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   8603篇
  免费   385篇
  国内免费   264篇
电工技术   259篇
技术理论   1篇
综合类   3900篇
化学工业   451篇
金属工艺   121篇
机械仪表   281篇
建筑科学   696篇
矿业工程   70篇
能源动力   52篇
轻工业   177篇
水利工程   144篇
石油天然气   50篇
武器工业   26篇
无线电   543篇
一般工业技术   333篇
冶金工业   952篇
原子能技术   8篇
自动化技术   1188篇
  2024年   14篇
  2023年   38篇
  2022年   93篇
  2021年   110篇
  2020年   128篇
  2019年   114篇
  2018年   87篇
  2017年   109篇
  2016年   175篇
  2015年   244篇
  2014年   657篇
  2013年   566篇
  2012年   726篇
  2011年   798篇
  2010年   662篇
  2009年   739篇
  2008年   591篇
  2007年   629篇
  2006年   535篇
  2005年   457篇
  2004年   367篇
  2003年   284篇
  2002年   232篇
  2001年   177篇
  2000年   124篇
  1999年   78篇
  1998年   43篇
  1997年   45篇
  1996年   24篇
  1995年   19篇
  1994年   19篇
  1992年   14篇
  1987年   12篇
  1985年   11篇
  1984年   12篇
  1976年   9篇
  1975年   10篇
  1966年   12篇
  1965年   15篇
  1964年   25篇
  1963年   19篇
  1962年   9篇
  1961年   15篇
  1960年   13篇
  1959年   20篇
  1958年   20篇
  1957年   12篇
  1956年   15篇
  1955年   16篇
  1954年   13篇
排序方式: 共有9252条查询结果,搜索用时 62 毫秒
1.
沈青 《中兴通讯技术》2006,12(3):51-53,60
中国电信企业经过多年的高速发展,逐渐步入成熟期,增长率下降、利润降低将是必然趋势,因此目前亟需探索新的运营模式,向综合型全业务电信运营商的方向发展。法国电信集团历史悠久,市场转型起步早.其发展经验有许多地方值得借鉴,包括法国电信集团具有特色的品牌战咯、灵活的经营模式、为企业提供全方位服务的经营手段。中国电信企业应积极开展全业务经营,加快发展企业网市场,完善合作运营模式,争取早日走向世界。  相似文献   
2.
郑春香  董甲东 《信息技术》2006,30(10):53-55
探讨分类挖掘技术在高校实际工作中的应用方式与应用领域。以高校人事管理为模型,应用数据挖掘中决策树算法,对高校人力资源数据源中的信息进行分析,发现其中有价值的数据模式,寻找其中存在的关系和规则,对高校人才规划提供比较客观的决策支持。  相似文献   
3.
In recent years, constructing a virtual backbone by nodes in a connected dominating set (CDS) has been proposed to improve the performance of ad hoc wireless networks. In general, a dominating set satisfies that every vertex in the graph is either in the set or adjacent to a vertex in the set. A CDS is a dominating set that also induces a connected sub‐graph. However, finding the minimum connected dominating set (MCDS) is a well‐known NP‐hard problem in graph theory. Approximation algorithms for MCDS have been proposed in the literature. Most of these algorithms suffer from a poor approximation ratio, and from high time complexity and message complexity. In this paper, we present a new distributed approximation algorithm that constructs a MCDS for wireless ad hoc networks based on a maximal independent set (MIS). Our algorithm, which is fully localized, has a constant approximation ratio, and O(n) time and O(n) message complexity. In this algorithm, each node only requires the knowledge of its one‐hop neighbours and there is only one shortest path connecting two dominators that are at most three hops away. We not only give theoretical performance analysis for our algorithm, but also conduct extensive simulation to compare our algorithm with other algorithms in the literature. Simulation results and theoretical analysis show that our algorithm has better efficiency and performance than others. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   
4.
