全文获取类型
收费全文 | 683篇 |
免费 | 24篇 |
国内免费 | 5篇 |
学科分类
工业技术 | 712篇 |
出版年
2023年 | 12篇 |
2022年 | 17篇 |
2021年 | 24篇 |
2020年 | 26篇 |
2019年 | 31篇 |
2018年 | 43篇 |
2017年 | 28篇 |
2016年 | 32篇 |
2015年 | 17篇 |
2014年 | 42篇 |
2013年 | 59篇 |
2012年 | 38篇 |
2011年 | 62篇 |
2010年 | 36篇 |
2009年 | 44篇 |
2008年 | 29篇 |
2007年 | 26篇 |
2006年 | 21篇 |
2005年 | 17篇 |
2004年 | 6篇 |
2003年 | 13篇 |
2002年 | 5篇 |
2001年 | 10篇 |
2000年 | 11篇 |
1999年 | 2篇 |
1998年 | 7篇 |
1997年 | 8篇 |
1996年 | 4篇 |
1995年 | 1篇 |
1994年 | 3篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1991年 | 3篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 5篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 3篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1976年 | 2篇 |
1975年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有712条查询结果,搜索用时 29 毫秒
11.
Non-edible filtered high viscous (72 cSt at 40 °C) and high acid value (44 mg KOH/gm) polanga (Calophyllum inophyllum L.) oil based mono esters (biodiesel) produced by triple stage transesterification process and blended with high speed diesel (HSD) were tested for their use as a substitute fuel of diesel in a single cylinder diesel engine. HSD and polanga oil methyl ester (POME) fuel blends (20%, 40%, 60%, 80%, and 100%) were used for conducting the short-term engine performance tests at varying loads (0%, 20%, 40%, 60%, 80%, and 100%). Tests were carried out over entire range of engine operation at varying conditions of speed and load. The brake specific fuel consumption (BSFC) and brake thermal efficiency (BTE) were calculated from the recorded data. The engine performance parameters such as fuel consumption, thermal efficiency, exhaust gas temperature and exhaust emissions (CO, CO2, HC, NOx, and O2) were recorded. The optimum engine operating condition based on lower brake specific fuel consumption and higher brake thermal efficiency was observed at 100% load for neat biodiesel. From emission point of view the neat POME was found to be the best fuel as it showed lesser exhaust emission as compared to HSD. 相似文献
12.
Evaluation of AMSR-E soil moisture results using the in-situ data over the Little River Experimental Watershed, Georgia 总被引:2,自引:0,他引:2
Alok K. Sahoo Paul R. Houser Craig Ferguson Paul A. Dirmeyer 《Remote sensing of environment》2008,112(6):3142-3152
An operational global soil moisture data product is currently generated from the observations of the Advanced Microwave Scanning Radiometer (AMSR-E) aboard NASA's Aqua satellite using the retrieval procedure described in Njoku and Chan [Njoku, E.G. and Chan, S.K., 2006. Vegetation and surface roughness effects on AMSR-E land observations, remote sensing environment, 100(2), 190-199]. We have generated another soil moisture dataset from the same AMSR-E observed brightness temperature data using the Land Surface Microwave Emission Model (LSMEM) adopting a different estimation method. This paper focuses on a comparison study of soil moisture estimates from the above two methods. The soil moisture data from current AMSR-E product and LSMEM are compared with the in-situ measured soil moisture datasets over the Little River Experimental Watershed (LREW), Georgia, USA for the year 2003. The comparison study was carried out separately for the AMSR-E daytime and night time overpasses. The LSMEM method performed better than the current operational AMSR-E retrieval algorithm in this study. The differences between the AMSR-E and LSMEM results are mostly due to differences in various simplifications and assumptions made for variables in the radiative transfer equations and the soil and vegetation based physical models and the accuracy of the input surface temperature datasets for the LSMEM forward model approach. This study confirms that remote sensing data have the potential to provide useful hydrologic information, but the accuracy of the geophysical parameters could vary depending on the estimation methods. It cannot be concluded from this study whether the soil moisture estimation by the LSMEM approach will perform better in other geographic, climatic or topographic conditions. Nevertheless, this study sheds light on the effects of different approaches for the estimation of geophysical parameters, which may be useful for current and future satellite missions. 相似文献
13.
