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   6874篇
  免费   512篇
  国内免费   123篇
电工技术   71篇
技术理论   6篇
综合类   321篇
化学工业   914篇
金属工艺   119篇
机械仪表   231篇
建筑科学   262篇
矿业工程   54篇
能源动力   247篇
轻工业   3633篇
水利工程   54篇
石油天然气   76篇
武器工业   57篇
无线电   126篇
一般工业技术   442篇
冶金工业   217篇
原子能技术   40篇
自动化技术   639篇
  2024年   35篇
  2023年   116篇
  2022年   165篇
  2021年   227篇
  2020年   321篇
  2019年   296篇
  2018年   355篇
  2017年   381篇
  2016年   408篇
  2015年   386篇
  2014年   513篇
  2013年   637篇
  2012年   677篇
  2011年   605篇
  2010年   359篇
  2009年   279篇
  2008年   257篇
  2007年   251篇
  2006年   212篇
  2005年   154篇
  2004年   120篇
  2003年   96篇
  2002年   115篇
  2001年   80篇
  2000年   71篇
  1999年   47篇
  1998年   45篇
  1997年   44篇
  1996年   40篇
  1995年   21篇
  1994年   33篇
  1993年   32篇
  1992年   13篇
  1991年   8篇
  1990年   10篇
  1989年   8篇
  1988年   10篇
  1987年   6篇
  1986年   5篇
  1985年   6篇
  1984年   5篇
  1983年   6篇
  1982年   8篇
  1980年   5篇
  1978年   3篇
  1977年   4篇
  1966年   3篇
  1965年   4篇
  1961年   3篇
  1955年   5篇
排序方式: 共有7509条查询结果,搜索用时 0 毫秒
31.
To maximize the number of vehicles passing by the stop-line in a cycle and improve the operation efficiency of intersection in China,the settlement of left-turn lane waiting-zone is becoming prevailing. Based on conflicting-point method,the internal mechanism of left-turn flow after stopping line was analyzed through taking postposition left-turn lane waiting-zone intersection for instance. The relationship between the first left-turn vehicle and the last vehicle of previous phase passing the conflicting point was expounded. According to the time of successive arriving of two vehicle flows at conflicting-point,the reasonable layout for waiting area of left-turn vehicles was researched when the clearance index was less than 0. The results suggest that the appropriate layout for waiting area of left-turning vehicles can improve the operation efficiency of intersections.  相似文献   
32.
针对直招士官专升本学员的特点,给出了结合学制学时进行程序设计课程总体设计的具体思路,结合模块化方法对教学内容进行整体优化的详细方案,以及以活跃理论课、强化实验课、开展讨论课、完善配套微课程和学员互助为核心的教学模式方法改革举措。为提高士官本科学员程序设计课程的教学效果,进行了教学改革的具体探索,经验对其他课程也具有一定的参考价值。  相似文献   
33.
Large scale open cut coal mining operations have significant impacts to groundwater in surrounding areas in both active and post-mining phases. The prediction of water inflows into a surface mine excavation is one of the many components involved in mine design phase. Groundwater performance also reacts to mining activities from the operational, economic and safety implications perspective. Under NSW planning legislation, as part of the comprehensive risk assessment, a groundwater impact assessment has to be conducted for a coal project to predict and mitigate the impacts in consideration of the government requirements. In this paper, the groundwater assessment modelling of mine pits was discussed in predicting of groundwater inflows and reviewing analytical and numerical approaches. A methodology of groundwater impact assessment for an open cut mine in NSW with a three-dimensional groundwater flow model Modflow Surfact demonstrated its functions in simulating the project's impacts on the groundwater regime. The key findings with mitigations are discussed and recommended in the paper to reduce impacts on groundwater and fulfil regulation requirements in NSW.  相似文献   
34.
本文在冷斜轧理论研究的基础上 ,探讨了冷斜轧复合工艺生产双金属管的可行性。文中首先建立了考虑应变、应变率、润滑条件和材料加工硬化等因素的钢管冷斜轧过程的数学模型 ,然后利用塑性成形问题的刚塑性有限元算法计算了钢管冷斜轧过程中塑性变形区的各种分布量 ,如速度场、应力、应变场等 ,其结果对选择合理的工艺参数、生产大直径双金属复合管具有重要意义。  相似文献   
35.
