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   432805篇
  免费   13848篇
  国内免费   6379篇
电工技术   13014篇
技术理论   9篇
综合类   8887篇
化学工业   68772篇
金属工艺   27706篇
机械仪表   20871篇
建筑科学   14622篇
矿业工程   7664篇
能源动力   7931篇
轻工业   20112篇
水利工程   7538篇
石油天然气   20742篇
武器工业   1073篇
无线电   39816篇
一般工业技术   94008篇
冶金工业   42815篇
原子能技术   13959篇
自动化技术   43493篇
  2022年   6276篇
  2021年   8514篇
  2020年   6488篇
  2019年   6271篇
  2018年   14911篇
  2017年   15761篇
  2016年   13465篇
  2015年   8521篇
  2014年   11828篇
  2013年   17883篇
  2012年   17536篇
  2011年   23199篇
  2010年   20159篇
  2009年   19566篇
  2008年   19914篇
  2007年   20434篇
  2006年   12999篇
  2005年   13244篇
  2004年   11013篇
  2003年   10715篇
  2002年   9912篇
  2001年   8802篇
  2000年   8278篇
  1999年   7172篇
  1998年   9445篇
  1997年   7678篇
  1996年   6128篇
  1995年   5134篇
  1994年   4678篇
  1993年   4565篇
  1992年   4088篇
  1991年   4061篇
  1990年   4097篇
  1989年   3937篇
  1988年   3748篇
  1987年   3681篇
  1986年   3502篇
  1985年   3619篇
  1984年   3517篇
  1983年   3411篇
  1981年   3304篇
  1980年   3337篇
  1979年   3565篇
  1978年   3785篇
  1977年   3773篇
  1976年   4228篇
  1975年   3525篇
  1974年   3593篇
  1973年   3613篇
  1972年   3305篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
A technology for slag formation in the ladle–furnace unit is considered; the slag is based on the CaO–SiO2–MgO–Al2O3–B2O3 system. This technology permits both microalloying of the steel with boron (reduced from the oxide phase) and desulfurization of the steel. The resulting boron content in the steel is 0.001–0.008%; the sulfur content in low-alloy steel and pipe steel is low (0.004–0.010%); and the consumption of manganese ferroalloys is reduced to 0.5 kg/t for 08кп steel and 1.4 kg/t for 09Г2C steel. In addition, the proposed technology increases the strength of the rolled steel, without loss in its plasticity; and reduces the environmental impact thanks to the replacement of fluorspar by colemanite.  相似文献   
62.
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   
63.
基于光纤技术的采空区发火监测系统由传感器、数据传输、数据分析与控制三大部分构成,研发新一代适合煤矿安全领域应用的先进传感器、并以此为基础构建新型煤矿安全灾害监测预警系统,对于实现煤矿安全发展具有十分重要的意义。  相似文献   
64.
65.
66.
Hyperspectral imaging (HSI) is a spectroscopic method that uses densely sampled measurements along the electromagnetic spectrum to identify the unique molecular composition of an object. Traditionally HSI has been associated with remote sensing-type applications, but recently has found increased use in biomedicine, from investigations at the cellular to the tissue level. One of the main challenges in the analysis of HSI is estimating the proportions, also called abundance fractions of each of the molecular signatures. While there is great promise for HSI in the area of biomedicine, large variability in the measurements and artifacts related to the instrumentation has slow adoption into more widespread practice. In this article, we propose a novel regularization and variable selection method called the spatial LASSO (SPLASSO). The SPLASSO incorporates spatial information via a graph Laplacian-based penalty to help improve the model estimation process for multivariate response data. We show the strong performance of this approach on a benchmark HSI dataset with considerable improvement in predictive accuracy over the standard LASSO. Supplementary materials for this article are available online.  相似文献   
67.
68.
69.
70.
Powder Metallurgy and Metal Ceramics - Multiphase La 2 MgNi 9 alloys are synthesized by induction melting. The crystalline structures of all phases in the alloys are determined with X-ray...  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