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   1014篇
  免费   33篇
  国内免费   2篇
电工技术   74篇
化学工业   355篇
金属工艺   14篇
机械仪表   15篇
建筑科学   25篇
矿业工程   1篇
能源动力   37篇
轻工业   76篇
水利工程   1篇
石油天然气   1篇
无线电   49篇
一般工业技术   202篇
冶金工业   70篇
原子能技术   22篇
自动化技术   107篇
  2023年   4篇
  2022年   10篇
  2021年   15篇
  2020年   12篇
  2019年   10篇
  2018年   10篇
  2017年   11篇
  2016年   12篇
  2015年   16篇
  2014年   25篇
  2013年   56篇
  2012年   46篇
  2011年   47篇
  2010年   44篇
  2009年   54篇
  2008年   52篇
  2007年   51篇
  2006年   44篇
  2005年   46篇
  2004年   47篇
  2003年   35篇
  2002年   38篇
  2001年   16篇
  2000年   28篇
  1999年   37篇
  1998年   44篇
  1997年   35篇
  1996年   27篇
  1995年   19篇
  1994年   16篇
  1993年   10篇
  1992年   15篇
  1991年   9篇
  1990年   8篇
  1989年   9篇
  1988年   5篇
  1987年   5篇
  1986年   11篇
  1985年   6篇
  1984年   10篇
  1983年   9篇
  1982年   10篇
  1981年   7篇
  1980年   4篇
  1979年   7篇
  1978年   4篇
  1976年   5篇
  1975年   3篇
  1973年   2篇
  1968年   1篇
排序方式: 共有1049条查询结果,搜索用时 15 毫秒
71.
The authors have proposed an architecture for a compact image-capturing system called TOMBO (thin observation module by bound optics), which uses compound-eye imaging for a compact hardware configuration [Appl. Opt. 40, 1806 (2001)]. The captured compound image is decomposed into a set of unit images, then the pixels in the unit images are processed with digital processing to retrieve the target image. A new method for high-resolution image reconstruction, called a pixel rearrange method, is proposed. The relation between the target object and the captured signals is estimated and utilized to rearrange the original pixel information. Experimental results show the effectiveness of the proposed method. In the experimental TOMBO system, the resolution obtained is four times higher than that of the unit image that did not undergo reconstruction processing.  相似文献   
72.
The release behaviour of a drug from flat circular capsules obtained by radiation-induced polymerization at low temperatures and with different hydrophilic properties has been studied. The effect of various factors on release property was investigated. The release process could be divided into three parts, an initial quick release stage, stationary state release stage and a retarded release stage. Release behaviour in the stationary state was examined using Noyes-Whitney and Higuchi equations. It was shown that the hydrophilic property of polymer matrix expressed by water content was the most important effect on diffusion and release rate. Rigidity of the polymer may also affect diffusivity. The first quick release step could be attributed to rapid dissolution of drug in the matrix surface due to polymer swelling.  相似文献   
73.
闪速炼铜“高效反应区”的形成条件与应用效果   总被引:1,自引:0,他引:1  
运用闪速炉反应塔“高效反应区”模型,研究闪速炉操作的优化与强化。结果表明,形成“高效反应区”的主要条件是高温、氧气和颗粒群的集中。“高效反应区”模型在生产中的初步应用获得了显著效果。“高效反应区”的形成有利于强化生产、降低油耗和烟尘率、延长反应塔寿命、提高氧利用率和铜直收率。  相似文献   
74.
In order to determine the superconducting gap structure of the borocarbide superconductor YNi2B2C, we have measured the angular variation of the c-axis thermal conductivity zz in magnetic field rotated within the ab-planes. A clear fourfold symmetry with narrow cusps was observed in the angular variation of zz . These results provide a strong evidence that the gap function has point nodes which are located along the a- and b-axes of the crystal.  相似文献   
75.
Ferroelectric Pb(Zr0.53Ti0.47)O3 fibers were reproducibly fabricated by sol-gel technique using triethanolamine (TEA) complexed alkoxide. The phase transition from pyrochlore to perovskite took place about 400°C and a stable single perovskite phase was obtained at 550°C. PZT gel fibers spun through nozzle were heat-treated at 700°C, and at 1000°C for 1 h to certify the effect of heat-treatment temperature on the electrical properties. The PZT fibers had elliptical cross sections with diameter of 72 m–92 m, and dense microstructure was obtained by heating at 1000°C. In the PZT fibers heat-treated at 1000°C, a distinguishable relative permittivity peak and a pyroelectric current peak were observed at their Curie temperature. The P-E hysteresis loops of the crystalline PZT fibers were also observed.  相似文献   
76.
