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   16986篇
  免费   1689篇
  国内免费   708篇
电工技术   908篇
综合类   1089篇
化学工业   2898篇
金属工艺   334篇
机械仪表   1246篇
建筑科学   1142篇
矿业工程   218篇
能源动力   561篇
轻工业   1118篇
水利工程   85篇
石油天然气   906篇
武器工业   98篇
无线电   4273篇
一般工业技术   2744篇
冶金工业   292篇
原子能技术   207篇
自动化技术   1264篇
  2025年   23篇
  2024年   374篇
  2023年   414篇
  2022年   529篇
  2021年   632篇
  2020年   756篇
  2019年   713篇
  2018年   590篇
  2017年   714篇
  2016年   763篇
  2015年   733篇
  2014年   1095篇
  2013年   977篇
  2012年   1078篇
  2011年   1127篇
  2010年   925篇
  2009年   939篇
  2008年   857篇
  2007年   869篇
  2006年   803篇
  2005年   695篇
  2004年   595篇
  2003年   562篇
  2002年   426篇
  2001年   361篇
  2000年   359篇
  1999年   265篇
  1998年   221篇
  1997年   167篇
  1996年   132篇
  1995年   112篇
  1994年   119篇
  1993年   103篇
  1992年   62篇
  1991年   46篇
  1990年   50篇
  1989年   32篇
  1988年   23篇
  1987年   12篇
  1986年   20篇
  1985年   23篇
  1984年   28篇
  1983年   16篇
  1982年   17篇
  1981年   3篇
  1979年   3篇
  1976年   3篇
  1964年   2篇
  1959年   2篇
  1951年   2篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
22.
我国的公共照明设备的电能源浪费现象非常严重,以学校图书馆借阅室的照明灯为例,几乎常年、整天的照明造成大量的电能源浪费。结合电子专业的技术知识,通过设计电路图以及对电路图的仿真,并应用相关电子元器件,设计出一个节能控制电路,根据当日的光照水平和阅览室内学生人数,决定照明灯的开关,实物运行效果良好。  相似文献   
23.
研究红外场曝露对于高血糖疾病模型大鼠的影响.主要利用红外场曝露高血糖大鼠30天,然后通过考查红外场曝露对于高血糖大鼠血液组织红外光谱特征的影响来研究红外线曝露对于大鼠血糖水平产生的影响,研究结果认为红外场曝露有助于高血糖大鼠血糖水平的恢复,并进一步通过红外光谱数据的二阶导数谱的分析探讨了红外场曝露对于大鼠血糖水平产生影响的机理.  相似文献   
24.
In order to prevent and eliminate the asphaltene precipitation during gas flooding, the rules of the changes of the pressure under different conditions are systematically studied by the laser solid detection system, the light transmission method, and the PT phase diagram when the asphaltene precipitation occurs. When the pressure is reducing to a certain value, the penetrating light intensity of the crude oil is markedly decreased, which shows that the pressure at this point is the pressure of the onset of asphaltene precipitation (AOPP). The AOPP value decreases with an increase in the temperature. During gas flooding, the AOPP value increases with an increase in the content of gas in the crude oil, and these two nearly do have a linear relationship. According to the PT phase behaviors of the gas–crude oil system, with an increase in the content of gas in the crude oil, the asphaltene precipitation envelope curve (APE) is gradually moved up, which shows that the possibility of asphaltene precipitation is much higher. During oil production, for the oil reservoirs with rich asphaltene, the production pressure drop should be kept a small value to ensure that the flowing bottom-hole pressure is higher than AOPP and it is necessary to help complement producing energy timely by using water injection, gas injection, etc. Besides, according to the intersection of TP curve and APE curve in the PT phase diagram, the location where the asphaltene precipitation occurs in the wellbore can be roughly predicted. The experimental results can provide the theoretical foundation for taking measures to prevent and eliminate the asphaltene precipitation.  相似文献   
25.
Staphylococcus saprophyticus is a common contaminant in meat and poultry, and causes urinary tract infections after colonization of the gastrointestinal tract, followed by accidental transfer of contaminated feces to the urethra. There is limited information regarding the inactivation kinetics of S. saprophyticus in meat and poultry. When S. saprophyticus was suspended in ground chicken meat (GCM) the thermal processing D10 was 6.26, 0.60 and 0.09 min at 55, 60 and 65 °C, respectively. When S. saprophyticus was inoculated into GCM and subjected to high pressure processing (5 °C, 0–25 min) at 200, 300 or 400 MPa the HPP D10 was 15.5, 9.43, and 3.54 min, respectively. When the S. saprophyticus cocktail was inoculated into GCM and irradiated (5 and −20 °C) the gamma radiation D10 were 0.64 and 0.77 kGy, respectively. When S. saprophyticus was inoculated into chicken purge which was then placed on food contact surfaces including stainless steel, and high density polyethylene and polypropylene and treated with UV-C (0–60 mJ/cm2) the UV-C D10 ranged from 14.9 to 18.5 mJ/cm2. These results indicate the inactivation kinetics for S. saprophyticus are consistent with those for other foodborne pathogens and could be controlled in poultry meat and purge without difficulty.  相似文献   
26.
The use of a nitrogen radio frequency plasma source together with an appropriate quantum well configuration have recently resulted in the successful realization of p-type ZnSe by molecular beam epitaxy. This has enabled a variety of pn heterojunction based devices to be built including the first semiconductor injection lasers operating in the blue/green portion of the spectrum first reported by 3M and the Brown/Purdue group. In this paper, we discuss two lattice matched multiple quantum well structures that produce laser emission in the blue and blue/green portion of the spectrum.  相似文献   
27.
马于光  刘式墉  朱江  沈家骢 《中国激光》1993,20(10):749-752
用溶液沉积的方法制备了染料分散红掺杂的聚苯乙烯膜,并用电场取向的方法对膜中的染料极性分子进行了取向。对取向膜进行的电光测试结果表明取向膜的电光系数r_(33)≈35pm/V较无机晶体要大。  相似文献   
28.
本文利用Karhunen—Loeve展开,在光源空域内对光源场互谱密度进行量子谐振子模分解,发展了一种计算光源场熵的新方法,并精确计算了高斯Schell模光源场的熵,讨论了光源场熵与光源全相干度,光源场模数的关系。  相似文献   
29.
Innovative daylighting systems have four key aims; to increase daylight levels deep within rooms, to improve daylight uniformity, to control direct sunlight and to reduce glare. Results from experimental studies at the Building Research Establishment (BRE) indicated that the systems tested (prismatic glazing, prismatic film, mirrored louvres and light shelves) usually reduced illuminances at the rear of rooms compared with unshaded windows. It is concluded that, in the UK at least, innovative daylighting systems should be designed primarily as shading devices, controlling glare while admitting more daylight than conventional blinds.  相似文献   
30.
崔浩然 《染整技术》1994,16(1):47-49
对棉防羽绒布卷染时,为提高日晒牢度,对各种直接染料进行筛选,并通过多种方法如固色、接枝等谋求提高日晒牢度。最后确定合理选用染料和工艺中提出合理要求。  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