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   13229篇
  免费   1864篇
  国内免费   726篇
电工技术   2060篇
综合类   1450篇
化学工业   643篇
金属工艺   312篇
机械仪表   1017篇
建筑科学   362篇
矿业工程   311篇
能源动力   201篇
轻工业   186篇
水利工程   80篇
石油天然气   404篇
武器工业   301篇
无线电   5030篇
一般工业技术   887篇
冶金工业   572篇
原子能技术   131篇
自动化技术   1872篇
  2024年   61篇
  2023年   246篇
  2022年   387篇
  2021年   476篇
  2020年   483篇
  2019年   387篇
  2018年   379篇
  2017年   499篇
  2016年   560篇
  2015年   629篇
  2014年   896篇
  2013年   820篇
  2012年   1060篇
  2011年   1054篇
  2010年   794篇
  2009年   858篇
  2008年   789篇
  2007年   943篇
  2006年   725篇
  2005年   660篇
  2004年   502篇
  2003年   499篇
  2002年   398篇
  2001年   346篇
  2000年   265篇
  1999年   203篇
  1998年   147篇
  1997年   130篇
  1996年   123篇
  1995年   119篇
  1994年   80篇
  1993年   51篇
  1992年   57篇
  1991年   35篇
  1990年   33篇
  1989年   28篇
  1988年   16篇
  1987年   6篇
  1986年   10篇
  1985年   9篇
  1984年   11篇
  1983年   6篇
  1982年   5篇
  1980年   4篇
  1966年   3篇
  1965年   4篇
  1964年   3篇
  1963年   2篇
  1959年   4篇
  1958年   3篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Most general‐purpose analyzers for harmonic analysis on distribution lines are designed to sample the data of one or two power supply periods. In other words, these analyzers process waveforms and display the results based on the assumption that the analyzed waveforms contain no noninteger components, such as subharmonics and interharmonics. When waveforms containing noninteger components are analyzed with these general‐purpose analyzers, the results often indicate components that are not actually present. This paper proposes a technique of waveform judgment and explains its method of application. The technique allows noninteger components to be recognized in analyzed waveforms from the properties of Lissajous figures, and clarifies the types of components and the time windows necessary for appropriate analysis. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 166(2): 32– 38, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20536  相似文献   
992.
Three experiments used the "list-before-the-last" free recall paradigm (Shiffrin, 1970) to investigate retrieval for context and the manner in which context changes. This paradigm manipulates target and intervening list lengths to measure the interference from each list, providing a measure of list isolation. Correct target list recall was only affected by the target list length when participants engaged in recall between the lists, whereas there were effects of both list lengths with other activities. This suggests that the act of recalling drives context change, thus isolating the target list from interference. Correspondingly, incorrect recall of intervening list items was affected only by the length of the intervening list when recall occurred between the lists, but was otherwise affected by both list lengths. Concurrent with these changes in context similarity, there were apparent changes in context retrieval, as indicated by the overall levels of target retrieval versus intervening recall. A multinomial model of sampling and recovery was implemented to assess the adequacy of this account and to quantify context similarity and context retrieval. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
993.
杜自成 《火控雷达技术》2000,29(1):52-55,63
使用“脉冲信号流统计理论”建立了由群体电磁干扰源产生的电磁干扰脉冲流的一维概率密度函数(pdf)统计模型具有普遍性特点。分析了建立了杂乱脉冲干扰流和来自有限,无限数量干扰源干扰流的统计模型。  相似文献   
994.
基于帆板驱动机构精确建模,对帆板及其驱动带来的影响进行分析;在分析帆板驱动特性的基础上,给出了微振动测试数据及其分析结果;并以某卫星为例给出了帆板驱动控制时微振动对姿态的影响,提出了频率约束和振动主动抑制控制相结合的解决措施及验证结果。  相似文献   
995.
