全文获取类型
收费全文 | 2208篇 |
免费 | 153篇 |
国内免费 | 16篇 |
专业分类
电工技术 | 28篇 |
综合类 | 8篇 |
化学工业 | 551篇 |
金属工艺 | 53篇 |
机械仪表 | 83篇 |
建筑科学 | 46篇 |
矿业工程 | 4篇 |
能源动力 | 172篇 |
轻工业 | 299篇 |
水利工程 | 13篇 |
石油天然气 | 32篇 |
无线电 | 191篇 |
一般工业技术 | 431篇 |
冶金工业 | 145篇 |
原子能技术 | 16篇 |
自动化技术 | 305篇 |
出版年
2024年 | 12篇 |
2023年 | 49篇 |
2022年 | 137篇 |
2021年 | 195篇 |
2020年 | 111篇 |
2019年 | 128篇 |
2018年 | 140篇 |
2017年 | 125篇 |
2016年 | 122篇 |
2015年 | 88篇 |
2014年 | 129篇 |
2013年 | 182篇 |
2012年 | 108篇 |
2011年 | 135篇 |
2010年 | 80篇 |
2009年 | 58篇 |
2008年 | 56篇 |
2007年 | 49篇 |
2006年 | 44篇 |
2005年 | 36篇 |
2004年 | 35篇 |
2003年 | 32篇 |
2002年 | 34篇 |
2001年 | 20篇 |
2000年 | 22篇 |
1999年 | 19篇 |
1998年 | 50篇 |
1997年 | 18篇 |
1996年 | 14篇 |
1995年 | 15篇 |
1994年 | 18篇 |
1993年 | 8篇 |
1992年 | 5篇 |
1991年 | 10篇 |
1990年 | 7篇 |
1989年 | 6篇 |
1988年 | 7篇 |
1987年 | 5篇 |
1986年 | 4篇 |
1985年 | 6篇 |
1984年 | 5篇 |
1983年 | 7篇 |
1982年 | 3篇 |
1980年 | 4篇 |
1979年 | 4篇 |
1977年 | 6篇 |
1976年 | 7篇 |
1975年 | 3篇 |
1971年 | 2篇 |
1969年 | 3篇 |
排序方式: 共有2377条查询结果,搜索用时 15 毫秒
51.
Raad S. Sabry Asaad M. Abbas Firas S. Mohammed Wisam J. Aziz 《Journal of Materials Science: Materials in Electronics》2016,27(4):3170-3174
ZnO nanoparticles were synthesized by liquid-phase pulse laser ablation of a Zn foil target immersed in deionized water. Nanosecond Q-switched Nd:YAG laser pulses of 532 nm were applied to the Zn foil target at a perpendicular and inclined (θ = 45°) angles. X-ray diffraction analysis revealed that both cases feature a ZnO nanostructure with a hexagonal wurtzite structure and that the particle size increases with the inclined target angle. Field emission scanning electron microscopy results of a colloidal drop cast on a glass substrate showed the ZnO has a nanorod structure in the case of a perpendicular target angle and an interlaced tattered nanosheet structure in the case of an inclined target angle. Photoluminescence spectra showed emission peaks in the UV, violet, blue, and green spectral regions, which correspond to excitonic and various defects resulting in an enhancement of emissions at inclined target angle. 相似文献
52.
Liu Daobin Wu Chuanqiang Chen Shuangming Ding Shiqing Xie Yaofeng Wang Changda Wang Tao Haleem Yasir A. ur Rehman Zia Sang Yuan Liu Qin Zheng Xusheng Wang Yu Ge Binghui Xu Hangxun Song Li 《Nano Research》2018,11(4):2217-2228
Nano Research - Atomically dispersed catalysts have attracted attention in energy conversion applications because their efficiency and chemoselectivity for special catalysis are superior to those... 相似文献
53.
Samra Rehman Muhammad Attique Khan Majed Alhaisoni Ammar Armghan Usman Tariq Fayadh Alenezi Ye Jin Kim Byoungchol Chang 《计算机、材料和连续体(英文)》2023,75(1):697-714
Identifying fruit disease manually is time-consuming, expert-required, and expensive; thus, a computer-based automated system is widely required. Fruit diseases affect not only the quality but also the quantity. As a result, it is possible to detect the disease early on and cure the fruits using computer-based techniques. However, computer-based methods face several challenges, including low contrast, a lack of dataset for training a model, and inappropriate feature extraction for final classification. In this paper, we proposed an automated framework for detecting apple fruit leaf diseases using CNN and a hybrid optimization algorithm. Data augmentation is performed initially to balance the selected apple dataset. After that, two pre-trained deep models are fine-tuning and trained using transfer learning. Then, a fusion technique is proposed named Parallel Correlation Threshold (PCT). The fused feature vector is optimized in the next step using a hybrid optimization algorithm. The selected features are finally classified using machine learning algorithms. Four different experiments have been carried out on the augmented Plant Village dataset and yielded the best accuracy of 99.8%. The accuracy of the proposed framework is also compared to that of several neural nets, and it outperforms them all. 相似文献
54.
The static fracture toughness of a series of eutectic Al-Si casting alloy with different microstructural features has been evaluated. The dominant influence of eutectic silicon in controlling the fracture toughness is thus clarified. The relationship between the fracture toughness and the microstructure was established. Fracture toughness was found to be strongly associated with the size and morphology of silicon particles. The other feature which greatly influences the fracture toughness is the ratio (/DE)Si, i.e. the silicon particle spacing divided by the equivalent particle diameter, rather than the silicon particle spacing, Si. Fracture toughness also correlates well with the void growth parameter, VGP (=y (/DE)Si), proposed by the authors. The results of the present work can be used to develop an understanding of the variation of fracture toughness with the microstructural features of eutectic Al-Si alloys. 相似文献
55.
