首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1001篇
  免费   43篇
  国内免费   1篇
电工技术   18篇
化学工业   265篇
金属工艺   11篇
机械仪表   13篇
建筑科学   34篇
矿业工程   3篇
能源动力   31篇
轻工业   98篇
水利工程   10篇
石油天然气   4篇
无线电   108篇
一般工业技术   143篇
冶金工业   37篇
自动化技术   270篇
  2024年   1篇
  2023年   9篇
  2022年   35篇
  2021年   27篇
  2020年   24篇
  2019年   34篇
  2018年   43篇
  2017年   27篇
  2016年   37篇
  2015年   28篇
  2014年   32篇
  2013年   59篇
  2012年   77篇
  2011年   64篇
  2010年   48篇
  2009年   49篇
  2008年   56篇
  2007年   61篇
  2006年   47篇
  2005年   31篇
  2004年   39篇
  2003年   16篇
  2002年   23篇
  2001年   15篇
  2000年   12篇
  1999年   15篇
  1998年   11篇
  1997年   16篇
  1996年   12篇
  1995年   7篇
  1994年   8篇
  1993年   6篇
  1992年   2篇
  1991年   8篇
  1990年   1篇
  1989年   7篇
  1988年   4篇
  1987年   7篇
  1986年   10篇
  1985年   6篇
  1984年   4篇
  1983年   9篇
  1982年   4篇
  1981年   1篇
  1980年   2篇
  1979年   3篇
  1977年   3篇
  1976年   3篇
  1973年   2篇
排序方式: 共有1045条查询结果,搜索用时 0 毫秒
81.
In this paper, the berth allocation problem with stochastic vessel handling times is formulated as a bi-objective problem. To solve the resulting problem, an evolutionary algorithm-based heuristic and a simulation-based Pareto front pruning algorithm is proposed. Computational examples show that the proposed approach provides solutions superior to the ones where the expected value of the vessel handling times is used.  相似文献   
82.
Multi-Camera Human Activity Monitoring   总被引:1,自引:0,他引:1  
With the proliferation of security cameras, the approach taken to monitoring and placement of these cameras is critical. This paper presents original work in the area of multiple camera human activity monitoring. First, a system is presented that tracks pedestrians across a scene of interest and recognizes a set of human activities. Next, a framework is developed for the placement of multiple cameras to observe a scene. This framework was originally used in a limited X, Y, pan formulation but is extended to include height (Z) and tilt. Finally, an active dual-camera system for task recognition at multiple resolutions is developed and tested. All of these systems are tested under real-world conditions, and are shown to produce usable results. This work has been supported by the NSF through grants #IIS-0219863, #CNS-0224363, #CNS-0324864, #IIP-0443945, #CNS-0420836, #IIP-0726109, and #CNS-0708344.  相似文献   
83.
The use of renewable feedstocks, derived from biomass, for the chemical industry is discussed. The modern chemical industry is based around platform chemicals, e.g. ethene, propene, benzene and xylenes, which are readily derived from oil, and using these intermediates a broad range of finished products can be derived. While it is feasible that biomass can be converted to syngas and hence to existing key platform chemicals, this loses all of the chemical complexity that is inherent in bio-derived molecules. In this paper some of the options are considered and, in particular, the oxidation of glucose and glycerol using gold nanoparticles supported on carbon is described. We also contrast the oxidation of glycerol using supported gold and gold–palladium alloys prepared using an impregnation technique, since the gold–palladium alloys have been shown to be highly effective for the oxidation of alcohols and the synthesis of hydrogen peroxide.  相似文献   
84.
