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   88739篇
  免费   3903篇
  国内免费   4201篇
电工技术   4027篇
技术理论   5篇
综合类   8443篇
化学工业   12659篇
金属工艺   5625篇
机械仪表   3005篇
建筑科学   4296篇
矿业工程   1246篇
能源动力   2741篇
轻工业   5863篇
水利工程   1929篇
石油天然气   4085篇
武器工业   687篇
无线电   6701篇
一般工业技术   13985篇
冶金工业   2457篇
原子能技术   2174篇
自动化技术   16915篇
  2024年   91篇
  2023年   260篇
  2022年   376篇
  2021年   594篇
  2020年   970篇
  2019年   922篇
  2018年   1038篇
  2017年   962篇
  2016年   1477篇
  2015年   2111篇
  2014年   3887篇
  2013年   4638篇
  2012年   3933篇
  2011年   4575篇
  2010年   3846篇
  2009年   5234篇
  2008年   5242篇
  2007年   5588篇
  2006年   5129篇
  2005年   4293篇
  2004年   3707篇
  2003年   3637篇
  2002年   3705篇
  2001年   2763篇
  2000年   3151篇
  1999年   2941篇
  1998年   2483篇
  1997年   2365篇
  1996年   2548篇
  1995年   2649篇
  1994年   2404篇
  1993年   1460篇
  1992年   1486篇
  1991年   1021篇
  1990年   747篇
  1989年   664篇
  1988年   632篇
  1987年   371篇
  1986年   222篇
  1985年   369篇
  1984年   411篇
  1983年   429篇
  1982年   328篇
  1981年   404篇
  1980年   270篇
  1979年   114篇
  1978年   112篇
  1977年   69篇
  1976年   40篇
  1975年   55篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
A procedure to design reconfigurable systems capable to recover their operability in the case of fault of an arbitrary EPLD cell or connection was proposed. The most important advantages of the procedure lie in the retention of the signal propagation delays guaranteeing system operability after reconfiguration, as well as in low redundancy of the fault-tolerant system which at the limit may correspond only to one standby cell. The package methods enable one to design fault-tolerant systems based on the closed intelligent core without their upgrading. Efficiency of the procedure was estimated, and possible limitations of its application were discussed.  相似文献   
992.
993.
针对750m^3高炉铁水生产富余状况,制订了富余铁水向铸铁机铸铁的调送方案,通过创新思维、系统挖潜、优化资源配置等措施的实施,保证了750m^3高炉的正常生产,取得了良好效果。  相似文献   
994.
Imitated GE ware was one of the most famous products of Jingdezhen porcelain field in Ming dynasty (AD 1368-1644). The exterior features of its body and glaze are very marvelous. Black foot, purple mouth and crazing glaze are the main features of imitated GE ware. Until now, the key conditions of resulting these features are not clearly identified. In order to find the critical elements for firing these features, instrumental neutron activation analysis (INAA) and wavelength-dispersive X-ray fluorescence (WDXRF) were used to determine the element abundance patterns of imitated GE ware body and glaze. The experimental data was compared with that of imitated Longquan celadon and of Longquan celadon. The analytical results indicated that Fe, Ti and Na were the critical elements. The body of imitated GE ware which contains high Fe and Ti are the basic conditions of firing its black body, black foot and purple mouth. The glaze of imitated GE ware which contains high Na is the main condition of producing its crazing glaze. Na is the critical element which enlarges the difference in expansion coefficients between the glaze and body of imitated GE ware. Furthermore, Zijin soil was added into kaolin to make the body rich in Fe and Ti. And something which was rich in Na was used to produce crazing glaze in the manufacturing process of imitated GE ware.  相似文献   
995.
996.
In projection-based Virtual Reality (VR) systems, typically only one headtracked user views stereo images rendered from the correct view position. For other users, who are presented a distorted image, moving with the first user's head motion, it is difficult to correctly view and interact with 3D objects in the virtual environment. In close-range VR systems, such as the Virtual Workbench, distortion effects are especially large because objects are within close range and users are relatively far apart. On these systems, multi-user collaboration proves to be difficult. In this paper, we analyze the problem and describe a novel, easy to implement method to prevent and reduce image distortion and its negative effects on close-range interaction task performance. First, our method combines a shared camera model and view distortion compensation. It minimizes the overall distortion for each user, while important user-personal objects such as interaction cursors, rays and controls remain distortion-free. Second, our method retains co-location for interaction techniques to make interaction more consistent. We performed a user experiment on our Virtual Workbench to analyze user performance under distorted view conditions with and without the use of our method. Our findings demonstrate the negative impact of view distortion on task performance and the positive effect our method introduces. This indicates that our method can enhance the multi-user collaboration experience on close-range, projection-based VR systems.  相似文献   
997.
This paper addresses a new concept for generating bills of quantities (B.o.Qs) using AutoCAD drawings for a building project, which demonstrates the application of Industry Foundation Class (IFC), developed by International Alliance for Interoperability (IAI). The procedure considers types of materials and the structural shapes of the AutoCAD drawings to compute the cost of the structural skeleton elements using interactive automation. The main concept focuses on using layer computation of the AutoCAD drawing after converting it into a drawing inter-exchangeable file format (DXF). Once the coordinates are detected, it is easier to determine the area and volume for any structural shape, including circles and polygons. The extracting method is a new technique for structural engineers and quantity surveyors to estimate required material for beam, columns, slabs and foundations. The algorithm extracts and recognizes the layers and objects from a two dimensional DXF drawing along with the coordinates information. The results obtained using this technique are more accurate and reliable than manual procedures or any other traditional techniques. In this paper, an automated and interactive procedure for B.o.Q computation is demonstrated. The process involves a user-friendly interface, dynamic linking to the structural drawings and tracking of B.o.Q modifications at the same time.  相似文献   
998.
段锦文 《包钢科技》2007,33(B03):14-15,52
文章根据电机负荷理论对φ3m分级机螺旋轴进行受力分析,避免了复杂的推导计算和疲劳强度校核。根据现场实际,将机械技术与电气技术结合,分析其断裂原因,提出改进措施,具有较好的效果和借鉴价值。  相似文献   
999.
介绍了在VC .net的运行环境下运用拆分窗口功能实现界面切换的步骤及具体实现方法,并给出了关键的实现函数与事例.  相似文献   
1000.
Prompt gamma activation analysis (PGAA), available at The University of Texas at Austin (UT), has been employed for the direct determination of hydrogen content in a series of metal oxide materials typically used as cathodes in lithium ion battery systems. Special attention was given to the experimental setup including potential sources of error and system calibration for the detection of hydrogen. Spectral interference with hydrogen arising from cobalt was identified and corrected for. Limits of detection as a function of cobalt mass present in a given sample are also discussed. PGAA has proven to be a novel and precise technique for the determination of hydrogen in metal oxides. This type of investigation could provide valuable insight regarding the factors that limit the practical capacities of lithium ion oxide cathodes.  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