全文获取类型
收费全文 | 1543篇 |
免费 | 70篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 22篇 |
化学工业 | 336篇 |
金属工艺 | 29篇 |
机械仪表 | 44篇 |
建筑科学 | 21篇 |
矿业工程 | 5篇 |
能源动力 | 112篇 |
轻工业 | 187篇 |
水利工程 | 44篇 |
石油天然气 | 1篇 |
无线电 | 155篇 |
一般工业技术 | 252篇 |
冶金工业 | 76篇 |
原子能技术 | 9篇 |
自动化技术 | 322篇 |
出版年
2024年 | 4篇 |
2023年 | 35篇 |
2022年 | 60篇 |
2021年 | 57篇 |
2020年 | 38篇 |
2019年 | 58篇 |
2018年 | 74篇 |
2017年 | 52篇 |
2016年 | 62篇 |
2015年 | 47篇 |
2014年 | 64篇 |
2013年 | 122篇 |
2012年 | 63篇 |
2011年 | 100篇 |
2010年 | 69篇 |
2009年 | 86篇 |
2008年 | 60篇 |
2007年 | 68篇 |
2006年 | 49篇 |
2005年 | 40篇 |
2004年 | 29篇 |
2003年 | 35篇 |
2002年 | 26篇 |
2001年 | 16篇 |
2000年 | 18篇 |
1999年 | 15篇 |
1998年 | 21篇 |
1997年 | 28篇 |
1996年 | 17篇 |
1995年 | 23篇 |
1994年 | 15篇 |
1993年 | 11篇 |
1992年 | 17篇 |
1991年 | 15篇 |
1990年 | 15篇 |
1989年 | 14篇 |
1988年 | 15篇 |
1987年 | 8篇 |
1986年 | 9篇 |
1985年 | 8篇 |
1984年 | 6篇 |
1983年 | 5篇 |
1982年 | 12篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1979年 | 6篇 |
1977年 | 5篇 |
1976年 | 4篇 |
1975年 | 2篇 |
1972年 | 3篇 |
排序方式: 共有1615条查询结果,搜索用时 15 毫秒
21.
This study performed a quantitative evaluation of the impact of water-saving irrigation on the groundwater regime in the Hebei Province plains area. In this work, the change in groundwater regime and the contributions of precipitation and water-saving irrigation development were investigated. The results indicate that the groundwater overdraft has been mitigated to some extent, mainly due to changes in precipitation and the implementation of water-saving irrigation, with contributions of 64.3% and 35.7%, respectively, when considering only these two factors. Water-saving irrigation is accepted as an important means for reducing groundwater depletion, but should be used in conjunction with other measures. 相似文献
22.
A novel technique that uses microwave power for joining and repair of thermoplastic and thermoset composites and ceramics is discussed. Enhanced microwave heating resulting from the use of conducting polymers and chiral microinclusions shows considerable promise for joining and repair of composites. The method is attractive because it produces clean and reliable interfacial joints, it is fast, it does not entail alteration of the bulk materials, and it does not result in volumetric heating. System details, including magnetron, waveguides, circulators, coupling iris, and the applicator for delivering microwave power, are described. Material requirements for the efficient absorption of microwave power are discussed. Microwave heating can be increased by doping the components to be joined or by the use of microwave adhesive films. Recent developments in electromagnetic chirality for microwave absorption are introduced and the design of composite materials for enhanced absorptivity is discussed. Results are presented for the welding and repair of thermoplastic, thermoset, and ceramic components. 相似文献
23.
Yinzhong Guo Vijay M. Mannari Pulin Patel John L. Massingill 《Journal of Coatings Technology and Research》2006,3(4):327-331
A series of soybean oil phosphate ester polyols (SOPEP) was prepared by reaction of fully epoxidized soybean oil with phosphoric
acid and simultanoeous hydrolysis in the presence of a polar solvent. The polyols were characterized by determination of acid
value, oxirane number, hydroxyl value, molecular weight (GPC), and FTIR spectra. These polyols with varying amounts of acid
phosphate groups could be self-emulsified to form aqueous dispersions after neutralization with organic base. These aqueous
dispersion showed varying degrees of stability and their appearance ranged from opaque dispersions to translucent to clear
solutions. Waterborne coating compositions were prepared using these aqueous dispersions as principal components and their
thermally cured film properties were studied. it was found that by careful selection and formulation, SOPEPs can be successfully
used for low-VOC waterborne coating formulations. SOPEPs with 3.5% phosphate ester content showed visibly superior corrosion
resistance properties. 相似文献
24.
25.
Huddar Mahesh G. Sannakki Sanjeev S. Rajpurohit Vijay S. 《Multimedia Tools and Applications》2021,80(9):13077-13077
Multimedia Tools and Applications - A Correction to this paper has been published: https://doi.org/10.1007/s11042-021-10591-y 相似文献
26.
