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   362646篇
  免费   31836篇
  国内免费   21764篇
电工技术   57808篇
技术理论   30篇
综合类   38985篇
化学工业   18017篇
金属工艺   12632篇
机械仪表   31943篇
建筑科学   32272篇
矿业工程   14604篇
能源动力   12281篇
轻工业   8571篇
水利工程   11029篇
石油天然气   11506篇
武器工业   6548篇
无线电   32892篇
一般工业技术   18960篇
冶金工业   12833篇
原子能技术   3168篇
自动化技术   92167篇
  2024年   568篇
  2023年   3560篇
  2022年   6367篇
  2021年   8327篇
  2020年   9363篇
  2019年   7094篇
  2018年   6426篇
  2017年   9300篇
  2016年   10766篇
  2015年   12484篇
  2014年   23792篇
  2013年   20300篇
  2012年   26992篇
  2011年   28895篇
  2010年   21773篇
  2009年   21982篇
  2008年   22309篇
  2007年   27858篇
  2006年   24938篇
  2005年   22033篇
  2004年   18136篇
  2003年   16268篇
  2002年   12651篇
  2001年   10474篇
  2000年   8685篇
  1999年   6926篇
  1998年   5218篇
  1997年   4399篇
  1996年   3767篇
  1995年   3204篇
  1994年   2668篇
  1993年   1860篇
  1992年   1519篇
  1991年   1126篇
  1990年   888篇
  1989年   762篇
  1988年   540篇
  1987年   322篇
  1986年   208篇
  1985年   220篇
  1984年   237篇
  1983年   196篇
  1982年   170篇
  1981年   123篇
  1980年   92篇
  1979年   91篇
  1978年   71篇
  1977年   66篇
  1976年   28篇
  1959年   28篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
This study aims to investigate the trajectory of the truckers' uprising in Brazil in May 2018 - one of the hitherto largest social movement enabled by WhatsApp in the world - in order to understand its relationship with the use of this mobile instant messaging app. Thus, by applying the Actor-Network Theory as the theoretical and methodological lens associated with a single case study, one identified the relevant actors in the development of the socio-technical network related to this truckers' strike that occurred in Brazil. The study sets forth that this movement comprised sundry actors aligned around a single obligatory passage point – the social networks enabled by WhatsApp – and reveals that WhatsApp, with its specific dynamics, played a crucial role in an uprising that took place in a country of continental dimensions such as Brazil, favoring change in the way the demonstrators gathered and interacted, leading formal organizations to be less necessary and broadening the political participation of the society. Finally, one concluded that WhatsApp enabled a power shift from government to truck drivers and their unions, which indicates the need for a new digital governance based on distribution and transparency of information, accountability, and participation of citizens in government decisions to curb new uprisings enabled by mobile instant messaging apps.  相似文献   
992.
While technological transformations have redrawn the boundaries of regional innovation systems, the effect of such transformations on the development of cross-border regional innovation systems (CBRISs) – defined here as the innovation system spanning neighboring territories belonging to different nation-states – has not been well understood. The Hong Kong-Shenzhen region presents a unique opportunity to study the potential of CBRISs, as Hong Kong and Shenzhen are adjacent to each other though there is a border between them and the two cities have their own political and legal systems under the “one country, two systems” arrangement. In this research, we examine the development of the Hong Kong-Shenzhen region by focusing on cognitive proximity, innovation actors, collaboration, and global connectivity through an analysis of patent and publication data for the 2001–2015 period. Our findings point to a good potential given the growing convergence in scientific research among the two cities, steadily increasing collaboration output, and a complementarity among innovation actors. However, compared with other cross-border regions, the technological linkages between Hong Kong and Shenzhen remain limited.  相似文献   
993.
Motivated by real-world applications of satellites and wireless sensor networks, this paper models and evaluates a dynamic k-out-of-n phase-AND mission system (k/n-PAMS). The mission task conducted by a k/n-PAMS involves multiple consecutive phases; the mission is successful as long as the task is successful in any of the phases. Due to factors, such as scheduled maintenance, location changes in task execution during different phases, and resource sharing with other tasks, the total number of available components n for the considered mission task and the required number of working components k may change from phase to phase. In addition, due to varying load and working environments, component failure time distributions are also phase dependent. This paper proposes an analytical modeling approach based on multivalued decision diagrams (MDDs) for assessing reliability of the considered k/n-PAMS. The approach encompasses a new and fast MDD model generation algorithm that considers behaviors of all the mission phases simultaneously based on node labeling. As demonstrated through empirical studies on k/n-PAMSs with different sizes (different numbers of phases and different numbers of system components), the proposed algorithm is more efficient than the traditional phase-by-phase model generation method.  相似文献   
994.
