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   1574179篇
  免费   26965篇
  国内免费   6882篇
电工技术   34083篇
综合类   6484篇
化学工业   255141篇
金属工艺   65583篇
机械仪表   44660篇
建筑科学   44650篇
矿业工程   11605篇
能源动力   50012篇
轻工业   122958篇
水利工程   16332篇
石油天然气   36641篇
武器工业   153篇
无线电   197287篇
一般工业技术   295258篇
冶金工业   220669篇
原子能技术   34243篇
自动化技术   172267篇
  2021年   13410篇
  2020年   12061篇
  2019年   14789篇
  2018年   17574篇
  2017年   16900篇
  2016年   21688篇
  2015年   16849篇
  2014年   28174篇
  2013年   87721篇
  2012年   37489篇
  2011年   51678篇
  2010年   44196篇
  2009年   51855篇
  2008年   47904篇
  2007年   45557篇
  2006年   46565篇
  2005年   41617篇
  2004年   43425篇
  2003年   42719篇
  2002年   39990篇
  2001年   37211篇
  2000年   34538篇
  1999年   35204篇
  1998年   60320篇
  1997年   47813篇
  1996年   39976篇
  1995年   34384篇
  1994年   31619篇
  1993年   31543篇
  1992年   26645篇
  1991年   24075篇
  1990年   24254篇
  1989年   23239篇
  1988年   21825篇
  1987年   20034篇
  1986年   19483篇
  1985年   22775篇
  1984年   22466篇
  1983年   20387篇
  1982年   19358篇
  1981年   19525篇
  1980年   18210篇
  1979年   18570篇
  1978年   17898篇
  1977年   18636篇
  1976年   21416篇
  1975年   16058篇
  1974年   15522篇
  1973年   15625篇
  1972年   13156篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Nagourney  Tal  Jordan  Jonathan  Marsh  Laban  Scardino  Dennis  May  Brian M. 《Fire Technology》2022,58(2):1065-1066
Fire Technology - The original publication of the article unfortunately contained a mistake in Figure 2c.  相似文献   
2.
Gao  Dongli  Chen  Xingchao  Yang  Xinyu  Tong  Y. O.  Lin  Peng 《Fire Technology》2022,58(1):571-590
Fire Technology - The critical velocity is the minimum velocity blowing towards the fire seat in tunnels to reduce the length of back-layering to zero, and it has been extensively adopted in the...  相似文献   
3.
Fire Technology - Reinforced concrete beams lose resistance at high temperatures and so as to guarantee their good performance, it is mandatory to consider this accidental action in design. As an...  相似文献   
4.
Fire Technology - Fires occurring at the wildland-urban interface (WUI) have rapidly increased in frequency and severity over the past few decades. As a result of these extreme fires, multiple...  相似文献   
5.
Fire Technology - The directional flame thermometer (DFT) is a device used to measure radiative heat flux in fire scenarios. In many DFT applications, radiation is the dominant mode of heat...  相似文献   
6.
Soil Mechanics and Foundation Engineering - The present article describes a procedure for predicting the settlement of structures surrounding deep excavations in Vietnam that takes the...  相似文献   
7.
Zhu  C.  Liu  H.  Niu  X.  Ma  H.  Jiao  Z. 《Soil Mechanics and Foundation Engineering》2022,59(3):253-260
Soil Mechanics and Foundation Engineering - Mining activity reduces the strength and stability of coal and can lead to frequent coal/rock instability disasters. To address this problem, the soft...  相似文献   
8.
Herein, the rational design micromilieus involved silk fibroin (SF)-based materials have been used to encapsulate the osteoblasts, forming an extracellular coated shell on the cells, which exhibited the high potential to shift the regulation of osteoblasts to osteocytes by encapsulation cues. SF coating treated cells showed a change in cell morphology from osteoblasts-like to osteocytes-like shape compared with untreated ones. Moreover, the expression of alkaline phosphatase (ALP), collagen I (Col I) and osteocalcin (OCN) further indicated a potential approach for inducing osteoblasts regulation, which typically accelerates calcium deposition and cell calcification, presenting a key role for the SF encapsulation in controlling osteoblasts behavior. This discovery showed that SF-based cell encapsulation could be used for osteoblasts behavior regulation, which offers a great potential to modulate mammalian cells’ phenotype involving alternating surrounding cues.  相似文献   
9.
Digital twin (DT) has garnered attention in both industry and academia. With advances in big data and internet of things (IoTs) technologies, the infrastructure for DT implementation is becoming more readily available. As an emerging technology, there are both potential and challenges. DT is a promising methodology to leverage the modern data explosion to aid engineers, managers, healthcare experts and politicians in managing production lines, patient health and smart cities by providing a comprehensive and high fidelity monitoring, prognostics and diagnostics tools. New research and surveys into the topic are published regularly, as interest in this technology is high although there is a lack of standardization to the definition of a DT. Due to the large amount of information present in a DT system and the dual cyber and physical nature of a DT, augmented reality (AR) is a suitable technology for data visualization and interaction with DTs. This paper seeks to classify different types of DT implementations that have been reported, highlights some researches that have used AR as data visualization tool in DT, and examines the more recent approaches to solve outstanding challenges in DT and the integration of DT and AR.The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-021-00375-w  相似文献   
10.
Time does not go backward. A negative duration, such as “time period” at first sight is difficult to interpret. Previous network techniques (CPM/PERT/PDM) did not support negative parameters and/or loops (potentially necessitating recursive calculations) in the model because of the limited computing and data storage capabilities of early computers. Monsieur Roy and John Fondahl implicitly introduced negative weights into network techniques to represent activities with fixed or estimated durations (MPM/PDM). Subsequently, the introduction of negative lead and/or lag times by software developers (IBM) apparently overcome the limitation of not allowing negative time parameters in time model. Referring to general digraph (Event on Node) representation where activities are represented by pairs of nodes and pairwise relative time restrictions are represented by weighted arrows, we can release most restraints in constructing the graph structure (incorporating the dynamic model of the inner logic of time plan), and a surprisingly flexible and handy network model can be developed that provides all the advantages of the abovementioned techniques. This paper aims to review the theoretical possibilities and technical interpretations (and use) of negative weights in network time models and discuss approximately 20 types of time-based restrictions among the activities of construction projects. We focus on pure relative time models, without considering other restrictions (such as calendar data, time-cost trade-off, resource allocation or other constraints).  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