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   10074篇
  免费   464篇
  国内免费   226篇
电工技术   302篇
综合类   301篇
化学工业   1447篇
金属工艺   339篇
机械仪表   461篇
建筑科学   1057篇
矿业工程   124篇
能源动力   659篇
轻工业   387篇
水利工程   275篇
石油天然气   175篇
武器工业   37篇
无线电   398篇
一般工业技术   2004篇
冶金工业   207篇
原子能技术   42篇
自动化技术   2549篇
  2024年   12篇
  2023年   133篇
  2022年   143篇
  2021年   205篇
  2020年   223篇
  2019年   279篇
  2018年   283篇
  2017年   381篇
  2016年   435篇
  2015年   417篇
  2014年   457篇
  2013年   1062篇
  2012年   411篇
  2011年   537篇
  2010年   383篇
  2009年   493篇
  2008年   476篇
  2007年   451篇
  2006年   423篇
  2005年   374篇
  2004年   351篇
  2003年   321篇
  2002年   287篇
  2001年   198篇
  2000年   212篇
  1999年   204篇
  1998年   236篇
  1997年   180篇
  1996年   227篇
  1995年   147篇
  1994年   149篇
  1993年   104篇
  1992年   106篇
  1991年   87篇
  1990年   44篇
  1989年   47篇
  1988年   40篇
  1987年   40篇
  1986年   22篇
  1985年   40篇
  1984年   33篇
  1983年   35篇
  1982年   21篇
  1981年   10篇
  1980年   20篇
  1979年   8篇
  1978年   10篇
  1977年   5篇
  1975年   2篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
981.
The latest developments regarding autonomous vehicles (AVs) have drawn the attention of tech-savvy individuals and marketers. AVs are expected to cause a major change in the markets of vehicle selling, transportation and logistics. Therefore, it is crucial to understand consumer acceptance so that the companies in these markets can develop their penetration strategies accordingly and technology companies can shape their technology development strategies. This study aims to examine individuals' adoption attitudes toward AVs by considering trust and sustainability concerns. This was achieved by expanding the technology acceptance model (TAM). A survey of 391 participants was conducted and the data were analyzed using structural equation modeling (SEM). The results confirmed previous technology acceptance models by showing the relationships between perceived usefulness, perceived ease of use, and behavioral intention. Moreover, the direct and indirect effects of trust on behavioral intention were also shown. This study provides evidence to extend the TAM to the adoption of AVs by uncovering individuals’ sustainability concerns.  相似文献   
982.
The mechanical properties of technical materials depend on their structure. They are influenced not only by their chemical composition, but particularly by the structural grain size. Significant changes in the mechanical behaviour of materials are related both to surface and volume properties, and not only in the field of mechanical parameters. A wide range of physical and chemical parameters changes as well. Nano‐materials are the materials, the structural grain size of which is in the dimensional area from 10?9 to 10?7 m. Nano‐particles and nanostructures are thus so small that their behaviour is affected by atomic forces, properties of chemical bonding, and quantum phenomena. The wave nature of the very small particles begins to manifest itself. The aim of the authors is to contribute by their paper to the solution of the problems in the field of material engineering. This means to investigate the specifics in the behaviour of technical materials depending on the change in the structural grain size towards the nano‐areas, as well as the design and use of new techniques of mathematical and physical modelling including the operative measurement method.  相似文献   
983.
We present a novel approach allowing for a simple, fast and automated morphological analysis of three-dimensional image stacks (z-stacks) featuring fibrillar structures from optically cleared soft biological tissues. Five non-atherosclerotic tissue samples from human abdominal aortas were used to outline the multi-purpose methodology, applicable to various tissue types. It yields a three-dimensional orientational distribution of relative amplitudes, representing the original collagen fibre morphology, identifies regions of isotropy where no preferred fibre orientations are observed and determines structural parameters throughout anisotropic regions for the analysis and numerical modelling of biomechanical quantities such as stress and strain. Our method combines optical tissue clearing with second-harmonic generation imaging, Fourier-based image analysis and maximum-likelihood estimation for distribution fitting. With a new sample preparation method for arteries, we present, for the first time to our knowledge, a continuous three-dimensional distribution of collagen fibres throughout the entire thickness of the aortic wall, revealing novel structural and organizational insights into the three arterial layers.  相似文献   
984.
One-shot anonymous unselfishness in economic games is commonly explained by social preferences, which assume that people care about the monetary pay-offs of others. However, during the last 10 years, research has shown that different types of unselfish behaviour, including cooperation, altruism, truth-telling, altruistic punishment and trustworthiness are in fact better explained by preferences for following one''s own personal norms—internal standards about what is right or wrong in a given situation. Beyond better organizing various forms of unselfish behaviour, this moral preference hypothesis has recently also been used to increase charitable donations, simply by means of interventions that make the morality of an action salient. Here we review experimental and theoretical work dedicated to this rapidly growing field of research, and in doing so we outline mathematical foundations for moral preferences that can be used in future models to better understand selfless human actions and to adjust policies accordingly. These foundations can also be used by artificial intelligence to better navigate the complex landscape of human morality.  相似文献   
985.