Text characters embedded in images represent a rich source of information for content-based indexing and retrieval applications. However, these text characters are difficult to be detected and recognized due to their various sizes, grayscale values, and complex backgrounds. Existing methods cannot handle well those texts with different contrast or embedded in a complex image background. In this paper, a set of sequential algorithms for text extraction and enhancement of image using cellular automata are proposed. The image enhancement includes gray level, contrast manipulation, edge detection, and filtering. First, it applies edge detection and uses a threshold to filter out for low-contrast text and simplify complex background of high-contrast text from binary image. The proposed algorithm is simple and easy to use and requires only a sample texture binary image as an input. It generates textures with perceived quality, better than those proposed by earlier published techniques. The performance of our method is demonstrated by presenting experimental results for a set of text based binary images. The quality of thresholding is assessed using the precision and recall analysis of the resultant text in the binary image. 相似文献
14.
Prasant Ku. Dash Lopamudra Hota Madhumita Panda N. Z. Jhanjhi Kshira Sagar Sahoo Mehedi Masud 《计算机系统科学与工程》2023,44(3):2225-2242
The 3D Underwater Sensor Network (USNs) has become the most optimistic medium for tracking and monitoring underwater environment. Energy and collision are two most critical factors in USNs for both sparse and dense regions. Due to harsh ocean environment, it is a challenge to design a reliable energy efficient with collision free protocol. Diversity in link qualities may cause collision and frequent communication lead to energy loss; that effects the network performance. To overcome these challenges a novel protocol Forwarder Selection Energy Efficient Routing (FSE2R) is proposed. Our proposal’s key idea is based on computation of node distance from the sink, Residual Energy (RE) of each node and Signal to Interference Noise Ratio (SINR). The node distance from sink and RE is computed for reliable forwarder node selection and SINR is used for analysis of collision. The novel proposal compares with existing protocols like H2AB, DEEP, and E2LR to achieve Quality of Service (QoS) in terms of throughput, packet delivery ratio and energy consumption. The comparative analysis shows that FSE2R gives on an average 30% less energy consumption, 24.62% better PDR and 48.31% less end-to-end delay compared to other protocols. 相似文献
15.
Kuldeep Chouhan Mukesh Yadav Ranjeet Kumar Rout Kshira Sagar Sahoo NZ Jhanjhi Mehedi Masud Sultan Aljahdali 《计算机系统科学与工程》2023,45(2):1113-1128
Twitter is a radiant platform with a quick and effective technique to analyze users’ perceptions of activities on social media. Many researchers and industry experts show their attention to Twitter sentiment analysis to recognize the stakeholder group. The sentiment analysis needs an advanced level of approaches including adoption to encompass data sentiment analysis and various machine learning tools. An assessment of sentiment analysis in multiple fields that affect their elevations among the people in real-time by using Naive Bayes and Support Vector Machine (SVM). This paper focused on analysing the distinguished sentiment techniques in tweets behaviour datasets for various spheres such as healthcare, behaviour estimation, etc. In addition, the results in this work explore and validate the statistical machine learning classifiers that provide the accuracy percentages attained in terms of positive, negative and neutral tweets. In this work, we obligated Twitter Application Programming Interface (API) account and programmed in python for sentiment analysis approach for the computational measure of user’s perceptions that extract a massive number of tweets and provide market value to the Twitter account proprietor. To distinguish the results in terms of the performance evaluation, an error analysis investigates the features of various stakeholders comprising social media analytics researchers, Natural Language Processing (NLP) developers, engineering managers and experts involved to have a decision-making approach. 相似文献
16.
