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   825篇
  免费   23篇
  国内免费   2篇
电工技术   41篇
综合类   1篇
化学工业   283篇
金属工艺   25篇
机械仪表   19篇
建筑科学   15篇
能源动力   39篇
轻工业   101篇
石油天然气   3篇
无线电   43篇
一般工业技术   172篇
冶金工业   24篇
原子能技术   22篇
自动化技术   62篇
  2023年   4篇
  2022年   8篇
  2021年   19篇
  2020年   13篇
  2019年   10篇
  2018年   13篇
  2017年   11篇
  2016年   20篇
  2015年   20篇
  2014年   23篇
  2013年   51篇
  2012年   38篇
  2011年   51篇
  2010年   37篇
  2009年   34篇
  2008年   55篇
  2007年   47篇
  2006年   38篇
  2005年   30篇
  2004年   27篇
  2003年   30篇
  2002年   19篇
  2001年   16篇
  2000年   8篇
  1999年   18篇
  1998年   12篇
  1997年   17篇
  1996年   12篇
  1995年   11篇
  1994年   9篇
  1993年   20篇
  1992年   8篇
  1991年   6篇
  1990年   5篇
  1989年   14篇
  1988年   10篇
  1987年   14篇
  1986年   10篇
  1985年   10篇
  1984年   11篇
  1983年   12篇
  1982年   4篇
  1981年   7篇
  1980年   6篇
  1979年   5篇
  1978年   1篇
  1977年   3篇
  1976年   1篇
  1974年   1篇
  1971年   1篇
排序方式: 共有850条查询结果,搜索用时 625 毫秒
41.
This study investigated the influence of PUFA on the properties of mouse skin. Mice (3 wk old) were given free access to oils high in linoleic acid, CLA, or DHA for 4 wk. At the end of the experiment, their skins were compared by both biochemical and histological methods. No significant differences in lipid and collagen contents were detected among treatments, although the FA composition in the skin was altered depending upon the FA composition of the supplemented oils. Electron microscopy revealed that the subcutaneous tissue layers in the CLA and DHA groups were significantly thinner than that in the high linoleic acid group, whereas no differences in the thickness of dermis layers were observed among the three groups. These results suggest that skin properties in mice are readily modified by dietary FA sources within 4 wk of dietary oil supplementation.  相似文献   
42.
我国煤炭年产量中,1400℃以上的高灰熔点煤约占50%以上。为探索固态排渣方式的高灰熔点煤气流床气化,本文选出具有代表性的三种高灰熔点煤种和一种低灰熔点煤种,在TGA-51H型高温热天平上进行了煤焦-CO2和煤焦-水蒸汽气化反应特性的实验研究,并利用SEM考察了气化条件下煤焦及灰的微观结构。实验结果表明:在煤焦-CO2、H2O反应过程中,反应速度明显表现出高温区域的扩散反应和低温区域的化学反应;无论在1273K~1573K的低温区域,还是在高于1573K的高温区域,反应速率随燃料比(FC/V)的增加而减小。  相似文献   
43.
We demonstrate the novel dispersion compensation for time-spread/wavelength-hop (TS-WH) optical code-division multiplexing (OCDM). The single-mode-fiber transmission, up to 80 km long, on TS-WH OCDM was achieved by a combination of the dispersion-compensated decoder and the multichannel-type dispersion-slope compensator.  相似文献   
44.
In image classification based on bag of visual words framework, image patches used for creating image representations affect the classification performance significantly. However, currently, patches are sampled mainly based on processing low-level image information or just extracted regularly or randomly. These methods are not effective, because patches extracted through these approaches are not necessarily discriminative for image categorization. In this paper, we propose to utilize both bottom-up information through processing low-level image information and top-down information through exploring statistical properties of training image grids to extract image patches. In the proposed work, an input image is divided into regular grids, each of which is evaluated based on its bottom-up information and/or top-down information. Subsequently, every grid is assigned a saliency value based on its evaluation result, so that a saliency map can be created for the image. Finally, patch sampling from the input image is performed on the basis of the obtained saliency map. Furthermore, we propose a method to fuse these two kinds of information. The proposed methods are evaluated on both object categories and scene categories. Experiment results demonstrate their effectiveness.  相似文献   
45.
ABSTRACT

Parametric analyses of the strain-stress in the drying process are performed to study the influence of the intermittent drying on the behaviors of drying-induced strain-stress and deformation as well as the drying characteristic. The transient three-dimensional problem of strain-stress and heat and moisture transfer in a slab is solved simultaneously by the finite element method. The dimensionless parameters are introduced to generalize the problem in the conservation equations of heat and moisture transfer. The intermittent drying is modeled by applying periodically smaller and larger Biot numbers to the boundary conditions. The maximum tensile and compressive stresses fluctuate, and fall remarkably during the smaller Biot number period when a slab is heated intermittently. The peak stress of the fluctuation exceeds beyond the case in the continuous healing where the overall drying rate is almost equivalent to that in the intermittent beating, but the reduction of the stresses takes place rapidly in the low heating period.  相似文献   
46.
Abstract— A full-color 5.2-inch 1/4-VGA passive-matrix organic LED display has been developed, adopting selective deposition for the different emitting materials. The display features 320 (×3) × 240 pixels with an equivalent pixel size of 0.33 × 0.33 mm, white peak luminance of over 150 cd/m2, and power consumption of 6 W.  相似文献   
47.
Nojima  T. Nishiki  S. Chiba  K. 《Electronics letters》1987,23(10):512-513
A 1.7 GHz-based class-F GaAs FET amplifier is proposed. To achieve high-efficiency performance, a precisely adjustable terminating circuit constructed with lumped elements is introduced. Power-added efficiency of 68% at 1.5 W output is attained with the amplifier.  相似文献   
48.
A solution containing Mg2+ and Ta5+ was added to an aqueous ammonia solution of oxine, resulting in a precipitate. After the precipitate was thermally decomposed and fired, it was mixed with BaCO3 powder and fired again at high temperatures to obtain Ba(Mg1/3Ta2/3)O3 (BMT). This method resulted in BMT formation at temperatures lower than those used in the conventional mixed-oxide method, and single-phase BMT formed directly at 1300°C without intermediates.  相似文献   
49.
50.
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