全文获取类型
收费全文 | 677篇 |
免费 | 36篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 11篇 |
化学工业 | 170篇 |
金属工艺 | 32篇 |
机械仪表 | 31篇 |
建筑科学 | 3篇 |
矿业工程 | 3篇 |
能源动力 | 59篇 |
轻工业 | 33篇 |
水利工程 | 5篇 |
石油天然气 | 3篇 |
无线电 | 71篇 |
一般工业技术 | 159篇 |
冶金工业 | 69篇 |
自动化技术 | 70篇 |
出版年
2024年 | 4篇 |
2023年 | 14篇 |
2022年 | 26篇 |
2021年 | 44篇 |
2020年 | 40篇 |
2019年 | 24篇 |
2018年 | 33篇 |
2017年 | 41篇 |
2016年 | 28篇 |
2015年 | 22篇 |
2014年 | 51篇 |
2013年 | 62篇 |
2012年 | 35篇 |
2011年 | 36篇 |
2010年 | 47篇 |
2009年 | 25篇 |
2008年 | 34篇 |
2007年 | 25篇 |
2006年 | 20篇 |
2005年 | 11篇 |
2004年 | 9篇 |
2003年 | 11篇 |
2002年 | 9篇 |
2001年 | 12篇 |
2000年 | 6篇 |
1999年 | 6篇 |
1998年 | 3篇 |
1997年 | 5篇 |
1996年 | 5篇 |
1995年 | 3篇 |
1994年 | 2篇 |
1993年 | 3篇 |
1992年 | 7篇 |
1991年 | 1篇 |
1990年 | 3篇 |
1989年 | 6篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1983年 | 1篇 |
排序方式: 共有719条查询结果,搜索用时 343 毫秒
21.
Multiple-input multiple-output (MIMO) wireless systems can achieve significant diversity and array gain by using transmit beamforming and receive combining techniques. In the absence of full channel knowledge at the transmitter, the transmit beamforming vector can be quantized at the receiver and sent to the transmitter using a low-rate feedback channel. In the literature, quantization algorithms for the beamforming vector are designed and optimized for a particular channel distribution, commonly the uncorrelated Rayleigh distribution. When the channel is not uncorrelated Rayleigh, however, these quantization strategies result in a degradation of the receive signal-to-noise ratio (SNR). In this paper, switched codebook quantization is proposed where the codebook is dynamically chosen based on the channel distribution. The codebook adaptation enables the quantization to exploit the spatial and temporal correlation inherent in the channel. The convergence properties of the codebook selection algorithm are studied assuming a block-stationary model for the channel. In the case of a nonstationary channel, it is shown using simulations that the selected codebook tracks the distribution of the channel resulting in improvements in SNR. Simulation results show that in the case of correlated channels, the SNR performance of the link can be significantly improved by adaptation, compared with nonadaptive quantization strategies designed for uncorrelated Rayleigh-fading channels 相似文献
22.
Y. L. Saraswathi S. Das D. P. Mondal 《Metallurgical and Materials Transactions A》2005,36(8):2259-2262
The erosion-corrsosion behavior of SiC particle-reinforced Al-Si alloy has been studied in NaOH slurry simulating the mining
atmosphere. The study was performed at two different sand concentrations, namely, 20 and 30 wt pct, and at a speed of 900
rpm. It is depicted that the wear rates decreased with increasing sand content, indicating that corrosion is the dominating
mode of material removal. Further composite exhibited lower wear resistance than the laloys irrespective of the sand concentration.
Scanning electron microscope (SEM) observations indicated the dissolution of dendrites of Al due to severe corrosion, leaving
behind the network of Si. This ultimately results in the falling of Si particles from the matrix, leaving behind voids. This
also results in the formation of voids around the SiC particles and leads to pullout of SiC particles from the matrix during
the wear process. 相似文献
23.
Anupam Ojha Barun Das Shyamal Kumar Mondal Manoranjan Maiti 《Applied Soft Computing》2013,13(8):3703-3712
This paper presents the recently introduced modified subgradient method for optimization and its effectiveness in a fuzzy transportation model. Here a multi-item balanced transportation problem (MIBTP) is formulated where unit transportation costs are imprecise. Also available spaces and budgets at destinations are limited but imprecise. The objective is to find a shipment schedule for the items that minimizes the total cost subjected to imprecise warehouse and budget constraints at destinations. The proposed model is reduced to a multi-objective optimization problem using tolerances, then to a crisp single-objective one using fuzzy non-linear programming (FNLP) technique and Zimmermann's method. The above fuzzy MIBTP is also reduced to another form of deterministic one using modified sub-gradient method (MSM). These two crisp optimization problems are solved by Genetic Algorithm (GA). As an extension, fuzzy multi-item balanced solid transportation problems (STPs) with and without restrictions on some routes and items are formulated and reduced to deterministic ones following FNLP and Zimmermann's methods. These models are also solved by GA. Models are illustrated numerically, optimum results of fuzzy MIBTP from two deductions are compared. Results are also presented for different GA parameters. 相似文献
24.
Multiple-bonded iron-oxo and -nitrido species have been identified or proposed as key intermediates in a range of important chemical transformations. The reported model complexes feature various coordination geometries and distinct electronic structures, and therefore exhibit diverse reactivity. The present contribution highlights the synergy from both experimental and theoretical standpoints to elucidate their different bonding situations and delineate their common mechanistic features in hydrogen-atom abstraction processes. Our analysis reveals that a radical centered on the abstracting atom E (E=O, N), which is generated via homolysis of covalent Fe−E bonds upon approaching the transition state, is an intrinsic C−H cleaving agent. The iron-oxo species is predicted to be more reactive than its nitride congener, in general, because the O−H bond formed in the H-atom transfer process is often stronger than the corresponding N−H bond. 相似文献
25.
