全文获取类型
收费全文 | 5648篇 |
免费 | 578篇 |
国内免费 | 205篇 |
专业分类
电工技术 | 475篇 |
综合类 | 495篇 |
化学工业 | 367篇 |
金属工艺 | 76篇 |
机械仪表 | 332篇 |
建筑科学 | 825篇 |
矿业工程 | 83篇 |
能源动力 | 70篇 |
轻工业 | 1356篇 |
水利工程 | 52篇 |
石油天然气 | 83篇 |
武器工业 | 64篇 |
无线电 | 668篇 |
一般工业技术 | 558篇 |
冶金工业 | 129篇 |
原子能技术 | 43篇 |
自动化技术 | 755篇 |
出版年
2024年 | 24篇 |
2023年 | 99篇 |
2022年 | 167篇 |
2021年 | 192篇 |
2020年 | 266篇 |
2019年 | 197篇 |
2018年 | 178篇 |
2017年 | 204篇 |
2016年 | 234篇 |
2015年 | 235篇 |
2014年 | 392篇 |
2013年 | 342篇 |
2012年 | 445篇 |
2011年 | 468篇 |
2010年 | 326篇 |
2009年 | 315篇 |
2008年 | 262篇 |
2007年 | 377篇 |
2006年 | 320篇 |
2005年 | 283篇 |
2004年 | 191篇 |
2003年 | 181篇 |
2002年 | 158篇 |
2001年 | 105篇 |
2000年 | 94篇 |
1999年 | 71篇 |
1998年 | 53篇 |
1997年 | 34篇 |
1996年 | 35篇 |
1995年 | 22篇 |
1994年 | 26篇 |
1993年 | 19篇 |
1992年 | 12篇 |
1991年 | 17篇 |
1990年 | 15篇 |
1989年 | 11篇 |
1988年 | 6篇 |
1987年 | 8篇 |
1986年 | 3篇 |
1985年 | 6篇 |
1983年 | 2篇 |
1981年 | 2篇 |
1980年 | 6篇 |
1979年 | 2篇 |
1976年 | 2篇 |
1975年 | 3篇 |
1965年 | 3篇 |
1964年 | 5篇 |
1959年 | 2篇 |
1951年 | 1篇 |
排序方式: 共有6431条查询结果,搜索用时 46 毫秒
71.
采用单自由度反应谱方法对满足一定条件的减隔震桥梁进行地震反应分析可以简化计算过程,但需要解决精度问题。针对规范反应谱阻尼修正方法对计算精度的影响进行了分析并提出了改进方法。为了验证改进方法的合理性,对一座常规减隔震桥梁分别采用不同计算方法进行了比较分析,结果表明采用改进的阻尼修正公式后,简化反应谱方法的计算精度得到很大提高,且结果偏于安全。 相似文献
72.
钟灿雄 《长沙通信职业技术学院学报》2014,(2):58-63
针对GRE、IPSEC构建的虚拟私有网络存在数据隔离、互访控制难于实现等问题。文章分析了产生这些问题的根源,提出采用MPLS和BGP技术构建虚拟私有网络的设计思想,并通过仿真平台加以验证。实践证明,采用这种方法在解决路由冲突、数据隔离、站点间访问控制等方面要优于传统的VPN技术。 相似文献
73.
控水压裂工艺方法及效果分析 总被引:1,自引:0,他引:1
针对不同储层的渗流特征以及压裂裂缝扩展规律,探讨油井控水压裂技术实施效果。分别通过选择性控水支撑剂、透油阻水压裂液、人工隔离层等工艺进行现场先导实验,观察分析控水工艺使用前后含水率与产油量的情况。根据不同高含水井区的工程地质特征,提出控水压裂工艺优化选择方案。 相似文献
74.
The ability to trap precise quantities of cells or particles into confined areas has numerous applications for biological purposes. In particular, single cell trapping has received considerable attention because it permits the study of heterogeneity in a population, while trapping larger groups of cells have been used to form aggregates. Among several methods, the use of microwell offers a simple platform to capture cells or particles using hydrodynamic forces. This review examines the use of microwells in both static and microfluidic environments, and the application of microfluidic geometric arrays for trapping. This paper discusses the design and fabrication methods of microwells and compares the trapping and release techniques used in both static and microfluidics‐integrated microwells. Finally, we will summarize novel microfluidic geometric arrays used to capture cells or particles through hydrodynamic trapping. 相似文献
75.
