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   758篇
  免费   17篇
  国内免费   3篇
电工技术   16篇
综合类   1篇
化学工业   63篇
金属工艺   20篇
机械仪表   13篇
建筑科学   51篇
矿业工程   62篇
能源动力   19篇
轻工业   34篇
水利工程   3篇
石油天然气   8篇
武器工业   1篇
无线电   97篇
一般工业技术   148篇
冶金工业   68篇
原子能技术   1篇
自动化技术   173篇
  2023年   3篇
  2022年   8篇
  2021年   9篇
  2020年   14篇
  2019年   7篇
  2018年   14篇
  2017年   7篇
  2016年   14篇
  2015年   15篇
  2014年   23篇
  2013年   72篇
  2012年   42篇
  2011年   39篇
  2010年   51篇
  2009年   49篇
  2008年   54篇
  2007年   33篇
  2006年   43篇
  2005年   41篇
  2004年   26篇
  2003年   26篇
  2002年   31篇
  2001年   14篇
  2000年   15篇
  1999年   13篇
  1998年   12篇
  1997年   11篇
  1996年   5篇
  1995年   7篇
  1994年   7篇
  1993年   9篇
  1992年   8篇
  1991年   5篇
  1990年   5篇
  1989年   3篇
  1988年   4篇
  1987年   4篇
  1986年   4篇
  1985年   4篇
  1984年   6篇
  1983年   5篇
  1981年   4篇
  1980年   2篇
  1979年   2篇
  1978年   2篇
  1974年   1篇
  1973年   1篇
  1971年   1篇
  1967年   1篇
  1961年   1篇
排序方式: 共有778条查询结果,搜索用时 0 毫秒
31.
The introduction of inexpensive microcomputer hardware and innovative user‐oriented software packages has had a significant impact on the traditional data processing procedures of the construction industry. Copyrighted electronic spreadsheet packages such as VisiCalc and SuperCalc are now available to practically all microcomputer users. These spreadsheet packages provide construction contractors, owners and managers with a versatile management tool that can be applied to a wide range of construction‐related problems. The overall capabilities of spreadsheet packages are examined and specific applications of interest to the construction management community are presented.  相似文献   
32.
33.
Walker HW  Bob MM 《Water research》2001,35(4):875-882
In this research, the influence of two natural organic polymers (polysaccharide and humic acid) on the stability of colloidal aggregates was examined. The primary objective of this research was to determine whether addition of organic matter to floc suspensions results in the fragmentation or stabilization of aggregates. A second objective was to determine how the size of aggregates and the composition of organic matter influence the floc breakup or stabilization process. It was found that the stability of aggregates depended on the type of organic material present as well as floc size. For example, humic acid increased the stability of aggregates more effectively than polysaccharides of larger size. It was also found that the addition of humic acid or polysaccharide generally decreased the rate of coagulation of small aggregates but had less influence on large aggregates. In no case did the addition of polysaccharide or humic acid result in the fragmentation of particle aggregates. The existence of strong interparticle forces within flocs prevented aggregate breakup upon adsorption of natural organic polymers. The results presented here provide important new information regarding the influence of NOM on the behavior of particles in aquatic systems.  相似文献   
34.
Users of web sites often do not know exactly which information they are looking for nor what the site has to offer. The purpose of their interaction is not only to fulfill but also to articulate their information needs. In these cases users need to pass through a series of pages before they can use the information that will eventually answer their questions. Current systems that support navigation predict which pages are interesting for the users on the basis of commonalities in the contents or the usage of the pages. They do not take into account the order in which the pages must be visited. In this paper we propose a method to automatically divide the pages of a web site on the basis of user logs into sets of pages that correspond to navigation stages. The method searches for an optimal number of stages and assigns each page to a stage. The stages can be used in combination with the pages’ topics to give better recommendations or to structure or adapt the site. The resulting navigation structures guide the users step by step through the site providing pages that do not only match the topic of the user’s search, but also the current stage of the navigation process.  相似文献   
35.
