全文获取类型
收费全文 | 3864篇 |
免费 | 47篇 |
国内免费 | 11篇 |
专业分类
电工技术 | 41篇 |
综合类 | 7篇 |
化学工业 | 362篇 |
金属工艺 | 36篇 |
机械仪表 | 68篇 |
建筑科学 | 123篇 |
矿业工程 | 14篇 |
能源动力 | 87篇 |
轻工业 | 220篇 |
水利工程 | 21篇 |
石油天然气 | 12篇 |
无线电 | 451篇 |
一般工业技术 | 402篇 |
冶金工业 | 1819篇 |
原子能技术 | 34篇 |
自动化技术 | 225篇 |
出版年
2022年 | 13篇 |
2021年 | 29篇 |
2020年 | 16篇 |
2019年 | 25篇 |
2018年 | 24篇 |
2017年 | 26篇 |
2016年 | 26篇 |
2015年 | 23篇 |
2014年 | 37篇 |
2013年 | 138篇 |
2012年 | 79篇 |
2011年 | 96篇 |
2010年 | 78篇 |
2009年 | 76篇 |
2008年 | 90篇 |
2007年 | 90篇 |
2006年 | 94篇 |
2005年 | 73篇 |
2004年 | 76篇 |
2003年 | 68篇 |
2002年 | 66篇 |
2001年 | 76篇 |
2000年 | 51篇 |
1999年 | 92篇 |
1998年 | 539篇 |
1997年 | 305篇 |
1996年 | 221篇 |
1995年 | 137篇 |
1994年 | 104篇 |
1993年 | 130篇 |
1992年 | 53篇 |
1991年 | 48篇 |
1990年 | 58篇 |
1989年 | 44篇 |
1988年 | 42篇 |
1987年 | 45篇 |
1986年 | 55篇 |
1985年 | 60篇 |
1984年 | 52篇 |
1983年 | 37篇 |
1982年 | 41篇 |
1981年 | 40篇 |
1980年 | 35篇 |
1979年 | 21篇 |
1978年 | 25篇 |
1977年 | 72篇 |
1976年 | 146篇 |
1975年 | 17篇 |
1973年 | 24篇 |
1971年 | 13篇 |
排序方式: 共有3922条查询结果,搜索用时 15 毫秒
101.
Green CS Sugarman MA Medford K Klobusicky E Daphne Bavelier 《Computers in human behavior》2012,28(3):984-994
There is now a substantial body of work demonstrating that action video game experience results in enhancements in a wide variety of perceptual skills. More recently, several groups have also demonstrated improvements in abilities that are more cognitive in nature, in particular, the ability to efficiently switch between tasks. In a series of four experiments, we add to this body of work, demonstrating that the action video game player advantage is not exclusively due to an ability to map manual responses onto arbitrary buttons, but rather generalizes to vocal responses, is not restricted to tasks that are perceptual in nature (e.g. respond to a physical dimension of the stimulus such as its color), but generalizes to more cognitive tasks (e.g. is a number odd or even), and is present whether the switch requires a goal-switch or only a motor switch. Finally, a training study establishes that the relationship between the reduction in switch cost and action game playing is causal. 相似文献
102.
Geoffrey Levine Ugur Kuter Antons Rebguns Derek Green Diana Spears 《Computational Intelligence》2012,28(3):329-357
We present a Bayesian approach to learning flexible safety constraints and subsequently verifying whether plans satisfy these constraints. Our approach, called the Safety Constraint Learner/Checker (SCLC), infers safety constraints from a single expert demonstration trace and minimal background knowledge, and applies these constraints to the solutions proposed by multiple planning agents in an integrated and heterogeneous ensemble. The SCLC calculates how much to blame plan fragments (partial solutions) generated by the individual planning agents. This information is used when composing these fragments into a final overall plan. In particular, fragments whose safety violations exceed a threshold are rejected. This facilitates the generation of safe plans. We have integrated the SCLC within the Generalized Integrated Learning Architecture, which was designed for Defense Advanced Research Projects Agency (DARPA)’s Integrated Learning (IL) program. The main goal of the IL program is to promote the development and success of sophisticated systems that learn to solve challenging real‐world problems based on a simple demonstration by a human expert and exiguous domain knowledge. We present experimental results showing the advantages of the SCLC on two multiagent problem‐solving tasks that were benchmark applications in DARPA’s IL program. 相似文献
103.
