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   440篇
  免费   21篇
电工技术   3篇
化学工业   100篇
金属工艺   1篇
机械仪表   9篇
建筑科学   32篇
矿业工程   2篇
能源动力   41篇
轻工业   56篇
水利工程   4篇
无线电   25篇
一般工业技术   91篇
冶金工业   13篇
原子能技术   3篇
自动化技术   81篇
  2023年   3篇
  2021年   8篇
  2020年   3篇
  2019年   7篇
  2018年   10篇
  2017年   14篇
  2016年   11篇
  2015年   10篇
  2014年   16篇
  2013年   29篇
  2012年   22篇
  2011年   30篇
  2010年   14篇
  2009年   18篇
  2008年   21篇
  2007年   23篇
  2006年   21篇
  2005年   25篇
  2004年   7篇
  2003年   15篇
  2002年   13篇
  2001年   4篇
  2000年   6篇
  1999年   12篇
  1998年   5篇
  1997年   4篇
  1995年   4篇
  1994年   5篇
  1993年   7篇
  1992年   6篇
  1991年   6篇
  1990年   6篇
  1989年   3篇
  1988年   4篇
  1987年   2篇
  1986年   3篇
  1985年   7篇
  1984年   3篇
  1983年   4篇
  1982年   9篇
  1981年   4篇
  1980年   6篇
  1979年   2篇
  1978年   3篇
  1977年   3篇
  1976年   2篇
  1974年   2篇
  1972年   5篇
  1963年   3篇
  1956年   1篇
排序方式: 共有461条查询结果,搜索用时 171 毫秒
71.
Development of thin-film deodorizers started in the 1970ies, and they have been in industrial use since the middle of the 1980ies. The latest type is the SoftColumnTM, a deodorizer specially developed for mild, low cost processing of seed oils. This deodorizer consists of a structured packing section and a flexible holding section. Regenerative oil heating/cooling and final heating is carried out in external, sparged vacuum heat exchangers, and the design of the heat exchangers leads to superior heat recovery and savings in fuel consumption. This set-up provides major advantages with regard to oil quality, economy, and flexibility. The extremely effective stripping of free fatty acids (FFAs) leads to shorter overall holding times of the oil at elevated temperatures, and steam consumption is cut to a third of the amount required in conventional deodorizers. The product oil has not only low acidity, low colour, good taste and stability, but also low trans fatty acid (TFA) concentrations. By adjusting the stripping steam flow the plant can be optimized both for tocopherol retention or removal. Flexible holding times allow optimization of heat bleaching/TFA formation without compromising on capacity. In this paper product analysis data on tocopherol and trans fatty acids from thin-film deodorizers in industrial operation are shown.  相似文献   
72.
Hydrothermal Treatment of Starch in Presence of α-Amylase. Part 3: Changes of Rheological Properties of Wheat Starch by Hydrothermal Enzymatic Treatment . In order to change functional properties of wheat starch the feasibility for a hydrothermal enzymatic modification under conditions of excess water (annealing) has been tested. The granular structure of the starch should remain unchanged at the same time. Since wheat starch may be changed negligiblely at usual conditions of annealing (T=50°C) as a consequence of its rather low swelling temperature a bacterial α-amylase has been used for partial degradation of these portions of starch granules which gelatinize irreversiblely at higher levels of annealing temperatures. The resulting spectrum of saccharides consisting mainly of maltose (approx. 50%) allows the protection of the wheat starch matrix even at higher annealing temperatures (54°C). However, the gelatinization and gelation behaviour is changed in a characteristic way, in particular by a serious increase of the hot paste consistency at 95°C. In the following, the obtained consistency collapses significantly and arrives by cooling a level below the corresponding figures of the native starch. With respect to yield of annealed starch the reaction time at elevated temperature is of main importance. In order to demonstrate the protecting activity of the produced saccharides in particular with higher concentrations of maltose samples have been annealed in maltose sirups of varied concentration (6, 12, 25%m/m). Up to concentrations of 12%m/m and reaction temperatures of 50°C the Brabender consistency curves could be raised by 300 to 500BU. The application of 54°C limited the effect of modification. Using a 25%m/m maltose syrup allowed, of course, successfully the annealing at 54°C. As expected, yield losses remained low (< 10%). In applying a temperature-time-regime by steps together with a treatment by α-Amylase or alternatively 25%m/m maltose syrup the expected shifting of consistency curves could be observed as well, however, to a limited amount. Finally, pronounced differences could be found for the yield of modified starches.  相似文献   
73.