In many applications, the Poisson count data with varying sample sizes are monitored using statistical process control charts. Among these applications, the weighted CUSUM charts are developed to deal with the effect of the varying sample sizes. However, some of them use limited information of the sample size or the count data while assigning the weights. To gain more information of the process, the self-information weight functions are developed based on both the sample size and the observed count data. Then, the weighted CUSUM charts are proposed with the self-information-based weight. Simulation studies show the self-information-based weighted CUSUM charts perform better than the benchmark methods in detecting small shifts. Moreover, the performance of proposed method with estimated parameters is investigated via simulation. Finally, an example is given to illustrate the application of the proposed weighted CUSUM charts.  相似文献   
995.
A solid oxide cell-based energy system is proposed for a solar-powered stand-alone building. The system is comprised of a 5 kWel solid oxide fuel cell (SOFC), a 9.5 kWel solid oxide electrolysis cell (SOEC), and the required balance of plant. The SOFC supplies: 1- building demand in the absence of sufficient solar power, 2- heat for SOEC in endothermic and standby modes. Thermal integration of SOFC and SOEC is implemented through a network of heat exchangers, combined with set of control algorithms. Two control strategies were implemented to actuate the SOFC in response to endothermic heat demands of SOEC by manipulating: 1- electric power, 2- fuel utilization. The results of dynamic simulation of system for two scenarios (sunny day and cloudy day) showed successful compliance of temperature constraints with both methods. Manipulation of fuel utilization, however, resulted in better system performance in terms of efficiency and H2 balance.  相似文献   
996.
997.
为研发具有优良动态调湿控温性能的立体针织物,采用双股70 dtex(72 f)的DRYARN®纱线与30 dtex DRYARN®纱线包覆30 dtex氨纶长丝为原料,提出了立体针织物拓扑优化设计方法。通过优化设计各控温单元的排列方式,使控温单元按V字、Y字等斜向错位排列,然后采用单面提花工艺对织物进行局部拉伸与压褶以形成褶皱片状结构。结果表明:当人体流汗时,褶皱片状结构里层吸收汗滴并转移至面层以快速蒸发,当人体感到寒冷时,内部空气通道储藏静止空气有效控温;所制备织物的保温率均大于54%,具有出色的控温性能,整体液态水分传递能力达到3级以上,液态水动态传递性能良好,同时保持优良的拉伸回复性能,为冬季运动保暖内衣用立体针织物的研发提供了新思路。  相似文献   
998.
999.
Workflow management technologies have been dramatically improving their deployment architectures and systems along with the evolution and proliferation of cloud distributed computing environments. Especially, such cloud computing environments ought to be providing a suitable distributed computing paradigm to deploy very large-scale workflow processes and applications with scalable on-demand services. In this paper, we focus on the distribution paradigm and its deployment formalism for such very large-scale workflow applications being deployed and enacted across the multiple and heterogeneous cloud computing environments. We propose a formal approach to vertically as well as horizontally fragment very large-scale workflow processes and their applications and to deploy the workflow process and application fragments over three types of cloud deployment models and architectures. To concretize the formal approach, we firstly devise a series of operational situations fragmenting into cloud workflow process and application components and deploying onto three different types of cloud deployment models and architectures. These concrete approaches are called the deployment-driven fragmentation mechanism to be applied to such very large-scale workflow process and applications as an implementing component for cloud workflow management systems. Finally, we strongly believe that our approach with the fragmentation formalisms becomes a theoretical basis of designing and implementing very large-scale and maximally distributed workflow processes and applications to be deployed on cloud deployment models and architectural computing environments as well.  相似文献   
1000.
Exponentially weighted moving average (EWMA) control chart has a significant effect in improving product quality and is widely used in various fields. In addition to continuous data, there are many Count Data in life that need to be monitored. Poisson distribution is one of the models that study the probability distribution of discrete data, and has a wide range of applications. In previous monitoring, it was considered that the mean value of Poisson distribution in normal state was a constant value after it was determined. But in the actual situation, there are many unavoidable objective conditions that will affect the final results. We cannot monitor all situations according to the same criteria. If we ignore the conditions that affect the occurrence of the event and directly monitor the final result, on the one hand, it will increase the probability of false alarms from the control chart. On the other hand, the control chart will not be able to detect problems in time due to the untimely update of conditions. In response to this situation, this paper proposes a regression-adjusted EWMA control chart to monitor the Poisson process. The control chart can continuously adjust and update the expected values according to the actual situation. It can make the monitoring process more reasonable and the monitoring results more valuable.  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