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   17219篇
  免费   538篇
  国内免费   248篇
电工技术   1312篇
技术理论   2篇
综合类   1416篇
化学工业   1364篇
金属工艺   495篇
机械仪表   556篇
建筑科学   4608篇
矿业工程   1178篇
能源动力   660篇
轻工业   598篇
水利工程   1187篇
石油天然气   662篇
武器工业   36篇
无线电   590篇
一般工业技术   697篇
冶金工业   1256篇
原子能技术   257篇
自动化技术   1131篇
  2025年   67篇
  2024年   172篇
  2023年   170篇
  2022年   256篇
  2021年   294篇
  2020年   361篇
  2019年   218篇
  2018年   185篇
  2017年   231篇
  2016年   344篇
  2015年   395篇
  2014年   1796篇
  2013年   1081篇
  2012年   1388篇
  2011年   1583篇
  2010年   1342篇
  2009年   1203篇
  2008年   872篇
  2007年   1043篇
  2006年   889篇
  2005年   740篇
  2004年   664篇
  2003年   592篇
  2002年   488篇
  2001年   391篇
  2000年   308篇
  1999年   212篇
  1998年   142篇
  1997年   110篇
  1996年   77篇
  1995年   63篇
  1994年   56篇
  1993年   26篇
  1992年   33篇
  1991年   25篇
  1990年   18篇
  1989年   15篇
  1988年   28篇
  1987年   15篇
  1986年   14篇
  1985年   13篇
  1984年   13篇
  1983年   5篇
  1964年   5篇
  1960年   5篇
  1959年   4篇
  1958年   5篇
  1957年   5篇
  1956年   4篇
  1954年   5篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
In recent years, the Asia-Pacific region has experienced several financial setbacks, including speculative attacks in 1998 and the SARS outbreak in 2003. Financial stresses of this nature are unanticipated, and not all of the dangers can be predicted by the examination of market information and macroeconomic indicators. The Early Warning System (EWS) that has been adopted by the International Monetary Fund may not be able to predict future financial crises for all possible scenarios, because shocks come in many different forms. To supplement the EWS, this paper proposes a data mining framework to measure the resilience of an economy. The resilience framework does not predict a crisis, but rather assesses the current state of health of an economy and its ability to withstand a financial shock should one occur. The framework is based on a feedback system consisting of two stages. The first stage assigns a resilience score to each economy based on a fuzzy logic scoring scheme that is built on the ambiguous reasoning of experts. The second stage uses the classification tree approach to estimate thresholds for each economic indicator, and examines the quality of the fuzzy score. The result from the second stage is then passed back to the first stage as feedback. The final result is obtained when the feedback system reaches its equilibrium state. The proposed resilience framework is applied to the external-sector and the public-sector economies of several countries to illustrate its applicability.  相似文献   
2.
Evaluating the design of flexible manufacturing systems is complex. Developing a measure of performance useful for evaluating alternate designs continues to be interesting. Here, total productivity of the system is proposed as an appropriate measure. Specification of parameters based upon strategic considerations for this measure are discussed. Finally, the usefulness of the measure is demonstrated through an example.  相似文献   
3.
长距离大断面顶管施工不可避免的引起土体扰动和土层损失,导致土体塌陷和地表拉裂等现象.以某长距离超大断面顶管工程为工程研究背景,对顶管施工引起土体变形的机理展开了分析,对顶进施工过程中土体产生塌陷、地表出现张拉裂缝的原因进行了阐释,探讨了地表变位对周边建筑(构筑)物的影响,以及分析了该工程中运用的进出洞、中继器、触变泥浆减阻、加强现场监测、以及其他应急措施这5种关键控制技术,得到了一些保证工程施工安全的有益的经验.  相似文献   
4.
针对西阜高速公路石家庄段建设过程中弃渣量大的实际情况,在分析弃渣场选址与治理思路的基础上,提出了工程措施、植物措施和临时拦挡措施相结合的综合防治体系,并对弃渣场水保措施进行典型设计。  相似文献   
5.
近年来,在所有的网络安全事件中,有超过70%的安全事件是发生在内网上的,并且随着网络的庞大化和复杂化,这一比例仍有增长的趋势。因此内网安全一直是网络安全建设关注的重点,但是由于内网以纯二层交换环境为主、节点数量多、分布复杂、终端用户安全应用水平参差不齐等原因,一直以来也都是安全建设的难点。  相似文献   
6.
太湖流域水灾害应急对策研究   总被引:1,自引:0,他引:1  
吴浩云  金科 《中国水利》2012,(13):40-43
太湖流域是我国经济社会高度发达的地区之一,发生水灾害时往往会造成重大经济损失。对发生各类水灾害时的应急对策展开研究总结,以减轻水灾害,避免人员伤亡,保障经济社会可持续健康稳定发展,并通过分析典型案例的实际应对过程,为今后开展类似工作提供参考。  相似文献   
7.
Operational risk is commonly analyzed in terms of the distribution of aggregate yearly losses. Risk measures can then be computed as statistics of this distribution that focus on the region of extreme losses. Assuming independence among the operational risk events and between the likelihood that they occur and their magnitude, separate models are made for the frequency and for the severity of the losses. These are then combined to estimate the distribution of aggregate losses. While the detailed form of the frequency distribution does not significantly affect the risk analysis, the choice of model for the severity often has a significant impact on operational risk measures. For heavy-tailed distributions these measures are dominated by extreme losses, whose probability cannot be reliably extrapolated from the available data. With limited empirical evidence, it is difficult to distinguish among alternative models that produce very different values of the risk measures. Furthermore, the estimates obtained can be unstable and overly sensitive to the presence or absence of single extreme events. Setting a bound on the maximum amount that can be lost in a single event reduces the dependence on the distributional assumptions and improves the robustness and stability of the risk measures, while preserving their sensitivity to changes in the risk profile. This bound should be determined by expert assessment on the basis of economic arguments and validated by the regulator, so that it can be used as a control parameter in the risk analysis.  相似文献   
8.
本文分析了广钢集团电炉炼钢厂小方坯连铸机拉矫机打滑的原因并提出了预防措施。  相似文献   
9.
介绍珠钢连铸采用Co60为放射源的结晶器液位控制系统配置、控制方式和控制算法.  相似文献   
10.
A fuzzy constraint satisfaction approach for electronic shopping assistance   总被引:1,自引:0,他引:1  
The Internet and World Wide Web offer an additional channel for consumers to find, select, and buy products. However, unlike shopping in the traditional store, consumers have no direct contact with human clerks to get the required information in the electronic store. The objective of this paper is to propose a fuzzy constraint satisfaction approach to help buyers find fully satisfactory or replacement products in electronic shopping. For the buyer who can give precise product requirements, the proposed approach can generate product-ranking lists based on the satisfaction degrees of each product to the given requirements. For the buyer who may not input accurate requirements, a similarity analysis approach is proposed to assess buyer requirements automatically during his browsing process. The proposed approach could help buyers find the preferred products on the top of the ranking list without further searching the remaining pages. The experimental results show the applicability of the proposed approach for electronic shopping assistance.  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