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   443篇
  免费   41篇
电工技术   3篇
化学工业   143篇
金属工艺   8篇
机械仪表   8篇
建筑科学   15篇
能源动力   11篇
轻工业   67篇
水利工程   3篇
无线电   49篇
一般工业技术   59篇
冶金工业   13篇
原子能技术   5篇
自动化技术   100篇
  2023年   5篇
  2022年   16篇
  2021年   21篇
  2020年   19篇
  2019年   18篇
  2018年   26篇
  2017年   17篇
  2016年   21篇
  2015年   16篇
  2014年   23篇
  2013年   28篇
  2012年   31篇
  2011年   34篇
  2010年   23篇
  2009年   14篇
  2008年   30篇
  2007年   29篇
  2006年   16篇
  2005年   22篇
  2004年   11篇
  2003年   6篇
  2002年   6篇
  2001年   5篇
  2000年   9篇
  1999年   7篇
  1998年   4篇
  1997年   6篇
  1996年   3篇
  1995年   2篇
  1994年   2篇
  1993年   6篇
  1991年   1篇
  1990年   1篇
  1989年   1篇
  1988年   1篇
  1984年   1篇
  1983年   2篇
  1977年   1篇
排序方式: 共有484条查询结果,搜索用时 15 毫秒
91.
Our analysis of the microwave dielectric properties of the δ-Bi2O3–Nb2O5 solid solution (δ-BNss) showed a continuous increase in permittivity and dielectric losses with an increasing concentration of Nb2O5. The only discontinuity was found for the temperature coefficient of resonant frequency, which is negative throughout the entire homogeneity range but reaches a minimum value for the sample with 20 mol% Nb2O5. At the same composition there is a discontinuity in the grain size of the δ-BNss ceramics. For the sample containing 25 mol% Nb2O5 two structural modifications were observed. A single-phase tetragonal Bi3NbO7, in the literature referred to as a Type-III phase, is formed in a very narrow temperature range from 850° to 880°C. A synthesis performed below or above this temperature range resulted in the formation of the end member of the δ-BNss homogeneity range. Compared with the δ-BNss the Bi3NbO7 ceramics exhibit lower microwave dielectric losses, an increased conductivity, and a positive temperature coefficient of resonant frequency.  相似文献   
92.
The inverse fiuidization airlift bioreactor offers a simple solution to the problem of handling shear sensitive cultures and/or systems requiring biofilm growth control. This unit combines in a single vessel the hydrodynamic behavior of concentric tube airlift aerators or contactors and liquid-solid fluidized beds. The effects of the diameter of the concentric tubes, liquid level, bed properties and gas flow rate on gas holdup, bed expansion and liquid circulation velocity were investigated in this study. The Zuber and Findlay relation (1965) gives satisfactory results for gas holdup. The inverse bed expansion can be predicted by the Richardson and Zaki correlation (1953). The liquid circulation velocity can be calculated using a mechanical energy balance  相似文献   
93.
Aspect-oriented programming (AOP) has been successfully applied to application code thanks to techniques such as Java bytecode instrumentation. Unfortunately, with existing AOP frameworks for Java such as AspectJ, aspects cannot be woven into the standard Java class library. This restriction is particularly unfortunate for aspects that would benefit from comprehensive aspect weaving with complete method coverage, such as profiling or debugging aspects. In this article we present MAJOR, a new tool for comprehensive aspect weaving, which ensures that aspects are woven into all classes loaded in a Java Virtual Machine, including those in the standard Java class library. MAJOR includes the pluggable module CARAJillo, which supports efficient access to a complete and customizable calling context representation. We validate our approach with three case studies. Firstly, we weave existing profiling aspects with MAJOR which otherwise would generate incomplete profiles. Secondly, we introduce an aspect for memory leak detection that also benefits from comprehensive weaving. Thirdly, we present an aspect subsuming the functionality of ReCrash, an existing tool based on low-level bytecode instrumentation techniques that generates unit tests to reproduce program failures. Our aspect-based tools are concisely implemented in a few lines of code, and leverage MAJOR and CARAJillo for comprehensive aspect weaving and for efficient access to calling context information.  相似文献   
94.
This paper is concerned with the computational efficiency of fuzzy clustering algorithms when the data set to be clustered is described by a proximity matrix only (relational data) and the number of clusters must be automatically estimated from such data. A fuzzy variant of an evolutionary algorithm for relational clustering is derived and compared against two systematic (pseudo-exhaustive) approaches that can also be used to automatically estimate the number of fuzzy clusters in relational data. An extensive collection of experiments involving 18 artificial and two real data sets is reported and analyzed.  相似文献   
95.
