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   30937篇
  免费   3795篇
  国内免费   2015篇
电工技术   5021篇
技术理论   5篇
综合类   3857篇
化学工业   1185篇
金属工艺   883篇
机械仪表   2425篇
建筑科学   3728篇
矿业工程   811篇
能源动力   808篇
轻工业   465篇
水利工程   907篇
石油天然气   811篇
武器工业   424篇
无线电   5368篇
一般工业技术   2520篇
冶金工业   548篇
原子能技术   285篇
自动化技术   6696篇
  2024年   164篇
  2023年   463篇
  2022年   885篇
  2021年   1017篇
  2020年   1243篇
  2019年   1034篇
  2018年   817篇
  2017年   1129篇
  2016年   1271篇
  2015年   1348篇
  2014年   2340篇
  2013年   1890篇
  2012年   2497篇
  2011年   2767篇
  2010年   1988篇
  2009年   2063篇
  2008年   1920篇
  2007年   2250篇
  2006年   1850篇
  2005年   1553篇
  2004年   1229篇
  2003年   1040篇
  2002年   828篇
  2001年   704篇
  2000年   538篇
  1999年   432篇
  1998年   312篇
  1997年   254篇
  1996年   205篇
  1995年   169篇
  1994年   117篇
  1993年   82篇
  1992年   83篇
  1991年   55篇
  1990年   45篇
  1989年   52篇
  1988年   42篇
  1987年   11篇
  1986年   4篇
  1985年   10篇
  1984年   7篇
  1983年   5篇
  1982年   4篇
  1981年   5篇
  1980年   5篇
  1979年   7篇
  1975年   2篇
  1970年   2篇
  1969年   3篇
  1951年   2篇
排序方式: 共有10000条查询结果,搜索用时 234 毫秒
941.
BPMN: An introduction to the standard   总被引:1,自引:0,他引:1  
The Business Process Model and Notation (BPMN) is the de-facto standard for representing in a very expressive graphical way the processes occurring in virtually every kind of organization one can think of, from cuisine recipes to the Nobel Prize assignment process, incident management, e-mail voting systems, travel booking procedures, to name a few. In this work, we give an overview of BPMN and we present what are the links with other well-known machineries such as BPEL and XPDL. We give an assessment of how the OMG's BPMN standard is perceived and used by practitioners in everyday business process modeling chores.  相似文献   
942.
An approach based on geometric invariance and sliding mode ideas is proposed for redundancy resolution in robotic systems to fulfill configuration and workspace constraints caused by robot mechanical limits, collision avoidance, industrial security, etc. Some interesting features of the proposal are that: (1) it can be interpreted as a limit case of the classical potential field-based approach for collision avoidance which requires using variable structure control concepts, (2) it allows reaching the limit surface of the constraints smoothly, depending on a free design parameter, and (3) it can be easily added as a supervisory block to pre-existing redundancy resolution schemes. The algorithm is evaluated in simulation on a 6R planar robot and on the freely accessible 6R robot model PUMA-560, for which the main features of the method are illustrated.  相似文献   
943.
It is increasingly common to see computer-based simulation being used as a vehicle to model and analyze business processes in relation to process management and improvement. While there are a number of business process management (BPM) and business process simulation (BPS) methodologies, approaches and tools available, it is more desirable to have a systemic BPS approach for operational decision support, from constructing process models based on historical data to simulating processes for typical and common problems. In this paper, we have proposed a generic approach of BPS for operational decision support which includes business processes modeling and workflow simulation with the models generated. Processes are modeled with event graphs through process mining from workflow logs that have integrated comprehensive information about the control-flow, data and resource aspects of a business process. A case study of a credit card application is presented to illustrate the steps involved in constructing an event graph. The evaluation detail is also given in terms of precision, generalization and robustness. Based on the event graph model constructed, we simulate the process under different scenarios and analyze the simulation logs for three generic problems in the case study: 1) suitable resource allocation plan for different case arrival rates; 2) teamwork performance under different case arrival rates; and 3) evaluation and prediction for personal performances. Our experimental results show that the proposed approach is able to model business processes using event graphs and simulate the processes for common operational decision support which collectively play an important role in process management and improvement.  相似文献   
944.
