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   26087篇
  免费   3082篇
  国内免费   1592篇
电工技术   2175篇
技术理论   2篇
综合类   2151篇
化学工业   3844篇
金属工艺   1444篇
机械仪表   1866篇
建筑科学   2185篇
矿业工程   972篇
能源动力   951篇
轻工业   1997篇
水利工程   661篇
石油天然气   1047篇
武器工业   258篇
无线电   3134篇
一般工业技术   2878篇
冶金工业   1058篇
原子能技术   264篇
自动化技术   3874篇
  2024年   129篇
  2023年   489篇
  2022年   1032篇
  2021年   1359篇
  2020年   1008篇
  2019年   842篇
  2018年   906篇
  2017年   979篇
  2016年   847篇
  2015年   1255篇
  2014年   1461篇
  2013年   1741篇
  2012年   2007篇
  2011年   1939篇
  2010年   1763篇
  2009年   1607篇
  2008年   1619篇
  2007年   1479篇
  2006年   1339篇
  2005年   1077篇
  2004年   864篇
  2003年   888篇
  2002年   1043篇
  2001年   965篇
  2000年   552篇
  1999年   388篇
  1998年   222篇
  1997年   185篇
  1996年   187篇
  1995年   117篇
  1994年   95篇
  1993年   97篇
  1992年   58篇
  1991年   47篇
  1990年   39篇
  1989年   25篇
  1988年   27篇
  1987年   15篇
  1986年   16篇
  1985年   9篇
  1984年   7篇
  1983年   6篇
  1982年   4篇
  1981年   8篇
  1980年   7篇
  1979年   6篇
  1959年   4篇
  1951年   2篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
A camera‐free 3D air‐touch system was proposed. Hovering, air swiping, and 3D gestures for further interaction with the floated 3D images on the mobile display were demonstrated. By embedding multiwavelength optical sensors into the display pixels and adding angular‐scanning illuminators with multiwavelength on the edge of the display, the flat panel can sense images reflected by a bare finger from different heights. In addition, three axis (x, y, z) information of the reflected image of the fingertip can be calculated. Finally, the proposed 3D air‐touch system was successfully demonstrated on a 4‐inch mobile 3D display.  相似文献   
93.
In recent years, hashing-based methods for large-scale similarity search have sparked considerable research interests in the data mining and machine learning communities. While unsupervised hashing-based methods have achieved promising successes for metric similarity, they cannot handle semantic similarity which is usually given in the form of labeled point pairs. To overcome this limitation, some attempts have recently been made on semi-supervised hashing which aims at learning hash functions from both metric and semantic similarity simultaneously. Existing semi-supervised hashing methods can be regarded as passive hashing since they assume that the labeled pairs are provided in advance. In this paper, we propose a novel framework, called active hashing, which can actively select the most informative labeled pairs for hash function learning. Specifically, it identifies the most informative points to label and constructs labeled pairs accordingly. Under this framework, we use data uncertainty as a measure of informativeness and develop a batch mode algorithm to speed up active selection. We empirically compare our method with a state-of-the-art passive hashing method on two benchmark data sets, showing that the proposed method can reduce labeling cost as well as overcome the limitations of passive hashing.  相似文献   
94.
装备虚拟仿真训练应用研究   总被引:1,自引:0,他引:1  
在培训过程中,为了减轻受训人员心理“畏惧感”,研制了对应的模拟训练器和虚拟仿真训练软件.受训人员通过虚拟仿真训练软件、模拟训练器逐步到实装的阶梯式培训,能够很快适应实装岗位需求,快速达到培训目的.论文基于虚拟仿真思想,在计算机虚拟仿真环境下建立了装备虚拟仿真模型,对仿真训练软件进行应用研究.同时给出了一种虚拟仿真开发的方法和步骤,可以在不同武器系统平台间移植应用.  相似文献   
95.
Light detecting and ranging(LiDAR)technology has become an efective way to generate highresolution digital terrain models(DTMs).To generate DTMs,point measurements from non-ground features,such as buildings,vegetation and vehicles,have to be identifed and removed while preserving the terrain points.This paper proposes an efcient mathematical morphology-based multi-level flter to generate DTMs from airborne LiDAR data.Preliminary non-ground points are frst identifed with the characteristics of the multiecho airborne LiDAR data.The localized mathematical morphology opening operations are then immediately applied to the remaining points.By gradually increasing the window size of the flter and using a dynamic critical gradient threshold,the non-ground points are removed,while the ground points are preserved.Eight samples were chosen from eight sites provided with the ISPRS Commission III,Working Group 3,to evaluate the accuracy of our algorithm.Both the qualitative and quantitative experiment analyses show that our morphologybased multi-level flter method achieves promising results,not only in flat urban areas but also in rural areas,especially in preserving complex terrain details,while non-ground spatial objects are removed.  相似文献   
96.
This article considers stabilization of a one‐dimensional Schrödinger equation with variable coefficient and boundary observation which suffers from an arbitrary given time delay. We design an observer and predictor to stabilize the system. The state is estimated in the time span where the observation is available, and also predicted in the time interval where the observation is not available. It is shown that the estimated state feedback stabilizes the system exponentially. A numerical simulation is presented to illustrate the effect of the stabilizing controller.  相似文献   
97.
The reliability of blades is vital to the system reliability of a hydrokinetic turbine. A time-dependent reliability analysis methodology is developed for river-based composite hydrokinetic turbine blades. Coupled with the blade element momentum theory, finite element analysis is used to establish the responses (limit-state functions) for the failure indicator of the Tsai–Hill failure criterion and blade deflections. The stochastic polynomial chaos expansion method is adopted to approximate the limit-state functions. The uncertainties considered include those in river flow velocity and composite material properties. The probabilities of failure for the two failure modes are calculated by means of time-dependent reliability analysis with joint upcrossing rates. A design example for the Missouri river is studied, and the probabilities of failure are obtained for a given period of operation time.  相似文献   
98.
系统采用主从式结构,采用T89C51AC2作为控制元件.在从站电路中,根据PT100铂电阻的温度特性,设计测温电桥,输出电压变量,并将此变量由测温点,经过集成运放TL064组成的精密放大电路放大输出,经A/D转换送至从控制器.从控制器处理转换并显示当前测控点的温度,通过RS485总线将温度值传送到主站.主站采用轮询的方...  相似文献   
99.
针对IC卡读写器的二次开发在VC 6.0环境下的实现中的关键问题,以深圳庆通公司的便携式接触式IC卡读写器为例,本文结合管理信息演示系统的设计与实现,进行详细的说明。  相似文献   
100.
在粗糙集理论中,精度是量化由粗糙集边界引起的不精确性的一种重要数字特征,但传统精度没有考虑到由关系覆盖导出的颗粒大小。本文通过引入独立邻域集的概念,给出一种新的广义粗糙集精度的度量。  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