Children and youth who are hospitalized for a short or long term become socially isolated from their family, school and classmates. As their isolation increases, so does their vulnerability as a result of disrupted schooling. Research studies suggest different ways of using technologies to overcome this isolation and support children during this critical time of their lives. With technology for children in hospitals becoming increasingly commonplace, evaluating how it is used and its impact on children's learning and well‐being is necessary. In this paper, we systematically evaluated existing research on use of technologies for communication, support and educational purposes and its contribution to the well‐being of hospitalized children. A rigorous selection process yielded 14 research articles meeting the following criteria: empirical studies, using technologies for network of support, targeting hospitalized children and adolescents and targeting learning or social and emotional well‐being in the last decade. This review indicates that the use of technologies with children and youth in hospitals generally increased their potential for learning and improved connectivity with school. Our findings revealed that implementing digital pedagogies and creating online communities were helpful but underutilized features in the research. 相似文献
76.
This work considers the application of classification algorithms for data-driven fault diagnosis of batch processes. A novel data selection methodology is proposed which enables online classification of detected disturbances without requiring the estimation of unknown (future) process behavior, as is the case in previously reported approaches.The proposed method is benchmarked in two case studies using the Pensim process model of Birol et al. (2002) implemented in RAYMOND. Both a simple k Nearest Neighbors (k-NN) and complex Least Squares Support Vector Machine (LS-SVM) are employed for classification to demonstrate the generic nature of the proposed approach. In addition, the influence of different data pretreatment methods on the classification performance is discussed, together with a motivation for selecting the correct pretreatment steps. Finally, the influence of the number of available training batches is studied.The results demonstrate that a good classification performance can be achieved with the proposed data selection method even with a low number of faulty training batches by exploiting knowledge on the nature of the to-be-diagnosed faults in the data pretreatment. This provides a proof of concept for classification-based batch diagnosis and demonstrates the importance of incorporating process insight in the construction of data-driven process monitoring and diagnosis tools. 相似文献
77.
电流互感器二次侧开路,会危及人身安全及损坏电路.实现一种用于电流互感器测试平台的二次侧开路保护器,以保护操作人员和测试电路.保护器主要由氧化锌压敏电阻、保护继电器、二次侧开路监控电路、硬件处理保护电路和单片机等组成.二次侧发生开路时,压敏电阻限制开路电压,监控电路同时控制保护继电器触点闭合短接二次侧两端,单片机通过串口上传开路报警信息.多工位实时保护,集中监控多路互感器测试通道.保护器既可由硬件独立完成保护工作,也能受PC机管理控制.它对互感器二次侧相关电路影响小,开路保护反应时间短,保护效果好.现场运行一年多来,表明保护器性能可靠、稳定. 相似文献
78.
79.
嵌入式实时操作系统的研究与开发是嵌入式领域的一个研究热点。分区(Partition)技术的时间、空间隔离与调度机制,保证了嵌入式实时系统资源在时间和空间方面的确定性和应用程序之间的安全性。介绍了嵌入式实时操作系统中的分区技术,并联系航空实际,重点研究了分区技术的设计与实现。 相似文献
80.
Dual polarized triple band hybrid MIMO cylindrical dielectric resonator antenna for LTE2500/WLAN/WiMAX applications
下载免费PDF全文
![点击此处可从《国际射频与微波计算机辅助工程杂志》网站下载免费的PDF全文](/ch/ext_images/free.gif)
In this communication, triple band hybrid multi‐input–multi‐output (MIMO) cylindrical dielectric resonator antenna (CDRA) with high isolation is examined. The proposed MIMO antenna includes two symmetric folded microstrip line feeding structures along with CDRA at two different ends of substrate. Two inverted L‐shaped strips on the ground plane are used to enhance the isolation (S12 < ?15 dB) as well as to generates 2.7 GHz frequency band. Metallic strip on the ground plane act as an electromagnetic reflector and also enhance the isolation between two antennas (S12 < ?20 dB). Archetype of proposed MIMO antenna design has been fabricated and tested to validate the simulated results. The proposed antenna operates at three different frequency bands 2.24–2.38 GHz, 2.5–3.26 GHz, and 4.88–7.0 GHz (S11 < ?6 dB) with the fractional bandwidth 6.06%, 26.4%, and 35.7%, respectively. Folded microstrip lines generate path delay between the electric field lines and originate circular polarization characteristics in the frequency range 5.55–5.75 GHz with the fractional bandwidth of 3.55%. In order to satisfy the different performance requirement of MIMO antenna such as envelop correlation coefficient, mean effective gain, effective diversity gain, peak gain are also examined. The proposed antenna is found suitable for LTE2500, WLAN, and WiMAX applications. © 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2016. 相似文献