一种新的变步长ICA自适应算法   总被引:3,自引:0,他引:3  
结合互信息极小的优化判据,基于估计函数期望平方准则、外点法和最速下降法的思想,本文导出了一种新的变步长独立分量分析(ICA)自适应算法。该算法克服了固定步长在分离矩阵推导过程中出现的稳态失调问题,比基于模拟退火步长的ICA算法有更快的仞始收敛速度和较高的分离精度。同时,该算法还具有较好的时变系统跟踪能力。理论分析和仿真计算结果证实了其可以有效地提高ICA的自适虚性,更准确地完成盲信号分离。  相似文献   
5.
Structural equation modeling was used to test the mediational role of social environmental selection on alcohol use in cross-sectional samples of 447 students from a rural state university and 421 students from an urban private university. Results showed that male gender, White ethnicity, and sensation seeking were uniquely associated with greater alcohol use. Mediational analyses indicated that socioenvironmental factors (i.e., Greek involvement, friends' approval of drinking/getting drunk) were positively associated with alcohol use and significantly accounted for parts of the effects of ethnicity and sensation seeking, but not gender, on alcohol use. Results suggest that White students and those high on sensation seeking may drink more heavily in college, in part because they select social environments in which alcohol use is encouraged. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
6.
The present studies demonstrated the moderation of self-construal orientation on mimicry. Recent research has indicated that an interdependent self-construal is associated with assimilation of the other to the self whereas an independent self-construal is associated with minimizing the influence of others on the self (H. R. Markus & S. Kitayama, 1991; D. Stapel & W. Koomen, 2001). Therefore, the authors hypothesized that an interdependent self-construal would be associated with more mimicry than an independent self-construal. When self-construal orientations were experimentally primed. as in Studies 1 and 2, independent self-construals produced less nonconscious mimicry than interdependent self-construals. When self-construals were examined as cultural differences with either a chronically dominant independent (Americans) or interdependent (Japanese) construal of the self, these results were replicated. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
7.
According to the knowledge partitioning framework, people sometimes master complex tasks by creating multiple independent parcels of partial knowledge. Research has shown that knowledge parcels may contain mutually contradictory information, and that each parcel may be used without regard to knowledge that is demonstrably present in other parcels. This article reports 4 experiments that investigated knowledge partitioning in categorization. When component boundaries of a complex categorization were identified by a context cue, a significant proportion of participants learned partial and independent categorization strategies that were chosen on the basis of context. For those participants, a strategy used in one context was unaffected by knowledge demonstrably present in other contexts, suggesting that knowledge partitioning in categorization can be complete. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
8.
9.
This study tested a partial version of R. W. Lent, S. D. Brown, and G. Hackett's (1994) social-cognitive career theory model. Among 204 high school girls who attended science, math, and engineering (SME) career conferences, the authors used a 4-year longitudinal design to predict the choice of an SME college major and SME self-efficacy and outcome expectations in college. In addition, among students who had declared SME majors, variables assessed in high school and college were used to predict aspirations to become leaders in SME fields. The results generally provided empirical validation of the model. Regression analyses revealed that college SME outcome expectations were associated with plans to become a leader in an SME field. Implications for research and interventions are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
10.
利用独立分量分析法去除地震噪声   总被引:2,自引:0,他引:2  
 独立分量分析(ICA)作为盲源分离(BSS)的一种新方法,是分解观测数据中独立信息的有力工具。以往的ICA算法一般假设噪声可以忽略不计,而实际的观测数据中又常常包含一些加性噪声。对于加性噪声的影响不能忽略的情况下,改进的ICA算法首先利用非零时间滞后协方差,应用两步特征值分解法(EVD)可成功地去除部分加性噪声的影响;再利用ICA算法就能更好地分离出原信号。本文通过对地震理论模型和实际资料的试验,说明改进的ICA算法能够有效地克服加性噪声对常规ICA算法的影响,能够分离出地震资料中的有效信号,从而实现利用独立分量分析压制地震资料噪声的目的。  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