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   413004篇
  免费   39019篇
  国内免费   22043篇
电工技术   30398篇
技术理论   38篇
综合类   42245篇
化学工业   46543篇
金属工艺   17153篇
机械仪表   27830篇
建筑科学   51995篇
矿业工程   19744篇
能源动力   16317篇
轻工业   30538篇
水利工程   18147篇
石油天然气   21762篇
武器工业   5150篇
无线电   26907篇
一般工业技术   35053篇
冶金工业   18928篇
原子能技术   4651篇
自动化技术   60667篇
  2024年   1863篇
  2023年   5478篇
  2022年   10780篇
  2021年   13341篇
  2020年   13333篇
  2019年   10521篇
  2018年   10175篇
  2017年   12560篇
  2016年   15137篇
  2015年   16179篇
  2014年   27335篇
  2013年   25881篇
  2012年   30213篇
  2011年   33449篇
  2010年   24453篇
  2009年   24891篇
  2008年   23132篇
  2007年   27814篇
  2006年   24536篇
  2005年   21080篇
  2004年   17594篇
  2003年   15128篇
  2002年   12363篇
  2001年   10145篇
  2000年   8636篇
  1999年   7004篇
  1998年   5444篇
  1997年   4657篇
  1996年   3852篇
  1995年   3184篇
  1994年   2761篇
  1993年   2000篇
  1992年   1726篇
  1991年   1253篇
  1990年   1093篇
  1989年   957篇
  1988年   698篇
  1987年   483篇
  1986年   405篇
  1985年   413篇
  1984年   411篇
  1983年   354篇
  1982年   261篇
  1981年   177篇
  1980年   178篇
  1979年   105篇
  1978年   73篇
  1977年   71篇
  1976年   58篇
  1959年   58篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
981.
一种预测油气田产量及可采储量的新模型   总被引:3,自引:1,他引:3  
基于概率统计学中的Γ(x2)分布,提出了一种新的预测模型。该模型可用于预测油气田的产量、可采储量、最高年产量及其发生的时间。实际应用结果表明,该模型比较实用,预测的各项指标是比较可靠的。  相似文献   
982.
Industrial continuous processes are usually operated under closed-loop control, yielding process measurements that are autocorrelated, cross correlated, and collinear. A statistical process monitoring (SPM) method based on state variables is introduced to monitor such processes. The statistical model that describes the in-control variability is based on a canonical variate (CV) state space model. The CV state variables are linear combinations of the past process measurements which explain the variability of the future measurements the most, and they are regarded as the principal dynamic dimensions. A T2 statistic based on the CV state variables is utilized for developing the SPM procedure. The CV state variables are also used for monitoring sensor reliability. An experimental application to a high temperature short time (HTST) pasteurization process illustrates the proposed methodology.  相似文献   
983.
This paper addresses the recovery of structure and motion from uncalibrated images of a scene under full perspective or under affine projection. Particular emphasis is placed on the configuration of two views, while the extension to $N$ views is given in Appendix. A unified expression of the fundamental matrix is derived which is valid for any projection model without lens distortion (including full perspective and affine camera). Affine reconstruction is considered as a special projective reconstruction. The theory is elaborated in a way such that everyone having knowledge of linear algebra can understand the discussion without difficulty. A new technique for affine reconstruction is developed, which consists in first estimating the affine epipolar geometry and then performing a triangulation for each point match with respect to an implicit common affine basis.  相似文献   
984.
A basic requirement of autonomous vehicles is that of guaranteeing the safety of the vehicle by avoiding hazardous situations. This paper analyses this requirement in general terms of real-time response, throughput, and the resolution and accuracy of sensors and computations. Several nondimensional expressions emerge which characterize requirements in canonical form.The automatic generation of dense geometric models for autonomously navigating vehicles is a computationally expensive process. Using first principles, it is possible to quantify the relationship between the raw throughput required of the perception system and the maximum safely achievable speed of the vehicle. We derive several useful expressions for the complexity of terrain mapping perception under various assumptions. All of them can be reduced to polynomials in the response distance.The significant time consumed by geometric perception degrades real-time response characteristics. Using our results, several strategies of active geometric perception arise which are practical for autonomous vehicles and increasingly important at higher speeds.  相似文献   
985.
A robust method is presented for computing rotation angles of image sequences from a set of corresponding points containing outliers. Assuming known rotation axis, a least-squares (LS) solution are derived to compute the rotation angle from a clean data set of point correspondences. Since clean data is not guaranteed, we introduce a robust solution, based on the M-estimator, to deal with outliers. Then we present an enhanced robust algorithm, called the annealing M-estimator (AM-estimator), for reliable robust estimation. The AM-estimator has several attractive advantages over the traditional M-estimator: By definition, the AM-estimator involves neither scale estimator nor free parameters and hence avoids instabilities therein. Algorithmically, it uses a deterministic annealing technique to approximate the global solution regardless of the initialization. Experimental results are presented to compare the performance of the LS, M- and AM-estimators for the angle estimation. Experiments show that in the presence of outliers, the M-estimator outperforms the LS estimator and the AM-estimator outperforms the M-estimator.  相似文献   
986.
Bayesian Landmark Learning for Mobile Robot Localization   总被引:10,自引:0,他引:10  
To operate successfully in indoor environments, mobile robots must be able to localize themselves. Most current localization algorithms lack flexibility, autonomy, and often optimality, since they rely on a human to determine what aspects of the sensor data to use in localization (e.g., what landmarks to use). This paper describes a learning algorithm, called BaLL, that enables mobile robots to learn what features/landmarks are best suited for localization, and also to train artificial neural networks for extracting them from the sensor data. A rigorous Bayesian analysis of probabilistic localization is presented, which produces a rational argument for evaluating features, for selecting them optimally, and for training the networks that approximate the optimal solution. In a systematic experimental study, BaLL outperforms two other recent approaches to mobile robot localization.  相似文献   
987.
控制系统校正环节优化设计的计算机辅助分析   总被引:2,自引:0,他引:2  
结合共轭梯度法,借助于MATLAB软件,提出一种控制系统校正环节优化设计的新方法.该方法利用了MAT-LAB软件中的符号数学工具箱、控制系统工具箱和优化设计工具箱,使设计简单、快捷,提高了编程效率.  相似文献   
988.
论文介绍爆炸产生原因,综合比较自动化仪表各种防爆方法,介绍了最切实有效,最安全可靠的本质安全防爆方法,以本质安全防爆的原理为基础,设计利用隔离变压器来实现安全区和危险区隔离的一种新型的无源隔离式安全栅.  相似文献   
989.
汪海江 《陕西电力》2006,34(4):42-44
本文从热电厂的盈亏分析入手,找出了最佳的盈亏平衡点,从而给出热价函数和电价函数,在一定程度上解决了热价制定难的问题。  相似文献   
990.
采用了电缆材料绿色化的两大指标———毒性和有害元素含量的两种检测方法,即细胞毒性试验和电感耦合等离子体发射光谱仪法,认为这两种方法具有简便、精确、快速和省钱等优点,文中也提供了某电缆阻水膏和某种电缆护套料分别进行毒性试验和有害元素检测和分析。  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