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   323篇
  免费   2篇
电工技术   5篇
化学工业   35篇
金属工艺   6篇
机械仪表   6篇
建筑科学   15篇
矿业工程   1篇
能源动力   4篇
轻工业   25篇
无线电   49篇
一般工业技术   38篇
冶金工业   73篇
原子能技术   12篇
自动化技术   56篇
  2023年   2篇
  2022年   3篇
  2021年   7篇
  2019年   8篇
  2018年   5篇
  2017年   3篇
  2016年   3篇
  2015年   4篇
  2014年   2篇
  2013年   10篇
  2012年   13篇
  2011年   21篇
  2010年   20篇
  2009年   10篇
  2008年   13篇
  2007年   8篇
  2006年   10篇
  2005年   14篇
  2004年   5篇
  2003年   9篇
  2002年   4篇
  2001年   4篇
  2000年   4篇
  1999年   8篇
  1998年   23篇
  1997年   14篇
  1996年   11篇
  1995年   7篇
  1994年   7篇
  1993年   6篇
  1992年   3篇
  1991年   9篇
  1990年   4篇
  1989年   2篇
  1988年   3篇
  1986年   2篇
  1985年   3篇
  1984年   3篇
  1982年   2篇
  1980年   4篇
  1977年   2篇
  1976年   4篇
  1973年   2篇
  1970年   2篇
  1968年   2篇
  1967年   2篇
  1965年   2篇
  1963年   2篇
  1955年   1篇
  1952年   1篇
排序方式: 共有325条查询结果,搜索用时 15 毫秒
41.
The objectives of this study were (1) to develop an algorithm for the acceleration sensor of the Smartbow Eartag (Smartbow GmbH, Weibern, Austria) to distinguish between postures (lying and standing or locomotion) and to detect 6 kinds of activities (milk intake, water intake, solid feed intake, ruminating, licking or sucking without milk intake, and other activities) in dairy calves and (2) to evaluate this sensor for identifying these behaviors in dairy calves compared with observations from video. Accelerometers were applied to the left ears of 15 preweaned Holstein dairy calves. Calves were kept in a group pen and received milk replacer from an automatic calf feeder. Based on 38 h of acceleration data and video observation, an algorithm was established to detect the predefined behaviors. Using cross-validation, video recordings were used to analyze whether a behavior was detected correctly by the developed algorithm. For posture, sensitivity (94.4%), specificity (94.3%), precision (95.8%), and accuracy (94.3%) were high. Cohen's kappa was calculated as 0.88. For the 6 defined activities, overall (i.e., aggregated for all activities) accuracy was 70.8% and kappa was calculated as 0.58. Some activities (e.g., ruminating, feed intake, other activities) were identified better than others. In conclusion, the developed algorithm based on the acceleration data of the Smartbow Eartag was successful in detecting lying behavior, rumination, feed intake, and other activities in calves, but further development of the underlying algorithm will be necessary to produce reliable results for milk and water intake.  相似文献   
42.
The ability of the "conceptual-area" scoring system to differentiate between tuberculous, process schizophrenic, reactive schizophrenic, and brain-damaged patients was tested by administering the Object Sorting Test to 125 hospitalized veterans. The diagnostic groups were equivalent in mean education, intelligence, and length of hospitalization, but the tuberculous and brain-damaged patients averaged 8 yr. older than the schizophrenics. None of the scores differentiated the groups at the .05 level. In discussing these results, it was maintained that, contrary to comment in the literature, "conceptual area" has never conclusively differentiated, in a simultaneous comparison, between nonpsychiatric, brain-damaged, and schizophrenic patients, and may not be appropriate for this purpose. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
43.
This paper proposes a basic structured light system for pose estimation. It consists of a circular laser pattern and a camera rigidly attached to the laser source. We develop a geometric modeling that allows to efficiently estimate the pose at scale of the system, relative to a reference plane onto which the pattern is projected. Three different robust estimation strategies, including two minimal solutions, are also presented with this geometric formulation. Synthetic and real experiments are performed for a complete evaluation, both quantitatively and qualitatively, according to different scenarios and environments. We also show that the system can be embedded for UAV experiments.  相似文献   
44.
Recnik A  Möbus G  Sturm S 《Ultramicroscopy》2005,103(4):285-301
We have developed a new method for processing distorted high-resolution scanning transmission electron microscopy (STEM) images. The method is based on finding the displaced vertices in the experimental STEM image and warping to geometrically correct reference grid of the object. As a reference grid for warping a structural model obtained using a high-resolution transmission electron microscopy (HRTEM) analysis of the area of interest is utilised. Combined with quantitative HRTEM analysis the IMAGE-WARP method provides a real-space restoration of high-resolution high-angle annular dark-field (HAADF) STEM images without affecting the original Z-contrast information. The method can be applied to extract valuable compositional atomic-column data from any HAADF-STEM image of any kind of bulk crystals with local occupancy or chemistry fluctuations, stacking faults, special grain boundaries or interfaces, for which we have an available structural model. After the warping, distortion-corrected images can be further enhanced using conventional image-filtering techniques, and finally quantified with HAADF-STEM image simulations. The applicability of the IMAGE-WARP method was illustrated using experimental HAADF-STEM images of a strontium titanate crystal disrupted with a Ruddlesden-Popper-type antiphase boundary.  相似文献   
45.