Govinda Krishnan A. Varshney Venkitanarayanan Parameswaran K. Mondal 《Journal of Materials Engineering and Performance》2017,26(6):2619-2631
The current work analyzes the effect of the dynamic change in strain rate during tensile loading of a mild steel on its mechanical and stress corrosion behavior in 3.5 wt.% NaCl solution. The sample experiences high strain rate (10?2 s?1) up to 10, 15 and 20% of total deformation and then very low strain rate of 10?6 s?1 till fracture without any unloading in between. The behavioral characteristics of the steel under these circumstances are found to be different from that exhibited during complete loading till fracture both at high and slow strain rates separately. Total strain increases with the increase in the strain at which change in strain rate happens, and this is attributed to the generation of large number of dislocations at higher strain rate and subsequently release of dislocation at low strain rate during change over due to more time available for dynamic recovery. This observation is common for both in air and corrosive environment. One unique observation in this study is the higher total strain and lower strength observed during dynamic change in strain rate in the corrosive environment compared to that in air, which is attributed to the hydrogen-induced plasticity mechanism. 相似文献
26.
A. K. Manna B. Das J. K. Dey S. K. Mondal 《Journal of Intelligent Manufacturing》2018,29(7):1515-1531
One of the economic production quantity problems that have been of interest to researchers is the production with reworking of the imperfect items including waste most disposal form and vending the units. The available models in the literature assumed that the decay rate of the items is satisfied from three different points of view: (i) minimum demands of the customer’s requirement, (ii) demands to be enhanced for lower selling price and (iii) demands of the customers who are motivated by the advertisement. The model is developed over a finite random planning horizon, which is assumed to follow the exponential distribution with known parameters. The model has been illustrated with a numerical example, whose parametric inputs are estimated from market survey. Here the model is optimized by using a population varying genetic algorithm. 相似文献
27.
In this research work, electrical conductivity of a novel cast 6351 Al–Al4SiC4 composite has been studied for varying Al4SiC4 particle content (2–7 vol%). Analytical models were developed on the basis of free electron theory and local resistance approach in order to predict electrical conductivity of metal matrix composites. The electrical conductivity of cast 6351 Al–Al4SiC4 composite was found to decrease with increasing Al4SiC4 content. Overprediction of results and more % deviation of the predicted electrical conductivity from experimental value were observed for local-resistance-approach-based model. However, the model developed on the basis of electron theory considering scattering of electrons at particle–matrix interface accurately predicted the experimental electrical conductivity data. 相似文献
28.
Nilrudra Mandal H. Roy B. Mondal N. C. Murmu S. K. Mukhopadhyay 《Journal of Materials Engineering and Performance》2012,21(1):17-24
In the light of attractive wear characteristics as well as high strength to weight ratio, extensive research on Al-based Metal
Matrix Composite (MMC) have been carried out globally in the last two decades. However, very limited research has been pursued
on tribological behavior of Al-based MMC under combined action of rolling and sliding. This study investigates the wear behavior
of 6061 Al-alloy/SiC with 10 vol.% SiCp against hardened and tempered AISI 4340 steel under combined rolling-sliding conditions. 23 factorial design of experiments have been carried out to see the effect of few parameters, i.e., contact stress, speed and
duration with respect to wear. The interaction effect has also been studied by 3D graphical contours. A mathematical model
is developed using regression analysis technique for prediction of wear behavior of the MMC and adequacy of the model has
been validated using analysis of variance (ANOVA) techniques. Finally, the optimization of parameter has also been done using
Design Expert software. The results have shown that Response Surface Methodology (RSM) is an effective tool for prediction
of wear behavior under combined sliding and rolling action. It is also found that the wear of MMC is much lower than hardened;
tempered AISI 4340 steel and rolling speed has the maximum influence in wear of both materials under investigation. 相似文献
29.
We consider a Lorentzian manifold M which is globally hyperbolic. We define a metric on C(p, q), the set of all equivalence classes of causal curves connecting two causally related points p and q. We show that C(p, q) is a complete metric space with the metric thus defined. Here, by completeness we mean that every Cauchy sequence (a sequence with a tendency to converge) in C(p, q) finds a point in it to converge. We also give an example to show that the result does not hold in general when the spacetime is not globally hyperbolic. The work is in line with research on causality in relativistic spacetimes. 相似文献
30.
Swapan Kumar Ghosh Rajib Bhattacharyya Murari Mohan Mondal Tapobrata Sanyal 《Journal of Natural Fibers》2015,12(5):457-480
In the last quarter of the twentieth century, a new class of materials, Geosynthetics, emerged prospectively leading significant innovation in the design of geotechnical and geoenvironmental systems. Geotextiles have proven to be among the most versatile and techno-economically viable ground modification materials playing a significant role in modern pavement design and maintenance techniques. With the growing environmental concern across the globe, technologists, researchers have inclined towards the natural geotextile where Jute Geotextile (JGT) is one of the potential candidates. But, JGT has been restricted mainly as underlay in road construction. Hence, there is an urgent need to design and develop a precise innovative fabric as overlay on existing pavements and other emerging civil works to stay technically and economically competitive in the global market. Such a fabric will not only prove techno-economically viable but will also reduce the carbon foot-print generation to a large extent. This paper delineates the development of Grey Jute Paving Fabric (GJPF) followed by its bituminization with suitable type and grade of bitumen to develop Bituminized Jute Paving Fabric (BJPF). The BJPF will enhance the life of the overlay thereby reducing the cost of maintenance as well as serving as a partial substitute of bitumen mastic. 相似文献