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   326篇
  免费   12篇
化学工业   87篇
金属工艺   1篇
机械仪表   4篇
建筑科学   14篇
能源动力   16篇
轻工业   77篇
水利工程   1篇
无线电   28篇
一般工业技术   33篇
冶金工业   45篇
原子能技术   1篇
自动化技术   31篇
  2024年   1篇
  2023年   2篇
  2022年   21篇
  2021年   19篇
  2020年   4篇
  2019年   5篇
  2018年   4篇
  2017年   7篇
  2016年   10篇
  2015年   7篇
  2014年   17篇
  2013年   22篇
  2012年   14篇
  2011年   18篇
  2010年   6篇
  2009年   24篇
  2008年   22篇
  2007年   21篇
  2006年   13篇
  2005年   16篇
  2004年   10篇
  2003年   10篇
  2002年   4篇
  2001年   4篇
  2000年   7篇
  1999年   6篇
  1998年   10篇
  1997年   8篇
  1996年   5篇
  1995年   1篇
  1994年   4篇
  1993年   4篇
  1992年   1篇
  1991年   1篇
  1990年   3篇
  1989年   1篇
  1985年   1篇
  1978年   2篇
  1977年   1篇
  1976年   2篇
排序方式: 共有338条查询结果,搜索用时 15 毫秒
81.
The mechanical properties of fibre composite materials are largely determined by the orientation of fibres within the matrix. Which orientation distribution short fibres follow in different parts of a structural element is still a subject for research and discussions in the scientific community. In this article, we present a modern and advanced method for measuring the orientation of short fibres in steel fibre-reinforced concrete (SFRC) by X-ray microtomography. With this method, a voxel image of the fibres is obtained directly in 3D, and the orientation of each individual fibre is calculated based on a skeletonized representation of this image. Scans of 12 SFRC samples, taken from the central height region of real-size floor slabs, reveal the fibres to be mostly horizontally oriented near the centre of a floor slab and more vertically oriented near the edge; here the alignment with the formwork dominates. The fibre orientation distributions are characterized by several orientation parameters as quantitative measures for the alignment. On the practical side, this method has the potential to be incorporated into the development and production process of SFRC structures to verify how the fibres contribute to capacity.  相似文献   
82.
这是一个位于火车站的车库项目,该项目的目的是建立一个平台。其作用是对火车进行保护,同时保证和提高列车对气候的适应度。这些作用到目前为止尚未开发。该建筑被认为是一个大型的透明容器,拥有足够大的容量对火车进行庇护,保证车辆远离外界的恶意破坏,并减少对周围环境的视觉冲击。无论是周围的乡村景观、茂密的植被还是季节的变化,这座建筑都将它们整合到了一起。  相似文献   
83.
Static high pressure treatment has become a gentle alternative in sterilization of fluids, but due to high costs, this technology is currently restricted to high‐quality products. The innovative use of dynamic high pressure has the potential to overcome these restrictions as the introduction of additional process parameters allows for amplification of lethal effects on microorganisms. In addition, through the possibility to further convey the product during low‐pressure periods, the dynamic treatment also enables quasi‐continuous modes of operation, which opens a broader field of applications.  相似文献   
84.
Investigations of environmental pollution by endocrine-disrupting chemicals are now in progress. Up to now, several in vitro bioassays have been developed for evaluation of the endocrine disruptive activity; however, there is still a lack of comparative studies of their sensitivity.In this work comparison of the estrogen screening assay based on β-galactosidase expression and a bioluminescent estrogen screen revealed differences in the sensitivity and specificity of the two tests. With the β-galactosidase screen a slight estrogen-like activity of Delor 103, a commercial mixture of PCB congeners, and a fungicide triclosan was measured whereas no activity was detected using the bioluminescent assay. A bioluminescent androgen test negated previously suggested androgenic potential of triclosan.Further, this work demonstrates the androgenic activity of Delor 103, with an EC50 value of 2.29 × 10− 2 mg/L. On the other hand, chlorobenzoic acids (CBAs), representing potential PCB degradation metabolites, exhibited no androgenic activity but were slightly estrogenic. Their estrogenicity varied with their chemical structure, with 2,3-CBA, 2,3,6-CBA, 2,4,6-CBA and monochlorinated compounds exhibiting the highest activity. Thus the results indicated possible transitions of the hormonal activity of PCBs during bacterial degradation.  相似文献   
85.
86.
