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:从到   被引次数:从到   他引次数:从到 提示：输入*表示无穷大
全文获取类型
  收费全文   10101篇
  免费   218篇
  国内免费   209篇
专业分类
电工技术   204篇
综合类   304篇
化学工业   951篇
金属工艺   1326篇
机械仪表   2231篇
建筑科学   512篇
矿业工程   228篇
能源动力   286篇
轻工业   176篇
水利工程   31篇
石油天然气   293篇
武器工业   64篇
无线电   642篇
一般工业技术   1894篇
冶金工业   309篇
原子能技术   130篇
自动化技术   947篇
出版年
  2025年   21篇
  2024年   48篇
  2023年   102篇
  2022年   191篇
  2021年   184篇
  2020年   177篇
  2019年   155篇
  2018年   190篇
  2017年   185篇
  2016年   204篇
  2015年   272篇
  2014年   419篇
  2013年   808篇
  2012年   477篇
  2011年   708篇
  2010年   532篇
  2009年   506篇
  2008年   525篇
  2007年   562篇
  2006年   578篇
  2005年   466篇
  2004年   382篇
  2003年   381篇
  2002年   343篇
  2001年   312篇
  2000年   301篇
  1999年   268篇
  1998年   254篇
  1997年   200篇
  1996年   169篇
  1995年   158篇
  1994年   110篇
  1993年   51篇
  1992年   58篇
  1991年   56篇
  1990年   42篇
  1989年   39篇
  1988年   24篇
  1987年   16篇
  1986年   13篇
  1985年   7篇
  1984年   10篇
  1983年   5篇
  1982年   2篇
  1980年   5篇
  1979年   3篇
  1978年   2篇
  1977年   2篇
  1973年   1篇
  1971年   1篇
排序方式： 共有10000条查询结果，搜索用时 15 毫秒
101.
    
Safe and Economic Operation of Power Plants – Research Results in the Field of Materials, Design and Maintenance Components of power plants which undergo high temperatures are subjected to complex loading situations. The requirements on the used materials result from the special operation conditions of the plants and have to be adjusted to the steadily growing requirements on higher efficiency of the complete power plant as well as to those of safe and economic operation. The expenses for control and downtimes are directly connected with economic efficiency and availability. However, in case of new procedures or components it is not possible to revert to the existing know‐how. Different failure mechanisms than known before can occur. The same goes for the load situation. Therefore the knowledge base has to be extended to in‐advance or even parallely running scientific examinations that life assessment and maintenance strategies can be applied which guarantee the operational reliability and the efficiency of the plant. The main emphasis of these F&E works has to be put on condition monitoring based on actual operational data, the standard materials’ and component’s behaviour (deformation, damage and failure behaviour) in connection with design of components and the related material laws. In the framework of applied AVIF projects, following problems are handled:. – qualification of materials by determinating parameters related to practise. – optimal design of components by making available material laws and numerical tools. – economic manufacturing of components by qualifying processing methods such as welding. – The results can be transferred to concepts for safe and economic operation of power plants, especially for newly introduced materials for which there is no operational experience available.  相似文献   
102.
    
  相似文献   
103.
    
  相似文献   
104.
    
  相似文献   
105.
    
