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   102072篇
  免费   14352篇
  国内免费   10124篇
电工技术   15737篇
技术理论   9篇
综合类   12065篇
化学工业   3834篇
金属工艺   2063篇
机械仪表   5289篇
建筑科学   4125篇
矿业工程   2528篇
能源动力   2258篇
轻工业   1446篇
水利工程   2048篇
石油天然气   1834篇
武器工业   1007篇
无线电   20682篇
一般工业技术   4429篇
冶金工业   1689篇
原子能技术   281篇
自动化技术   45224篇
  2024年   746篇
  2023年   2204篇
  2022年   4221篇
  2021年   4607篇
  2020年   4627篇
  2019年   3297篇
  2018年   2717篇
  2017年   3168篇
  2016年   3336篇
  2015年   3865篇
  2014年   6618篇
  2013年   5958篇
  2012年   7554篇
  2011年   7891篇
  2010年   6146篇
  2009年   6595篇
  2008年   6853篇
  2007年   7634篇
  2006年   6458篇
  2005年   5830篇
  2004年   4900篇
  2003年   4347篇
  2002年   3452篇
  2001年   2922篇
  2000年   2443篇
  1999年   1997篇
  1998年   1483篇
  1997年   1197篇
  1996年   984篇
  1995年   735篇
  1994年   531篇
  1993年   367篇
  1992年   238篇
  1991年   150篇
  1990年   117篇
  1989年   92篇
  1988年   57篇
  1987年   29篇
  1986年   35篇
  1985年   33篇
  1984年   20篇
  1983年   20篇
  1982年   27篇
  1981年   7篇
  1980年   3篇
  1979年   8篇
  1975年   3篇
  1963年   3篇
  1959年   4篇
  1951年   6篇
排序方式: 共有10000条查询结果,搜索用时 390 毫秒
991.
This paper presents a segment-based probabilistic approach to robustly recognize continuous sign language sentences. The recognition strategy is based on a two-layer conditional random field (CRF) model, where the lower layer processes the component channels and provides outputs to the upper layer for sign recognition. The continuously signed sentences are first segmented, and the sub-segments are labeled SIGN or ME (movement epenthesis) by a Bayesian network (BN) which fuses the outputs of independent CRF and support vector machine (SVM) classifiers. The sub-segments labeled as ME are discarded and the remaining SIGN sub-segments are merged and recognized by the two-layer CRF classifier; for this we have proposed a new algorithm based on the semi-Markov CRF decoding scheme. With eight signers, we obtained a recall rate of 95.7% and a precision of 96.6% for unseen samples from seen signers, and a recall rate of 86.6% and a precision of 89.9% for unseen signers.  相似文献   
992.
Yihu Song  Norio Nemoto 《Polymer》2005,46(17):6522-6530
The molecular orientation and deformation mechanisms of a quenched isotactic polypropylene (iPP) film deformed at temperatures between 303 K and the melting point are studied. At draw temperature TE less than 400 K where the degree of crystallinity does not change markedly, a linear relationship between molecular orientations of the crystalline and the amorphous phases is revealed and the slope is estimated about 1.82. The interpenetrating network (IPN) model, that takes into account the plastic response of the crystalline (C) network formed by a small portion of crystallites adhered through intercrystalline links and the pseudo-affine deformation of the crystallite enhanced amorphous matrix (CEAM) network, is able to account for inhomogeneous deformation behavior on the mesoscale accompanied with the localized necking in this TE range. Meanwhile, the initial Young's modulus and the true yield stress exerted by the deformation of the rigid C network exhibit the Arrhenius type of dependence on TE. The apparent shear modulus of the CEAM network as a function of TE is discussed in relation to variations in numbers and average molecular weights of the crystalline and the amorphous sequences being manifested by small consecutive endothermic and exothermic peaks in the DSC curve. The IPN model becomes invalid for deformations above TE=400 K where morphological changes are induced due to melting of crystallites as proved from the DSC measurement.  相似文献   
993.
This paper proposes a novel QoS-aware and congestion-aware Network-on-Chip architecture that not only enables quality-oriented network transmission and maintains a feasible implementation cost but also well balance traffic load inside the network to enhance overall throughput. By differentiating application traffic into different service classes, bandwidth allocation is managed accordingly to fulfill QoS requirements. Incorporating with congestion control scheme which consists of dynamic arbitration and adaptive routing path selection, high priority traffic is directed to less congested areas and is given preference to available resources. Simulation results show that average latency of high priority and overall traffic is improved dramatically for various traffic patterns. Cost evaluation results also show that the proposed router architecture requires negligible cost overhead but provides better performance for both advanced mesh NoC platforms.  相似文献   
994.
Engagement in virtual worlds has become pervasive, particularly among the young. At the same time, the number of virtual environments has increased rapidly. Due to intensifying competition, promoting sustained usage, i.e. continuance, has become a top priority for virtual world operators. Prior research has shown that network externalities play a key role in the adoption of communication technologies. However, a small amount of research has examined the role of network externalities in continued IT usage in general or with respect to the virtual world participation in particular. To fill in this gap, we examine how perceived network externalities affect the continuance of social virtual worlds. To this end, we introduce the concept of perceived aggregate network exposure (PANE). We extend the original information systems (IS) continuance model with perceived enjoyment and position PANE as a moderator. We test the model with data collected from 2134 Finnish Habbo Hotel users and employ structural equation modelling in the analysis. The results demonstrate that PANE moderates the influence of motivational factors on continued use intention and satisfaction.  相似文献   
995.
996.
本文基于作者提出的含层间分层损伤层合板的动力有限元分析模型和方法,计算了分层长度和位置对含层间分层损伤层合板结构的固有频率的影响,然后应用MATLAB的神经网络工具箱建立了人工神经网络,通过典型结构的仿真结果比较,证明了采用有限元动力分析和BP网络技术相结合的方法是一种可用于复合材料层合板的分层损伤诊断的有效方法.  相似文献   
997.
以工艺管式炉有关数据为例,将BP网络有效应用于数据的压缩存储和快速计算,为加热炉效率评定软件提供了BP网络模型。利用MATLAB软件实现了BP网络的训练及仿真分析,并讨论了应用过程中参数的选择以及训练数据的特点对网络训练产生的影响。  相似文献   
998.
介绍季戊四醇的超分子化学,包括超分子网状结构、螺环冠醚、非常规液晶、富勒烯衍生物、固相光催化反应、Janus树枝状分子等等。  相似文献   
999.
张娟  瞿金平 《中国塑料》2002,16(6):23-26
假设聚合物熔体的缠结网络形变是非仿射的,运用瞬态网络结构原理,采用在本课题第一部分^[1]中所建立的动态速率方程,并对上随体Maxwell本构方程加以修正来建立一个非仿射网络结构模型,利用这一模型来研究振动剪切作用下LDPE熔体的流变行为,研究表明,随着应变振幅和频率的增加,LDPE熔体的剪切应力也增加,同时指出了非仿射网络结构模型的精确变比仿射结构模型有较大提高,这表明在振动力场作用下,网络形变发生了非仿射形变,因此在建立振动力场作用下聚烯烃熔体本构方程时,不能假设其网络是仿射形变的。  相似文献   
1000.
塑料老化性能及使用寿命预测的新方法   总被引:2,自引:0,他引:2  
提出了利用人工神经网络方法对塑料自然老化性能时间序列进行预测的方法,并建立了计算模型,在此基础上本方法也可对塑料使用寿命进行预测。实例计算证实了这种方法具有良好的精度。  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