用非线性建模选取选矿工艺参数值   总被引:1,自引:0,他引:1  
神经网络在用于选矿厂建模过程中,一般只用于预测选矿效果,很少用于指导选矿现场。本研究利用神经网络,从选矿生产历史数据本身出发,找到精矿品位和回收率与药剂用量的非线性关系,利用此关系确定药剂的用量,可用于指导选厂实际生产过程。  相似文献   
986.
为了改进工业建筑立面呆板、空间单调、使用条件落后的现状,利用钢结构的特殊造型、大柱距、大跨度等特点来达到工业建筑设计中技术与艺术完美的结合。  相似文献   
987.
J.F. Lyness  BSc  MSc  PhD  CEng  MICE  MIStructE  W. R. C. Myers  BA  BSc  PhD  CEng  MICE  J. B. Wark  BEng  PhD 《Water and Environment Journal》1997,11(5):335-340
Flow measurements have been taken for steady and unsteady flows on a reach of a river having a compact compound channel. The 'single channel', 'divided channel' and 'lateral' distribution methods have been used to calculate conveyances for use in a one-dimensional unsteady flow model of the reach. Comparisons with measured flows show that the divided channel method and the lateral distribution method both underestimate floodplain flow depths. The lateral distribution method gives the closest accuracy in the relative depth range 0.15 ≤ Yr < 0.40. For large flow depths the single channel method becomes more accurate and slightly over-estimates flow depths.
The accuracy of unit width discharge distributions, calculated from the lateral distribution method are assessed by comparison with observed distributions for overbank flows.  相似文献   
988.
Barat R  Montoya T  Seco A  Ferrer J 《Water research》2011,45(12):3744-3752
The biologically induced precipitation processes can be important in wastewater treatment, in particular treating raw wastewater with high calcium concentration combined with Enhanced Biological Phosphorus Removal. Currently, there is little information and experience in modelling jointly biological and chemical processes. This paper presents a calcium phosphate precipitation model and its inclusion in the Activated Sludge Model No 2d (ASM2d). The proposed precipitation model considers that aqueous phase reactions quickly achieve the chemical equilibrium and that aqueous-solid change is kinetically governed. The model was calibrated using data from four experiments in a Sequencing Batch Reactor (SBR) operated for EBPR and finally validated with two experiments. The precipitation model proposed was able to reproduce the dynamics of amorphous calcium phosphate (ACP) formation and later crystallization to hydroxyapatite (HAP) under different scenarios. The model successfully characterised the EBPR performance of the SBR, including the biological, physical and chemical processes.  相似文献   
989.
This paper presents the results of an experimental programme for a new blind bolted connection to unfilled hollow section (HS) columns under static loading. In this connection, channels with side plates connect beam flanges to the side face of HS columns. This is a simple alternative connection to typical face connections, i.e. the extended endplate connection or the T-stub connection (with T-stubs connecting the top and bottom flanges of the beam to the face of the column). The channel side plate connection was found to be much stiffer than a typical face connection and has the potential to achieve a rigid connection status for braced frames according to the EC3 classifications. Comparison of the test results and three dimensional finite element (FE) modelling indicates that the FE analyses can be used to predict the connection behaviour with sufficient accuracy. The preliminary investigation for the channel side plate connection shows promising results and forms the basis for the development of other blind bolted side connections for applications in the low rise construction industry.  相似文献   
990.
Obstacles considerably influence boundary layer processes. Their influences have been included in mesoscale models (MeM) for a long time. Methods used to parameterise obstacle effects in a MeM are summarised in this paper using results of the mesoscale model METRAS as examples. Besides the parameterisation of obstacle influences it is also possible to use a joint modelling approach to describe obstacle induced and mesoscale changes. Three different methods may be used for joint modelling approaches: The first method is a time-slice approach, where steady basic state profiles are used in an obstacle resolving microscale model (MiM, example model MITRAS) and diurnal cycles are derived by joining steady-state MITRAS results. The second joint modelling approach is one-way nesting, where the MeM results are used to initialise the MiM and to drive the boundary values of the MiM dependent on time. The third joint modelling approach is to apply multi-scale models or two-way nesting approaches, which include feedbacks from the MiM to the MeM. The advantages and disadvantages of the different approaches and remaining problems with joint Reynolds-averaged Navier-Stokes modelling approaches are summarised in the paper.  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