A dislocation-density based multiple-slip crystalline formulation and computational schemes have been developed and used for a detailed understanding and accurate prediction of interrelated physical mechanisms that occur on different length scales in fcc polycrystalline aggregates separated by grain boundary interfacial regions of random orientations and distributions. This constitutive framework accounts for the generation, trapping, interaction, and annihilation of mobile and immobile dislocation densities that are generally associated with finite-strain deformation and failure modes in fcc aggregates. Specialized interfacial regions have been introduced to account for dislocation-density and slip transmission, intersection, and blockage at GBs. It is shown that this blockage may result in the formation of pile-ups.  相似文献   
106.
ＩｍｐｒｏｖｉｎｇＷｅａｒＲｅｓｉｓｔａｎｃｅｏｆｔｈｅＮｉｂａｓｅＴｈｅｒｍａｌＳｐｒａｙＷｅｌｄｉｎｇＣｏａｔｉｎｇＵｓｉｎｇＲａｒｅＥａｒｔｈｓＺｈａｉＧｕａｎｇｊｉｅ（翟光杰）（ＩｎｓｔｉｔｕｔｅｏｆＰｈｙｓｉｃｓ,ＡｃａｄｅｍｉｃａＳｉ...  相似文献   
107.
岳琦  王登来 《有色设备》2002,(3):37-38,41
介绍了铁谱技术在设备工监测中的应用及主要监测原理,针对应用实践中存在的问题,对多种监测技术相结合的综合诊断方法进行了探讨。  相似文献   
108.
研究了不同短切纤维（改性聚丙烯纤维MPPF、仿钢纤维ISF、玄武岩纤维BF）及掺量对珊瑚混凝土力学性能的影响,并对其破坏形态进行了分析。结果表明,纤维珊瑚混凝土早期抗压强度增长速率快而后期强度增长速率缓慢;当珊瑚混凝土中分别掺入1 kg/m3、2 kg/m3和3 kg/m3的MPPF与ISF时,珊瑚混凝土的抗压强度、劈裂抗拉强度与抗折强度较空白组均有所增加;相比于ISF,MPPF对珊瑚混凝土力学性能的改善效果更为显著,且最佳MPPF掺量为2 kg/m3;当珊瑚混凝土中掺入BF时,珊瑚混凝土的力学性能有所降低;掺加纤维可以改善混凝土的脆性,使其破坏时表现出良好的延性。  相似文献   
109.
  总被引：8，自引：0，他引：8  
A composite grid-stiffened structure concept was selected for the payload fairing of the Minotaur launch vehicle. Compared to sandwich structures, this concept has an advantage of smaller manufacturing costs and lighter weight. To reduce weight the skin pockets are allowed to buckle visibly up to about 0.5 cm peak displacement.

Various failure modes were examined for the composite grid-stiffened structure. The controlling criterion for this design was a joint failure in tension between the ribs and skin of the structure. The identification of this failure mechanism and the assessment of bounding strains required to control it required extensive test and analysis effort. Increasing skin thickness to control skin buckling resulted in reduced strains between the skin and ribs.

Following the identification of the relevant failure criteria, a final design for the fairing was generated. The resulting 6 m tall fairing was constructed of a tow-placed carbon fiber composite grid structure that was over-wrapped to create a laminated skin. Upon completion of curing and machining, the fairing was cut in half to create the classic “clam-shell” fairing. Static qualification testing demonstrated the structural integrity of the fairing, thereby proving the design and manufacturing process. Loads were applied incrementally in a static loading scenario. The applied load envelope exceeded worst-case dynamic flight conditions with an added safety factor of 25%. At peak load the fairing maintained structural integrity while remaining within the required displacement envelope for payload safety.

Data were collected during the test from a variety of sensors including traditional displacement transducers and strain gages. In addition, full field displacement was monitored at critically loaded fairing sections by means of digital photogrammetry. This paper summarizes the test results, presents the overall performance of the fairing under the test loads, correlates test response and analysis, and identifies lessons learned.

Work continues at the Air Force Research Laboratory (AFRL) and Boeing to identify means of further controlling tensile failure of the un-reinforced polymer bonded joint between the ribs and skin. Stiffening of skin adjacent to the joints and introduction of lightweight foam jackets at the interior of the fairing both show promise of delaying joint failure to higher loads.  相似文献   

110.
    
Qualification frequently is a time‐critical activity at the end of a development project. As time‐to‐market is a competitive issue, the most efficient qualification efforts are of interest. A concept is outlined, which proactively integrates qualification into the development process and provides a systematic procedure as a support tool to development and gives early focus on required activities. It converts requirements for a product into measures of development and qualification in combination with a risk and opportunity assessment step and accompanies the development process as a guiding and recording tool for advanced quality planning and confirmation. The collected data enlarge the knowledge database for DFR/BIR (designing for reliability/building‐in reliability) to be used for future projects. The procedure challenges and promotes teamwork of all the disciplines involved. Based on the physics‐of‐failure concept the reliability qualification methodology is re‐arranged with regard to the relationships between design, technology, manufacturing and the different product life phases at use conditions. It makes use of the physics‐of‐failure concept by considering the potential individual failure mechanisms and relates most of the reliability aspects to the technology rather than to the individual product design. Evaluation of complex products using common reliability models and the definition of sample sizes with respect to systematic inherent product properties and fractions of defects are discussed. Copyright © 2002 John Wiley & Sons, Ltd.  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