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   468851篇
  免费   6893篇
  国内免费   1688篇
电工技术   8620篇
综合类   519篇
化学工业   68665篇
金属工艺   16971篇
机械仪表   14355篇
建筑科学   11855篇
矿业工程   1554篇
能源动力   12489篇
轻工业   46010篇
水利工程   4287篇
石油天然气   5605篇
武器工业   73篇
无线电   61130篇
一般工业技术   87574篇
冶金工业   86761篇
原子能技术   7967篇
自动化技术   42997篇
  2021年   3530篇
  2020年   2702篇
  2019年   3451篇
  2018年   5580篇
  2017年   5672篇
  2016年   6137篇
  2015年   4153篇
  2014年   7087篇
  2013年   21478篇
  2012年   12152篇
  2011年   16911篇
  2010年   13224篇
  2009年   14885篇
  2008年   15989篇
  2007年   15924篇
  2006年   14543篇
  2005年   13184篇
  2004年   12783篇
  2003年   12469篇
  2002年   11826篇
  2001年   12103篇
  2000年   11183篇
  1999年   11852篇
  1998年   27972篇
  1997年   19838篇
  1996年   15284篇
  1995年   11798篇
  1994年   10420篇
  1993年   10198篇
  1992年   7738篇
  1991年   7273篇
  1990年   6933篇
  1989年   6505篇
  1988年   6308篇
  1987年   5368篇
  1986年   5120篇
  1985年   6241篇
  1984年   5675篇
  1983年   5167篇
  1982年   4823篇
  1981年   4940篇
  1980年   4605篇
  1979年   4352篇
  1978年   4064篇
  1977年   4804篇
  1976年   5933篇
  1975年   3641篇
  1974年   3524篇
  1973年   3589篇
  1972年   2789篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
Trust on a Nationwide Scale   总被引:1,自引:0,他引:1  
Singapore is a small island nation with roughly 4.5 million inhabitants, but it has a highly developed international economy based on trade, services, and knowledge management. Singapore launched its lofty goals by defining the nationpsilas e-security. Current research in the Singaporean telecommunications and IT security community attempts to model such peer-to-peer ad hoc transactions and leverage the existing standard infrastructure described in this article.  相似文献   
992.
The Magtalo prototype environment harnesses dialogue protocols to support flexible, intuitive interaction with data in complex, contentious domains and provides mechanisms for eliciting structured knowledge. Magtalo represents the first example of an implemented online system that uses a closely specified argument-based dialogue protocol combined with a rich language for representing monologic argument to provide a tool for intuitive user exploration of a disagreement space. This approach also enables the expansion of argument resources through knowledge elicitation, which is structured by the argument dialogue protocol. The continuing aim of our research is to use advances in argumentation theory to push the practice of argumentation technology in providing tools and interfaces that have wide appeal.  相似文献   
993.
Existing wireless networks provide dynamically varying resources with only limited support for the quality of service required by the bandwidth-intense, loss-tolerant and delay-sensitive multimedia applications. This variability of resources does not significantly impact delay insensitive data transmission (e.g., file transfers), but has considerable consequences for multimedia applications. Recently, the research focus has been to adapt existing algorithms and protocols at the lower layers of the protocol stack to better support multimedia transmission applications and conversely, to modify application layer solutions to cope with the varying wireless networks resources. In this paper, we show that significant improvements in wireless multimedia performance can be obtained by deploying a joint application-layer adaptive packetization and prioritized scheduling and MAC-layer retransmission strategy. We deploy a state-of-the-art wavelet coder for the compression of the video data that enables on-the-fly adaptation to changing channel conditions and inherent prioritization of the video bitstream. We pose the cross-layer problem as a distortion minimization given delay constraints and derive analytical solutions by modifying existing joint source-channel coding theory aimed at fulfilling rate, rather than delay, constraints. We also propose real-time algorithms that explicitly consider the available information about previously transmitted packets. The obtained results show significant improvements in terms of video quality as opposed to ad-hoc optimizations currently deployed, while the complexity associated with performing this optimization in real time, i.e., at transmission time, is limited  相似文献   
994.
The US Centers for Disease Control and Prevention (CDC) created the Public Health Information Network to advance fully capable, interoperable information systems in public health organizations. PHIN prioritizes public health information systems' functional requirements, capabilities, performance measures, and operational characteristics while letting the architects of those systems choose enabling approaches, methods, and concepts to meet the requirements. PHIN also provides a certification process for public health administrators to evaluate their information infrastructure's quality. The certification process is important because affected organizations often depend on certification for continued funding.  相似文献   
995.
996.
This paper discusses a new application of data mining, quantifying the importance of responding to trigger events with reactive contacts. Trigger events happen during a customer’s lifecycle and indicate some change in the relationship with the company. If detected early, the company can respond to the problem and retain the customer; otherwise the customer may switch to another company. It is usually easy to identify many potential trigger events. What is needed is a way of prioritizing which events demand interventions. We conceptualize the trigger event problem and show how survival analysis can be used to quantify the importance of addressing various trigger events. The method is illustrated on four real data sets from different industries and countries.  相似文献   
997.
This study investigated the ability of the Millon Clinical Multiaxial Inventory--Third Edition (MCMI-III) to discriminate students malingering psychopathology (n=106) from bona fide psychiatric inpatients (n=202). Students were randomly assigned to a fake-bad or an honest-responding condition. Analyses investigated the ability of the modifier indices to discriminate fake-bad group participants from the psychiatric inpatients. Scale X raw cutoff score >178 yielded a positive predictive power (PPP) of 0.0, a negative predictive power (NPP) of 63.1, and a hit rate of 63.1%. Optimal cutoff scores were developed. Scale X Base Rate (BR) >84 provided a PPP of 55.6, an NPP of 72.1, and a hit rate of 65.2%. Scale Y BR  相似文献   
998.
A construction of a globally asymptotically stable time-invariant system which can be destabilized by some integrable perturbation is given. Besides its intrinsic interest, this serves to provide counterexamples to an open question regarding Lyapunov functions.  相似文献   
999.
When we test boards, we usually think in terms of traditional electrical test (in-circuit, flying probe) and nonelectrical test (optical, x-ray). This Orebro University article develops an alternative, connectionless technique based on scanning the electromagnetic field generated by active on-board devices. Could this make it into industry as an additional diagnostic tool?.  相似文献   
1000.
An increasing number of connectionist models have been proposed to explain behavioral deficits in developmental disorders. These simulations motivate serious consideration of the theoretical implications of the claim that a developmental disorder fits within the parameter space of a particular computational model of normal development. The authors examine these issues in depth with respect to a series of new simulations investigating past-tense formation in Williams syndrome. This syndrome and the past-tense domain are highly relevant because both have been used to make strong theoretical claims about the processes underlying normal language acquisition. The authors conclude that computational models have great potential to advance psychologists' understanding of developmental deficits because they focus on the developmental process itself as a pivotal causal factor in producing atypical phenotypic outcomes. (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