High strength compacted graphite iron (CGI) or alloyed cast iron components are substituting previously used non-ferrous castings in automotive power train applications.The mechanical engineering industry has recognized the value in substituting forged or welded structures with stiff and light-weight cast iron castings.New products such as wind turbines have opened new markets for an entire suite of highly reliable ductile iron cast components.During the last 20 years,casting process simulation has developed from predicting hot spots and solidification to an integral assessment tool for foundries for the entire manufacturing route of castings.The support of the feeding related layout of the casting is still one of the most important duties for casting process simulation.Depending on the alloy poured,different feeding behaviors and self-feeding capabilities need to be considered to provide a defect free casting.Therefore,it is not enough to base the prediction of shrinkage defects solely on hot spots derived from temperature fields.To be able to quantitatively predict these defects,solidification simulation had to be combined with density and mass transport calculations,in order to evaluate the impact of the solidification morphology on the feeding behavior as well as to consider alloy dependent feeding ranges.For cast iron foundries,the use of casting process simulation has become an important instrument to predict the robustness and reliability of their processes,especially since the influence of alloying elements,melting practice and metallurgy need to be considered to quantify the special shrinkage and solidification behavior of cast iron.This allows the prediction of local structures,phases and ultimately the local mechanical properties of cast irons,to asses casting quality in the foundry but also to make use of this quantitative information during design of the casting.Casting quality issues related to thermally driven stresses in castings are also gaining increasing attention.State-of-the-art tools allow the prediction of residual stresses and iron casting distortion quantitatively.Cracks in castings can be assessed,as well as the reduction of casting stresses during heat treatment.As the property requirements for cast iron as a material in design strongly increase,new alloys and materials such as ADI might become more attractive,where latest software developments allow the modeling of the required heat treatment.Phases can be predicted and parametric studies can be performed to optimize the alloy dependent heat treatment conditions during austenitization,quenching and ausferritization.All this quantitative information about the material’s performance is most valuable if it can be used during casting design.The transfer of local properties into the designer’s world,to predict fatigue and durability as a function of the entire manufacturing route,will increase the trust in this old but highly innovative material and will open new opportunities for cast iron in the future.The paper will give an overview on current capabilities to quantitatively predict cast iron specific defects and casting performance and will highlight latest developments in modeling the manufacture of cast iron and ADI as well as the prediction of iron casting stresses.  相似文献   
46.
Benzotriazole (BT) and tolyltriazole (TT) are high production volume chemicals which are used in various industrial and household applications. In this study, the distribution of benzotriazoles in the estuaries of different rivers of central Europe and in the North Sea was analyzed by solid-phase extraction (SPE) and liquid chromatography-mass spectrometry (HPLC-MS/MS). BT as well as TT was detected in all water samples. The concentrations for total benzotriazoles (BTs) ranged from 1.7 to 40 ng/L in the North Sea in costal areas. Concentrations in rivers are from 200 to 1250 ng/L, respectively. The mass flux of total benzotriazoles from the major rivers of central Europe into the North Sea was calculated to 78 t/a, dominated by the Rhine with an individual flux of 57 t/a of BTs. The analysis of the distribution profile in the North Sea showed that the decrease of the concentration was mostly caused by dilution and that the benzotriazoles are poorly degradable in the North Sea. This paper presents the first report of benzotriazoles in the marine environment.  相似文献   
47.
Road traffic is a dominant source of air pollution. Therefore it is necessary to provide decision-makers with up-to-date emission information in an easily understandable form. To achieve this goal we have integrated existing emission calculation software with a graphical user interface, which includes a GIS (geographical information system) component. The paper first gives a summary of the basic road traffic emission model and then focuses on the design and implementation of the computer application with the emphasis on the used component and GIS technology. The integrated emission evaluation system offers entirely new ways of using the emission model and gives additional visualization and analysis possibilities.  相似文献   
48.
October 1, 2001 is approaching Austria’s power supplying companies with giant strides. From that time on these companies have to meet the general conditions of the EIWOG 2000 as well as they have to fulfil the directive of the internal market of the European Union and further published statute basics from the regulator. An increased readiness for changing regarding household customers is not predictable, however, it is foreseeable that one or another power customer will switch to an alternative provider. This and further facts caused by the liberalization process lead to the situation, that on one hand there are completely new and on the other hand changed conventional business processes for the power suppliers. Traditional methods and equipment will not suffice anymore. Therefore it is necessary, that energy supply companies and offerers of IT-solutions create the appropriate solution, which is adapted for the particular power supplying company. Energy Sales & Care, a modularly constructed and always expandable product for tomorrow’s power supplier can cover this shortage in a responsible way.  相似文献   
49.
Rapid thermal chemical vapor deposition (RTCVD) is a competing technology for the growth of Si1?xGex strained-layer structures for the development of silicon-based heterojunctions. High-quality epitaxial films with growth temperatures as low as 600°C and 4.5 nm-period superlattices have been demonstrated without the use of ultrahigh-vacuum techniques. Narrow-bandgap-base heterojunction bipolar transistors made of Si/Si1?xGex/Si have been shown to have superior characteristics compared to all-silicon homojunction devices, and extend the scaling limits of bipolar transistors. Finally, RTCVD strained Si1?xGex films exhibit well-resolved band-edge photoluminescence—the first step on the way to developing silicon-based light-emitting devices.  相似文献   
50.
提出可以增加集合住宅受欢迎度的共鸣设计方法策略,这些策略不仅考虑到建筑本身的一些可能性,同时考虑到在空间和社会环境方面的要求,涵盖了物理的、心理的以及社会的因素;指出这类策略的应用带来了高度的用户接受度并使得适应性建筑在一个长时期内可以保持其价值.阐释在设计方法的帮助下,建筑物被记录和相互比较.  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