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   65729篇
  免费   3610篇
  国内免费   91篇
电工技术   576篇
综合类   39篇
化学工业   13708篇
金属工艺   1211篇
机械仪表   1378篇
建筑科学   2941篇
矿业工程   165篇
能源动力   1800篇
轻工业   8846篇
水利工程   764篇
石油天然气   289篇
武器工业   6篇
无线电   3739篇
一般工业技术   10809篇
冶金工业   12101篇
原子能技术   360篇
自动化技术   10698篇
  2023年   485篇
  2022年   679篇
  2021年   1526篇
  2020年   1200篇
  2019年   1400篇
  2018年   2059篇
  2017年   1947篇
  2016年   2205篇
  2015年   1753篇
  2014年   2272篇
  2013年   4856篇
  2012年   3635篇
  2011年   3969篇
  2010年   3140篇
  2009年   2917篇
  2008年   3165篇
  2007年   2985篇
  2006年   2403篇
  2005年   2103篇
  2004年   1813篇
  2003年   1723篇
  2002年   1585篇
  2001年   1103篇
  2000年   873篇
  1999年   967篇
  1998年   2528篇
  1997年   1818篇
  1996年   1320篇
  1995年   1000篇
  1994年   854篇
  1993年   849篇
  1992年   616篇
  1991年   375篇
  1990年   496篇
  1989年   463篇
  1988年   423篇
  1987年   438篇
  1986年   377篇
  1985年   498篇
  1984年   486篇
  1983年   360篇
  1982年   335篇
  1981年   348篇
  1980年   334篇
  1979年   300篇
  1978年   280篇
  1977年   335篇
  1976年   418篇
  1975年   227篇
  1973年   204篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
31.
32.
33.
34.
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   
35.
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   
36.
37.
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   
38.
ABSTRACT

In this paper, we review some algebraic control system. Precisely, linear and bilinear systems on Euclidean spaces and invariant and linear systems on Lie groups. The fourth classes of systems have a common issue: to any class, there exists an associated subgroup. From this object, we survey the controllability property. Especially, from those coming from our contribution to the theory.  相似文献   
39.
Context: The administration of pharmabiotics is a promising alternative to antimicrobial drugs for the treatment and/or prevention of female urogenital infections.

Objective: To design pharmabiotic formulations including bioactive ingredients of microbial origin combined with non-microbial substances and then to evaluate the stability of the combinations during freeze-drying and storage.

Materials and methods: Different formulations including Lactobacillus gasseri CRL 1263, Lactobacillus salivarius CRL 1328, salivaricin CRL 1328 (a bacteriocin) and non-microbial compounds (lactose, inulin and ascorbic acid) were assayed, and the ingredients were freeze-dried together or separately. The formulations were stored in gelatin capsules at 4?°C for 360?d.

Results: The viability of lactobacilli was affected to different extents depending on the strains and on the formulations assayed. L. salivarius and ascorbic acid were successfully combined only after the freeze-drying process. Salivaricin activity was not detected in formulations containing L. gasseri. However, when combined with ascorbic acid, lactose, inulin or L. salivarius, the bacteriocin maintained its activity for 360?d. The selected microorganisms proved to be compatible for their inclusion in multi-strain formulations together with lactose, inulin and ascorbic acid. Salivaricin could be included only in a L. salivarius CRL 1328 single-strain formulation together with non-microbial substances.

Conclusions: This study provides new insights into the design of urogenital pharmabiotics combining beneficial lactobacilli, salivaricin CRL 1328 and compounds with different functionalities.  相似文献   
40.
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