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   4367篇
  免费   189篇
  国内免费   9篇
电工技术   79篇
综合类   9篇
化学工业   575篇
金属工艺   67篇
机械仪表   87篇
建筑科学   330篇
矿业工程   15篇
能源动力   146篇
轻工业   395篇
水利工程   55篇
石油天然气   16篇
无线电   419篇
一般工业技术   779篇
冶金工业   470篇
原子能技术   24篇
自动化技术   1099篇
  2023年   19篇
  2022年   33篇
  2021年   81篇
  2020年   57篇
  2019年   85篇
  2018年   120篇
  2017年   129篇
  2016年   123篇
  2015年   111篇
  2014年   126篇
  2013年   328篇
  2012年   246篇
  2011年   309篇
  2010年   253篇
  2009年   227篇
  2008年   286篇
  2007年   266篇
  2006年   241篇
  2005年   185篇
  2004年   147篇
  2003年   134篇
  2002年   142篇
  2001年   91篇
  2000年   84篇
  1999年   77篇
  1998年   76篇
  1997年   71篇
  1996年   67篇
  1995年   59篇
  1994年   40篇
  1993年   33篇
  1992年   37篇
  1991年   28篇
  1990年   25篇
  1989年   22篇
  1988年   16篇
  1987年   21篇
  1986年   17篇
  1985年   24篇
  1984年   21篇
  1983年   11篇
  1982年   12篇
  1981年   11篇
  1980年   8篇
  1979年   17篇
  1978年   8篇
  1977年   5篇
  1976年   9篇
  1975年   5篇
  1974年   8篇
排序方式: 共有4565条查询结果,搜索用时 15 毫秒
31.
The objective of this research is to develop a non-destructive method for predicting cooked beef tenderness using optical scattering of light on fresh beef muscle tissue. A hyperspectral imaging system (λ = 496–1,036 nm) that consists of a CCD camera and an imaging spectrograph, was used to acquire beef steak images. The hyperspectral image consisted of 120 bands with spectral intervals of 4.54 nm. Sixty-one fresh beef steaks, including 44 strip loin and 17 tenderloin cuts, were collected. After imaging, the steaks were cooked and Warner-Bratzler shear (WBS) force values were collected as tenderness references. The optical scattering profiles were derived from the hyperspectral images and fitted to the modified Lorentzian function. Parameters, such as the peak height, full scattering width at half maximum (FWHM), and the slope around the FWHM were determined at each wavelength. Stepwise regression was used to identify 7 key wavelengths and parameters. The parameters were then used to predict the WBS scores. The model was able to predict WBS scores with an = 0.67. Optical scattering implemented with hyperspectral imaging shows limited success for predicting current status of tenderness in beef steak.  相似文献   
32.
日益精密且成本逐渐下降的的显示技术使人们对下一代户内、户外广告的"数字化"充满了期待。然而运行显示网络必不可少的"大脑"是不容忽略的。下面综述了成功的数字广告系统的软件需求,以及这些系统的工作方式。  相似文献   
33.
Environmentally responsive hydrogels have become attractive research subjects for many applications. In this work, a series of pH‐sensitive and color‐changing nanoparticles (nanogels) with core–shell structures were synthesized. The cores were blue latex particles synthesized by a miniemulsion technique with styrene and methacrylic acid as monomers and Neozapon Blue 807 as a dye. The shell was a pH‐sensitive polymer that was precipitation‐polymerized onto the core from 2‐(diethylamino) ethyl methacrylate with N,N′‐methylenebisacrylamide, poly(propylene glycol) diacrylate, and divinylbenzene as crosslinking agents. In the resultant latexes, the color was observed to change from deep blue to pale blue as the pH of the system was changed from a high of 10 to a low of 3. The synthesized latexes and particles (gels) were then characterized with an ultraviolet–visible spectrometer, dynamic light scattering, Fourier transform infrared, and nuclear magnetic resonance. Atomic force microscopy was also used to investigate the different morphologies of the particles after the synthesized latexes were dried at different pH values. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008  相似文献   
34.
印度的开放     
印度在对外国公司开放零售市场上已经迈出了第一步,但仍然有很长的路要走。  相似文献   
35.
Thailand has recently introduced net metering legislation that provides streamlined procedures for small renewable energy generators to connect to the grid, and guarantees both a market and good prices. The new laws create income opportunities for rural communities based on locally produced, clean, renewable energy supplies and offer significant potential to reduce Thailand's dependence on imported oil and coal. Chris Greacen, Chuenchom Sangarasri Greacen and Rich Plevin report.  相似文献   
36.
37.
Chris Moss 《AI & Society》1989,3(4):345-356
The introduction of massive parallelism and the renewed interest in neural networks gives a new need to evaluate the relationship of symbolic processing and artificial intelligence. The physical symbol hypothesis has encountered many difficulties coping with human concepts and common sense. Expert systems are showing more promise for the early stages of learning than for real expertise. There is a need to evaluate more fully the inherent limitations of symbol systems and the potential for programming compared with training. This can give more realistic goals for symbolic systems, particularly those based on logical foundations.  相似文献   
38.
The interactivity effect in multimedia learning   总被引:4,自引:1,他引:3  
  相似文献   
39.
Abstract: Sensing and control functions are the fundamental technologies on which many civil infrastructure control and monitoring systems are constructed. Early civil infrastructure control and monitoring systems employed a centralized computing model for sensor processing and actuator control. These systems required extensive wiring to route power, sensor, and control signals among the distributed input and output devices. Furthermore, the operation of the entire system depended on one or two computers. Abstractly, these civil infrastructure applications are a realtime data acquisition and control system. Due to the dramatic decrease in computing costs, it is now feasible to construct these real-time systems using dozens or even hundreds of distributed processors linked with a data communication network. This allows the controllers to be located adjacent to sensors and actuators, thereby reducing the need for long lengths of multiconductor wire that is subject to noise and breakage. Also, failure of a single processor does not necessarily cause the entire system to fail. This paper introduces the reader to a technology called LonWorks for constructing distributed sensing and control systems. The LonWorks technology is essentially a data communication network that links together extremely small computers called Neurons. Particular emphasis is placed on describing the communication architecture and emphasizing how the distributed Neuron communication processors are designed to ensure a truly modular and open architecture.  相似文献   
40.
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