The Candida albicans CDR1 gene encodes a member of the ABC-type family of multidrug transporters which has been shown to be involved in azole resistance. Using an in-frame gene fusion between the CDR1 open reading frame and the green fluorescent protein allele yEGFP3, an optimized derivative for its use in C. albicans, we show here how the CDR1-yEGFP3 gene expression is induced in response to azoles as well as to other structurally unrelated drugs like cycloheximide. Moderate increases were observed for calcofluor, canavanine, 5′-fluorcytosine, cilofungin and caffeine, while no induction was found for the antifungals benomyl and amphotericin B or hydrogen peroxide at subinhibitory concentrations. The use of confocal microscopy enabled us to localize the Cdr1p fusion protein at the cell periphery, thus suggesting a cytoplasmic membrane localization. These results suggest deregulation of CDR1 gene as a putative mechanism for the generation of azole resistance in this clinically important pathogenic fungus. © 1998 John Wiley & Sons, Ltd.  相似文献   
87.
Acute lung injury (ALI) is a group of lung illnesses characterized by severe inflammation, with no treatment. The fatty acid amide hydrolase (FAAH) enzyme is an integral membrane protein responsible for the hydrolysis of the main endocannabinoids, such as anandamide (AEA). In pre-clinical pain and inflammation models, increasing the endogenous levels of AEA and other bioactive fatty acid amides (FAAs) via genetic deletion or the pharmacological inhibition of FAAH produces many analgesic benefits in several different experimental models. To date, nobody has investigated the role of FAAH inhibition on an ALI mouse model. Mice were subjected to a carrageenan injection and treated orally 1 h after with the FAAH inhibitor URB878 dissolved in a vehicle consisting of 10% PEG-400, 10% Tween-80 and 80% saline at different doses: The inhibition of FAAH activity was able to counteract not only the CAR-induced histological alteration, but also the cascade of related inflammatory events. URB878 clears the way for further studies based on FAAH inhibition in acute lung pathologies.  相似文献   
88.
The current article focuses on the possibilities of applying bumblebees as one of the biodiversity indicators in the monitoring and evaluation of the Estonian Agri-Environmental Programme (AEP) at landscape level. The need for agri-environmental indicators arises, at least partially, because the desired state of the environment sought by policy makers may not be directly observable. To develop agri-environmental measures favourable to landscape quality, it is necessary to know more about the relationship between landscape structure and composition and the number of different species. This study tested the relationship between the data sets of landscape elements and bumblebee communities from 11 agricultural areas in Estonia. The localities were divided into two groups: intensively used agricultural areas (IA) (the percentage of arable land was >65%) and less intensively used agricultural areas (LIA) (the percentage of arable land was <45%). The following elements of landscape structure were analysed: buffer zones narrower than 5 m and wider than 5 m, ecotones between cultivated land and broad-leaved forests, ecotones between cultivated land and mixed or coniferous forests, ditches and brooks, fallow land, mixed forests, coniferous forests, broad-leaved forests, bushes, wetlands, cultivated grasslands, pastures, legumes, arable land, semi-natural grasslands. Fifteen bumblebee species were recorded in LIA and 13 in IA. The most widely distributed and abundant species were Bombus lucorum, Bombus pascuorum and Bombus lapidarius. These species dominated in both types of agricultural area. Two species, Bombus jonellus and Bombus hypnorum were found only in LIA. Principal component analysis (PCA) was applied to the landscape elements and the bumblebee species found. Results showed that there was a significant co-structure between the data sets of landscape elements and bumblebee communities. The most important landscape features that correlated with the distribution of the bumblebee species were the ecotone length between cultivated land and forests, and the size of the area covered with mixed forests and wetlands.  相似文献   
89.
90.
This article deals with the development of a multicriteria analysis, and its application to the optimization of batch emulsion polymerization processes. This new approach in the domain of polymer reaction engineering illustrates how a multiobjective optimization aided by a genetic algorithm and using the Pareto concept of domination is useful. In this process (emulsion homopolymerization of styrene), several objectives were simultaneously required, e.g., a high quality of the resulting products together with a high productivity. The aim of this study was to find the optimal experimental conditions to obtain simultaneously the minimum reaction time and designed values for both average molecular weights and particles size. To do that, an adapted mathematical model, able to describe all the process physicochemical phenomena, was been first elaborated. The multicriteria analysis then gave a set of nondominated points with conflicting criteria. A decision support system was then developed and applied to rank the Pareto solutions set and to propose some good solutions by taking into account the decision maker's preferences. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2383–2396, 2003  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