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   17848篇
  免费   2178篇
  国内免费   1707篇
电工技术   694篇
技术理论   6篇
综合类   2452篇
化学工业   1010篇
金属工艺   497篇
机械仪表   827篇
建筑科学   1555篇
矿业工程   429篇
能源动力   369篇
轻工业   1107篇
水利工程   2121篇
石油天然气   1396篇
武器工业   115篇
无线电   1907篇
一般工业技术   1068篇
冶金工业   479篇
原子能技术   156篇
自动化技术   5545篇
  2024年   71篇
  2023年   220篇
  2022年   403篇
  2021年   439篇
  2020年   512篇
  2019年   430篇
  2018年   444篇
  2017年   560篇
  2016年   599篇
  2015年   715篇
  2014年   997篇
  2013年   1036篇
  2012年   1165篇
  2011年   1398篇
  2010年   1131篇
  2009年   1191篇
  2008年   1210篇
  2007年   1456篇
  2006年   1281篇
  2005年   1095篇
  2004年   958篇
  2003年   769篇
  2002年   651篇
  2001年   500篇
  2000年   410篇
  1999年   349篇
  1998年   278篇
  1997年   220篇
  1996年   200篇
  1995年   195篇
  1994年   184篇
  1993年   120篇
  1992年   96篇
  1991年   70篇
  1990年   56篇
  1989年   59篇
  1988年   33篇
  1987年   25篇
  1986年   21篇
  1985年   37篇
  1984年   28篇
  1983年   19篇
  1982年   17篇
  1981年   14篇
  1980年   12篇
  1979年   12篇
  1978年   8篇
  1977年   10篇
  1975年   5篇
  1973年   4篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
In order to evaluate the stability and reproducibility of roughness measurements, calibrations of the same roughness standard were held over four years. Calibrations were performed in the Laboratório de Medição de Superfícies Ópticas (LMSO), on Mondays, between late January to early December every year. Here are presented and analyzed the calibration results and also the measurements of lab temperature and relative humid, at the time of calibration, in order to assess if there is any correlation between these influence factors in the obtained results. The LMSO lab is accredited by INMETRO (Brazilian NMI).  相似文献   
992.
This paper reports an experimental result obtained by additionally using unlabeled data together with labeled ones to improve the classification accuracy of dissimilarity-based methods, namely, dissimilarity-based classifications (DBC) [25]. In DBC, classifiers among classes are not based on the feature measurements of individual objects, but on a suitable dissimilarity measure among the objects instead. In order to measure the dissimilarity distance between pairwise objects, an approach using the one-shot similarity (OSS) [30] measuring technique instead of the Euclidean distance is investigated in this paper. In DBC using OSS, the unlabeled set can be used to extend the set of prototypes as well as to compute the OSS distance. The experimental results, obtained with artificial and real-life benchmark datasets, demonstrate that designing the classifiers in the OSS dissimilarity matrices instead of expanding the set of prototypes can further improve the classification accuracy in comparison with the traditional Euclidean approach. Moreover, the results demonstrate that the proposed setting does not work with non-Euclidean data.  相似文献   
993.
Online social networks allow users to tag their posts with geographical coordinates collected through the GPS interface of smart phones. The time- and geo-coordinates associated with a sequence of posts/tweets manifest the spatial–temporal movements of people in real life. This paper aims to analyze such movements to discover people and community behavior. To this end, we defined and implemented a novel methodology to mine popular travel routes from geo-tagged posts. Our approach infers interesting locations and frequent travel sequences among these locations in a given geo-spatial region, as shown from the detailed analysis of the collected geo-tagged data.  相似文献   
994.
995.
C?亚历山大教授在其出版的《俄勒冈实验》一书中,以俄勒冈大学为实验母体,界定出一种设计方式,以适用任何社区的总体规划,并归纳为6种主要原则。文章从现实角度出发,针对俄勒冈大学规划现状,提取6种原则中的模式原则并选择其中较为重要的几项模式对其论述进行比较研究,并依照现有实施状况进行一般性评价。对俄勒冈大学规划现状的研究将为我国高校下一阶段的校园规划和校园更新建设提供一定参考价值。  相似文献   
996.
《Ergonomics》2012,55(2):178-191
The study investigated the natural work–pause pattern of computer users and the possible effects of imposing pause regimes on this pattern. Hereto, the precise timing of computer events was recorded across a large number of days. It was found that the distribution of the pause durations was extremely skewed and that pauses with twice the duration are twice less likely to occur. The effects of imposing pause regimes were studied by performing a simulation of commercially available pause software. It was found that depending on the duration of the introduced pause, the software added 25–57% of the pauses taken naturally. Analysis of the timing of the introduced pauses revealed that a large number of spontaneous pauses were taken close to the inserted pause. Considering the disappointing results of studies investigating the effects of introducing (active) pauses during computer work, this study has cast doubt on the usefulness of introducing short duration pauses.  相似文献   
997.
The emphasis in this work is on the practical application of ideas set forth in Part I. Two studies involving spatial distribution are discussed: the distribution of human population in the Indianapolis, Indiana Region, and the world distribution of mammals. In the first, populations over the period 1890–1980 of Ihe 393 townships making up the study area are used to produce classifications involving various numbers of classes of township types. A test of the theoretical structure posed in Part I is then detailed. On the theory that the underlying relations involved cannot sustain a real world structure involving more than five functional classes, it is hypothesized that classifications involving more than five classes will be associated with township distribution patterns that conflict with Central Place Theory. This is shown to be clearly so. In the second study, the derivation of a five region partitioning of world mammalian distribution patterns is described. Discussion includes the introduction of a wholly new rationale for taxonomic revision based on biogeographic criteria (and ultimately the principles described in Part I). The study closes with a short argument regarding why the model described in Part I should not be labelled as either social physics or anti-humanistic.  相似文献   
998.
999.
通过对中规院主持的两江、天府、兰州和贵安等西部国家级(准国家级)新区的前期研究、规划设计和后续实施咨询服务等工作,以及新区相应所在省(直辖市)的省域城镇体系规划的规划编制工作的总结,从实证的角度出发,提出西部国家级(准国家级)新区的设立不是东部先发地区的翻版,而是国家从战略高度给西部发展提供平台,使西部地区发挥国家层面应有作用.  相似文献   
1000.
This paper is addressing problems related to the construction of classifiers based on the Similarity Discriminant Function (SDF), in which the traditional vector representation of a pattern is replaced with matrix data. We introduce potential modifications of the matrix data structure and propose new variants of the SDF. The algorithms that we present were tested on images of handwritten digits and on photographs of human faces, taken from the ORL and CMU‐PIE databases. The results of experiments show that our modifications significantly improved the performance of the original SDF classifier.  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