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   2250篇
  免费   118篇
  国内免费   114篇
电工技术   63篇
综合类   120篇
化学工业   122篇
金属工艺   28篇
机械仪表   129篇
建筑科学   170篇
矿业工程   17篇
能源动力   77篇
轻工业   17篇
水利工程   14篇
石油天然气   45篇
武器工业   12篇
无线电   168篇
一般工业技术   155篇
冶金工业   13篇
原子能技术   16篇
自动化技术   1316篇
  2024年   3篇
  2023年   18篇
  2022年   22篇
  2021年   29篇
  2020年   18篇
  2019年   20篇
  2018年   34篇
  2017年   36篇
  2016年   60篇
  2015年   52篇
  2014年   135篇
  2013年   220篇
  2012年   127篇
  2011年   154篇
  2010年   91篇
  2009年   118篇
  2008年   119篇
  2007年   113篇
  2006年   103篇
  2005年   98篇
  2004年   54篇
  2003年   63篇
  2002年   65篇
  2001年   59篇
  2000年   59篇
  1999年   55篇
  1998年   44篇
  1997年   48篇
  1996年   59篇
  1995年   39篇
  1994年   37篇
  1993年   30篇
  1992年   25篇
  1991年   23篇
  1990年   20篇
  1989年   20篇
  1988年   16篇
  1987年   17篇
  1986年   23篇
  1985年   55篇
  1984年   25篇
  1983年   25篇
  1982年   18篇
  1981年   13篇
  1980年   7篇
  1979年   3篇
  1976年   2篇
  1975年   2篇
  1974年   2篇
  1971年   2篇
排序方式: 共有2482条查询结果,搜索用时 15 毫秒
1.
The ability of landscape architectural projects to mitigate the worst effects of climate change will depend upon designed ecological systems. These systems will be built with plants. Despite the recognition of ecology as an essential driver of landscapes, the professionals of landscape architecture too often lack the knowledge and practical skills to create robust vegetative systems. New approaches and tools are required. This article outlines principles and methods for designing biodiverse plant systems for urban sites. Planting methods that increase species richness, functional diversity, and spatial complexity are emphasized as a way of developing more resilient plantings. Selecting species with similar evolutionary adaptions to stress, disturbance, and competition—as well as creating multi-layered compositions of diverse plant morphologies—allows designers to create compatible, long-lived plant mixes. To balance the increased visual complexity of diverse plant mixes, the article explores design techniques to make plantings more appealing to the public. The strategies explored here are based on the projects, experience, and research of Phyto Studio, a Washington, D.C. based studio. The methods build on work described in the author’s book, Planting in a Post-Wild World, an exploration of how to create designed plant communities.  相似文献   
2.
The persistent overrepresentation of young drivers in road crashes is universally recognised. A multitude of factors influencing their behaviour and safety have been identified through methods including crash analyses, simulated and naturalistic driving studies, and self-report measures. Across the globe numerous, diverse, countermeasures have been implemented; the design of the vast majority of these has been informed by a driver-centric approach. An alternative approach gaining popularity in transport safety is the systems approach which considers not only the characteristics of the individual, but also the decisions and actions of other actors within the road transport system, along with the interactions amongst them. This paper argues that for substantial improvements to be made in young driver road safety, what has been learnt from driver-centric research needs to be integrated into a systems approach, thus providing a holistic appraisal of the young driver road safety problem. Only then will more effective opportunities and avenues for intervention be realised.  相似文献   
3.
While creativity is essential for developing students’ broad expertise in Science, Technology, Engineering, and Math (STEM) fields, many students struggle with various aspects of being creative. Digital technologies have the unique opportunity to support the creative process by (1) recognizing elements of students’ creativity, such as when creativity is lacking (modeling step), and (2) providing tailored scaffolding based on that information (intervention step). However, to date little work exists on either of these aspects. Here, we focus on the modeling step. Specifically, we explore the utility of various sensing devices, including an eye tracker, a skin conductance bracelet, and an EEG sensor, for modeling creativity during an educational activity, namely geometry proof generation. We found reliable differences in sensor features characterizing low vs. high creativity students. We then applied machine learning to build classifiers that achieved good accuracy in distinguishing these two student groups, providing evidence that sensor features are valuable for modeling creativity.  相似文献   
4.
