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   45113篇
  免费   4772篇
  国内免费   3862篇
电工技术   3449篇
技术理论   3篇
综合类   7160篇
化学工业   2515篇
金属工艺   882篇
机械仪表   2772篇
建筑科学   3920篇
矿业工程   1141篇
能源动力   1157篇
轻工业   2782篇
水利工程   1731篇
石油天然气   957篇
武器工业   496篇
无线电   5360篇
一般工业技术   4002篇
冶金工业   1663篇
原子能技术   499篇
自动化技术   13258篇
  2024年   178篇
  2023年   568篇
  2022年   1016篇
  2021年   1132篇
  2020年   1210篇
  2019年   1087篇
  2018年   1101篇
  2017年   1332篇
  2016年   1521篇
  2015年   1579篇
  2014年   2396篇
  2013年   2703篇
  2012年   3076篇
  2011年   3426篇
  2010年   2703篇
  2009年   2899篇
  2008年   2972篇
  2007年   3432篇
  2006年   3042篇
  2005年   2665篇
  2004年   2257篇
  2003年   1886篇
  2002年   1563篇
  2001年   1314篇
  2000年   1109篇
  1999年   933篇
  1998年   742篇
  1997年   637篇
  1996年   584篇
  1995年   509篇
  1994年   442篇
  1993年   308篇
  1992年   286篇
  1991年   231篇
  1990年   220篇
  1989年   184篇
  1988年   122篇
  1987年   74篇
  1986年   46篇
  1985年   48篇
  1984年   33篇
  1983年   40篇
  1982年   31篇
  1981年   14篇
  1980年   18篇
  1979年   13篇
  1978年   10篇
  1977年   6篇
  1976年   10篇
  1973年   5篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
This paper presents an application of digital signal processing to data acquired by the radio imaging method (RIM) that was adopted to measure moisture distribution inside the human body. RIM was originally developed for the mining industry; we are applying the method to a biomedical measurement because of its simplicity, economy, and safety. When a two‐dimensional image was constructed from the measured data, the method provided insufficient resolution because the wavelength of the measurement medium, a weak electromagnetic wave in a VHF band, was longer than human tissues. We built and measured a phantom, a model simulating the human body, consisting of two water tanks representing large internal organs. A digital equalizer was applied to the measured values as a weight function, and images were reconstructed that corresponded to the original shape of the two water tanks. As a result, a two‐dimensional image containing two individual peaks corresponding to the original two small water tanks was constructed. The result suggests the method was applicable to biomedical measurement by the assistance of digital signal processing. This technique may be applicable to home‐based medical care and other situations in which safety, simplicity, and economy are important.  相似文献   
72.
The degree to which real and hypothetical rewards were discounted across delays ranging from 6 hr to 1 year was explored in a within-subjects design. An adjusting-amounts procedure was used to estimate the subjective value of real and hypothetical rewards at each delay. A hyperbolic discounting function provided a significantly better fit to individual participants' preferences than did an exponential function. No significant effect of reward type on degree of hyperbolic discounting or area under the discounting curves was detected. These findings offer some support for the validity of using hypothetical rewards to estimate discounting rates in substance-abusing and other populations, but caution is suggested because this support is gleaned from a failure to detect an effect of reward type. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
73.
黄玲 《冶金动力》2003,(6):49-51
通过高炉鼓风机扩压叶片断裂事故,从化学分析、物理检验,结合使用情况对扩压叶片断裂原因进行了详细分析,并提出了改进措施。  相似文献   
74.
基于PSOS的TM1300应用系统中的BSP研究   总被引:1,自引:0,他引:1  
通过在应用软件与板级支持包BSP之间加一层库函数的方法较好地解决了应用程序与板级支持包函数间的通信问题,减少了板级支持包函数的维护复杂度,从而为嵌入式系统板级支持包的实现提供了一个有价值的思路。  相似文献   
75.
滕红华 《包装工程》2003,24(1):51-52,55
随着设备高速化的日益发展,传统的螺杆设计方法及相应的供送特性评价体系已显落后。参照蜗型凸轮动力学性能的评价方法,建立了高速供送螺杆的动态性能评价体系,为高速化供送螺杆的设计提供了性能参照指标。  相似文献   
76.
论述了参数设计法在铝电解电容器设计开发阶段的应用。文中阐明了铝电解电容器的主要质量特性(损耗因子、电容量)及芯包外径的参数设计原理,并建立了归一化函数作为优选设计方案的判据。实例证明在铝电解电容器的设计过程中应用参数设计法以减小产品质量特性变异是有效的。  相似文献   
77.
The boundary knot method (BKM) of very recent origin is an inherently meshless, integration‐free, boundary‐type, radial basis function collocation technique for the numerical discretization of general partial differential equation systems. Unlike the method of fundamental solutions, the use of non‐singular general solution in the BKM avoids the unnecessary requirement of constructing a controversial artificial boundary outside the physical domain. The purpose of this paper is to extend the BKM to solve 2D Helmholtz and convection–diffusion problems under rather complicated irregular geometry. The method is also first applied to 3D problems. Numerical experiments validate that the BKM can produce highly accurate solutions using a relatively small number of knots. For inhomogeneous cases, some inner knots are found necessary to guarantee accuracy and stability. The stability and convergence of the BKM are numerically illustrated and the completeness issue is also discussed. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   
78.
采用注视控制器实现复杂运动的仿真   总被引:1,自引:1,他引:0  
注视控制器是3DS MAX软件的众多控件之一,它能使多个物体彼此间产生运动约束。通过使用注视控制器功能,笔者成功制作出八足爬壁式仿生机械昆虫的运动场景动画,并使该仿生机械昆虫各足的行走动作符合机械零件作平面复杂运动时所应遵守的正确运动规律。由此证明,3DS MAX软件注视控制器对正确模拟特殊机械装置的复杂运动可产生极大作用。  相似文献   
79.
The engineering and management of human safety is an important societal objective that includes extensive efforts by governments, both legislative and administrative, to enhance the health and safety of the public. Although the achievement of safety goals depend primarily on individuals and organizations responsible for safety, much support is drawn from expertise in diverse scientific and engineering disciplines. The activities range from structural safety (dams, tunnels, bridges to tall buildings) to safe operation of hazardous industrial installations (energy generation facilities, LNG terminals, petrochemical plants) to transportation systems (airline, rail, car safety) to technologies designed to minimize adverse impacts on the environment. All these activities are crucially concerned with risk: with the likelihood and the probable effects of various measures on life and health. We have developed a unified rationale and a clear basis for effective strategic management of risk across diverse sectors. Safety is an important objective in society but it is not the only one. The allocation of society's resources devoted to safety must be continually appraised in light of competing needs, because there is a limit on the resources that can be expended to extend life. The paper presents the Life Quality Index (LQI) as a tool for the assessment of risk reduction initiatives that would support the public interest and enhance safety and quality of life. The paper provides an intuitive reformulation of the LQI as equivalent to a valid utility function that is consistent with the principles of rational decision analysis. The LQI is further refined to consider the issues of discounting of life years, competing background risks, and population age and mortality distribution. The LQI is applied to quantify the societal willingness-to-pay, which is an acceptable level of public expenditure in exchange for a reduction in the risk of death that results in improved life-quality.  相似文献   
80.
褶积与逆褶积技术在核物理测量中的应用   总被引:1,自引:1,他引:0  
讨论了褶积与逆褶积技术在核物理测量,主要是波形和能谱测量中的应用。还介绍了褶积与逆褶积的数值计算方法,给出了计算公式。  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