Yadav Rakesh Kumar Abhishek Yadav Vijay Kumar Verma Shekhar Venkatesan S. 《Pattern Analysis & Applications》2021,24(4):1667-1683
Pattern Analysis and Applications - The performance of graph-based learning techniques largely relies on the edges defined between the vertices of the graph. These edges that represent the affinity... 相似文献
27.
Andrew A. Sobek Vijay Rastogi Donald A. Benedetti 《Mine Water and the Environment》1990,9(1-4):133-148
In pyritic environments, the bacteriaThiobacillus ferrooxidans catalyze acid formation by increasing the oxidation rate of pyrite by a factor of one million. This acid solubilizes metals and pollutes adjacent streams and lands. Bactericide sprays during mining and waste disposal operations attack the source of the problem by preventing acid formation and metals solubilization. Used in conjunction with current water treatment systems, bactericides can dramatically reduce operating costs. Controlled release bactericides contribute to successful reclamation by providing assurance against revegetation failure and post-reclamation water quality problems that can necessitate perpetual water treatment. While inhibitingT. ferrooxidans these organic compounds aid in the establishment of beneficial heterotrophic bacteria which support vegetation. These conditions continue to persist after the bactericide is depleted from the controlled release system. Case Studies I and II show that bactericides inhibit acid generation during hard rock and coal mining operations and they are cost effective. Case Studies III and IV illustrate the improvement in water quality and vegetation after reclamation when controlled release bactericides were used. Economic analyses show cost benefits are achieved when controlled-release bactericides are part of the reclamation plan. 相似文献
28.
Nazanin Pourmand Vijay Parsa Angela Weaver 《International Journal of Speech Technology》2013,16(4):363-379
The performance of several noise reduction algorithms intended for wideband telephony was evaluated both subjectively and objectively. The chosen algorithms were based on statistical modeling, spectral subtraction, Wiener filtering, or subspace modelling principles. A customized wideband noise reduction database containing speech samples corrupted by three types of background noises at three SNR levels, along with their enhanced versions was created. The overall quality of the speech samples in the database was subsequently rated by a group of listeners with normal hearing capabilities. Comprehensive statistical analyses were performed to assess the reliability of the subjective data, and to assess the performance of noise reduction algorithms across varied noisy conditions. The subjective quality ratings were then used to investigate the performance of several auditory model-based objective quality metrics. Key results from these investigations include: (a) there was a high degree of inter- and intra-subject reliability in the subjective ratings, (b) noise reduction algorithms enhance speech quality for only a subset of the noise conditions, and (c) auditory model-based metrics perform similarly in predicting speech quality ratings, when speech quality scores pertaining to a particular noise condition were averaged. 相似文献
29.
Michael Westrick Mohammad Almalkawi Vijay Devabhaktuni Charles Bunting 《国际射频与微波计算机辅助工程杂志》2013,23(1):111-117
A novel wire antenna for future dedicated short range communications vehicle‐to‐vehicle communications is introduced. The proposed antenna carries low‐profile and low‐cost features, and possesses an improved gain performance. This article also includes a specific feed network design for the proposed antenna to meet the mechanical and manufacturing requirements. Two different numerical techniques using CST Microwave Studio and HFSS have been applied for evaluating the performance of the proposed antenna. The whole system including the feed network and the antenna elements is integrated, and its performance is also assessed. © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2013. 相似文献
30.
Rachid El-Azouzi Francesco De Pellegrini Habib B.A. Sidi Vijay Kamble 《Computer Networks》2013,57(4):1003-1018
In this paper, we apply evolutionary games to non-cooperative forwarding control in Delay Tolerant Networks (DTNs). The main focus is on mechanisms to rule the participation of the relays to the delivery of messages in DTNs. Thus, we express the success probability as a function of the competition that takes place within a large population of mobiles, and we characterize the effect of reward-based mechanisms on the performance of such systems. Devices acting as active relays, in fact, sacrifice part of their batteries in order to support message replication and thus increase the probability to reach the destination. In our scheme, a relay can choose the strategy by which they participate to the message relaying. A mobile that participates receives a unit of reward based on the reward mechanism selected by the network. A utility function is introduced as the difference between the expected reward and the energy cost, i.e., the cost spent by the relay to sustain forwarding operations. We show how the evolution dynamics and the equilibrium behavior (called Evolutionary Stable Strategy – ESS) are influenced by the characteristics of inter contact time, energy expenditure and pricing characteristics.We extend our analysis to mechanisms that the system can introduce in order to have the message delivered to the destination with high probability within a given deadline and under energy constraints which bound the number of released copies per message. Finally, we apply our findings in order to devise decentralized forwarding algorithms that are rooted in the theory of stochastic approximations. Thus, we demonstrate that the ESS can be attained without complete knowledge of the system state and letting the source monitor number of released copies per message only. We provide extensive numerical results to validate the proposed scheme. 相似文献