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   785篇
  免费   56篇
  国内免费   3篇
电工技术   3篇
综合类   1篇
化学工业   327篇
金属工艺   11篇
机械仪表   19篇
建筑科学   32篇
能源动力   24篇
轻工业   121篇
水利工程   6篇
石油天然气   3篇
无线电   25篇
一般工业技术   166篇
冶金工业   23篇
原子能技术   5篇
自动化技术   78篇
  2024年   4篇
  2023年   14篇
  2022年   73篇
  2021年   74篇
  2020年   36篇
  2019年   40篇
  2018年   21篇
  2017年   37篇
  2016年   27篇
  2015年   18篇
  2014年   34篇
  2013年   54篇
  2012年   46篇
  2011年   64篇
  2010年   36篇
  2009年   42篇
  2008年   44篇
  2007年   29篇
  2006年   44篇
  2005年   12篇
  2004年   20篇
  2003年   17篇
  2002年   18篇
  2001年   9篇
  2000年   2篇
  1999年   5篇
  1998年   4篇
  1996年   3篇
  1995年   4篇
  1994年   1篇
  1992年   1篇
  1989年   2篇
  1988年   1篇
  1985年   1篇
  1980年   1篇
  1979年   2篇
  1977年   2篇
  1963年   2篇
排序方式: 共有844条查询结果,搜索用时 15 毫秒
101.
102.
Mechanochemical interaction of Fe powder with the liquid Ga–In eutectic in the Fe-rich concentration corner of the Fe–Ga–In phase diagram was studied and compared with binary Fe–Ga and Fe–In specimens. Slow formation of diluted solid solutions in the Fe–In system was confirmed. In the Fe–Ga system, the dominant concentrated A2 solid solution is formed with Heff?=?236 kOe, accompanied by ordered D03 and L12 phases. The Fe–Ga–In system features a stationary equilibrium between the concentrated A2 phase and D03 in the iron matrix.  相似文献   
103.
104.
Carbon is the most abundant dust-forming element in the interstellar medium. Tremendous amount of meteorites containing plentiful carbon and carbon-enriched dust particles have reached the Earth daily. National Institute of Health panel accumulates evidences that nano-sized air pollution components may have a significant impact on the central nervous system (CNS) in health and disease. During inhalation, nano-/microsized particles are efficiently deposited in nasal, tracheobronchial, and alveolar regions and can be transported to the CNS. Based on above facts, here we present the study, the aims of which were: 1) to upgrade inorganic Martian dust simulant derived from volcanic ash (JSC-1a/JSC, ORBITEC Orbital Technologies Corporation, Madison, Wisconsin) by the addition of carbon components, that is, nanodiamonds and carbon dots; 2) to analyse acute effects of upgraded simulant on key characteristics of synaptic neurotransmission; and 3) to compare above effects with those of inorganic dust and carbon components per se. Acute administration of carbon-containing Martian dust analogues resulted in a significant decrease in transporter-mediated uptake of L-[14C]glutamate (the major excitatory neurotransmitter) and [3H]GABA (the main inhibitory neurotransmitter) by isolated rat brain nerve terminals. The extracellular level of both neurotransmitters increased in the presence of carbon-containing Martian dust analogues. These effects were associated with action of carbon components of upgraded Martian dust simulant, but not with its inorganic constituent. This fact indicates that carbon component of native Martian dust can have deleterious effects on extracellular glutamate and GABA homeostasis in the CNS, and so glutamate- and GABA-ergic neurotransmission disballansing exitation and inhibition.  相似文献   
105.
106.
107.
Industrial production of lactose hydrolyzed milk powder (LHMP) remains challenging. Due to the presence of the monosaccharides glucose and galactose, lactose-free powders tend to suffer stickiness, caking, and browning during drying and storage. We sought to find ideal conditions spray dryer inlet air temperature (θair,in) and concentrated milk flow rate (mCM) for LHMP production. We tested θair,in settings of 115–160°C and mCM of 0.3–1.5?kg?·?h?1, and also applied mass and energetic balances. LHMP generally exhibited higher mass and energetic losses than the control (milk powder containing lactose), as a consequence of the relatively low dryability of LHMP. For a lab scale spray dryer, the ideal conditions settings for LHMP production were θair,in?=?145?±?2°C and mCM?=?1.0?kg?·?h?1, taking into account the mass yield and energetic cost (kJ?·?kg?1 of powder) of the process. These ideal conditions are a potential tool for the industrial development of lactose-free dairy powders.  相似文献   
108.
Abstract

This article draws on in-depth research on the nature and intensity of neighbour relations in an area in Peckham, London, which underwent urban regeneration aimed at improving the urban environment and increasing the area’s tenure mix. Drawing on the literature on neighbouring, the article explores residents’ perceptions and attitudes towards their neighbours and the dynamics of their routine interactions. Despite findings pointing towards a general atmosphere of cordiality and solidarity, interactions were casual, coexisted with prejudiced views towards certain groups and areas, and were viewed by residents as part of their everyday social practices of community. As a result, very little else was exchanged between tenures, putting into question some policy assumptions that the increased physical proximity between housing tenures can potentially lead to instrumental interaction that can benefit low-income households in social housing. Reflecting on these findings, the article discusses some implications that have relevance for policy and research.  相似文献   
109.
We consider infrastructure-based mobile networks that are assisted by a single relay transmission where both the downstream destination and relay nodes are mobile. Selecting the optimal transmission path for a destination node requires up-to-date link quality estimates of all relevant links. If the relay selection is based on link quality measurements, the number of links to update grows quadratically with the number of nodes, and measurements need to be updated frequently when nodes are mobile. In this paper, we consider a location-based relay selection scheme where link qualities are estimated from node positions; in the scenario of a node-based location system such as GPS, the location-based approach reduces signaling overhead, which in this case only grows linearly with the number of nodes. This paper studies these two relay selection approaches and investigates how they are affected with varying information update interval, node mobility, location inaccuracy, and inaccurate propagation model parameters. Our results show that location-based relay selection performs better than SNR-based relay selection at typical levels of location error when medium-scale fading can be neglected or accurately predicted.  相似文献   
110.
Abstract and Key Results
▪  Subsidiary managers are faced with complex managerial roles involving both the interests of the multinational corporation (MNC) and the subsidiary. We suggest complex roles are best fulfilled when managers develop dual organizational identification towards both entities.
▪  Based on a conceptualization of dual organizational identification in terms of relative magnitude, we test the effect of dual identification on subsidiary manager roles and role conflict.
▪  Results indicate that high identification with both entities is associated with high role fulfillment and that similarity in organizational identities directly affects role conflict.
  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