Müller T  Müller D  Dubois R 《Applied optics》2006,45(10):2295-2305
Spectral particle extinction coefficients of atmospheric aerosols were measured with, to the best of our knowledge, a newly designed differential optical absorption spectroscopy (DOAS) instrument. A closure study was carried out on the basis of optical and microphysical aerosol properties obtained from nephelometer, particle soot/absorption photometer, hygroscopic tandem differential mobility analyzer, twin differential mobility particle sizer, aerodynamic particle sizer, and Berner impactors. The data were collected at the urban site of Leipzig during a period of 10 days in March 2000. The performance test also includes a comparison of the optical properties measured with DOAS to particle optical properties calculated with a Mie-scattering code. The computations take into account dry and ambient particle conditions. Under dry particle conditions the linear regression and the correlation coefficient for particle extinction are 0.95 and 0.90, respectively. At ambient conditions these parameters are 0.89 and 0.97, respectively. An inversion algorithm was used to retrieve microphysical particle properties from the extinction coefficients measured with DOAS. We found excellent agreement within the retrieval uncertainties.  相似文献   
74.
In the past flavor research and the development of new flavorings were constantly driven by the interaction of flavor analysis, structure elucidation, and chemical synthesis accompanied by sensory. Highly potent flavor compounds were identified in numerous food products and helped to establish a powerful toolbox for flavorists. Nowadays we experience the merging of various scientific disciplines, for example medicine, biology, chemistry, and various technologies in the field of flavor research, which shows direct impact on our understanding of flavors. At the same time modern life has profoundly changed our eating habits. This situation generates new challenges for product development teams, which represent all facets of technologies. This paper will illustrate different examples for the evolution of product-oriented flavor research and future trends.  相似文献   
75.
The development of electric mobility systems with fuel cells is associated with a special constellation of circumstances. The definition of powertrain systems on board electric vehicles is dependent on the refueling infrastructure. At the same time, the development of a hydrogen infrastructure is dependent on vehicle definition and introduction. The joint development of powertrain and infrastructure is a unique opportunity to optimize both the systems. In this paper, we select a number of tradeoffs between the powertrain design and the infrastructure design and calculate technical and financial effects. By way of example we show an optimization of the fuel cell, battery and tank size subject to user behavior and infrastructure constraints. Using powertrain simulations we calculate hybridization ratio and tank size. We then show an exemplary infrastructure layout consisting of transmission and distribution networks. In this paper we consider the infrastructure in Germany by 2030. We then proceed to show the implications of the mutual dependencies between vehicle and infrastructure and to analyze technical potentials and overall system costs. Our main conclusions show ways that could be beneficial for the introduction of electric mobility with fuel cells and a hydrogen infrastructure.  相似文献   
76.
Laser ablation-inductively coupled plasma mass spectrometry (LA-ICPMS) is a powerful method for elemental fingerprinting of solid samples in a quasi-nondestructive manner. In order to extend the field of application to objects outside the laboratory, a portable laser ablation sampling device was assembled using a diode pumped solid state laser and fiber-optics. The ablated materials were sampled on membrane filters and subsequently quantified by means of LA-ICPMS. The analytical performance of this approach was investigated for glass and gold reference materials. Accuracies of better than 20% were reached for most elements and typical limits of detection were found to be in the range of 0.01-1 μg/g. In summary, this approach combines spatially resolved sampling with the detection power of ICPMS and enables elemental fingerprinting of objects which cannot be transferred to the laboratory, e.g., archeological artifacts in museums.  相似文献   
77.
78.
79.
Uncertainties in energy demand modelling allow for the development of different models, but also leave room for different calibrations of a single model. We apply an automated model calibration procedure to analyse calibration uncertainty of residential sector energy use modelling in the TIMER 2.0 global energy model. This model simulates energy use on the basis of changes in useful energy intensity, technology development (AEEI) and price responses (PIEEI). We find that different implementations of these factors yield behavioural model results. Model calibration uncertainty is identified as influential source for variation in future projections: amounting 30% to 100% around the best estimate. Energy modellers should systematically account for this and communicate calibration uncertainty ranges.  相似文献   
80.
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