Karimulla Shah Rishav Kumar Sibasis Sahoo R. S. Pais Nirupam Chakraborti 《Materials and Manufacturing Processes》2017,32(10):1201-1208
Data-driven models have been constructed for Dual Phase (DP) and Interstitials Free (IF) steels using an evolutionary approach. DP steel data are utilized from an existing database, while for the IF steels, data generated at an integrated steel plant have been used. The objective function for Ultimate Tensile Strength (UTS) and % elongation, created as data-driven models, is simultaneously optimized for an optimum strength-ductility balance and the results indicate the possibilities of developing steels with better mechanical properties than what are known to have been existing so far. 相似文献
17.
In this paper, the forced convective heat transfer enhancement with nanofluids in a 90° pipe bend has been presented. Numerical investigation is carried out for the turbulent flow through the pipe employing finite volume method. The governing differential equations are discretized using hexahedral cells, and the resulting algebraic equations are solved using Commercial solver Fluent 6.3. In order to close the time averaged Navier–Stokes equations, the two-equation k–? turbulence model with a standard wall function have been used. The duct Reynolds number is varied in the range of 2,500–6,000. It is observed that the heat transfer is enhanced significantly by varying the volume fraction of the nanofluid. It is also found that the heat transfer is increased with Reynolds number. A strong secondary flow is observed due to the presence of the wall. Turbulent kinetic energy near outer wall is found to be higher than the inner wall of the bend. A comparative assessment for the heat transfer enhancement with different types of nanofluids is also presented. The computed results of area weighted average Nusselt numbers are validated with some of the existing literature. 相似文献
18.
Prasan Kumar Sahoo Chih-Yung Chang Sheng-Wen Chang 《Journal of Network and Computer Applications》2008,31(4):535-558
Bluetooth technology is specially designed for the wireless personal area networks to replace cable. Several challenges exist in Bluetooth scatternet formation and routing, since nodes can arrive and depart at arbitrary times. In this paper, novel route maintenance algorithms are proposed for the Bluetooth ad hoc networks, where nodes can enter or exit from the piconets time to time. Our protocols guarantee the connectivity among nodes and reconstruct the routes dynamically by considering location information of the nodes. Besides, it is proposed how to reduce the number of hops and to form the shortest route between the source and the destination due to addition of new nodes to a piconet. Performance analysis of our protocols show that they outperform in terms of end to end transmission delay, bandwidth consumption and average hop counts as compared to similar Bluetooth routing protocols that we have considered. 相似文献
19.
Solving shortest path problem using particle swarm optimization 总被引:6,自引:0,他引:6
This paper presents the investigations on the application of particle swarm optimization (PSO) to solve shortest path (SP) routing problems. A modified priority-based encoding incorporating a heuristic operator for reducing the possibility of loop-formation in the path construction process is proposed for particle representation in PSO. Simulation experiments have been carried out on different network topologies for networks consisting of 15–70 nodes. It is noted that the proposed PSO-based approach can find the optimal path with good success rates and also can find closer sub-optimal paths with high certainty for all the tested networks. It is observed that the performance of the proposed algorithm surpasses those of recently reported genetic algorithm based approaches for this problem. 相似文献
20.
In this paper, dimensional analysis has been carried out to derive general equations that predict: the total gas transferred to the ambient reservoir water from an air bubbler, total volume entrained, and total energy consumed for a known or equivalent linear stratification. The equations are tested by comparison with a one-dimensional bubbler model developed by the authors. It is shown that the oxygen transfer to the water column can be significant if small bubbles are used. The mechanical destratification efficiency ηmech (%), destratification time per unit surface area Γ?(s/m2), oxygen dissolution efficiency Ω (%), and oxygen transferred per unit input energy are examined as functions of bubble size. It is concluded that an average bubble radius of 1?mm should be considered for design purposes. However, if oxygen transfer from the bubbler is not considered important, then a bubble size of up to 4?mm is acceptable for destratification purposes. 相似文献