The paper reports our research aiming at utilization of human interactive communication modeling principles in application to a novel interaction paradigm designed for brain–computer/machine-interfacing (BCI/BMI) technologies as well as for socially aware intelligent environments or communication support systems. Automatic procedures for human affective responses or emotional states estimation are still a hot topic of contemporary research. We propose to utilize human brain and bodily physiological responses for affective/emotional as well as communicative interactivity estimation, which potentially could be used in the future for human–machine/environment interaction design. As a test platform for such an intelligent human–machine communication application, an emotional stimuli paradigm was chosen to evaluate brain responses to various affective stimuli in an emotional empathy mode. Videos with moving faces expressing various emotional displays as well as speech stimuli with similarly emotionally articulated sentences are presented to the subjects in order to further analyze different affective responses. From information processing point of view, several challenges with multimodal signal conditioning and stimuli dynamic response extraction in time frequency domain are addressed. Emotions play an important role in human daily life and human-to-human communication. This is why involvement of affective stimuli principles to human–machine communication or machine-mediated communication with utilization of multichannel neurophysiological and periphery physiological signals monitoring techniques, allowing real-time subjective brain responses evaluation, is discussed. We present our preliminary results and discuss potential applications of brain/body affective responses estimation for future interactive/smart environments.  相似文献   
96.
In the last three decades, several vernacular names of medicinal plants related to manufactured drugs names have been recognized in ethnobotanical surveys throughout Brazil. The medicalization may be the primarily responsible process for the rise of that type of vernacular names of Brazilian medicinal plants differentially for each geopolitical region of Brazil. We attempt to trace the regionalization of medicalization on vernacular names of medicinal plants through ethnobotanical studies carried out in Brazil since the 1980s. Articles were consulted in nine journals published between 1980 and 2014. Richness estimation by Jackknife 1 and correspondence analysis by contingency tables were performed, both by the occurrence of medicalized names collected in the surveys for each region. The South region presented the highest number of reported and estimated medicalized names, in addition to present the highest number of medicalized names in exclusive occurrence. Northeast and Southeast regions presented a great similarity of medicalized names probably due to the migration flows occurring in both regions over the twentieth century.  相似文献   
97.
Nowadays visual search is one of the most active branches of computer vision. It relies on finding invariant points inside images, describing them into features and then matching these features against a reference database to identify objects in the scene or the entire photo (environment). In this paper, we discuss an approach to feature matching that exploits the capabilities of modern GPUs to speed up the aforementioned and that keeps low the number of false matches.  相似文献   
98.
In striving to achieve autonomous navigation, the guidance system plays an essential role. In this article, the authors present two recently developed vision-based methods to estimate the heading angle of the vehicle. The authors propose a real-time guidance application based on edge and color information using an omnidirectional image. First, line segments were extracted. Second, the Random Sample Consensus (RANSAC) curve fitting method was implemented. Third, the set of intersection points for each pair of curves was extracted. Finally, by implementing the Density Based Spatial Clustering of Applications with Noise (DBSCAN) algorithms, the heading angle was computed. The main contribution of this work is in the evaluation of the methods applied, which included the “edge-based extraction in road scenes” method, which uses the spatial density information around the vehicle (curbs, barrier, gutters, side strip areas), and the “edge-based lane marking segmentation.” Both of these methods were evaluated in terms of the performance assessment of the length of the line segments in relation to the heading angle measurement. In that sense, the experiments were conducted for the purpose of testing the processing time and the number of extracted line segments. The preliminary results were gathered and tested on a group of consecutive frames to demonstrate the effectiveness of the proposed methods.  相似文献   
99.
100.
Unique among the intracellular lipid binding proteins, acyl-CoA binding protein (ACBP) exclusively binds long-chain fatty acyl-CoAs (LCFA-CoAs). To test if ACBP is an essential protein in mammals, the ACBP gene was ablated by homologous recombination in mice. While ACBP heterozygotes appeared phenotypically normal, intercrossing of the heterozygotes did not produce any live homozygous deficient (null) ACBP(−/−) pups. Heterozygous and wild type embryos were detected at all post-implantation stages, but no homozygous ACBP-null embryos were obtained—suggesting that an embryonic lethality occurred at a pre-implantation stage of development, or that embryos never formed. While ACBP-null embryos were not detected at any blastocyst stage, ACBP-null embryos were detected at the morula (8-cell), cleavage (2-cell), and zygote (1-cell) pre-implantation stages. Two other LCFA-CoA binding proteins, sterol carrier protein-2 (SCP-2) and sterol carrier protein-x (SCP-x) were significantly upregulated at these stages. These findings demonstrate for the first time that ACBP is an essential protein required for embryonic development and its loss of function may be initially compensated by concomitant upregulation of two other LCFA-CoA binding proteins, but only at the earliest pre-implantation stages. The fact that ACBP is the first known intracellular lipid binding protein whose deletion results in embryonic lethality suggests its vital importance in mammals.  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