Gradient histogram: Thresholding in a region of interest for edge detection   总被引:1,自引:0,他引:1  
Selecting a threshold from the gradient histogram, a histogram of gradient magnitudes, of an image plays a crucial role in a gradient based edge detection system. This paper presents a methodology to determine the threshold from a gradient histogram generated using any kind of linear gradient operator on an image. We consider the image as a random process with dependent samples, model the gradient histogram using theories of random process and random input to a system, and determine a region of interest in the gradient histogram using certain properties of a probability density function. Standard histogram thresholding techniques are then used within the region of interest to get the threshold value. To obtain the edges, this threshold value is then used as the upper threshold of the hysteresis thresholding technique that follows the non-maximum suppression operation applied on the gradient magnitude image. The proposed methodology of determining a threshold in a gradient histogram is deduced through rigorous analysis and hence it helps in achieving consistently appreciable edge detection performance. Experimental results using different real-life and benchmark images are shown to demonstrate the effectiveness of the proposed technique.  相似文献   
996.
The time slotted system with rate regulation, which adapts the transmission rate to the interference for each time slot, is proposed to enhance the throughput while meeting the SINR requirement for cochannel interference limited wireless ad hoc networks. We show that the throughput of the rate regulated TDMA system is larger than that of the rate regulated TDMA/CDMA system. Furthermore, we also propose a scheduling algorithm to maximize the total throughput of the rate regulated TDMA system.  相似文献   
997.
提出了一种新的K空间权重导航技术(DKWN),该技术有利于缩短磁共振冠脉成像扫描时间同时获得好的图像质量.并将该导航技术应用到25位健康志愿者.经过实验分析,相比于常规固定窗导航技术而言,DKWN可以使导航效率提高30%(P<0.05),同时平均扫描时间由2.12 min缩短至1.64 min(P<0.05),并且图像质量相当.冠脉的直径和长度没有显著差异.  相似文献   
998.
E. Dhooge and R. J. Hartsuiker (2010) reported experiments showing that picture naming takes longer with low- than high-frequency distractor words, replicating M. Miozzo and A. Caramazza (2003). In addition, they showed that this distractor-frequency effect disappears when distractors are masked or preexposed. These findings were taken to refute models like WEAVER++ (A. Roelofs, 2003) in which words are selected by competition. However, Dhooge and Hartsuiker do not take into account that according to this model, picture-word interference taps not only into word production but also into attentional processes. Here, the authors indicate that WEAVER++ contains an attentional mechanism that accounts for the distractor-frequency effect (A. Roelofs, 2005). Moreover, the authors demonstrate that the model accounts for the influence of masking and preexposure, and does so in a simpler way than the response exclusion through self-monitoring account advanced by Dhooge and Hartsuiker. (PsycINFO Database Record (c) 2011 APA, all rights reserved)  相似文献   
999.
The real-time information of the distant ionosphere can be acquired by using the Wuhan ionospheric oblique backscattering sounding system (WIOBSS), which adopts a discontinuous wave mechanism. After the characteristics of the ionospheric echo Doppler spectra were analyzed, the signal preprocessing was developed in this paper, which aimed at improving the Doppler spectra. The results indicate that the preprocessing not only makes the system acquire a higher ability of target detection but also suppresses the radio frequency interference by 6–7 dB. __________ Translated from Journal of Wuhan University (Natural Science), 2006, 52(1): 114–118 [译自: 武汉大学学报(理学版)]  相似文献   
1000.
The authors attempted to replicate previous findings that weight suppression is a significant predictor of treatment completion and treatment outcome (M. L. Butryn, M. R. Lowe, D. L. Safer, & W. S. Agras, 2006) and weight gain over treatment (M. R. Lowe, W. Davis, D. Lucks, R. A. Annunziato, & M. L. Butryn, 2006) among women with bulimic disorders. The authors also examined 2 alternative measures of weight variability. Participants were 132 women with bulimia nervosa treated with cognitive-behavioral therapy. Participants who dropped out of treatment did not have significantly higher levels of weight suppression than did treatment completers. Among those who completed treatment, weight suppression did not significantly predict binge eating and purging at post-treatment. Weight suppression did significantly predict weight change and, in particular, weight gain (≥5 kg) over treatment. Alternative measures of weight variability did not significantly predict treatment completion or treatment outcome, but 1 measure significantly predicted weight gain over treatment. In conclusion, the authors failed to replicate the previous finding that weight suppression predicts treatment compliance and treatment outcome, but they did replicate the finding that weight suppression predicts weight gain over treatment. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  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