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   26359篇
  免费   2395篇
  国内免费   1400篇
电工技术   1582篇
技术理论   6篇
综合类   1780篇
化学工业   4725篇
金属工艺   1577篇
机械仪表   1632篇
建筑科学   2058篇
矿业工程   814篇
能源动力   696篇
轻工业   1986篇
水利工程   490篇
石油天然气   1522篇
武器工业   163篇
无线电   3076篇
一般工业技术   3246篇
冶金工业   1347篇
原子能技术   289篇
自动化技术   3165篇
  2024年   152篇
  2023年   510篇
  2022年   839篇
  2021年   1137篇
  2020年   893篇
  2019年   739篇
  2018年   818篇
  2017年   909篇
  2016年   816篇
  2015年   1090篇
  2014年   1386篇
  2013年   1598篇
  2012年   1838篇
  2011年   2015篇
  2010年   1495篇
  2009年   1453篇
  2008年   1486篇
  2007年   1465篇
  2006年   1399篇
  2005年   1171篇
  2004年   780篇
  2003年   721篇
  2002年   764篇
  2001年   600篇
  2000年   589篇
  1999年   637篇
  1998年   506篇
  1997年   411篇
  1996年   405篇
  1995年   335篇
  1994年   317篇
  1993年   205篇
  1992年   156篇
  1991年   122篇
  1990年   93篇
  1989年   76篇
  1988年   54篇
  1987年   39篇
  1986年   31篇
  1985年   13篇
  1984年   19篇
  1983年   13篇
  1982年   18篇
  1981年   8篇
  1980年   10篇
  1979年   3篇
  1978年   5篇
  1977年   3篇
  1976年   4篇
  1959年   3篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
A Radiating Gradient Vector Flow (RGVF) Snake aiming at accurate extraction of both the nucleus and cytoplasm from a single-cell cervical smear image is proposed. After preprocessing, the areas in the image are roughly clustered into nucleus, cytoplasm and the background by a spatial K-means clustering algorithm. After initial contours are extracted, the image is segmented using RGVF. RGVF involves a new edge map computation method and a stack-based refinement, and is thus robust to contaminations and can effectively locate the obscure boundaries. The boundaries can also be correctly traced even if there are interferences near the cytoplasm and nucleus regions. Experiments performed on the Herlev dataset, which contains 917 images show the effectiveness of the proposed algorithm.  相似文献   
52.
This paper presents a novel ranking framework for content-based multimedia information retrieval (CBMIR). The framework introduces relevance features and a new ranking scheme. Each relevance feature measures the relevance of an instance with respect to a profile of the targeted multimedia database. We show that the task of CBMIR can be done more effectively using the relevance features than the original features. Furthermore, additional performance gain is achieved by incorporating our new ranking scheme which modifies instance rankings based on the weighted average of relevance feature values. Experiments on image and music databases validate the efficacy and efficiency of the proposed framework.  相似文献   
53.
Recent years have witnessed the growing popularity of sensor and sensor-network technologies, supporting important practical applications. One of the fundamental issues is how to accurately locate a user with few labeled data in a wireless sensor network, where a major difficulty arises from the need to label large quantities of user location data, which in turn requires knowledge about the locations of signal transmitters or access points. To solve this problem, we have developed a novel machine learning-based approach that combines collaborative filtering with graph-based semi-supervised learning to learn both mobile users' locations and the locations of access points. Our framework exploits both labeled and unlabeled data from mobile devices and access points. In our two-phase solution, we first build a manifold-based model from a batch of labeled and unlabeled data in an offline training phase and then use a weighted k-nearest-neighbor method to localize a mobile client in an online localization phase. We extend the two-phase colocalization to an online and incremental model that can deal with labeled and unlabeled data that come sequentially and adapt to environmental changes. Finally, we embed an action model to the framework such that additional kinds of sensor signals can be utilized to further boost the performance of mobile tracking. Compared to other state-of-the-art systems, our framework has been shown to be more accurate while requiring less calibration effort in our experiments performed on three different testbeds.  相似文献   
54.
许多大学生学习英语的动力局限于考试、升学、就业,实际上,除此以外,英语学习可以使大学生树立远大的理想,培养良好的道德,激发创造的潜能,只有这些才可以增强大学生学习英语的持久学习动力。英语里蕴藏的文化借鉴是增强英语学习动力的有效手段。  相似文献   
55.
基于模糊神经网络的感应加热电源温度控制   总被引:1,自引:0,他引:1  
周跃庆  尹中明 《电气自动化》2005,27(4):22-23,26
通过对原有感应加热电源温度控制方法的分析,提出了一种适合于非线性系统基于模糊神经网络的温度控制方法,并介绍了该系统的组成及实现方法。  相似文献   
56.
X.-Y. Lu  X.-Z. Yin 《Acta Mechanica》2005,175(1-4):197-215
Summary. A numerical simulation is performed to investigate the viscous flow over a smooth wavy wall undergoing transverse motion in the form of a streamwise travelling wave, which is similar to the backbone undulation of swimming fish. The objective of this study is to elucidate hydrodynamic features of the flow structure over the travelling wavy wall and to get physical insights to the understanding of fish-like swimming mechanisms in terms of drag reduction and optimal propulsive efficiency. The effect of phase speed, amplitude and Reynolds number on the flow structure over the wavy wall, the drag force acting on the wall, and the power consumption required for the propulsive motion of the wall is investigated. The phase speed and the amplitude, which are two important parameters in this problem, predicted based on the optimal propulsive efficiency agree well with the available data obtained for the wave-like swimming motion of live fish in nature.  相似文献   
57.
扩展到任意质量体的宇宙主胁量描述。宇宙主胁量同质量之间只差一个常量系数。宇宙主胁量创造了粒子的质量,造就了粒子的微观临界尺寸,构筑了恒定而有限的真空光速。  相似文献   
58.
讨论了98王码WB9801五笔字型输入法软件在Windows环境下使用时应注意的问题、出现异常现象的解决方法及使用技巧。  相似文献   
59.
This paper presents a new route about producing carbon black,by wich the natural gas cracking is carried out in the absence of oxygen thanks to an electric energy supply externally given by a plasma jet.The carbon black produced by this process has a narrow size distribution and a small average diameter of 38nm as well as a highly branched aggregate.The higher DBP value of 1.40ml/g shows it should be a high structure carbon black.The FTIR spectra shows that there are lots of aromatic c-c bonds and a large amount of nitrogen-coutaining functional groups on the carbon blacks surface,such as-NH,-CN as we3ll as -CH,-OH,-COOH groups.  相似文献   
60.
以传递和扭矩和工作转速为设计条件,推导并建立了空气离心式离合器的承载能力方程式及其求解方法,并在此基础上提出了确定该种离合器主要结构参数的具体设计方法和步骤。使其更便于在实际中推广和应用。  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