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   2695篇
  免费   192篇
  国内免费   27篇
电工技术   51篇
综合类   14篇
化学工业   607篇
金属工艺   64篇
机械仪表   106篇
建筑科学   141篇
矿业工程   4篇
能源动力   182篇
轻工业   186篇
水利工程   44篇
石油天然气   27篇
无线电   252篇
一般工业技术   439篇
冶金工业   168篇
原子能技术   27篇
自动化技术   602篇
  2024年   8篇
  2023年   51篇
  2022年   98篇
  2021年   172篇
  2020年   152篇
  2019年   182篇
  2018年   176篇
  2017年   165篇
  2016年   153篇
  2015年   111篇
  2014年   183篇
  2013年   279篇
  2012年   197篇
  2011年   221篇
  2010年   142篇
  2009年   141篇
  2008年   82篇
  2007年   44篇
  2006年   54篇
  2005年   43篇
  2004年   26篇
  2003年   26篇
  2002年   27篇
  2001年   17篇
  2000年   14篇
  1999年   14篇
  1998年   22篇
  1997年   13篇
  1996年   12篇
  1995年   12篇
  1994年   6篇
  1993年   10篇
  1991年   5篇
  1990年   5篇
  1987年   4篇
  1986年   4篇
  1985年   4篇
  1984年   5篇
  1983年   4篇
  1982年   4篇
  1981年   2篇
  1980年   2篇
  1979年   2篇
  1978年   4篇
  1977年   5篇
  1975年   6篇
  1974年   1篇
  1970年   1篇
  1969年   1篇
  1965年   1篇
排序方式: 共有2914条查询结果,搜索用时 0 毫秒
91.
This study proposes a versatile criterion for estimating quality of images in electrical impedance tomography. The point spread function (PSF) is calculated throughout the domain based on the scattering of energy as responses to a small anomaly spirally moved from the centre to the boundary. The proposed PSF is a measure of weighted spatial variance (WSV) of the conductivity over the whole domain. For each element, the weighting factor is a normalized multiplication of the area of that element by its square intensity. The WSV collectively incorporates all image attributes, i.e., spatial resolution, artifact, amplitude response, positioning error and shape deformation. The location of artifacts, which significantly influences reconstructed images in reality, is taken into account as well. The results illustrate that the proposed measure is more tolerant than existing criteria in evaluating performance of EIT systems in both theory and practice.  相似文献   
92.
93.
In opportunistic networks due to the inconsistency of the nodes link, routing is carried out dynamically and we cannot use proactive routes. In these networks, nodes use opportunities gained based on store-carry-forward patterns to forward messages. Every node that receives a message when it encounters another node makes decision regarding the forwarding or not forwarding the node encountered. In some previous methods, the recognition of whether encounter with current node is considered as an appropriate opportunity or not has been carried out based on the comparison of the probability of carrier node and the node encountered. In these methods, if the message is delivered to the encountered node, a better opportunity would be lost. To fight with this challenge we have posed CPTR method by using conditional probability tree method through which in addition to the probability of the delivery of carrier and encountered nodes’ message delivery, the opportunities for after encounter will be involved in messages’ forwarding. Results of simulation showed that the proposed method can improve the ratio of delivery and delay of message delivery compared to other similar methods in networks with limited buffer.  相似文献   
94.
Green vehicles, such as electric vehicles (EVs), are getting noteworthy popularity among consumers worldwide. The purpose of this paper is to establish EVs as a feasible long‐term solution for the future of technology in the vehicle industry, which can decrease the current dependency on fossil fuels and also decrease greenhouse gas (GHG) emissions. As a part of long‐term benefits, the adoption of EVs gives environmentally friendly innovation to society. Despite positive environmental implications, the total number of EVs in usage is still inadequate. One of the major causes of this insubstantial adoption of EVs is largely dependent on the perceptions of consumers regarding EVs. However, this particular research study offers an inclusive outline on the existing hurdles for consumer adoption of EVs as well as a framework of the theoretical standpoints that were developed for the adoption behaviour, in addition to considering consumer intentions in the direction of EVs. In this particular study, the researcher found that the literature regarding EV adoption tried to address only the diffusion method of EVs. Whereas this study highlights consumer innovations, which provides a wide insight on consumer emotions to overlook the major aspect in consumer EVs' adoption research. The theme of this particular literature can be implemented in order to better understand the consumers' emotions and behaviour towards the adoption of EVs. The scholars further stated that there is a possible cause for more recent developments within the technological adoption part that can assist to be a standard for upcoming developments. For the last few years, knowledge regarding the problems surrounding the adoption and diffusion of EVs has gained less attention. This study expands this line of research by focusing on making a chance for developing the theoretical frameworks in terms of adding emotions in a psychological perspective where consumer behaviour and ethics are considered. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   
95.
Although much has been written about TQM in SMEs, little attention has been paid to the role of external consultant in the successful implementation of a TQM program in this kind of firms. Sometimes there are some candidates and companies have to select the best one. In general, many factors affect this problem which adheres to uncertain and imprecise data, and usually several people from different functional areas of the company are involved in this process. This study aims to improve the quality of decision in this area. In this paper a systematic decision process for selecting external consultant is proposed. The proposed method is based on TOPSIS method in fuzzy environment. Decision criteria are obtained from the nominal group technique (NGT). Additionally, a real case study is presented to illustrate the application of the proposed method.  相似文献   
96.
A multi-objective optimal phasor measurement unit placement model using integer linear programming is presented in this article. The proposed model simultaneously optimizes two objectives, i.e., minimization of phasor measurement unit numbers and maximization of measurement redundancy. To calculate the redundancy criteria, the single-line outage and the phasor measurement unit loss are considered simultaneously. A linear formulation is presented for both objective functions. Also herein, to address conflicting attributes and identify Pareto optimal solutions of the multi-objective optimal phasor measurement unit placement problem, a new multi-objective mathematical programming method is proposed. Finally, a new index, i.e., minimum distance to utopia point, is implemented to select the most preferred solution among the available Pareto front based options on the goal to achieve judicious decision makers. Two test systems, i.e., a modified 9-bus and an IEEE 118-bus test systems, are used to illustrate the effectiveness of the proposed framework.  相似文献   
97.
98.
99.
100.
Considering the deterioration of steel properties by temperature increase and the importance of the influence of connection behavior on the behavior of steel structures, we find that the exact understanding of the behavior of a specific steel connection in fire as well as the information about the effect of fire on the principal constitutive characteristics of the connection is necessary for safe design against fire. Thus, in this paper, the behavior of welded angle connections is studied at elevated temperatures using the abaqus finite element software. Steel members and connection components are considered to behave nonlinearly; the degradation of steel properties with increasing temperature is considered according to EC3, BS5950 recommendations. The results of finite element and experimental tests conducted on welded angle connections are compared, and the obtained failure modes and moment–rotation–temperature characteristics are in good agreement with those associated with the experimental tests. In the following, since the knowledge about moment–temperature–rotation behavior of a specific connection is needed for a fire‐resistant design, these properties are accurately determined, and finally, the effect of some parameters such as the moment applied on beam, change of column axial force and change of beam shear force on the stiffness of these connections at elevated temperatures is determined. Copyright © 2011 John Wiley & Sons, Ltd.  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