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   38249篇
  免费   2888篇
  国内免费   1582篇
电工技术   1895篇
技术理论   2篇
综合类   2279篇
化学工业   6463篇
金属工艺   2240篇
机械仪表   2289篇
建筑科学   2993篇
矿业工程   922篇
能源动力   905篇
轻工业   2293篇
水利工程   539篇
石油天然气   2646篇
武器工业   224篇
无线电   4692篇
一般工业技术   4828篇
冶金工业   2083篇
原子能技术   414篇
自动化技术   5012篇
  2024年   118篇
  2023年   604篇
  2022年   872篇
  2021年   1423篇
  2020年   1059篇
  2019年   887篇
  2018年   961篇
  2017年   1158篇
  2016年   1057篇
  2015年   1378篇
  2014年   1751篇
  2013年   2233篇
  2012年   2207篇
  2011年   2518篇
  2010年   2263篇
  2009年   2088篇
  2008年   2076篇
  2007年   2068篇
  2006年   2082篇
  2005年   1796篇
  2004年   1222篇
  2003年   1063篇
  2002年   1030篇
  2001年   898篇
  2000年   931篇
  1999年   1127篇
  1998年   961篇
  1997年   846篇
  1996年   841篇
  1995年   656篇
  1994年   553篇
  1993年   397篇
  1992年   355篇
  1991年   262篇
  1990年   207篇
  1989年   169篇
  1988年   135篇
  1987年   106篇
  1986年   76篇
  1985年   59篇
  1984年   59篇
  1983年   28篇
  1982年   35篇
  1981年   25篇
  1980年   16篇
  1979年   11篇
  1977年   7篇
  1976年   7篇
  1973年   5篇
  1970年   6篇
排序方式: 共有10000条查询结果,搜索用时 234 毫秒
991.
In this research we study the multi-product Economic Lot Scheduling Problem (ELSP) with manufacturing and remanufacturing opportunities. Manufacturing and remanufacturing operations are performed on the same production line. Both manufactured and remanufactured products have the same quality thus they fulfil the same demand stream. Tang and Teunter (2006) firstly studied this type of Economic Lot Scheduling Problem with Returns (ELSPR) and presented a complex algorithm for the optimal solution. More recently Teunter, Tang, and Kaparis (2009) proposed several heuristics to deal with the same problem using more computational efficient approaches. However, both studies have limited the attention to the common cycle policy with the assumption that a single (re)manufacturing lot is used for each item in each cycle. Relaxing the constraint of common cycle time and a single (re)manufacturing lot for each item in each cycle, we propose a simple, easy to implement algorithm, based on Segerstedt (1999), to solve the model using a basic period policy. Several numerical examples show the applicability of the algorithm and the cost savings.  相似文献   
992.
Making-a-stop: A new bufferless routing algorithm for on-chip network   总被引:1,自引:0,他引:1  
In the deep submicron regime, the power and area consumed by router buffers in network-on-chip (NoC) have become a primary concern. With buffers elimination, bufferless routing is emerging as a promising solution to provide power-and-area efficiency for NoC. In this paper, we present a new bufferless routing algorithm that can be coupled with any topology. The proposed routing algorithm is based on the concept of making-a-stop (MaS), aiming to deadlock and livelock freedom in wormhole-switched NoC. Performance evaluation is carried out by using a flit-level, cycle-accurate network simulator under synthetic traffic scenarios. Simulation results indicate that the proposed routing algorithm yields an improvement over the recent bufferless routing algorithm in average latency, power consumption, and area overhead by up to 10%, 9%, and 80%, respectively.  相似文献   
993.
994.
This paper made major research on the target representation problem, which plays a significant role in visual tracking, but has received little attention in most researches. In order to fulfill the requirements of tracking robustness and effectiveness in practical conditions, a dynamic appearance model is constructed. Due to particle filter's excellent characteristics, it is employed in this paper not only to estimate target's state, but also to construct the dynamic observation model integrated by multiple cues. In the proposed method, a dynamic multi-cue integration model is constructed for particle filter framework. And a systematic study is done on evaluating cue's weight. Specially, a particle filter based weight tracker is designed to update multi-cue's integrating manner online, so as to adapt the observation model to target's appearance changes. In such a way, a double-particle-filter based tracking framework is formed, and it is field tested on a variety of videos in different tracking conditions. In the experiments and comparisons, the applicable conditions of the proposed dynamic model are discussed, and its robustness and effectiveness are demonstrated.  相似文献   
995.
When the Newton-Raphson algorithm or the Fisher scoring algorithm does not work and the EM-type algorithms are not available, the quadratic lower-bound (QLB) algorithm may be a useful optimization tool. However, like all EM-type algorithms, the QLB algorithm may also suffer from slow convergence which can be viewed as the cost for having the ascent property. This paper proposes a novel ‘shrinkage parameter’ approach to accelerate the QLB algorithm while maintaining its simplicity and stability (i.e., monotonic increase in log-likelihood). The strategy is first to construct a class of quadratic surrogate functions Qr(θ|θ(t)) that induces a class of QLB algorithms indexed by a ‘shrinkage parameter’ r (rR) and then to optimize r over R under some criterion of convergence. For three commonly used criteria (i.e., the smallest eigenvalue, the trace and the determinant), we derive a uniformly optimal shrinkage parameter and find an optimal QLB algorithm. Some theoretical justifications are also presented. Next, we generalize the optimal QLB algorithm to problems with penalizing function and then investigate the associated properties of convergence. The optimal QLB algorithm is applied to fit a logistic regression model and a Cox proportional hazards model. Two real datasets are analyzed to illustrate the proposed methods.  相似文献   
996.
This paper presents an integration technology for RF passives using benzocyclobutene (BCB)/metal multilayer interconnection for system-in-package applications. This technology has been specially developed for RF subsystem packages in which a thick polymer, BCB (more than 15 μm thick), is adopted as dielectric with lossy silicon as substrate for its excellent characteristics. Both dry-etch BCB and photosensitive BCB are applied in this work, and their processes are briefly introduced and compared. An RF power divider, an MIM capacitor, different types of RF inductors as well as a coupled microstrip based band-pass filter are fabricated and measured at wafer level. The results show good electrical performances, and accordingly the passives are well applicable in RF band. Moreover, the subsystem models including monolithic chips connected with passives are presented.  相似文献   
997.
为研究一类具有时滞和HollingⅡ类功能反应捕食者-食饵模型,由于该模型的捕食者和食饵都具有密度制约,引入时滞对模型加以讨论,通过分析特征方程和构造适当的Lyapunov泛函,得到正平衡点存在及全局稳定的充分条件。研究结果表明,时滞对系统的稳定性起了重要作用,并为生物资源管理提供了策略。  相似文献   
998.
999.
为了减少节点间的通信数据量,降低无线传感器网络的通信能耗,提出一种基于GA-SVR的数据采集算法。通过构建感知数据预测模型,用节点的预测数据表示实际监测值,并能自主决策是否进行实测数据的传输。仿真实验结果表明,该感知数据预测模型预测结果准确率高,能有效地减少节点之间的数据通信量,降低网络的总能量消耗,延长网络的生命周期。  相似文献   
1000.
为了得到Schrdinger-KdV方程的行波解,运用平面动力系统理论方法,对其动力学行为进行研究,证明了该方程光滑孤立波解和光滑周期波解的存在性,并在不同的参数条件下,给出了各类解存在的充分条件,求出了所有显式精确行波解。  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