served VOD sessions by balancing the streaming load among the different STBs. Finally, we propose a complementary streaming resources reprovisioning mechanism that acts in real-time to reprovision the resources for serving VOD sessions to new STBs and to release trapped resources for new incoming VOD service requests.  相似文献   
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