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   14664篇
  免费   1591篇
  国内免费   1036篇
电工技术   1505篇
技术理论   2篇
综合类   1543篇
化学工业   776篇
金属工艺   220篇
机械仪表   800篇
建筑科学   1511篇
矿业工程   678篇
能源动力   472篇
轻工业   486篇
水利工程   1458篇
石油天然气   529篇
武器工业   126篇
无线电   1750篇
一般工业技术   1086篇
冶金工业   753篇
原子能技术   398篇
自动化技术   3198篇
  2024年   52篇
  2023年   139篇
  2022年   323篇
  2021年   375篇
  2020年   451篇
  2019年   371篇
  2018年   346篇
  2017年   480篇
  2016年   582篇
  2015年   577篇
  2014年   982篇
  2013年   971篇
  2012年   1172篇
  2011年   1208篇
  2010年   884篇
  2009年   927篇
  2008年   898篇
  2007年   998篇
  2006年   963篇
  2005年   799篇
  2004年   633篇
  2003年   604篇
  2002年   489篇
  2001年   394篇
  2000年   327篇
  1999年   270篇
  1998年   166篇
  1997年   131篇
  1996年   113篇
  1995年   106篇
  1994年   110篇
  1993年   69篇
  1992年   68篇
  1991年   48篇
  1990年   23篇
  1989年   34篇
  1988年   25篇
  1987年   13篇
  1986年   16篇
  1985年   14篇
  1984年   13篇
  1983年   7篇
  1982年   6篇
  1980年   7篇
  1979年   8篇
  1966年   9篇
  1964年   20篇
  1962年   8篇
  1958年   6篇
  1955年   6篇
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
11.
建立了高放废液中~(147)Pm的测定方法。用HDEHP萃取稀土,再用HDEHP萃淋树脂柱分离AM和稀土。然后用高效液相色谱法将~(147)Pm从Eu、Ce等其它稀土中分离出来,用液体闪烁法测量~(147)Pm的放射性活度。  相似文献   
12.
This research focused on the syllable as a processing unit in handwriting. Participants wrote, in uppercase letters, words that had been visually presented. The interletter intervals provide information on the timing of motor production. In Experiment 1, French participants wrote words that shared the initial letters but had different syllable boundaries. In Experiment 2, French- and Spanish-speaking participants wrote cognates and pseudowords with a letter sequence that was always intrasyllabic in French and intersyllabic in Spanish. In Experiment 3, French-Spanish bilinguals wrote the cognates and pseudowords with the same type of sequences. In the 3 experiments, the critical interletter intervals were longer between syllables than within syllables, indicating that word syllable structure constrains motor production both in French and Spanish. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
13.
李经涛 《宽厚板》2003,9(3):18-23
系统介绍了舞钢开发的针状铁素体型X70宽厚板的设计思路、工艺特点和实物水平;采用电炉 炉外精炼 连铸 TMCP工艺生产的X70宽厚板满足西气东输专用技术条件的要求,并批量应用在西气东输主干线工程中。  相似文献   
14.
Theorists have predicted that repetition blindness (RB) should be absent for nonwords because they do not activate preexisting mental types. The authors hypothesized that RB would be observed for nonwords because RB can occur at a sublexical level. Four experiments showed that RB is observed for word-nonword pairs (noon noof), orthographically similar nonwords (glome glame), and identical repetitions (plass plass). More RB was found for words than for nonwords. Prior researchers may have failed to find RB for nonwords because display conditions that allow 2 words to be reliably encoded are insufficient for nonwords, or because observers coped with low ability to encode nonwords by using guessing strategies that do not require creating a mental type or tokenizing it. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
15.
Legendre orthogonal moments have been widely used in the field of image analysis. Because their computation by a direct method is very time expensive, recent efforts have been devoted to the reduction of computational complexity. Nevertheless, the existing algorithms are mainly focused on binary images. We propose here a new fast method for computing the Legendre moments, which is not only suitable for binary images but also for grey level images. We first establish a recurrence formula of one-dimensional (1D) Legendre moments by using the recursive property of Legendre polynomials. As a result, the 1D Legendre moments of order p, Lp=Lp(0), can be expressed as a linear combination of Lp-1(1) and Lp-2(0). Based on this relationship, the 1D Legendre moments Lp(0) can thus be obtained from the arrays of L1(a) and L0(a), where a is an integer number less than p. To further decrease the computation complexity, an algorithm, in which no multiplication is required, is used to compute these quantities. The method is then extended to the calculation of the two-dimensional Legendre moments Lpq. We show that the proposed method is more efficient than the direct method.  相似文献   
16.
本文用凸集理论分析了平均声压级近似计算的误差,导出了最大误差计算公式,指出了测量数据在何种状态下误差达到最大值。  相似文献   
17.
A picture-word version of the Stroop task was used to test the automatic activation of psychological distance by words carrying various senses of psychological distance: temporal (tomorrow, in a year), social (friend, enemy), and hypotheticality (sure, maybe). The pictures implied depth, with the words appearing relatively close to or distant from the observer. The participants classified the spatial distance of words faster when the word's implicit psychological distance matched its spatial distance (e.g., a geographically close word was classified faster when it was "friend" than when it was "enemy"). The findings are consistent with the idea that psychological distance is accessed automatically, even when it is not directly related to people's current goals, and suggest that psychological distance is an important dimension of meaning, common to spatial distance, temporal distance, social distance, and hypotheticality. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
18.
Precise timing and asynchronous I/O are appealing features for many applications. Unix kernels provide such features on a per‐process basis, using signals to communicate asynchronous events to applications. Per‐process signals and timers are grossly inadequate for complex multithreaded applications that require per‐thread signals and timers that operate at finer granularity. To respond to this need, we present a scheme that integrates asynchronous (Unix) signals with user‐level threads, using the ARIADNE system as a platform. This is done with a view towards support for portable, multithreaded, and multiprotocol distributed applications, namely the CLAM (connectionless, lightweight, and multiway) communications library. In the same context, we propose the use of continuations as an efficient mechanism for reducing thread context‐switching and busy‐wait overheads in multithreaded protocols. Our proposal for integrating timers and signal‐handling mechanisms not only solves problems related to race conditions, but also offers an efficient and flexible interface for timing and signalling threads. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   
19.
为了解决我国水中兵器传统的仿真系统,局限于某些参数的数学仿真和部分半实物仿真,没有实现系统化、可视化,实时化,文章提出一种采用高层体系结构(HLA)作为分布交互的仿真体系框架,通过对水中兵器对抗系统仿真建模,解决了不同仿真应用之间的集成问题,较好地满足仿真系统的可视化、可操作性、强实时性及强交互性等要求。该仿真系统可以为水中兵器作战研究和武器装备论证提供仿真试验环境,检验装备各项战略战术指标,并为装备研制和战略战术决策提供依据,具有很高的实用价值。  相似文献   
20.
This paper presents a novel formulation for contour tracking.We model the second-order statistics of image regions and perform covariance matching under the variational level set framework.Specifically,covariance matrix is adopted as a visual object representation for partial differential equation(PDE) based contour tracking.Log-Euclidean calculus is used as a covariance distance metric instead of Euclidean distance which is unsuitable for measuring the similarities between covariance matrices,because the matrices typically lie on a non-Euclidean manifold.A novel image energy functional is formulated by minimizing the distance metric between the candidate object region and a given template,and maximizing the one between the background region and the template.The corresponding gradient flow is then derived according to a variational approach,enabling partial differential equations(PDEs) based contour tracking.Experiments on several challenging sequences prove the validity of the proposed method.  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