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   240016篇
  免费   22165篇
  国内免费   11332篇
电工技术   16553篇
技术理论   32篇
综合类   24255篇
化学工业   29023篇
金属工艺   9835篇
机械仪表   13121篇
建筑科学   31629篇
矿业工程   13122篇
能源动力   8518篇
轻工业   19821篇
水利工程   10892篇
石油天然气   13014篇
武器工业   3440篇
无线电   16037篇
一般工业技术   18143篇
冶金工业   12034篇
原子能技术   1805篇
自动化技术   32239篇
  2024年   1174篇
  2023年   3390篇
  2022年   6422篇
  2021年   8295篇
  2020年   8064篇
  2019年   6172篇
  2018年   5770篇
  2017年   7281篇
  2016年   8605篇
  2015年   9296篇
  2014年   16356篇
  2013年   14595篇
  2012年   17320篇
  2011年   19147篇
  2010年   14023篇
  2009年   14256篇
  2008年   13031篇
  2007年   15829篇
  2006年   14257篇
  2005年   12394篇
  2004年   10338篇
  2003年   8935篇
  2002年   7340篇
  2001年   5966篇
  2000年   5146篇
  1999年   4023篇
  1998年   2910篇
  1997年   2563篇
  1996年   2061篇
  1995年   1732篇
  1994年   1457篇
  1993年   1062篇
  1992年   855篇
  1991年   618篇
  1990年   530篇
  1989年   495篇
  1988年   276篇
  1987年   221篇
  1986年   190篇
  1985年   204篇
  1984年   161篇
  1983年   129篇
  1982年   86篇
  1981年   96篇
  1980年   109篇
  1979年   50篇
  1978年   35篇
  1977年   30篇
  1975年   21篇
  1959年   34篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
During the winter of 1988/1989, the relationships between the prevalence of work-related health and indoor climate complaints and a number of building, management, workplace and personal characteristics have been investigated in a study in more than 60 office buildings located throughout the Netherlands. To collect the information, a questionnaire was prepared on health and indoor climate complaints and personal and workplace characteristics. A checklist was used to obtain information on building characteristics More than 7000 questionnaires were completed by the regular users of the buildings investigated. The results showed that the prevalence of symptoms was higher in air-conditioned buildings than in naturally or mechanically ventilated buildings. some other variables were also related with most work-related complaints after adjustment for selected management, personal, workplace and job characteristics. These included gender, work satisfaction in general, presence of allergies and/or respiratory symptoms, and personal control over temperature at the workplace. No differences were found in symptom prevalences between buildings with spray and steam humidification. The combination of air-conditioning and humidification did not lead to further increases in the prevalence of complaints as compared to buildings with only airconditioning or only humidification.  相似文献   
92.
本文介绍了分站式系统、无分站式系统以及复全式系统的特点,主要论述了复合式微机安全生产监测监控的结构、性能和应用。  相似文献   
93.
应用分形维进行地震数据的压缩与恢复   总被引:8,自引:1,他引:7  
  相似文献   
94.
介绍了造成铁路油槽车底油收不尽的原因,一是节约意识差;二是设备设施陈旧或维护不够;三是操作不当。提出了增强节约意识,挖掘设备潜力,采用合理的吸油方法的对策。  相似文献   
95.
The synthesis of alternative reaction paths leading to a desired chemical has received increasing attention in the recent past. A procedure to develop new reaction schemes in a systematic manner was reviewed by the authors ( [ 1 -3] ). The algorithm presented in these earlier papers implied the generation of an infinite number of reaction paths. The thermodynamic feasibility is a preliminary screening which reduces the number of chemical production schemes. Further screening is necessary, taking into account considerations which are related to economics, processing, safety and so on. Some constraints related with role specification, gross added value and demand/supply requirements are analysed in this paper. Examples illustrate the application of the screening procedure, showing that the addition of a few constraints results in a dramatic decrease of alternative reaction paths.  相似文献   
96.
主要介绍了热电厂近几年来在技术管理方面取得的主要工作经验,以及围绕生产经营开展科技创新所取得的成绩,并且针对当前形势,进一步提出了热电厂今后一个时期科技工作的指导思想、任务目标和措施。  相似文献   
97.
房地产开发企业会计核算问题探讨   总被引:1,自引:0,他引:1  
本文就房地产开发企业会计核算的现状及特点进行了分析,并提出了完善房地产开发企业会计核算规范的对策。  相似文献   
98.
Istanbul is one of the most famous historical cities in the world. However, the project alignment selected as the best of a range of alignments cannot avoid passing beneath the historical and cultural heritages of Istanbul as well as under ancient and densely inhabited areas of the city. This paper will explain some of the challenges related to the bored tunnels.

Historical buildings are vulnerable. Yet many existing residential and office buildings are old and constructed on minimal foundations. As a consequence, it is vital that any drawdown of groundwater and any ground settlements have to be minimized.

In addition, the connection between the immersed and bored tunnels will be made directly and totally underground, without the usual intermediate shafts and beneath the deep waters of the Bosphorus Strait. This operation needs the utmost control of the tunnel excavation face to ensure its stability and to minimize water ingress. Based on such considerations, tunnel excavation by tunnel boring machine (TBM) using a slurry shield and having the ability to operate under high pore pressures was recommended as the method of excavation for the main running tunnels.

The paper will explain how the design team from Avrasyaconsult – the Employer’s Representative – arrived at the final minimum, specific and functional requirements of the bored tunneling works which are to be carried out using the ‘FIDIC EPC/Turnkey Project’ conditions.  相似文献   

99.
王惠华  周仁公 《化学与粘合》1996,(4):241-242,233
本文提出采用高分子有机材料配合,生产石膏制品防水防潮剂的生产方法和工艺。该剂还可以应用到氧化镁系列板材,同时提出开发珠光或彩色防水防潮剂,能达到满足的装饰效果,值提开发推广。  相似文献   
100.
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