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   637篇
  免费   50篇
  国内免费   4篇
电工技术   13篇
综合类   2篇
化学工业   174篇
金属工艺   12篇
机械仪表   18篇
建筑科学   11篇
能源动力   53篇
轻工业   47篇
水利工程   6篇
石油天然气   3篇
无线电   60篇
一般工业技术   150篇
冶金工业   47篇
原子能技术   5篇
自动化技术   90篇
  2023年   15篇
  2022年   27篇
  2021年   30篇
  2020年   18篇
  2019年   19篇
  2018年   25篇
  2017年   46篇
  2016年   25篇
  2015年   24篇
  2014年   23篇
  2013年   40篇
  2012年   29篇
  2011年   34篇
  2010年   17篇
  2009年   25篇
  2008年   36篇
  2007年   24篇
  2006年   13篇
  2005年   18篇
  2004年   8篇
  2003年   13篇
  2002年   17篇
  2001年   8篇
  2000年   10篇
  1999年   10篇
  1998年   10篇
  1997年   9篇
  1996年   19篇
  1995年   4篇
  1994年   8篇
  1993年   4篇
  1992年   5篇
  1991年   4篇
  1990年   7篇
  1989年   3篇
  1987年   4篇
  1986年   5篇
  1985年   7篇
  1984年   6篇
  1983年   5篇
  1981年   4篇
  1980年   5篇
  1979年   3篇
  1978年   4篇
  1977年   10篇
  1975年   2篇
  1974年   2篇
  1972年   1篇
  1971年   2篇
  1970年   1篇
排序方式: 共有691条查询结果,搜索用时 15 毫秒
1.
Wireless Personal Communications - In recent years, the emergence of Internet of things and cyber-physical system provide a proactive and efficacious solution to enable remote monitoring, machine...  相似文献   
2.
A two-dimensional plane strain finite element model with absorbing boundary condition has been developed to investigate the ultrasonic wave propagation in isotropic and orthotropic media. It is capable of simulating the experimental pulse echo technique to obtain A-scan data, when a short duration pulse is transmitted into a domain with or without a flaw. The flaw can either be a crack or an inclusion of different material such as a Teflon insert or a resin rich zone. After performing FFT on the A-scan data, frequency domain feature analysis is done. The study provides a guideline regarding the suitability of certain harmonics sensitive to certain types of flaw. The simulation shows other important artifacts of wave propagation such as mode conversion and scattering due to the presence of flaws.  相似文献   
3.
4.
An identification procedure to estimate the parameters of a thermoresistive solar radiation sensor is presented. The proposed technique employs only electrical excitation for the sensor. The estimation algorithm is recursive and is applied to the sensor model derived from the thermodynamic equilibrium differential equations. The simulation and the experimental results demonstrate the validity of the proposed approach  相似文献   
5.
Structural and electrical measurements of CdZnSe composite   总被引:1,自引:0,他引:1  
TheI—Vcharacterization and the electrical resistivity of selenium rich Se85Cd15-xZnx (x = 0, 3, 7, 11 and 15) system at room temperature have been studied. Samples were obtained using melt cooling technique. So prepared samples were then characterized in terms of their crystal structure and lattice parameter using X-ray diffraction method. The materials were found to be poly crystalline in nature, having zinc blend structure over the whole range of zinc concentration. The measurements ofI—V bdcharacteristics have been carried out at different temperatures from room to 140°C. The electrical resistivity of the samples with composition at room temperature has been found to vary between maximum 2.7 x 108 Ωm and minimum 7.3 x 105 Ωm and shows a maximum at 3 at. wt.% of Zn. The carrier activation energy of the samples with composition has also been determined and found to vary from 0.026 eV to 0.111 eV.  相似文献   
6.
The flow due to a rotating disk decelerating with an angular velocity inversely proportional to time with either surface suction (or injection) which again varies with time is investigated. The unsteady Navier-Stokes equations are transformed to non-linear ordinary differential equations using similarity transformations. The resulting equations are solved numerically using a globally convergent homotopy method. The flow depends on two non-dimensional parameters, namely an unsteadiness parameter S and a suction (or injection) parameter A. Some interesting numerical results are presented graphically and discussed.  相似文献   
7.
The promising potential of cloud computing and its convergence with technologies such as mobile computing, wireless networks, sensor technologies allows for creation and delivery of newer type of cloud services. In this paper, we advocate the use of cloud computing for the creation and management of cloud based health care services. As a representative case study, we design a Cloud Based Intelligent Health Care Service (CBIHCS) that performs real time monitoring of user health data for diagnosis of chronic illness such as diabetes. Advance body sensor components are utilized to gather user specific health data and store in cloud based storage repositories for subsequent analysis and classification. In addition, infrastructure level mechanisms are proposed to provide dynamic resource elasticity for CBIHCS. Experimental results demonstrate that classification accuracy of 92.59% is achieved with our prototype system and the predicted patterns of CPU usage offer better opportunities for adaptive resource elasticity.  相似文献   
8.
Syntactic foam slabs having uncoated microballoons and paraffin oil surface‐treated microballoons were fabricated and tested for short‐beam three‐point bend test. The work points to the role of paraffin oil coating first weakening the interface between the microballoons and the matrix and hence lowering the efficiency of load transfer from matrix to the fillers (i.e., microballoons). This led to an overall decrement of 71% in the experimentally measured strength value compared to the deduced value for uncoated microballoons' specimens. The large strengths for uncoated microballoons specimens can be traced to the presence of the curvilinear marks in the matrix that, incidentally, are absent in the case of paraffin oil coated specimens. These observations are revealed distinctly in the microscopy of test‐failed specimens. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 687–693, 2005  相似文献   
9.
Scanning Electron Microscopic (SEM) studies were carried out on the failure surface of syntactic foam material tested in a short beam three point bend test (SBT) by employing 21 × 15 × 3 mm3 dimension bearing specimens. The syntactic foams were fabricated using glass microballoons in epoxy binder. The failure of the tensile, compression, and shear dominated regions were studied by SEM at different magnifications. The tensile region had characteristic features, such as partial debonding of the microballoons from the matrix and cracking of glass microballoons, apart from matrix cracking and some river pattern features. The compression side was characterized by crushing and collapsing of microballoons, resulting in accumulation of debris with no apparent river pattern for matrix‐rich regions. The midway positions of the SBT failed surface comprised of deformation bands in the matrix and occasional debonding of microballoons. The morphology recorded in the tensile and compression regions corroborated well with the results obtained on these foam samples in those specimens that were subjected to pure uniaxial tension and compression, respectively. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 673–679, 2005  相似文献   
10.
Various natural and man-made disasters as well as major political events (like riots) have increased the importance of understanding geographic failures and how correlated failures impact networks. Since mission critical networks are overlaid as virtual networks over a physical network infrastructure forming multilayer networks, there is an increasing need for methods to analyze multilayer networks for geographic vulnerabilities. In this paper, we present a novel impact-based resilience metric. Our new metric uses ideas borrowed from performability to combine network impact with state probability to calculate a new metric called Network Impact Resilience. The idea is that the highest impact to the mission of a network should drive its resilience metric. Furthermore, we present a state space analysis method that analyzes multilayer networks for geographic vulnerabilities. To demonstrate the methods, the inability to provision a given number of upper layer services is used as the criteria for network failure. Mapping techniques for multilayer network states are presented. Simplifying geographic state mapping techniques to reduce enumeration costs are also presented and tested. Finally, these techniques are tested on networks of varying sizes.  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