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   999篇
  免费   30篇
  国内免费   23篇
电工技术   63篇
综合类   62篇
化学工业   144篇
金属工艺   119篇
机械仪表   97篇
建筑科学   90篇
矿业工程   65篇
能源动力   29篇
轻工业   68篇
水利工程   12篇
石油天然气   50篇
武器工业   25篇
无线电   36篇
一般工业技术   50篇
冶金工业   71篇
原子能技术   16篇
自动化技术   55篇
  2024年   1篇
  2023年   5篇
  2022年   8篇
  2021年   12篇
  2020年   9篇
  2019年   7篇
  2018年   15篇
  2017年   6篇
  2016年   23篇
  2015年   10篇
  2014年   44篇
  2013年   38篇
  2012年   78篇
  2011年   86篇
  2010年   49篇
  2009年   57篇
  2008年   56篇
  2007年   107篇
  2006年   68篇
  2005年   70篇
  2004年   51篇
  2003年   50篇
  2002年   41篇
  2001年   28篇
  2000年   29篇
  1999年   24篇
  1998年   13篇
  1997年   12篇
  1996年   15篇
  1995年   7篇
  1994年   12篇
  1993年   3篇
  1992年   2篇
  1991年   1篇
  1990年   3篇
  1989年   2篇
  1988年   2篇
  1987年   1篇
  1986年   1篇
  1985年   3篇
  1982年   1篇
  1976年   1篇
  1962年   1篇
排序方式: 共有1052条查询结果,搜索用时 15 毫秒
51.
The Nuclear Waste Management Organization is evaluating the safety and feasibility of the permanent disposal of used nuclear fuel in a deep geological repository. Their current design concept utilises copper-coated steel used fuel containers to isolate the waste from the environment. Immediately following repository closure, a finite quantity of O2 will be trapped inside the repository and could cause some amount of oxic corrosion to the outer copper layer of the containers. On a per container basis, 13?mol of O2 will be trapped in the repository rooms at the time of closure, based on reference design dimensions. This corresponds to a maximum depth of copper corrosion of 81?μm, assuming a uniform distribution. This work also considers the sensitivity of this oxic corrosion allowance to various hypothetical design changes to the repository that may occur before or during construction.  相似文献   
52.
A study was conducted to identity factors contributing to the difficult removal of used motor oil from textile materials by detergency. Infrared spectroscopy and gel permeation chromatography of used motor oil showed that the oil was a saturated aliphatic hydrocarbon with molecular weight around 950. X-ray analysis revealed that particulates present in the used motor oil contained S, Mg, Al, Si, K, Ca, Fe, Ni, Cu, and Zn. Used motor oil was distributed throughout the cotton fibers with similar concentration of oil in the lumen, secondary wall, and surface crenulation. Higher relative concentrations of used motor oil were observed in the secondary wall of the fiber than has been reported for human sebum. No oil was found in the interior of polyester fibers although high concentrations of oil were detected in the interfiber spaces and on the fiber surfaces of polyester fibers. Dispersant additives of motor oil are though to enhance penetration into the cotton structure and wicking over the polyester fibers, making the nonpolar used motor oil very difficult to remove by detergency.  相似文献   
53.
本文研究了废轮胎颗粒输送过程中固气比的影响因素。在轮胎颗粒输送过程中,载气流量,给料速度,轮胎颗粒大小,管径等对固气比皆有不同程度的影响。并将实验数据与数值模拟结果进行比较,两者较吻合并对实验数据进行了优化。研究结果能为工程设计和应用提供可靠的依据。  相似文献   
54.
In the paper the main goals and progress of the surveillance specimen programme for the RPVs WWER-440/213 in Jaslovské Bohunice V-2 and Mochovce NPPs are presented. At Jaslovské Bohunice V-2, the standard surveillance specimen programme (SSSP) was finished and so-called ‘Extended Surveillance Specimen Programme’ (ESSP) was prepared on the base of its critical analysis. For first two units of the Mochovce NPP completely new programmes of irradiation embrittlement monitoring called ‘Modern Surveillance Specimen Programme’ is prepared. It is based on the experience with SSSP and ESSP as well as the recommendations of IAEA experts. This programme will serve for Mochovce NPP during all planned service life. The experience of ESSP application on the 3rd and 4th units in Jaslovské Bohunice V-2 NPP are presented in the paper too.  相似文献   
55.
