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   1623811篇
  免费   28396篇
  国内免费   7226篇
电工技术   35480篇
综合类   6514篇
化学工业   270857篇
金属工艺   67151篇
机械仪表   47844篇
建筑科学   48008篇
矿业工程   12042篇
能源动力   50643篇
轻工业   125063篇
水利工程   16843篇
石油天然气   37958篇
武器工业   169篇
无线电   201524篇
一般工业技术   307504篇
冶金工业   220784篇
原子能技术   34802篇
自动化技术   176247篇
  2021年   15645篇
  2020年   12108篇
  2019年   14899篇
  2018年   19974篇
  2017年   19903篇
  2016年   23619篇
  2015年   17839篇
  2014年   28938篇
  2013年   88512篇
  2012年   39369篇
  2011年   55421篇
  2010年   47062篇
  2009年   54780篇
  2008年   50469篇
  2007年   48836篇
  2006年   47439篇
  2005年   43791篇
  2004年   44660篇
  2003年   44203篇
  2002年   42704篇
  2001年   39630篇
  2000年   37682篇
  1999年   37581篇
  1998年   62709篇
  1997年   50060篇
  1996年   42341篇
  1995年   35002篇
  1994年   31628篇
  1993年   31452篇
  1992年   26678篇
  1991年   24086篇
  1990年   24381篇
  1989年   23369篇
  1988年   21883篇
  1987年   20077篇
  1986年   19609篇
  1985年   22954篇
  1984年   22540篇
  1983年   20521篇
  1982年   19341篇
  1981年   19482篇
  1980年   18227篇
  1979年   18614篇
  1978年   17826篇
  1977年   18559篇
  1976年   20742篇
  1975年   16074篇
  1974年   15523篇
  1973年   15665篇
  1972年   13198篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
Extracellular vesicles (EVs) are membranous structures, which are secreted by almost every cell type analyzed so far. In addition to their importance for cell-cell communication under physiological conditions, EVs are also released during pathogenesis and mechanistically contribute to this process. Here we summarize their functional relevance in asthma, one of the most common chronic non-communicable diseases. Asthma is a complex persistent inflammatory disorder of the airways characterized by reversible airflow obstruction and, from a long-term perspective, airway remodeling. Overall, mechanistic studies summarized here indicate the importance of different subtypes of EVs and their variable cargoes in the functioning of the pathways underlying asthma, and show some interesting potential for the development of future therapeutic interventions. Association studies in turn demonstrate a good diagnostic potential of EVs in asthma.  相似文献   
132.
133.
Wireless Personal Communications - Multiple inputs multiple outputs (MIMO) is a reliable technique which can manage the increased wireless data traffic in the future generation of wireless...  相似文献   
134.
Wireless Personal Communications - This paper summarizes the ongoing research initiatives based on the advanced multiple access techniques towards the fifth generation (5G) wireless communication...  相似文献   
135.
Russian Engineering Research - The modernization of manufacturing by the comprehensive application of digital technology—in both production and management—is considered. Principles are...  相似文献   
136.
Exocytosis plays an essential role in the communication between cells in the nervous system. Understanding the regulation of neurotransmitter release during exocytosis and the amount of neurotransmitter content that is stored in vesicles is of importance, as it provides fundamental insights to understand how the brain works and how neurons elicit a certain behavior. In this minireview, we summarize recent progress in amperometric measurements for monitoring exocytosis in single cells and electrochemical cytometry measurements of vesicular neurotransmitter content in individual vesicles. Important steps have increased our understanding of the different mechanisms of exocytosis. Increasing evidence is firmly establishing that partial release is the primary mechanism of release in multiple cell types.  相似文献   
137.
A known strategy for improving the properties of layered oxide electrodes in sodium-ion batteries is the partial substitution of transition metals by Li. Herein, the role of Li as a defect and its impact on sodium storage in P2-Na0.67Mn0.6Ni0.2Li0.2O2 is discussed. In tandem with electrochemical studies, the electronic and atomic structure are studied using solid-state NMR, operando XRD, and density functional theory (DFT). For the as-synthesized material, Li is located in comparable amounts within the sodium and the transition metal oxide (TMO) layers. Desodiation leads to a redistribution of Li ions within the crystal lattice. During charging, Li ions from the Na layer first migrate to the TMO layer before reversing their course at low Na contents. There is little change in the lattice parameters during charging/discharging, indicating stabilization of the P2 structure. This leads to a solid-solution type storage mechanism (sloping voltage profile) and hence excellent cycle life with a capacity of 110 mAh g-1 after 100 cycles. In contrast, the Li-free compositions Na0.67Mn0.6Ni0.4O2 and Na0.67Mn0.8Ni0.2O2 show phase transitions and a stair-case voltage profile. The capacity is found to originate from mainly Ni3+/Ni4+ and O2-/O2-δ redox processes by DFT, although a small contribution from Mn4+/Mn5+ to the capacity cannot be excluded.  相似文献   
138.
Multimedia Tools and Applications - The design of robots capable of operating autonomously in changing and unstructured environments, requires using complex software architectures in which,...  相似文献   
139.
Russian Engineering Research - The stability of robot-mower motion in a specific direction is considered. The direction is regulated by means of an angular sensor and a programmable controller...  相似文献   
140.
Revin  A. A.  Mikhaylova  A. M.  Konakov  A. A.  Tsyplenkov  V. V.  Shastin  V. N. 《Semiconductors》2021,55(12):879-884
Semiconductors - The wave functions of electrons localized at P, As, and Sb shallow donors in Ge are calculated in the envelope function approximation taking into account valley–orbit...  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