Achieving ultra-high magnetic-recording density in hard disk drives (HDDs) requires clarification of flow-induced vibration issues. In particular, it is necessary to reduce the flow-induced disk vibration called disk flutter. Thus far, however, there has been no experimental research related to disk flutter in actual HDDs. For this study, therefore, the disk-flutter issues have been studied experimentally, using an actual 2.5-in. HDD with one disk and two magnetic heads. The aim was to study the effect of operating magnetic-head mechanisms on flow-induced disk flutter. This study evaluated disk flutter as well as static pressure distribution in the actual HDD, by taking measurements while changing the operating modes of the magnetic-head mechanism as well as the number of operating air-bearing sliders. The study demonstrated that the disk-flutter amplitude increases and its frequency decreases when the magnetic-head mechanisms are operating. It was also found that the amount of decrease in the disk-flutter frequency depends on the number of operating air-bearing sliders whose amplitude increase varies with the specific operating mode of the head mechanisms, such as whether it is in track-following or seek modes. In addition, operation of the magnetic-head mechanisms generated non-uniform static pressure distribution within the HDD. These factors suggest that a decrease in disk-flutter frequency results from the slider-coupled vibration and an increase in disk-flutter amplitude results from the static pressure changes as well as air-following changes, as these vary with the actual operation of the disk head mechanism. From these experimental results, it appears that the disk-flutter issues in actual HDDs should be considered as a system that includes the operation of the magnetic-head mechanisms and disk-coupled vibration.  相似文献   
77.
Previously, we carried out ultrasonic measurements for liquid 4He filled in a nanoporous glass (Gelsil), and observed an increase in the sound velocity due to decoupling of the superfluid component. At zero pressure, the superfluid transition temperature T C is suppressed to 1.4 K from the bulk lambda point, 2.17 K. This behavior is the same as torsional oscillator measurements by Yamamoto et al. (Phys. Rev. Lett. 93:075302, 2004). However, the pressure dependence of T C and the temperature dependence of the superfluid fraction are very different from the torsional oscillator measurements. In order to clarify the origin of the difference, we have developed a new technique of simultaneous measurement of an ultrasound and a torsional oscillator, and the system successfully works for a nanoporous glass. Here, we compare decoupling of the superfluid component for 4He films between an ultrasound and a torsional oscillator.  相似文献   
78.
79.
Fast Labelling of Natural Scenes Using Enhanced Knowledge   总被引:1,自引:0,他引:1  
A new technique for labelling natural scenes is proposed. This technique labels disjoint regions on an image of a natural scene on the basis of knowledge about the relationship among objects. The proposed technique consists of three stages: (1) segmentation, (2) initial labelling, and (3) label improvement. One of the most promising previous techniques uses simulated annealing to find the solution, while our technique uses local hill-climbing with enhanced knowledge for speeding up the processing. Local hill-climbing is known to be easy to be captured by a local minimum. We solved this problem by enhancing the knowledge being used as constraints for the search. Our knowledge represents 1-to-n relationships among regions, pair-wise relationships of regions, and relative locations of the regions to the image. In addition, we introduced two region features: an entropy in intensity; and a linearity of contours of each region. The linearity evaluation aims to distinguish artificial objects from natural objects. The validity of the technique is supported by some experiments. These experiments showed that the proposed technique is much faster with the almost same accurate.  相似文献   
80.

A moment method of the log-normal distribution with the smallest size is applied to evaporation by newly introducing correction factors obtained from the error function. In this article, the improved moment method is tested for the evaporation, and is compared with the exact solutions calculated by the CIP semi-Lagrangian (CIP-SL) method. In small particle regime, the size distributions and the time histories of the total number and volume per unit volume are reproduced by the moment method for the evaporation near the smallest size. In large particle regime, however, the differences between the moment and exact solutions are larger with time, after the exact distribution spreads to the smallest size. This new moment solver can reproduce the evaporation near the smallest size even when large time step size is given, and thus is expected to be used for the parameterization of the evaporation of small particles in aerosol-transport model.  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