The complexity of the data warehouse (DW) development process requires to follow a methodological approach in order to be successful. A widely accepted approach for this development is the hybrid one, in which requirements and data sources must be accommodated to a new DW model. The main problem is that we lose the relationships between requirements, elements in the multidimensional (MD) conceptual models and data sources in the process, since no traceability is explicitly specified. Therefore, this hurts requirements validation capability and increases the complexity of Extraction, Transformation and Loading processes. In this paper, we propose a novel trace metamodel for DWs and focus on the relationships between requirements and MD conceptual models. We propose a set of Query/View/Transformation rules to include traceability in DWs in an automatic way, allowing us to obtain a MD conceptual model of the DW, as well as a trace model. Therefore, we are able to trace every requirement to the MD elements, further increasing user satisfaction. Finally, we show the implementation in our Lucentia BI tool.  相似文献   
945.
Organizations actively managing their business processes face a rapid growth of the number of process models that they maintain. Business process model abstraction has proven to be an effective means to generate readable, high-level views on business process models by showing coarse-grained activities and leaving out irrelevant details. In this way, abstraction facilitates a more efficient management of process models, as a single model can provide for many relevant views. Yet, it is an open question how to perform abstraction in the same skillful way as experienced modelers combine activities into more abstract tasks. This paper presents an approach that uses semantic information of a process model to decide on which activities belong together, which extends beyond existing approaches that merely exploit model structural characteristics. The contribution of this paper is twofold: we propose a novel activity aggregation method and suggest how to discover the activity aggregation habits of human modelers. In an experimental validation, we use an industrial process model repository to compare the developed activity aggregation method with actual modeling decisions, and observe a strong correlation between the two. The presented work is expected to contribute to the development of modeling support for the effective process model abstraction.  相似文献   
946.
E-mail is used as the primary tool for business communication and collaboration. This paper presents a novel e-mail interaction mining method to discover and analyze e-mail-driven business processes. An e-mail-driven business process is perceived as a human collaboration process that consists of interactions between people who may each play different roles. The notion of message threads (i.e. sets of e-mail messages that are replies to each other) is used as the fundamental building block to construct the interactions in the e-mail-driven business process. The proposed method adopts an interaction-centric business process modeling language to visualize the discovered e-mail-driven business process. The method identifies message threads from an e-mail archive, and constructs an interaction-centric process model based on the temporal order and similarity of the threads. Process-related information is extracted from e-mail header fields. A software tool, named E-mail Interaction Miner, implements the proposed method. A case study is used to apply and evaluate the method on a set of e-mails collected from a Dutch gas transport company. The evaluation results are discussed. These results comprise business process improvement opportunities for the case organization, and contributions to theory and language development.  相似文献   
947.
为实现低成本、高可靠且传输距离达几千米的数据通信,提出一个以嵌入式Modem和单片机为核心的通信方案。单片机通过AT指令对嵌入式Modem MT9234模块进行设置。PC通过电平转换接口电路与MT9234模块相连,MT9234模块之间利用双绞线相连,并经过3个阶段的握手过程建立数据通信,从而实现PC与远方单片机间的通信。硬件仿真结果表明,与传统Modem相比,专线模式下的数据通信传输距离更远、速度更快。  相似文献   
948.
瞬态干扰是影响天波超视距雷达检测性能的主要因素之一,因此必须对瞬态干扰进行抑制.提出了一种改进复经验模式分解方法以抑制天波超视距雷达中的瞬态干扰.该方法利用小波包分解将回波信号先分解成一系列窄带信号,再对每一个窄带信号进行复经验模式分解,然后对各个固有模态函数进行归一化相关性筛选处理,最后对剩余信号进行瞬态干扰检测和剔除.该方法的主要优点是无须杂波抑制和数据预测重构.实测数据处理结果表明该方法能有效地检测和抑制瞬态干扰.  相似文献   
949.
文章以我校园林专业学生为对象,以园林专业学生实践能力培养为主线,以提高学生实践应用能力为目标,探索了园林(景观)专业的实践教学培养模式,改革了实践教学内容;构建了一个由条件体系、课程体系、H标体系、管理体系和评价体系五个部分组成的园林专业实践教学体系框架。  相似文献   
950.
以某高速公路长期养护为例,从结合预防性养护规划和单纯矫正性养护规划两个方面出发,建立两种长期的养护计划方案,得到两种养护方案下各路面性能指数的变化趋势.最后在高速公路的使用寿命、经济效益和路用性能三个方面,说明预防性养护在高速公路养护中的优越性,并倡导在高速公路养护中积极运用预防性养护.  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