UML(标准建模语言)是一种定义良好、易于表达、功能强大且普遍适用的建模语言,是开发软件系统分析和设计阶段的重要工具。GRAPPLE是一个可自适应的、灵活的开发过程方法学,本文以数字化医院信息系统的系统分析和设计为例,介绍了结合UML建模的GRAPPLE的实际开发过程。  相似文献   
36.
目的 为探究微波降解EGCG方法制备EGC的效果,以EGC得率最大化为目标,探究微波降解的最佳工艺参数,并建立反映各参数间关系的二次多元方程模型。方法 本研究采用EGCG溶液为原料,运用微波加热降解EGCG制备EGC,通过梯度设置EGCG浓度、微波时长、微波强度三个工艺参数,进行单因素实验、响应面分析及最佳工艺组合验证实验,优化确定EGCG微波降解制备EGC的最佳工艺参数。结果 综合单因素实验及响应面分析,得到的最佳微波降解参数为:EGCG浓度5mg/ml、微波时长3.5min、微波强度为400W,且利用响应面法建立了EGC得率(Y)与EGCG浓度(A)、微波时长(B)、微波强度(C)的二次多元方程模型:Y=59.52+8.38*A+5.38*B+3.53*C-4.04*AB+6.92*AC-9.19*BC-9.99A2+0.0786*B2-15.36*C2,模型中,EGC得率最高可达62.08%。对最佳微波降解工艺参数进行验证实验,EGC得率为63.40%,与模型预测值接近。结论 运用微波降解EGCG制备EGC具有操作简单,可行性高的优势,且EGC得率稳定性高。  相似文献   
37.
Most of the published literature on robust design is basically concerned with a single response. However, the reality is that common industrial problems usually involve several quality characteristics, which are often correlated. Traditional approaches to multidimensional quality do not offer much information on how much better or worse a process is when finding optimal settings. Köksoy and Fan [Engineering Optimization 44 (8): 935–945] pointed out that the upside-down normal loss function provides a more reasonable risk assessment to the losses of being off-target in product engineering research. However, they only consider the single-response case. This article generalizes their idea to more than one response under possible correlations and co-movement effects of responses on the process loss. The response surface methodology has been adapted, estimating the expected multivariate upside-down normal loss function of a multidimensional system to find the optimal control factor settings of a given problem. The procedure and its merits are illustrated through an example.  相似文献   
38.
针对触发器聚类的布局问题,提出了一种基于蒙特卡洛方法的触发器聚类布局算法。该方法的核心思想为设计合理的评分函数,并通过蒙特卡洛方法模拟触发器聚类在版图上的随机游走过程,获取样本,再通过评分函数评价样本质量,逐步地在可行域中搜索最优解。实验结果表明,相较于现有的方法,该方法在总线长与时序性能两方面,分别得到平均约9%与17%的改善与提升。此外,该方法具有较强的健壮性,适用于复杂度较高或者版图利用率较高的设计,并能够快速收敛,以较小的时间代价完成优化。  相似文献   
39.
Ken Uchiyama 《AI & Society》1998,12(4):287-295
The industries of Japan have developed by learning from Western industries, especially the USA, and by implementing many of their concepts and technologies. However, Japanese industries have often implemented these concepts and technologies in a very different way from the USA. For example, while the USA uses information systems in retail industries as a tool by which data are collected and analysed to control the market, in Japan this same technology is considered rather as a learning device to interpret the market. While in the USA the market is seen as a natural phenomenon capable of being controlled, the Japanese see it as an ambiguous phenomenon that is ever changing and is not capable of being controlled. Rather it is important to feel the change in the market itself.This paper introduces human centredness to the information system, and argues against modern rationalism, i.e. human versus technology, taking the case of use of POS data from the POS system (point of sale: a system that collects data on both the customer and goods sold by scanning bar codes that are attached to the surface of the goods) by the eminent Japanese retailer, Ito-Yokado. It emphasises an interactive concept of interaction between human and technology of the postmodern paradigm.  相似文献   
40.
基于整体效果的装备体系作战效能评估方法研究   总被引:1,自引:0,他引:1  
针对武器装备体系作战效能评估进行了研究,提出了基于整体效果的装备体系作战效能评估方法,包括任务完成情况分析、整体作战效果分析、基于价值中心的等效分析、灵敏度分析及装备贡献度分析等环节。在此基础上,建立了基于整体效果的装备体系作战效能评估元模型,并设计开发了装备体系作战效能评估分析系统。实践证明,所提出的方法是可行的。  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