We argue that an evaluation of system behavior at the level of the music is required to usefully address the fundamental problems of music genre recognition (MGR), and indeed other tasks of music information retrieval, such as autotagging. A recent review of works in MGR since 1995 shows that most (82 %) measure the capacity of a system to recognize genre by its classification accuracy. After reviewing evaluation in MGR, we show that neither classification accuracy, nor recall and precision, nor confusion tables, necessarily reflect the capacity of a system to recognize genre in musical signals. Hence, such figures of merit cannot be used to reliably rank, promote or discount the genre recognition performance of MGR systems if genre recognition (rather than identification by irrelevant confounding factors) is the objective. This motivates the development of a richer experimental toolbox for evaluating any system designed to intelligently extract information from music signals.  相似文献   
36.
37.
Silicon carbide fiber-reinforced silicon carbide matrix composites (SiCf/SiC) have been produced using microwave heated chemical vapor infiltration. Preferential densification of the composite from the inside out was clearly observed. Although an average relative density of only 55% was achieved in 24 h, representative of an ∼26% increase over the initial fiber vol%, the center of the preform densified to 73% of the theoretical. The densification mechanisms were investigated using X-ray absorptiometry and scanning electron microscopy. The initial inverse temperature profile obtained, which was found to result in the efficient filling of the intratow porosity, although not the intertow porosity, flattened out after approximately 6 h as the densification front moved outward toward the edges. Although not investigated directly, the evidence suggested that this was caused by changes in both the thermal conductivity and microwave absorption characteristics as the samples densified.  相似文献   
38.
The complex procurement process entailed by the private finance initiative (PFI) means that clients need new capacities to manage their relationships with bidders and to assess project proposals if the desired level of design quality is to be achieved. To assist local authorities in their client role, a new Architectural Design Quality Evaluation Tool was developed. The aim was to improve the quality of design in residential sheltered housing, procured through the PFI. The tool was developed for and applied to a programme that will see the replacement of a local authority's entire sheltered housing stock. The tool has two functions: (1) to inform the client's assessment process and assist with the selection of the preferred bidding consortium through a series of stages in the PFI process; and (2) to improve the quality of all the submitted designs through an iterative process. Although several existing mechanisms are available for evaluating the performance attributes of buildings, few also tackle the less tangible amenity attributes, which are vital to the feeling of home. The new tool emphasizes the amenity attributes without neglecting performance.  相似文献   
39.
This paper provides a postcolonial policy analysis of the Education Sector Development Plan: 2000-2005 and Beyond in the small Caribbean island nation of St Lucia. The specific focus is upon the nature of the lifelong learning policy as incorporated in the Plan. This is shown to be a globalised policy discourse. Drawing on a number of postcolonial theorists, the paper works with a concept of the postcolonial as an aspirational politics. Bourdieu's concept of 'national capital' is also utilised in the analysis in relation to the attempt to manage some autonomy for the nation in the process of policy text production in education. The analysis demonstrates the way a postcolonial politics, manifest as strengthening national capital, worked in relation to the production of the Plan in its consultative mode of production and in its extensive cross-sector coverage. However, the analysis also shows evidence of the effects of residues of the colonial past in the hegemony of English in the Plan's recommendations, in the restriction of lifelong learning facilitation to schools and in the denial of a place for indigenous knowledges. The mode of lifelong learning supported is also dominated by a human capital framework and neglect of other capitals (social, cultural, etc.) for constituting what might be seen as a postcolonial and creole learning society. The paper also reflects upon the extent of the postcoloniality of the analysis provided.  相似文献   
40.
This work deals with the formulation of a three-dimensional crystallographic time-incremental lifetime rule for face-centered cubic (fcc) single crystals used for gas-turbine blade applications. The damage contribution rate of each slip system to the total damage is governed by the current values of the resolved shear stress and the slip rate on the corresponding slip system. The damage rule is combined with a crystallographic viscoplastic deformation model. For the nickel-base single-crystal superalloy CMSX4 at 950 °C, various strain- and stress-controlled uniaxial cyclic tests with and without hold-times can be described for different crystal orientations by one set of material parameters. For verification, simulation results for a single-crystal specimen with a notch have been compared with corresponding experimental results. The predicted lifetime is within the factor of two of the measured one.  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