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   42522篇
  免费   3925篇
  国内免费   1970篇
电工技术   3267篇
技术理论   9篇
综合类   3307篇
化学工业   2707篇
金属工艺   514篇
机械仪表   1531篇
建筑科学   7099篇
矿业工程   3071篇
能源动力   1864篇
轻工业   5485篇
水利工程   3755篇
石油天然气   1856篇
武器工业   661篇
无线电   1726篇
一般工业技术   3476篇
冶金工业   1923篇
原子能技术   1166篇
自动化技术   5000篇
  2024年   250篇
  2023年   673篇
  2022年   1350篇
  2021年   1694篇
  2020年   1704篇
  2019年   1286篇
  2018年   1333篇
  2017年   1425篇
  2016年   1863篇
  2015年   1765篇
  2014年   3521篇
  2013年   3315篇
  2012年   3604篇
  2011年   3574篇
  2010年   2678篇
  2009年   2497篇
  2008年   2315篇
  2007年   2645篇
  2006年   2336篇
  2005年   1819篇
  2004年   1405篇
  2003年   1215篇
  2002年   917篇
  2001年   668篇
  2000年   510篇
  1999年   383篇
  1998年   298篇
  1997年   250篇
  1996年   193篇
  1995年   153篇
  1994年   143篇
  1993年   117篇
  1992年   70篇
  1991年   59篇
  1990年   47篇
  1989年   56篇
  1988年   56篇
  1987年   29篇
  1986年   26篇
  1985年   24篇
  1984年   25篇
  1983年   20篇
  1982年   11篇
  1981年   7篇
  1980年   12篇
  1979年   7篇
  1973年   4篇
  1965年   14篇
  1959年   10篇
  1951年   3篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
171.
Several studies have indicated that slip-resistant shoes may have a positive effect on reducing the risk of slips and falls, a leading cause of injury at work. Few studies, however, have examined how duration of shoe usage affects their slip-resistance properties. This study examined the association between the duration of slip-resistant shoes usage and the self-reported rate of slipping in limited-service restaurant workers. A total of 475 workers from 36 limited-service restaurants in the USA were recruited to participate in a 12-week prospective study of workplace slipping. Of the 475 participants, 83 reported changing to a new pair of shoes at least once during the 12-week follow-up. The results show that slip-resistant shoes worn for less than six months were moderately more effective than those worn for more than six months. Changing to a new pair of shoes among those wearing slip-resistant shoes at baseline was associated with a 55% reduction in the rate of slipping (RR = 0.45, 95% CI = 0.23–0.89). Further research is needed to develop criteria for the replacement of slip-resistant shoes.

Practitioner Summary: The duration of usage impacts the slip-resistance properties of slip-resistant shoes. Slip-resistant shoes worn for less than six months were moderately more effective in reducing slips than slip-resistant shoes worn for more than six months. Shoe use policies should not only encourage or require their use but also include guidance on replacing slip-resistant shoes at regular intervals.  相似文献   

172.
Texture analysis based on textons is extended by introducing a method for computing textons of arbitrary order. First-, second- and third-order textons are applied to classify screening mammograms as to indicate a low or high risk of breast cancer. First-order textons are found to provide better estimates of breast cancer risk than other orders on their own but the combination of first- and second-order textons outperforms first-order textons alone and other combinations of two orders. Combining all three orders of textons does not improve classification. This example indicates that including higher-order textons has the potential to improve classification performance.  相似文献   
173.
Sensor Web Enablement (SWE) technologies have been successfully applied to a great variety of outdoor scenarios but, in practical terms, little effort has been applied for indoor environments, and even less in the field of industrial applications. This article presents an intelligent SWE application for an indoor and industrial scenario, with the aim of improving and increasing the levels of human safety. The base low-level architecture is built on top of wireless sensor networks (WSN) connected to a Sensor Observation Service (SOS). Higher layers in the architecture include services that make real time decisions based on the collected data. Both simulation and experimental results are presented. The paper shows the viability of our approach in terms of performance, scalability, modularity and safety.  相似文献   
174.
