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   2956篇
  免费   168篇
  国内免费   1篇
电工技术   28篇
综合类   2篇
化学工业   840篇
金属工艺   65篇
机械仪表   58篇
建筑科学   136篇
矿业工程   16篇
能源动力   69篇
轻工业   265篇
水利工程   38篇
石油天然气   22篇
无线电   247篇
一般工业技术   554篇
冶金工业   529篇
原子能技术   10篇
自动化技术   246篇
  2023年   28篇
  2022年   75篇
  2021年   111篇
  2020年   63篇
  2019年   44篇
  2018年   66篇
  2017年   59篇
  2016年   94篇
  2015年   63篇
  2014年   98篇
  2013年   145篇
  2012年   131篇
  2011年   166篇
  2010年   116篇
  2009年   133篇
  2008年   129篇
  2007年   143篇
  2006年   104篇
  2005年   84篇
  2004年   62篇
  2003年   70篇
  2002年   57篇
  2001年   44篇
  2000年   38篇
  1999年   55篇
  1998年   130篇
  1997年   102篇
  1996年   72篇
  1995年   49篇
  1994年   58篇
  1993年   41篇
  1992年   24篇
  1991年   31篇
  1990年   29篇
  1989年   25篇
  1988年   22篇
  1987年   25篇
  1986年   26篇
  1985年   24篇
  1984年   28篇
  1983年   21篇
  1982年   20篇
  1981年   17篇
  1980年   25篇
  1978年   18篇
  1977年   19篇
  1976年   20篇
  1975年   13篇
  1974年   14篇
  1971年   14篇
排序方式: 共有3125条查询结果,搜索用时 0 毫秒
1.
The determination of a protein''s folding nucleus, i.e. a set of native contacts playing an important role during its folding process, remains an elusive yet essential problem in biochemistry. In this work, we investigate the mechanical properties of 70 protein structures belonging to 14 protein families presenting various folds using coarse-grain Brownian dynamics simulations. The resulting rigidity profiles combined with multiple sequence alignments show that a limited set of rigid residues, which we call the consensus nucleus, occupy conserved positions along the protein sequence. These residues'' side chains form a tight interaction network within the protein''s core, thus making our consensus nuclei potential folding nuclei. A review of experimental and theoretical literature shows that most (above 80%) of these residues were indeed identified as folding nucleus member in earlier studies.  相似文献   
2.
Anaerobic co-digestion of organic wastes from households, slaughterhouses and meat processing industries was optimised in a half technical scale plant. The plant was operated for 130 days using two different substrates under organic loading rates of 10 and 12 kgCOD.m(-3).d(-1). Since the substrates were rich in fat and protein components (TKN: 12 g.kg(-1) the treatment was challenging. The process was monitored on-line and in the laboratory. It was demonstrated that an intensive and stable co-digestion of partly hydrolysed organic waste and protein rich slaughterhouse waste can be achieved in the balance of inconsistent pH and buffering NH4-N. In the first experimental period the reduction of the substrate COD was almost complete in an overall stable process (COD reduction >82%). In the second period methane productivity increased, but certain intermediate products accumulated constantly. Process design options for a second digestion phase for advanced degradation were investigated. Potential causes for slow and reduced propionic and valeric acid degradation were assessed. Recommendations for full-scale process implementation can be made from the experimental results reported. The highly loaded and stable codigestion of these substrates may be a good technical and economic treatment alternative.  相似文献   
3.
A study was carried out using simulation to investigate driver responses to lineside signals and signs at various approach speeds. The objectives of the study were: (1) to find out whether train speed would significantly affect signal/sign reading; (2) to examine at which point certain types of signs or signals could be detected or recognised, and (3) to determine a speed cut-off level above which certain types of signs or signals are no longer recognisable or detectable. Fifty-seven train drivers from 12 Train Operating Companies in the UK participated in the trials. Twenty different types of lineside signs and ten types of signals were tested under six different approach speeds ranging from 100 to 350 km/h (62–218 mph). Driver performance measures were ‘time remaining to the signal/sign’ at the point of detection or recognition, and reading error rate. The results showed a significant influence of train speed on driver responses to lineside signals/signs and demonstrated a non-linear relationship between driver responses to signals/signs and approach speed. This has been used to estimate a maximum approach speed limit within which a specific signal or sign can be correctly detected or recognised. The findings and implications of the study are discussed in the paper.  相似文献   
4.
Automotive under-the-hood electronics often have to withstand temperatures up to 175 °C in combination with harsh environment conditions. This paper gives an overview about the reliability potential of epoxy based encapsulants for automotive applications. Therefore the resistance of epoxy molding compound against typical automotive fluids at temperature of use is analyzed. Six epoxy molding compounds available on the market, showing high temperature automotive potential have been carefully selected to undergo a media resistance testing. For this purpose a dedicated mold tool has been designed and manufactured to prepare these encapsulants for material testing. Thermo-mechanical, mechanical and thermal properties had been determined in initial state directly after molding and after storage in aggressive fluids typical for automotive applications as e.g. gas oil, automatic transmission fluid (ATF), brake fluid or accumulator acid at the respective temperature of use.  相似文献   
5.
A calorimeter of 25 bismuth germanate (BGO) crystals equipped with silicon photodiode readout has been tested at the CERN SPS in the energy range 1–50 GeV. The response for electrons has been shown to be linear in this energy range and the rms resolution obtained ( ) is approximately 1%, for E > 4 GeV. The electron/pion separation was found to be better than 1:500 in the energy range 1–20 GeV. Data on lateral and longitudinal shower development were compared with the results of a Monte Carlo simulation using the SLAC-EGS program and found to be in good agreement.  相似文献   
6.
Braun  C.-A. 《Multimedia, IEEE》2005,12(3):14-18
What if every public space and surface were transformed into an interactive experience - capturing our movements, gestures, sounds and actions and using these to produce new sounds, images, text and actions? Bus stops could come alive and talk back, advertisements could look back at you and talk to you and public park robotic devices could play games with you. Will public places eventually become our social barometer as well as director? Will billboards display the populace's discourse? The author look at some special streets in France where the city is literally alive with art and explores what it might mean for us to live in a world of artistic interactivity.  相似文献   
7.
8.
Experience with electrical diagnostic and high-potential tests, performed at the terminals of unshielded cables in older nuclear and thermal plants is presented. The three basic types of cable-low- and high-voltage power cables, control cables and instrumentation cables-that are important to the reliable operation of a generating station and large industrial plants are described, and their aging mechanisms are indicated. Dielectric testing of unshielded cables, the effect of grounding, field testing of station cables, and insulation characterization at low frequencies are discussed  相似文献   
9.
10.
Deformable contour models are useful tools for image segmentation. However, many fields depend mainly on local edge-based image features to guide the convergence of the contour. This makes the models sensitive to noise and the initial estimate. Our model incorporates region-based image features to improve its convergence and to reduce its dependence on initial estimation. Computational efficiency is achieved by an optimization strategy, modified from the greedy algorithm of Williams and Shah. The model allows a simultaneous optimization of multiple contours, making it useful for a large variety of segmentation problems.  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