沈振安 《矿冶》2007,16(4):51-53
高炉煤气清洗系统供水泵由于介质原因,泵体内部磨损、腐蚀严重,不但影响了泵的性能,而且由于磨损后增加了过流部分的摩擦,导致阻力增大,增加了能耗。本文通过采用高分子聚合材料对水泵进行修复,解决了其磨损及腐蚀,同时又能产生节能效果,对水泵的防腐有一定的借鉴作用。  相似文献   
5.
本文综述了20年来生物固体力学的研究与发展,包括肌肉骨骼系统,创伤,感觉系统,视觉系统,泌尿和生殖系统的生物力学。本文是应国家自然科学基金委员会生命科学部要求撰写的。  相似文献   
6.
阐述了保证和提高城市生命线工程系统的防(火)灾可靠度的重要意义。引用了大量火灾及故障案例说明评估城市生命线工程内消防系统的可靠度是一项复杂的系统工程。介绍了当前在不同行业中采用的对复杂系统的可靠度进行评估的一些方法。在对这些评估方法进行比较后介绍了故障树分析法的优、缺点,并指出这种方法完全可以胜任对城市生命线工程系统的防(火)灾可靠度的分析工作。  相似文献   
7.
AutoCAD平台下不同坐标系图形数据的转换   总被引:1,自引:0,他引:1  
在建设用地勘测定界及其他测绘工作中,时常遇到不同坐标系图形数据的转换,本文基于赫尔墨特相似变换参数,讨论了在AutoCAD平台下进行不同坐标系图形数据转换的方法、步骤,初步给出了不同坐标系图形数据转换的LISP语言程序.  相似文献   
8.
为了提高超宽带雷达生命信号检测准确率,提出了一种改进型YOLOV3检测算法。考虑到超宽带雷达探测的人体呼吸信号成像后宽高相差较大,采用多尺度训练时网络对宽高的敏感程度不一样,因此在设计损失函数时,对宽高损失给予不同的权重系数。为了提高网络通道以及空间特征表达能力,使得网络能够扩大对目标特征区域的感知范围,因此将通道注意力与空间注意力结构(CBAM)嵌入到YOLOV3基础网络Darknet53的每个shortcut层,得到CBAM-YOLOV3网络结构。对比改进前后的算法。实验结果表明,改进后的算法在IoU阈值为0.5时,mAP为98.09%,提升3.90%,在阈值为0.75时,mAP为76.49%,提升16.48%。  相似文献   
9.
Construction projects continue to suffer delays. Things go wrong and the project's completion date gets pushed back, with someone to be blamed for it. In practice, attempts are made to identify the causes of delays and schedules are modified to incorporate revised duration and new project time. The analysis itself is usually complex and can be aided by a computerized approach. This paper discusses different delay analysis techniques that are currently used by practitioners in the construction industry. It also discusses a proposed new delay analysis technique called the Isolated Delay Type (IDT). These techniques were tested against a case example and their strengths and weaknesses highlighted. The new technique can be used as a standalone module for delay analysis or could be incorporated within a computer system for construction delay analysis and claims preparation called Computerized Delay Claims Analysis (CDCA) that integrates different software including an expert system and management software such as scheduling and a database or spreadsheet.  相似文献   
10.
The objective of this study is to show that the core competence approach has validity when applied to construction. The focus is on the analysis of the fit between market strategies of firms in the building industry and their core capabilities. Certain strategies require specific core capabilities and key external and internal conditions supporting these capabilities. The resource-based approach focuses on the conditions in a firm, the internal capabilities, and supports a core capability that is demanded. The network literature will be related to external conditions that support a core capability of a firm active in a certain market. In a multiple case study, firms are analysed that are involved in different stages of the building process. The case studies demonstrate firms with consistent patterns of market strategies, core capabilities, and supporting internal and external conditions. The specific core capability of the firm under investigation determines the types of external and internal conditions that are critical.  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