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   1613954篇
  免费   28429篇
  国内免费   7054篇
电工技术   34972篇
综合类   6515篇
化学工业   274857篇
金属工艺   66072篇
机械仪表   46219篇
建筑科学   48617篇
矿业工程   11734篇
能源动力   50615篇
轻工业   125998篇
水利工程   16338篇
石油天然气   38117篇
武器工业   153篇
无线电   200069篇
一般工业技术   301579篇
冶金工业   218457篇
原子能技术   34470篇
自动化技术   174655篇
  2021年   15676篇
  2020年   12122篇
  2019年   14860篇
  2018年   18452篇
  2017年   17857篇
  2016年   22919篇
  2015年   17857篇
  2014年   29059篇
  2013年   88751篇
  2012年   38538篇
  2011年   53223篇
  2010年   45495篇
  2009年   53111篇
  2008年   49005篇
  2007年   46712篇
  2006年   47075篇
  2005年   42555篇
  2004年   43959篇
  2003年   43609篇
  2002年   42341篇
  2001年   39561篇
  2000年   37559篇
  1999年   37573篇
  1998年   61875篇
  1997年   49729篇
  1996年   42137篇
  1995年   34735篇
  1994年   31917篇
  1993年   31922篇
  1992年   27197篇
  1991年   24454篇
  1990年   24653篇
  1989年   23797篇
  1988年   22338篇
  1987年   20460篇
  1986年   19832篇
  1985年   23154篇
  1984年   22855篇
  1983年   20814篇
  1982年   19696篇
  1981年   19896篇
  1980年   18526篇
  1979年   18848篇
  1978年   18155篇
  1977年   18843篇
  1976年   21354篇
  1975年   16304篇
  1974年   15688篇
  1973年   15833篇
  1972年   13178篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
131.
132.
Small interfering RNA (siRNA) can effectively silence target genes through Argonate 2 (Ago2)-induced RNA interference (RNAi). It is very important to control siRNA activity in both spatial and temporal modes. Among different masking strategies, photocaging can be used to regulate gene expression through light irradiation with spatiotemporal and dose-dependent resolution. Many different caging strategies and caging groups have been reported for light-activated siRNA gene silencing. Herein, we describe a novel caging strategy that increases the blocking effect of RISC complex formation/process through host/guest (including ligand/receptor) interactions, thereby enhancing the inhibition of caged siRNA activity until light activation. This strategy can be used as a general approach to design caged siRNAs for the photomodulation of gene silencing of exogenous and endogenous genes.  相似文献   
133.
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   
134.
135.
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   
136.
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   
137.
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   
138.
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   
139.
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   
140.
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   
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