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   621篇
  免费   23篇
  国内免费   3篇
电工技术   3篇
综合类   1篇
化学工业   111篇
金属工艺   13篇
机械仪表   16篇
建筑科学   18篇
能源动力   21篇
轻工业   58篇
水利工程   3篇
无线电   68篇
一般工业技术   123篇
冶金工业   90篇
原子能技术   2篇
自动化技术   120篇
  2024年   1篇
  2023年   12篇
  2022年   16篇
  2021年   30篇
  2020年   23篇
  2019年   18篇
  2018年   26篇
  2017年   30篇
  2016年   23篇
  2015年   13篇
  2014年   21篇
  2013年   59篇
  2012年   42篇
  2011年   37篇
  2010年   26篇
  2009年   25篇
  2008年   24篇
  2007年   15篇
  2006年   21篇
  2005年   18篇
  2004年   12篇
  2003年   16篇
  2002年   8篇
  2001年   5篇
  2000年   3篇
  1999年   6篇
  1998年   14篇
  1997年   4篇
  1996年   12篇
  1995年   7篇
  1994年   7篇
  1993年   6篇
  1992年   12篇
  1991年   5篇
  1990年   7篇
  1989年   3篇
  1988年   4篇
  1987年   9篇
  1986年   4篇
  1985年   5篇
  1983年   1篇
  1982年   1篇
  1980年   2篇
  1979年   1篇
  1978年   3篇
  1977年   2篇
  1976年   6篇
  1969年   1篇
  1966年   1篇
排序方式: 共有647条查询结果,搜索用时 15 毫秒
21.
Scene change detection techniques for video database systems   总被引:1,自引:0,他引:1  
Scene change detection (SCD) is one of several fundamental problems in the design of a video database management system (VDBMS). It is the first step towards the automatic segmentation, annotation, and indexing of video data. SCD is also used in other aspects of VDBMS, e.g., hierarchical representation and efficient browsing of the video data. In this paper, we provide a taxonomy that classifies existing SCD algorithms into three categories: full-video-image-based, compressed-video-based, and model-based algorithms. The capabilities and limitations of the SCD algorithms are discussed in detail. The paper also proposes a set of criteria for measuring and comparing the performance of various SCD algorithms. We conclude by discussing some important research directions.  相似文献   
22.
A compact microwave driven plasma based multi-element focused ion beam system has been developed. In the present work, the effect of reduced beam limiter (BL) aperture on the focused ion beam parameters, such as current and spot size, and a method of controlling beam energy independently by introducing a biased collector at focal point (FP) are investigated. It is found that the location of FP does not change due to the reduction of BL aperture. The location of FP and beam size are found to be weakly dependent on the collector potential in the range from -8 kV to -18 kV.  相似文献   
23.
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.
Multipath transport protocols like Stream Control Transmission Protocol (SCTP) and Multipath TCP (MPTCP) have been introduced in the past as alternatives to traditional single path transport protocols like TCP and UDP. Various approaches to divide the flow on multiple paths have also been proposed in the literature. In this work, we show that the bandwidth estimation based resource pooling (BERP) congestion control algorithm is a practical implementation of the Min–Max optimization approach for flow division and verify this through ns-2 based simulations.  相似文献   
25.
Elucidation of the structure of naturally existing or synthesized substances is an important criterion in the study of materials to predict the application of the substance. In this study, polylactide was doped with nano-aluminium oxide and nano-cupric oxide with 1 and 3 mg of concentration variants. The interaction between the polymer matrix and the nanoparticles has been studied using Fourier transform infrared. Successful doping of the polymer has been observed. Attention has been drawn to check the intermolecular bonding in films having varying thicknesses, films prepared at higher sonication temperatures, and chemical homogeneity of the doped polymer films.  相似文献   
26.
A polymer-anchored iron(III) catalyst was synthesized and characterized. Its catalytic activity was evaluated for the oxidation of various alkenes, sulfides, aromatic alcohols and ethylbenzene with 30 % H2O2 as the oxidizing agent. The catalyst was also effective for the oxidative bromination reaction with 80–100 % selectivity of monobrominated products with H2O2/KBr at room temperature. The above reactions require a minimum amount of H2O2 and short reaction time. Most importantly, all the above reactions occur in aqueous medium. The catalyst can be facilely recovered and reused six-atimes without significant decrease in its activity and selectivity.  相似文献   
27.
The effect of change in strain path during cold rolling on the evolution of microstructure and texture is investigated. For this purpose, high purity aluminum and Al-2.5%Mg alloy are deformed (~90% reduction in thickness) by unidirectional and cross cold rolling. Irrespective of the alloy system, copper-type texture is observed in unidirectional processed materials, while strong brass ({011}〈112〉) texture is developed during cross rolling. Unidirectionally rolled aluminum showed higher HAGB fraction, but similar HAGB spacing as compared to the cross-rolled aluminum after 90% reduction in thickness. At the same time, the internal misorientation in the cross-rolled 2N-Al is higher than in the unidirectionally rolled material. In contrast, Al-2.5% Mg alloy processed differently in both ways shows similar HAGB fraction, spacing, and internal misorientation distribution. These observations indicate that microstructure evolution due to strain path change is more strongly affected by dynamic recovery as compared to texture evolution.  相似文献   
28.
Colour of light modulates the appearance of displayed artifacts in exhibition. To understand the effect of light on appearance of paintings, few studies have experimented to establish a relation between pleasantness with the correlated colour temperature (CCT) of light. However, some studies have found that CCT has no significant effect on pleasant appearance of painting. Therefore, in this article, an experiment with a qualitative (questionnaire on semantic differential scale, N = 30) approach was designed to understand the effect of CCT on appearance of paintings exhibited under LED lights. The findings from the experimental result depict that the appearance of paintings changes due to different CCTs of LEDs having the same illuminance. In addition, the result reveals that for both mediums of paintings considered in this study, in comparison to warm white LED and artificial daylight LED, cool white LED has appeared to be more pleasant having moderately warm feelings to the viewers.  相似文献   
29.
30.
This paper presents a crowding distance particle swarm optimization technique to optimize the design parameters of deep groove ball bearings. The design optimization problem is multi-objective in nature. The considered objectives are maximizing dynamic and static load bearing capacities and minimizing elasto-hydrodynamic film thickness. The technique is applied to bearings used in transmission system of a tractor for the purpose of farming. Pareto optimal solutions are obtained using the proposed technique. The results obtained from the technique are found to be superior compared with NSGA-II and catalogue values.  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