The main features of a passive thin film display cell based on the electrochemically reversible formation of a tungsten bronze according to the reaction where 0 < x < 1 are considered. Chemical analysis of an electrochemically coloured WO3 film has confirmed the presence of M. It is shown that a critical requirement of these cells is that Dτ(qCm/Q)2 ≈ 1, where the symbols are, in order, the M+ diffusion coefficient, the required device response time, the electronic charge, the maximum practical volume concentration of M in the WO3 film and lastly the area colouring charge. Typical energy requirements might be about 10 mJ cm?2 per complete cycle in a favourable case.Ionic injection overpotentials and ionic diffusion both appear to play a significant role in determining cell currents. Preliminary diffusion coefficient results for Li+ in r.f. sputtered WO3 films are reported, and their predicted dependence of film structure is discussed. The optical absorption of coloured WO3 films is presented, and it is interpreted as being predominantly due to free-electron intraband transitions. 相似文献
104.
Inhibition of HeLa cell messenger RNA translation by 7-methylguanosine 5'-monophosphate 总被引:2,自引:0,他引:2
LA Weber ER Feman ED Hickey MC Williams C Baglioni 《Canadian Metallurgical Quarterly》1976,251(18):5657-5662
Translation of HeLa cell RNA containing poly(A) in a wheat germ cell-free system is markedly but incompletely inhibited by 7-methylguanosine 5'-monophosphate (m7G5'p). We have analyzed the translation products synthesized in the presence of different concentrations of m7G5'p and find that translation of all mRNAs is equally inhibited. To demonstrate the specificity of the inhibitor for RNAs with 5'-terminal m7G5' ppp... we show that specific translation products of satellite tobacco necrosis virus RNA, which does not have this 5' terminus, are synthesized in the presence of m7G5' p. Protein synthesis programmed by endogenous mRNA in a HeLa cell-free system is inhibited after a 10-min lag by m7G5' p. Other guanosine nucleotides without the 7-methyl group or with the phosphate in a different position are not inhibitor. We show that translation of all mRNAs is inhibited to a similar extent by m7G5'p in the HeLa cell-free system, by synthesizing 35S-labeled proteins in the presence of different inhibitory concentrations of this nucleotide and analyzing the translation products by electrophoresis and autoradiography. Translation of encephalomyocarditis virus RNA added to the HeLa cell-free system is not inhibited by m7"g5p; this viral RNA does not have this nucleotide at the 5' terminus. This indicates that m7G5'p specifically inhibits translation of mRNAs with the 5' terminus m7G5'ppp... and suggests that initiation of translation of picornavirus RNA may proceed via a mechanism different from that of cellular mRNAs. 相似文献
105.
106.
Fault and attack management in all-optical networks 总被引:2,自引:0,他引:2
Ridha Rejeb Mark S. Leeson Roger J. Green 《Communications Magazine, IEEE》2006,44(11):79-86
Network management for optical networks faces additional security challenges that arise by using transparent optical network components in communication systems. While some available management mechanisms are applicable to different types of network architectures, many of these are not adequate for all-optical networks. These have unique features and requirements in terms of security and quality of service, thus requiring a much more targeted approach in terms of network management. In this article we consider management issues with particular emphasis on complications that arise due to the unique characteristics and peculiar behaviors of transparent network components. In particular, signal quality monitoring is still a major complication in all-optical networks. Despite new methods for detection and localization of attacks having been proposed, no robust standards or techniques exist to date for guaranteeing the quality of service in these networks. Therefore, sophisticated mechanisms that assist in managing and assessing the proper function of transparent network components are highly desirable. Accordingly, we present an algorithm for multiple attack localization and identification that can participate in some tasks for fault management of all-optical networks 相似文献
107.
Sergio L. González-Cortés Tian-Cun Xiao Nick Rees Dora Méhn Malcolm L.H. Green 《Materials Research Bulletin》2005,40(7):1112-1119
The first examples of mesostructured materials containing Mo- and W-oxo-sulphur species incorporated into a poorly ordered MCM-41 framework have been prepared under hydrothermal condition and alkaline medium. The incorporation of oxygen-sulphur derivates of molybdenum and tungsten not only increases significantly the pore diameter, but also improves the thermal stability of the MCM-41-related mesoporous material. 相似文献
108.
109.
110.
Houses in multiple occupation (HMOs) in which tenants share facilities are housing an increasing proportion of vulnerable adults who have limited affordable housing options. However, knowledge about how these types of property are managed is limited. In this paper, we examine the governance function of HMO landlords from the perspective of landlords/landlord agents and the tenants that live within their properties. The landlord exercises control through formal and informal risk assessment of tenants and close surveillance of them. These control mechanisms may also involve direct or indirect provision of support and care to some tenants. This illustrates the complex relationship between care and control and the extent to which both are integral to the housing management of vulnerable tenants living in HMOs. We suggest that this dual function calls for a critical examination of what constitutes a ‘good landlord’. 相似文献