In the present study, complexes of vanillin with β-cyclodextrin (β-CD) were prepared by the freeze-drying method. The formation of the inclusion complex was confirmed by differential scanning calorimetry (DSC). DSC thermograms indicated that the endothermic peak of vanillin and the physical mixture of vanillin with β-CD, due to the melting of vanillin crystals, were absent in DSC thermograms obtained for the freeze-dried inclusion complex. Moreover, the DSC studies under oxidation conditions indicate that the complex of vanillin with β-CD is protected towards oxidation since it remains intact at temperatures where the free vanillin is oxidising. The structure of the complex in aqueous solutions was established by nuclear magnetic resonance (NMR) studies and specifically by two-dimensional rotational frame NOE spectra. NMR studies showed inclusion of the entire vanillin molecule in the β-CD in a tilted manner and with the aldehyde group in the primary side. The stoichiometry of the complex was 1:1. A phase solubility study was performed by mixing an excess amount of vanillin with aqueous solutions containing increasing amounts of β-CD. The results indicated that the complex of a vanillin/β-CD inclusion is more soluble in water than vanillin alone.  相似文献   
85.
Autonomous stair-climbing with miniature jumping robots.   总被引:1,自引:0,他引:1  
The problem of vision-guided control of miniature mobile robots is investigated. Untethered mobile robots with small physical dimensions of around 10 cm or less do not permit powerful onboard computers because of size and power constraints. These challenges have, in the past, reduced the functionality of such devices to that of a complex remote control vehicle with fancy sensors. With the help of a computationally more powerful entity such as a larger companion robot, the control loop can be closed. Using the miniature robot's video transmission or that of an observer to localize it in the world, control commands can be computed and relayed to the inept robot. The result is a system that exhibits autonomous capabilities. The framework presented here solves the problem of climbing stairs with the miniature Scout robot. The robot's unique locomotion mode, the jump, is employed to hop one step at a time. Methods for externally tracking the Scout are developed. A large number of real-world experiments are conducted and the results discussed.  相似文献   
86.
87.
88.
The effect of domestic pan‐frying in virgin olive oil (VOO) on the proximate composition, energy content, cholesterol, squalene and fatty acids in the edible portion of six species of finfish, common squid and mussels just caught from several regions of the Aegean Sea (Mediterranean Sea) was investigated. The species selected are traditionally consumed pan‐fried in VOO by the Greeks. On a fresh weight basis, pan‐frying caused significant water loss and increase of total fat, crude protein and energy content. The amount of VOO absorbed during frying ranged from 4.5 to 14.2% of fresh matter, showing a non‐linear negative correlation with initial fat, fish length and fish weight. Cholesterol content increased from 25 to 106 mg 100 g?1 fresh weight (fw) to 33–130 mg 100 g?1 fw after frying. VOO absorbed during frying resulted in a 20–78 times increase of squalene content and in significant alteration of fatty acid composition, the major change being the increase of monounsaturated fatty acids which became predominant in all fried samples. The intakes of fat and major fatty acid classes by consuming the pan‐fried seafood were comparable with the respective average Greek values. Frying in VOO resulted in a two to three times decrease of the atherogenic index and a slightly less decrease of the thrombogenic index. Both indices remained lower than 0.45 in all fried samples. The cholesterol‐saturated fat index and the cholesterol index increased up to twice after frying, ranging between 3.4–9.9 and 2.9–9.3, respectively. From the results obtained it is concluded that fish and shellfish pan‐fried in VOO present a healthy lipid profile in terms of the n‐6/n‐3 ratio, major fatty acid classes and total fat content. Copyright © 2004 Society of Chemical Industry  相似文献   
89.
The implementation of novel and accurate quality and safety control methods in conjunction with chemometrics in various fields of science, particularly in food science, showed that this combination stands for a very powerful tool for detecting food authenticity. The latter reflects both geographic origin and variety. Dairy products, in particular, have repeatedly worried the public authorities in terms of authentication regarding origin and in view of the many illnesses occasionally due to products of specific origin. Therefore, the development of a robust and reliable system endowed with this discriminatory power (varietal and/or geographic) is of great importance, both in terms of public health and consumer protection.  相似文献   
90.
Metamaterials are artificial materials offering unique properties which render them useful for various applications. In the present paper, we examine whether it is possible to design a split ring resonators’ (SRRs) based metamaterial substrate for enhancing the performance of planar antennas operating at THz frequencies. Initially, the radiating characteristics of a simple rectangular patch antenna over two well-known SRR substrates are studied. The yielded results are then compared to those of two novel designs of metamaterial antenna substrate with SRRs of decreasing size which are proposed to improve the antenna’s performance.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号