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   619995篇
  免费   8571篇
  国内免费   2470篇
电工技术   11203篇
综合类   847篇
化学工业   92519篇
金属工艺   22842篇
机械仪表   18082篇
建筑科学   16141篇
矿业工程   2321篇
能源动力   16068篇
轻工业   57990篇
水利工程   5749篇
石油天然气   7373篇
武器工业   56篇
无线电   77531篇
一般工业技术   118654篇
冶金工业   115802篇
原子能技术   11860篇
自动化技术   55998篇
  2021年   4385篇
  2019年   4089篇
  2018年   6715篇
  2017年   6860篇
  2016年   7314篇
  2015年   5384篇
  2014年   9018篇
  2013年   28192篇
  2012年   15306篇
  2011年   21753篇
  2010年   16799篇
  2009年   19231篇
  2008年   20339篇
  2007年   20700篇
  2006年   18267篇
  2005年   16946篇
  2004年   16687篇
  2003年   16254篇
  2002年   15687篇
  2001年   15703篇
  2000年   14774篇
  1999年   15486篇
  1998年   36210篇
  1997年   26258篇
  1996年   20377篇
  1995年   15905篇
  1994年   14110篇
  1993年   13836篇
  1992年   10227篇
  1991年   9822篇
  1990年   9369篇
  1989年   9079篇
  1988年   8597篇
  1987年   7509篇
  1986年   7504篇
  1985年   8801篇
  1984年   8197篇
  1983年   7277篇
  1982年   6831篇
  1981年   6830篇
  1980年   6561篇
  1979年   6324篇
  1978年   6055篇
  1977年   7082篇
  1976年   9517篇
  1975年   5146篇
  1974年   4970篇
  1973年   4896篇
  1972年   4051篇
  1971年   3544篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
The primary goal of this study is to create and test a lecture‐capture system that can rearrange visual elements while recording is still taking place, in such a way that student performance can be positively influenced. The system we have devised is capable of integrating and rearranging multimedia sources, including learning content, the instructor and students' images, into lecture videos that are embedded in a website for students to review after school. The present study employed a two‐group experimental design, with 153 participants (145 females and 8 males) making up an experimental group in which lecture courses were recorded using the new lecture‐capture system, and 149 participants (140 females and 9 males) forming a control group whose lectures were recorded by traditional means. All participants were in the freshman college and studying Introduction to Computer and Information Science in one of six classes, and were randomly assigned to one of the two groups. The participants' midterm examination and final examination scores were collected as indicators of their academic performance, with their mathematics entrance scores used as a pre‐test. The findings obtained from analysis of covariance (ANCOVA) suggest that appropriate rearrangement of visual elements in lecture videos can significantly impact students' learning performance.  相似文献   
62.
The data on the use of solar photovoltaic plants (PVPs) for providing a reliable and guaranteed power supply to telecommunication systems and cellular communication systems in the conditions prevalent in Uzbekistan are given. The research-based structures developed by OOO MIR SOLAR and the selection of PVP elements ensuring their reliable operation are described. The main influencing factors are discussed, and the use of effective combinations of different types of panels (from monocrystalline and polycrystalline silicon) and a specially developed controller are considered.  相似文献   
63.
64.
65.
This study evaluated several physical and sensory parameters of different types of cheese available in the Polish market. The measurements of textural properties were conducted in an Instron universal testing machine, while the colour properties of cheeses were measured using a Minolta chromameter. The chemical composition was determined by means of the near‐infrared spectroscopy (NIRs). Moreover, a trained sensory panel was invited to assess the cheese texture‐related properties. Generally, cheeses with reduced fat content were characterised by higher hardness, adhesiveness, cohesiveness and elasticity. Texture‐related parameters of cheese with canola oil were comparable to that of most of full‐fat cheeses. The correlation analysis between physical and sensory attributes related to cheese textural properties indicated the potential applications of TPA, shear and penetration tests (= 0.766, = 0.75 and = 0.765, respectively) for the evaluation of sensory properties related to the hardness. Meanwhile, the elasticity of cheese obtained from sensory evaluation was strongly correlated with the elasticity determined from the shear test (= 0.722) and moderately correlated with the elasticity from penetration test (= 0.588), indicating a need to refine the method of penetration test. In addition, cheeses exhibited higher meltability during convection heating at 230 °C than microwave heating. The values of meltability for cheese with reduced fat content were lower than those of full‐fat cheese.  相似文献   
66.
67.
68.
69.
70.
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