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   13718篇
  免费   1835篇
  国内免费   1390篇
电工技术   712篇
综合类   1628篇
化学工业   412篇
金属工艺   857篇
机械仪表   1916篇
建筑科学   573篇
矿业工程   694篇
能源动力   215篇
轻工业   256篇
水利工程   275篇
石油天然气   697篇
武器工业   303篇
无线电   1898篇
一般工业技术   1637篇
冶金工业   338篇
原子能技术   119篇
自动化技术   4413篇
  2024年   53篇
  2023年   252篇
  2022年   359篇
  2021年   421篇
  2020年   470篇
  2019年   407篇
  2018年   378篇
  2017年   474篇
  2016年   525篇
  2015年   634篇
  2014年   875篇
  2013年   803篇
  2012年   1150篇
  2011年   1069篇
  2010年   818篇
  2009年   827篇
  2008年   839篇
  2007年   1016篇
  2006年   821篇
  2005年   747篇
  2004年   629篇
  2003年   512篇
  2002年   425篇
  2001年   418篇
  2000年   358篇
  1999年   298篇
  1998年   248篇
  1997年   208篇
  1996年   164篇
  1995年   144篇
  1994年   152篇
  1993年   88篇
  1992年   68篇
  1991年   58篇
  1990年   56篇
  1989年   42篇
  1988年   24篇
  1987年   15篇
  1986年   14篇
  1985年   20篇
  1984年   13篇
  1983年   8篇
  1982年   12篇
  1981年   3篇
  1980年   3篇
  1962年   2篇
  1959年   4篇
  1957年   2篇
  1956年   2篇
  1955年   2篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
本文首次进行了Al/C(SiC)复合材料定向凝固,研究了复合材料定向凝固过程以及组织形态与凝固速率的关系,获得了纤维束间胞晶和不同间距的树枝晶,发现非润湿系统复合材料定向凝固后性能降低,文中对其机制进行了探讨.  相似文献   
52.
The primary visual sources of depth and size information are binocular cues and motion parallax. Here, the authors determine the efficacy of these cues to control prehension by presenting them in isolation from other visual cues. When only binocular cues were available, reaches showed normal scaling of the transport and grasp components with object distance and size. However, when only motion parallax was available, only the transpont component scaled reliably. No additional increase in scaling was found when both cues were available simultaneously. Therefore, although equivalent information is available from binocular and motion parallax information, the latter may be of relatively limited use for the control of the grasp. Binocular disparity appears selectively important for the control of the grasp. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
53.
深过冷熔体激发快速定向凝固   总被引:11,自引:0,他引:11  
阐述了深过冷的方法,深过冷的遗传性,深过冷度的理论极限以及深过冷熔体激发发快速定向凝固的试验方法及其凝固过程,给出了深过冷熔体(Cu-5wt%)激发快速定向凝固与铸态试验激发快速定向凝固的初步试验结果。  相似文献   
54.
崔彦立 《油气井测试》2002,11(6):44-47,50
从侧钻井层、开窗工艺、井身剖面的优选和井眼轨迹控制、固井措施优化等方面,详细总结了套管开窗定向侧钻技术在吐哈油田老井改造中应用的经验,系统地描述了该技术应用的地质条件和工程要素,提出了吐哈侧钻井层优选的量化指标和固井质量的优化措施。近两年,该技术在老井治理、开采难动用储量、提高采收率、降低开发钻井成本等方面展现出广阔的前景。  相似文献   
55.
How to Control Robots Interacting with Dynamic Environment   总被引:7,自引:0,他引:7  
The goal of this paper is to shed light on the control problem of constrained robot motion from the aspect of the dynamical nature of the environment with which the robot is in contact. Therefore, the criticism of traditional hybrid control which allows position/force feedback loops to split into independent control with respect to position and force, is not the main point we want to make. Reference to the papers written by the founders of hybrid control and their numerous followers served only to better understand the reason and motivation for suggesting a different approach to control of robots interacting with environment.The paper has a predominantly review character, based on recently published work. It also contains some new, unpublished results in the framework of the unified approach to the position/force control of robots, proposed by the present author and his co-workers. By pointing to the possibility of introducing an environment dynamics in the contact tasks of the machining type, the author emphasizes that the proposed dynamically interactive control can be applied to a completely different class of tasks, in which a contact is made between the system (constructions or structure) and very specific kinds of dynamic environments.  相似文献   
56.
In this paper we propose a new method to extract the vortices, sources, and sinks from the dense motion field preliminary estimated between two images of a fluid video. This problem is essential in meteorology for instance to identify and track depressions or convective clouds in satellite images. The knowledge of such points allows in addition a compact representation of the flow which is very useful in both experimental and theoretical fluid mechanics. The method we propose here is based on an analytic representation of the flow. This approach has the advantage of being robust, simple, fast and requires few parameters.  相似文献   
57.
钱塘江光缆管穿越长度2454.15m,穿越深度为32m,穿越中采用了多项新技术、新工艺、新方法。文章介绍了导向孔对穿技术、套管技术、水下磁场电缆铺设技术、长距离泥浆回流技术、长距离穿越钻杆组合技术在钱塘江光缆管穿越施工中的应用。  相似文献   
58.
We introduce an effective computer aided learning visual tool (CALVT) to teach graph-based applications. We present the robot motion planning problem as an example of such applications. The proposed tool can be used to simulate and/or further to implement practical systems in different areas of computer science such as graphics, computational geometry, robotics and networking. In the robot motion planning example, CALVT enables users to setup the working environment by creating obstacles and a robot of different shapes, specifying starting and goal positions, and setting other path or environment parameters from a user-friendly interface. The path planning system involves several phases. Each of these modules is complex and therefore we provide the possibility of visualizing graphically the output of each phase. Based on our experience, this tool has been an effective one in classroom teaching. It not only cuts down, significantly, on the instructor’s time and effort but also motivates senior/graduate students to pursue work in this specific area of research.  相似文献   
59.
河南油田主力开发区已进入高含水开发后期,后备资源接替严重不足成为制约油田发展的瓶颈。“九五”期间,河南油田加大了难采储量评价和动用的工作力度,按照“整体研究、系统解剖、优选目标、重点突破、滚动发展”的工作思路,对目标区进行综合地质研究,同时运用简易开发、大斜度定向井、稠油冷采等多种开采方式动用难采储量,使资源利用程度逐年提高。“九五”期间共系统开发难采储量437×104t,增加可采储量63.3×104t,建成原油生产能力6.6×104t。文中以张店、新庄油田为重点,探讨了提高难采储量动用程度的途径。  相似文献   
60.
A new technology is considered for realizing the motion of solid body in the loose material due to alternating pulse ejections of compressed gas in the regime of traveling wave near the outer surface of the body. The dimensionless parameters are determined for scale modeling. The relation between the action factors and the value of motion is established empirically.  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