In this paper, we present general formulae for the mask of (2b + 4)-point n-ary approximating as well as interpolating subdivision schemes for any integers ${b\,\geqslant\,0}$ and ${n\,\geqslant\,2}$ . These formulae corresponding to the mask not only generalize and unify several well-known schemes but also provide the mask of higher arity schemes. Moreover, the 4-point and 6-point a-ary schemes introduced by Lian [Appl Appl Math Int J 3(1):18–29, 2008] are special cases of our general formulae. 相似文献
56.
Siew-Chin Neoh Morad N. Chee-Peng Lim Abdul Aziz Z. 《IEEE transactions on systems, man, and cybernetics. Part A, Systems and humans : a publication of the IEEE Systems, Man, and Cybernetics Society》2010,40(1):133-146
High-mix-low-volume (HMLV) production is currently a worldwide manufacturing trend. It requires a high degree of customization in the manufacturing process to produce a wide range of products in low quantity in order to meet customers' demand for more variety and choices of products. Such a kind of business environment has increased the conversion time and decreased the production efficiency due to frequent production changeover. In this paper, a layered-encoding cascade optimization (LECO) approach is proposed to develop an HMLV product-mix optimizer that exhibits the benefits of low conversion time, high productivity, and high equipment efficiency. Specifically, the genetic algorithm (GA) and particle swarm optimization (PSO) techniques are employed as optimizers for different decision layers in different LECO models. Each GA and PSO optimizer is studied and compared. A number of hypothetical and real data sets from a manufacturing plant are used to evaluate the performance of the proposed GA and PSO optimizers. The results indicate that, with a proper selection of the GA and PSO optimizers, the LECO approach is able to generate high-quality product-mix plans to meet the production demands in HMLV manufacturing environments. 相似文献
57.
Wind energy has emerged as a strong alternative to fossil fuels for power generation. To generate this energy, wind turbines are placed in a wind farm. The extraction of maximum energy from these wind farms requires optimal placement of wind turbines. Due to complex nature of micrositing of wind turbines, the wind farm layout design problem is considered a complex optimization problem. In the recent past, various techniques and algorithms have been developed for optimization of energy output from wind farms. The present study proposes an optimization approach based on the cuckoo search (CS) algorithm, which is relatively a recent technique. A variant of CS is also proposed that incorporates a heuristic-based seed solution for a better performance. The proposed CS algorithms are compared with genetic and particle swarm optimization (PSO) algorithms, which have been extensively applied to wind farm layout design. Empirical results indicate that the proposed CS algorithms outperformed the genetic and PSO algorithms for the given test scenarios in terms of yearly power output and efficiency. 相似文献
58.
Hafiz Shehzad Ahmed Hong-Dong Zhao Munawar Hussain Jing Wang 《Pattern Recognition and Image Analysis》2017,27(4):804-809
Image processing algorithm is implemented to detect the grain boundary of the crystal using (SEM) Scanning Electron Microscopy. This paper presents a method for edge-detection in color image based on Sobel, Canny operator’s algorithm and discrete wavelet transform. The performance of these methods is effective and faster. Filtering is another approach to clear the noise of an image. Scanning Electron Microscopy (SEM) used to inspect semiconductor materials and devices for several decades, continues to increase in importance. Removal of noise is an important step in the image restoration process, but de-noising of the image has remained a challenging problem in recent research associated with image process. De-noising is used to remove the noise from corrupted images, while retaining the edges and other detailed features too are an essential part of de-noising. 相似文献
59.
Fatih Çalışır Muhammet Baştan Özgür Ulusoy Uğur Güdükbay 《Multimedia Tools and Applications》2017,76(10):12433-12456
High user interaction capability of mobile devices can help improve the accuracy of mobile visual search systems. At query time, it is possible to capture multiple views of an object from different viewing angles and at different scales with the mobile device camera to obtain richer information about the object compared to a single view and hence return more accurate results. Motivated by this, we propose a new multi-view visual query model on multi-view object image databases for mobile visual search. Multi-view images of objects acquired by the mobile clients are processed and local features are sent to a server, which combines the query image representations with early/late fusion methods and returns the query results. We performed a comprehensive analysis of early and late fusion approaches using various similarity functions, on an existing single view and a new multi-view object image database. The experimental results show that multi-view search provides significantly better retrieval accuracy compared to traditional single view search. 相似文献
60.
H. M. Abdul Aziz Satish V. Ukkusuri Xianyuan Zhan 《Networks and Spatial Economics》2017,17(2):505-545
Personal mobility carbon allowance (PMCA) schemes are designed to reduce carbon consumption from transportation networks. PMCA schemes influence the travel decision process of users and accordingly impact the system metrics including travel time and greenhouse gas (GHG) emissions. We develop a multi-user class dynamic user equilibrium model to evaluate the transportation system performance when PMCA scheme is implemented. The results using Sioux-Falls test network indicate that PMCA schemes can achieve the emissions reduction goals for transportation networks. Further, users characterized by high value of travel time are found to be less sensitive to carbon budget in the context of work trips. Results also show that PMCA scheme can lead to higher emissions for a path compared with the case without PMCA because of flow redistribution. The developed network equilibrium model allows to examine the change in system states at different carbon allocation levels and to design parameters of PMCA schemes accounting for population heterogeneity. 相似文献