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   169924篇
  免费   12499篇
  国内免费   6080篇
电工技术   8713篇
技术理论   9篇
综合类   8756篇
化学工业   28186篇
金属工艺   10113篇
机械仪表   10409篇
建筑科学   9799篇
矿业工程   3910篇
能源动力   3923篇
轻工业   9484篇
水利工程   3157篇
石油天然气   9549篇
武器工业   1060篇
无线电   18142篇
一般工业技术   27641篇
冶金工业   11021篇
原子能技术   4870篇
自动化技术   19761篇
  2023年   2225篇
  2022年   4161篇
  2021年   6220篇
  2020年   4739篇
  2019年   4091篇
  2018年   5225篇
  2017年   5655篇
  2016年   5241篇
  2015年   5746篇
  2014年   7529篇
  2013年   9207篇
  2012年   9887篇
  2011年   10645篇
  2010年   9042篇
  2009年   8860篇
  2008年   8738篇
  2007年   8088篇
  2006年   7517篇
  2005年   6459篇
  2004年   4959篇
  2003年   4878篇
  2002年   4872篇
  2001年   4441篇
  2000年   3844篇
  1999年   3432篇
  1998年   2697篇
  1997年   2272篇
  1996年   2034篇
  1995年   1764篇
  1994年   1500篇
  1993年   1258篇
  1992年   1225篇
  1991年   1092篇
  1990年   1098篇
  1989年   1023篇
  1988年   894篇
  1987年   838篇
  1986年   757篇
  1985年   716篇
  1984年   706篇
  1982年   669篇
  1981年   672篇
  1979年   740篇
  1978年   781篇
  1977年   742篇
  1976年   755篇
  1975年   713篇
  1974年   719篇
  1973年   726篇
  1972年   707篇
排序方式: 共有10000条查询结果,搜索用时 18 毫秒
131.
Recently, InE has been regarded as a popular education strategy in Chinese universities. However, problems have been exposed in the adoption of InE, for example, in InE courses and competitions. The purpose of this paper is to provide a possible solution to the problems, which is to organize effective InE courses by integrating InE with Inter-Course-level Problem-Based Learning (ICPBL). A detailed case is demonstrated by an ICPBL elective course design with deep integration of InE in the teaching, learning, and assessments. This paper contributes to a new curriculum design for promoting InE education in practically for Chinese universities.  相似文献   
132.
133.
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   
134.
Powder Metallurgy and Metal Ceramics - The mechanisms of phase interactions in granular media were studied to elaborate the results obtained previously at the Nekrasov Iron and Steel Institute of...  相似文献   
135.
以用户为中心的可见光通信协作传输是近年来出现的新架构,这导致虚拟小区之间出现重叠。为避免导频污染问题,每个虚拟小区中的光接入点(AP)或者虚拟小区中选择相同AP的用户发送的训练序列应该是正交的。针对可见光通信中以用户为中心的协作网络,研究训练资源的正交分配问题,提出了一种新的导频分配算法,联合导频分配和用户选择问题,以期最大限度地增加虚拟小区内可被接入的用户数。分析和仿真结果表明,该导频分配方案可以有效改善导频污染问题,提高训练资源利用率,并且相比已有的导频分配方案,性能有所改进。  相似文献   
136.
137.
The development of bio‐based thermosetting resins with good thermal stability can potentially afford sustainable polymers as replacements for petroleum‐based polymers. We report a practical route to a novel catechin‐based phthalonitrile resin precursor (CA‐Ph), which contains free phenolic hydroxyl groups that result in ‘self‐curing’ at elevated temperatures to afford a thermostable polymer. Comparison of the performance of this CA‐Ph resin with that of a conventional petroleum‐based bisphenol A phthalonitrile resin (BPA‐Ph; containing 5 wt% of the curing agent 4,4′‐diaminodiphenylsulfone) revealed that CA‐Ph exhibits a lower melting point and curing temperature. Cured CA‐Ph resin retains 95% of its weight at 520 °C under a nitrogen atmosphere, which compares favorably with results obtained for BPA‐Ph resin that retains 95% of its weight at a lower temperature of 484 °C. Kinetic results indicated that the curing reactions of both CA‐Ph and BPA‐Ph systems follow an autocatalytic mechanism. These results suggest that catechin is a useful bio‐based feedstock for the preparation of self‐curing and thermally stable phthalonitrile resins for advanced technological applications. © 2017 Society of Chemical Industry  相似文献   
138.
Refractories and Industrial Ceramics - We study the problem of evaluation of the influence of design of the metal receiver of a large-capacity tundish of slab continuous-casting machine on the...  相似文献   
139.
Technical Physics Letters - We present the results of a comparative investigation of the friction and wear characteristics of MoSx and MoSex coatings in an oxidizing medium (argon–air...  相似文献   
140.
Technical Physics Letters - The C–V characteristics of Au/Al2O3/In0.52Al0.48As and Au/SiO2/In0.52Al0.48As metal–insulator–semiconductor structures have been studied. It has been...  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