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   341108篇
  免费   5442篇
  国内免费   766篇
电工技术   6532篇
综合类   585篇
化学工业   52685篇
金属工艺   10963篇
机械仪表   9491篇
建筑科学   9721篇
矿业工程   969篇
能源动力   9531篇
轻工业   33538篇
水利工程   2901篇
石油天然气   3775篇
武器工业   13篇
无线电   41850篇
一般工业技术   63837篇
冶金工业   62383篇
原子能技术   5691篇
自动化技术   32851篇
  2021年   2876篇
  2020年   2057篇
  2019年   2708篇
  2018年   4316篇
  2017年   4076篇
  2016年   4287篇
  2015年   3223篇
  2014年   5373篇
  2013年   16434篇
  2012年   8856篇
  2011年   11946篇
  2010年   9380篇
  2009年   10506篇
  2008年   11189篇
  2007年   11133篇
  2006年   9923篇
  2005年   9167篇
  2004年   8809篇
  2003年   8473篇
  2002年   8258篇
  2001年   8167篇
  2000年   7692篇
  1999年   8073篇
  1998年   18165篇
  1997年   13333篇
  1996年   10567篇
  1995年   8364篇
  1994年   7649篇
  1993年   7339篇
  1992年   5727篇
  1991年   5311篇
  1990年   5300篇
  1989年   5113篇
  1988年   4952篇
  1987年   4199篇
  1986年   4276篇
  1985年   5089篇
  1984年   4639篇
  1983年   4314篇
  1982年   3853篇
  1981年   4013篇
  1980年   3682篇
  1979年   3658篇
  1978年   3446篇
  1977年   4006篇
  1976年   5035篇
  1975年   2952篇
  1974年   2811篇
  1973年   2817篇
  1972年   2324篇
排序方式: 共有10000条查询结果,搜索用时 140 毫秒
51.
52.
Ischemic and hemorrhagic strokes are associated with severe functional disability and high mortality. Except for recombinant tissue plasminogen activator, therapies targeting the underlying pathophysiology of central nervous system (CNS) ischemia and hemorrhage are strikingly lacking. Sur1-regulated channels play essential roles in necrotic cell death and cerebral edema following ischemic insults, and in neuroinflammation after hemorrhagic injuries. Inhibiting endothelial, neuronal, astrocytic and oligodendroglial sulfonylurea receptor 1–transient receptor potential melastatin 4 (Sur1–Trpm4) channels and, in some cases, microglial KATP (Sur1–Kir6.2) channels, with glibenclamide is protective in a variety of contexts. Robust preclinical studies have shown that glibenclamide and other sulfonylurea agents reduce infarct volumes, edema and hemorrhagic conversion, and improve outcomes in rodent models of ischemic stroke. Retrospective studies suggest that diabetic patients on sulfonylurea drugs at stroke presentation fare better if they continue on drug. Additional laboratory investigations have implicated Sur1 in the pathophysiology of hemorrhagic CNS insults. In clinically relevant models of subarachnoid hemorrhage, glibenclamide reduces adverse neuroinflammatory and behavioral outcomes. Here, we provide an overview of the preclinical studies of glibenclamide therapy for CNS ischemia and hemorrhage, discuss the available data from clinical investigations, and conclude with promising preclinical results that suggest glibenclamide may be an effective therapeutic option for ischemic and hemorrhagic stroke.  相似文献   
53.
The environmental performance of 316L grade stainless steel, in the form of tensile specimens containing a single corrosion pit with various aspect ratios, under cyclic loading in aerated chloride solutions is investigated in this study. Results from environmental tests were compared and contrasted with those obtained using finite element analysis (FEA). Fractography of the failed specimens obtained from experiments revealed that fatigue crack initiation took place at the base of the shallow pit. The crack initiation shifted towards the shoulder and the mouth of the pit for pits of increasing depth. This process is well predicted by FEA, as the strain contour maps show that strain is the highest around the centric strip of the pit. However, for shallow pits, local strain is uniformly distributed around that strip but begins to concentrate more towards the shoulder and the mouth region for increasingly deep pits.  相似文献   
54.
55.
56.
57.
58.
The workforce ageing phenomenon is recently affecting most of the Organisation for Economic Co-operation and Development (OECD) member countries, due to a general ageing of their populations and a higher average retirement age of the workforce. In this paper, the topic of ageing workforce management is addressed from a production research standpoint, with the aim of understanding how older workers can be supported and involved in a manufacturing system. First, the current state of the art related to the ageing workforce in production systems is presented. This is structured according to four main topics: (1) analysis and evaluation of ageing workers’ functional capacities, (2) consideration of ageing workers’ capacities in industrial system modelling and management, (3) analysis and exploitation of ageing workers’ expertise, (4) acknowledgement, analysis, design and integration of supporting technologies. Next, the discussion on the impact of the ageing workforce on manufacturing systems’ performances leads to the comparison of some technological advances that are related to the Industry 4.0 paradigms. Finally, a future research agenda on this topic is proposed, based on the same topics classification proposed for the literature analysis. Five different research areas are derived, suggesting future directions for appropriate research concerning the employ of older workers in production environments.  相似文献   
59.
Litvyak  V. M.  Cherbunin  R. V.  Kalevich  V. K.  Kavokin  K. V. 《Semiconductors》2020,54(12):1728-1729
Semiconductors - We found bulk n-GaAs layers grown by liquid phase epitaxy to be irregularly stressed. Deformation created by this stress causes a small but detectable quadrupole splitting of...  相似文献   
60.
Wireless Personal Communications - A relatively new area of research and development is Swarm Robotics. It is a part of the swarm intelligence field. In the proposed paper, we shall use swarm...  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