ISO 26262 addresses development of safe in-vehicle functions by specifying methods potentially used in the design and development lifecycle. It does not indicate what is sufficient and leaves room for interpretation. Yet the architects of electric/electronic systems need design boundaries to make decisions during architecture evolutionary design without adding a risk of late changes. Correct selection of safety mechanisms from alternatives at early design stages is vital for time-to-market of critical systems. In this paper we present and discuss an iterative architecture design and refinement process that is centered around ISO 26262 requirements and model-based analysis of safety-related metrics. This process simplifies identification of the most sensitive parts of the architecture, selection of the best suitable safety mechanisms to reduce thereby failure rate on the system level and improve the metrics defined by the standard. To support the defined process we present the metamodels that can be integrated with existing DSL (domain-specific language) frameworks to extend them with information supporting further extraction of fault propagation behavior. We provide a framework for architecture model analysis and selection of safety mechanisms. We provide details on the model-based toolset that has been developed to support the proposed analysis and synthesis methods, and demonstrate its application to analysis of a steer-by-wire system model and selection of safety mechanisms for it.  相似文献   
175.
光气生产技术及光气化产品开发进展   总被引:3,自引:0,他引:3  
张建宇  雷粮林  汪影  涂小妹  高洪建 《农药》2004,43(6):245-248
综述了光气生产工艺技术、安全措施及主要光气下游产品种类。介绍了国内外光气生产及应用现状,涉及一氧化碳制备、氯气干燥、光气合成、废气处理和安全生产等技术。简述了光气化产品开发研究方向,提出重点开发IPDI(异佛尔酮二异氰酸酯)、NDI(1,5-萘二异氰酸酯)、氯磺酰异氰酸酯和较大分子量的氯代甲酸酯等光气化产品。  相似文献   
176.
某综合楼深基坑信息化施工   总被引:1,自引:0,他引:1  
开挖深度达 17m的深基坑施工中采用深基坑信息化施工技术进行安全监测。现场监测在确保基坑支护结构及邻近建筑的安全同时根据监测所提供的信息 ,及时组织了基坑抢险 ,保证基坑开挖工作顺利完成。  相似文献   
177.
能源行业标准《水电工程水工建筑物抗震设计规范》(NB35047-2015)已于2015年9月1日颁布实施。介绍了依据该规范开展的锦屏一级高拱坝抗震安全复核工作。主要内容包括:基于设定地震的场地相关设计反应谱研究;采用动力拱梁分载法、线弹性有限元法和非线性有限元法,进行设计和最大可信地震作用下的应力和坝肩岩体动力稳定分析;在选定的人工地震波基础上,采用以基岩峰值加速度在设计地震基础上比例放大的方式,进行大坝地基系统在超设计地震荷载下的地震超载能力分析。复核分析表明,锦屏一级高拱坝具有较高的抗震潜力;设计地震和最大可信地震作用下,坝体抗压强度安全满足现行抗震规范要求,且抗压强度安全有较大安全裕度,坝体拉应力基本未超过混凝土容许的应力范围,仅局部应力集中部位拉应力较大,能满足校核地震作用下"不溃坝"的设防要求。  相似文献   
178.
简述了孙家沟选煤厂工艺参数的选择和设计情况及投产后的运行效果,评价认为,该厂建设速度快,工艺流程合理,设备性能良好,产品质量合格、稳定。  相似文献   
179.
为强化上海市黄浦江供水系统的重要组成部分金泽水源地取水安全,又兼顾太湖流域及太浦河沿线区域防洪、供水需求,开展了太浦河太浦闸与沿线88个闸控口门的多目标联合调度研究。在分析太浦闸及两岸河道现有调度方式的基础上,拟定了两类共10个联合调度方案。采用细化后的太湖流域水量水质模型,对各调度方案进行了模拟。然后,构建了反映防洪、供水、水环境需求的多目标函数,采用蚁群优选算法对所有调度方案进行了优选。结果表明:与现状调度方案相比,太浦闸同时根据太湖水位和金泽断面水质情况加大下泄流量,同时太浦河沿线河道闸门有序控制,可显著提高金泽水源地关键水质指标达标率、抬升金泽水源地最低水位,又基本不影响流域及区域其他调度需求。  相似文献   
180.
本文阐述了高温矿床火区开采特高温炮孔的装药爆破安全技术。提出了掌握炸药安全使用温度,采取隔离、隔热包装,降低孔温及提高临界温度等安全措施。  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