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   6094篇
  免费   278篇
  国内免费   21篇
电工技术   54篇
综合类   23篇
化学工业   1181篇
金属工艺   100篇
机械仪表   127篇
建筑科学   302篇
矿业工程   10篇
能源动力   243篇
轻工业   468篇
水利工程   58篇
石油天然气   33篇
无线电   526篇
一般工业技术   1204篇
冶金工业   905篇
原子能技术   49篇
自动化技术   1110篇
  2023年   59篇
  2022年   124篇
  2021年   205篇
  2020年   130篇
  2019年   177篇
  2018年   219篇
  2017年   142篇
  2016年   165篇
  2015年   136篇
  2014年   205篇
  2013年   364篇
  2012年   326篇
  2011年   364篇
  2010年   274篇
  2009年   285篇
  2008年   292篇
  2007年   288篇
  2006年   213篇
  2005年   205篇
  2004年   174篇
  2003年   179篇
  2002年   146篇
  2001年   90篇
  2000年   103篇
  1999年   80篇
  1998年   252篇
  1997年   169篇
  1996年   117篇
  1995年   112篇
  1994年   81篇
  1993年   78篇
  1992年   60篇
  1991年   46篇
  1990年   35篇
  1989年   31篇
  1988年   41篇
  1987年   37篇
  1986年   20篇
  1985年   29篇
  1984年   22篇
  1983年   15篇
  1982年   27篇
  1981年   30篇
  1980年   22篇
  1979年   21篇
  1978年   19篇
  1977年   26篇
  1976年   48篇
  1975年   15篇
  1972年   13篇
排序方式: 共有6393条查询结果,搜索用时 15 毫秒
51.
In this letter, based on the exact pairwise-error probability, we derive the union bound on the symbol-error probability (SEP) of the differential unitary space-time (DUST) modulation employing group codes. Instead of using the rank-and-determinant or Euclidean distance criteria, we optimize the cyclic group codes such that the union bound on the SEP is minimized for a predetermined scenario, taking into account the number of transmit and receive antennas and the operating signal-to-noise ratio (SNR). Our simulation results show that for a wide range of SNRs, the codes with the minimum union bound for a particular SNR outperform the codes designed based on rank-and-determinant or Euclidean distance criteria.  相似文献   
52.
In the literature on statistical inference in software reliability, the assumptions of parametric models and random sampling of bugs have been pervasive. We argue that both assumptions are problematic, the first because of robustness concerns and the second due to logical and practical difficulties. These considerations motivate the approach taken in this paper. We propose a nonparametric software reliability model based on the order-statistic paradigm. The objective of the work is to estimate, from data on discovery times observed within a type I censoring framework, both the underlying distribution F from which discovery times are generated and N, the unknown number of bugs in the software. The estimates are used to predict the next time to failure. The approach makes use of Bayesian nonparametric inference methods, in particular, the beta-Stacy process. The proposed methodology is illustrated on both real and simulated data  相似文献   
53.
陆虎(Land Rover)G4越野挑战赛.是各大汽车公司彼此互相交流的重大活动。经过三年多的精心准备.2006年G4挑战赛正式拉开了帷幕——一个月时间,18组挑战者.4000公里行程.跨越泰国、老挝、巴西和波利维亚。本届赛事是2003年G4挑战赛的延续.它的前身就是2000年结束的“骆驼杯”越野挑战赛。  相似文献   
54.
This paper analyses inter-organizational networks that link together firms operating in the food processing and distribution industry in the UK. In doing so, the paper draws on insights recently developed by Mark Casson that treat inter-firm networks as an institutional response to the changing costs and opportunities of information management. Detailed analysis of product innovation and supply-chain management issues within the industry, exemplified by the growth of chilled ready-meals, leads to the identification of two distinct but complementary inter-firm networks: a network of control and a network of innovation. In each case, the study finds that the critical information is derived from the retailers' interface with consumers and thus that these information-based networks are effectively controlled by the leading supermarket chains. The study's conclusions are considered in relation to the recent findings of the UK Competition Commission following its investigation into grocery retailing in Britain.  相似文献   
55.
In 3 eye-tracking experiments, the authors investigated the use of morphological information during pronoun resolution. Experiments 1 and 2 showed that disruption occurred when a preferred assignment was inconsistent with gender information. Experiment 2 ensured that this difficulty was not due to the introduction of a new discourse entity. Experiment 3 showed that disruption also occurred when number information was inconsistent with the preferred assignment. The results indicate that the use of morphological information is delayed until after the computation of coreference relations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
56.
57.
A new evaluation model for SK combinator expressions is presented and used as a basis for the design of a novel processor. The resulting machine architecture resembles a dataflow ring, but executions are constrained to be fully lazy. An automatic dynamic load sharing mechanism for a distributed multiprocessor architecture is suggested, and initial simulation results are presented.  相似文献   
58.
59.
The clinical and pathological findings of a 43-year-old woman, diagnosed as having acute hemorrhagic leukoencephalitis at postmortem examination, are presented. The acute hemorrhagic leukoencephalitis affects mainly young adults and is the most fulminant from of demyelinating disease. It is frequently preceded by a respiratory infection. Diagnosis is facilitated by CT scanning and MRI, which reveal the massive lesion in the cerebral white matter. Many cases terminate fatally in 2 or 4 days, but in others survival is longer. The pathological findings are distinctive.  相似文献   
60.
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