酯硬化水玻璃砂工艺及其旧砂再生   总被引:1,自引:0,他引:1  
介绍了酯硬化水玻璃砂工艺及其旧砂的特点,对影响酯硬化水玻璃砂工艺推广应用的旧砂再生问题作了较详细的论述.  相似文献   
56.
作者在掌握了大量现场资料和文献资料的基础上,全面系统地论述了国内外汽车工业用铝材的发展现状与趋势,汽车用铝合金及主要零部件的铝化程度、汽车用铝合金的新开发,我国汽车用铝材的研发与应用状况等问题。指出汽车材料铝化是现代汽车轻量化的主要途径。对加速我国汽车工业用材的国产化和铝化提出了建议。  相似文献   
57.
The global environmental change research community requires improved and up-to-date land use/land cover (LULC) datasets at regional to global scales to support a variety of science and policy applications. Considerable strides have been made to improve large-area LULC datasets, but little emphasis has been placed on thematically detailed crop mapping, despite the considerable influence of management activities in the cropland sector on various environmental processes and the economy. Time-series MODIS 250 m Vegetation Index (VI) datasets hold considerable promise for large-area crop mapping in an agriculturally intensive region such as the U.S. Central Great Plains, given their global coverage, intermediate spatial resolution, high temporal resolution (16-day composite period), and cost-free status. However, the specific spectral-temporal information contained in these data has yet to be thoroughly explored and their applicability for large-area crop-related LULC classification is relatively unknown. The objective of this research was to investigate the general applicability of the time-series MODIS 250 m Enhanced Vegetation Index (EVI) and Normalized Difference Vegetation Index (NDVI) datasets for crop-related LULC classification in this region. A combination of graphical and statistical analyses were performed on a 12-month time-series of MODIS EVI and NDVI data from more than 2000 cropped field sites across the U.S. state of Kansas. Both MODIS VI datasets were found to have sufficient spatial, spectral, and temporal resolutions to detect unique multi-temporal signatures for each of the region's major crop types (alfalfa, corn, sorghum, soybeans, and winter wheat) and management practices (double crop, fallow, and irrigation). Each crop's multi-temporal VI signature was consistent with its general phenological characteristics and most crop classes were spectrally separable at some point during the growing season. Regional intra-class VI signature variations were found for some crops across Kansas that reflected the state's climate and planting time differences. The multi-temporal EVI and NDVI data tracked similar seasonal responses for all crops and were highly correlated across the growing season. However, differences between EVI and NDVI responses were most pronounced during the senescence phase of the growing season.  相似文献   
58.
A kinetic model of the rigid and flexible coupling system for terminally sensitive submunition is set up with Kane's method. The parachute is considered as a flexible body, the flexible displacement is expressed with modal spread method, the position of the parachute is expressed with a hybrid coordinate method, and the kinematics of the terminally sensitive submunition is analyzed. Ten generalized coordinates relative to the attitude of the terminally sensitive submunition are chosen, and the correlative generalized active forces, the generalized inertial forces, the generalized internal forces are calculated in turn. On the base of the Kane's method, the ten degrees of freedom dynamic equations for the coupled terminally sensitive submunition are finally set up. This model can be used to expediently simulate and analyze accurately the exterior ballistic trajectory of terminally sensitive submunition, and provide the overall design of the terminally sensitive submunition with some helpful references.  相似文献   
59.
介绍了一种新型双线制医用呼叫系统的实现原理。该系统采用电源载波技术,利用系统的两芯电源线,实现语音信息和呼叫信息的交换。系统主机由MCS51系列单片机实现,呼叫分机由PIC单片机实现。系统具有可靠性高、成本低、功能强大、安装方便等优点,具有较强的实用价值。  相似文献   
60.
基于Abaqus 6.11有限元分析LNG车用气瓶鞍座强度   总被引:1,自引:0,他引:1  
主要基于Abaqus 6.11有限元分析LNG车用气瓶鞍座强度。通过建模与施加载荷,分析其模拟工况条件下的稳定性,为评价气瓶鞍座在工况条件下的安全稳定性提供参考。  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