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   769篇
  免费   24篇
电工技术   14篇
综合类   9篇
化学工业   289篇
金属工艺   34篇
机械仪表   17篇
建筑科学   27篇
矿业工程   2篇
能源动力   49篇
轻工业   42篇
水利工程   8篇
石油天然气   2篇
无线电   61篇
一般工业技术   115篇
冶金工业   28篇
原子能技术   2篇
自动化技术   94篇
  2023年   4篇
  2022年   20篇
  2021年   46篇
  2020年   11篇
  2019年   9篇
  2018年   14篇
  2017年   17篇
  2016年   18篇
  2015年   13篇
  2014年   41篇
  2013年   58篇
  2012年   41篇
  2011年   54篇
  2010年   33篇
  2009年   37篇
  2008年   35篇
  2007年   30篇
  2006年   30篇
  2005年   23篇
  2004年   18篇
  2003年   27篇
  2002年   21篇
  2001年   14篇
  2000年   10篇
  1999年   6篇
  1998年   14篇
  1997年   12篇
  1996年   11篇
  1995年   13篇
  1994年   6篇
  1993年   6篇
  1992年   7篇
  1991年   6篇
  1990年   9篇
  1989年   6篇
  1988年   6篇
  1987年   5篇
  1986年   7篇
  1985年   9篇
  1984年   6篇
  1983年   5篇
  1981年   4篇
  1980年   5篇
  1979年   4篇
  1977年   3篇
  1976年   2篇
  1975年   2篇
  1971年   2篇
  1965年   2篇
  1956年   2篇
排序方式: 共有793条查询结果,搜索用时 15 毫秒
61.
Abstract

The paper examines the influence of a regional planning and development authority (the South West Development Authority) on economic growth in the South West Region of Western Australia. Employment and population changes are analysed along sectoral and spatial criteria. The findings show that between 1983 and 1989, the Authority's influence on the creation of employment opportunities was limited, being confined mostly to some gains in the public sector and to the promotion of the region and the city of Bunbury as tourist destinations. This ineffectiveness is associated with a lack of power to attract private and direct public investment to the region.  相似文献   
62.
Susceptibility of the steel for further cold processing strongly depends on the whole prior history of deformation in the hot working regime.In the industrial hot working processes,e.g.at the roughing stage of hot rolling,or forging,material undergoes complex deformation modes that leads to gradients of both microstructure and properties across the deformed cross-section.Torsion and multiaxial compression tests with different amounts of strain reversals were conducted at elevated temperatures to study the effect of applied strain path on the phenomena occurring during microstructure evolution of Nb-microalloyed steels.Gathered results will provide data for the modification of existing constitutive equations that mostly do not account for the strain path changes.Better through-process modelling will then enable to achieve better properties and quality of the products for further cold processing.  相似文献   
63.
The novel μ3-oxo-bridged heterotrinuclear iron(III)-copper(II) trichloroacetates of the composition [Fe2CuO(CCl3COO)6(THF)3] (1a) and [Fe2CuO(CCl3COO)6(4-DMAP)3] (1b) have been synthesized and characterized by X-ray crystallography, IR and Mossbauer spectroscopy. These clusters were used as precursors for the synthesis of the nanosized catalytic system (~5–6 nm of γ-Fe2O3/CuO), which works as an efficient organic phase catalyst (~0.02 mol%) in a one-pot three component Biginelli synthesis.  相似文献   
64.
In this paper, the influence of membrane separation of CO2 from flue gases and the impacts of the whole CCS process (CO2 separation and compression) on the performance of a coal-fired power plant are studied. First, the effects of the characteristics of the membrane (selectivity and permeability) and the parameters of the process (feed and permeate pressure) on two indices, CO2 recovery rate and CO2 purity are analysed. Next, a method for determining the minimum power loss and efficiency loss of the power plant as a function of these calculated indices is described. Then, the power requirements and efficiency loss (up to 15.4 percentage points) because of the CCS installation are calculated. A method for reducing these losses through the integration of the CCS installation with the power plant is also proposed. The main aims of the integration are heat exchange between media and a decrease in the CO2 temperature before compression. Implementing this process can result in a significant reduction of the efficiency loss by 8 percentage points.  相似文献   
65.
In developing and developed countries, an increasing elderly population is observed. This affects the growing percentage of people struggling with neurodegenerative diseases, including Alzheimer’s disease. Nevertheless, the pathomechanism of this disease is still unknown. This contributes to problems with early diagnosis of the disease as well as with treatment. One of the most popular hypotheses of Alzheimer’s disease is related to the pathological deposition of amyloid-β (Aβ) in the brain of ill people. In this paper, we discuss issues related to Aβ and its relationship in the development of Alzheimer’s disease. The structure of Aβ and its interaction with the cell membrane are discussed. Not only do the extracellular plaques affect nerve cells, but other forms of this peptide as well.  相似文献   
66.
The exoskeleton triglyceride fraction isolated from the Colorado beetle,Leptinotarsa decemlineata Say, was studied. Analysis of the hydrolysis products and direct capillary column gas chromatography showed that, apart from triglycerides, the fraction contained no diol lipids. The composition of the natural triacylglccerol mixture was assessed by gas chromatography and by field desorption and electron impact mass spectrometry. Triglycerides isolated from the Colorado beetle are typical glycerol triesters, with long chain (mainly oleic or palmitic) fatty acids. The structures of two major components (91%), i.e., trioleoyl glycerol and 1,2-dioleoyl-3-palmitoyl glycerol, were determined.  相似文献   
67.
A short survey of cellular automata based models for corrosion and passivation phenomena is given. Results of simulations based on the model of spatially separated anodic and cathodic reactions are presented for a cavity development from a point-like damage of a protective layer and from an initially flat unprotected surface. We show some new peculiar examples of the symmetry breaking in the cavity development. The results for the initially flat surface show roughening of the surface at the beginning of the corrosion process. After that, pit merging causes a resmoothing of the surface. An oscillatory behavior of the surface roughness is observed caused by a peninsula formation with subsequent island detachment. These results are obtained in 2D because of computational limitations. We plan simulations in 3D and point out the problems we encounter in their realization.  相似文献   
68.
69.
Wetting of Cu and Al pads by Sn-Zn eutectic-based alloys with 0.5, 1, and 1.5 wt.% of Cu was studied at 250 °C, in the presence of ALU33® flux, with wetting times of 15, 30, 60, and 180 s, respectively. With increasing wetting time the wetting angle decreases only slightly and the angles on Cu pads are higher than those on Al pads. Selected, solidified solder-pad couples were cross-sectioned and subjected to SEM-EDS study of the interfacial microstructure. The results revealed that the microstructure of the SnZnCu/Cu interface is much different from SnZnCu/Al interface. In the first case continuous interlayers are observed while in the latter case there is no interlayer but the alloy dissolves the substrate along grain boundaries.  相似文献   
70.
The transducer applied in sensors and measurement systems often have non-linear characteristics, which may depend on additional factors as temperature, humidity gases flow, etc. Therefore, it is important to find the function describing the dependence between input and output values of a transducer which takes into account all the influencing factors. This paper shows a method which, basing on measured data, allows to establish a multi-variable transducer transfer function.  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