全文获取类型
收费全文 | 8274篇 |
免费 | 518篇 |
国内免费 | 7篇 |
专业分类
电工技术 | 113篇 |
综合类 | 23篇 |
化学工业 | 2149篇 |
金属工艺 | 242篇 |
机械仪表 | 147篇 |
建筑科学 | 591篇 |
矿业工程 | 98篇 |
能源动力 | 282篇 |
轻工业 | 592篇 |
水利工程 | 50篇 |
石油天然气 | 20篇 |
武器工业 | 1篇 |
无线电 | 656篇 |
一般工业技术 | 1725篇 |
冶金工业 | 463篇 |
原子能技术 | 48篇 |
自动化技术 | 1599篇 |
出版年
2024年 | 9篇 |
2023年 | 107篇 |
2022年 | 166篇 |
2021年 | 326篇 |
2020年 | 199篇 |
2019年 | 209篇 |
2018年 | 231篇 |
2017年 | 268篇 |
2016年 | 351篇 |
2015年 | 293篇 |
2014年 | 377篇 |
2013年 | 596篇 |
2012年 | 533篇 |
2011年 | 717篇 |
2010年 | 506篇 |
2009年 | 475篇 |
2008年 | 484篇 |
2007年 | 424篇 |
2006年 | 380篇 |
2005年 | 306篇 |
2004年 | 254篇 |
2003年 | 187篇 |
2002年 | 169篇 |
2001年 | 103篇 |
2000年 | 96篇 |
1999年 | 114篇 |
1998年 | 123篇 |
1997年 | 95篇 |
1996年 | 86篇 |
1995年 | 52篇 |
1994年 | 59篇 |
1993年 | 37篇 |
1992年 | 47篇 |
1991年 | 26篇 |
1990年 | 39篇 |
1989年 | 23篇 |
1988年 | 28篇 |
1987年 | 27篇 |
1986年 | 23篇 |
1985年 | 20篇 |
1984年 | 29篇 |
1983年 | 17篇 |
1982年 | 18篇 |
1981年 | 15篇 |
1980年 | 20篇 |
1978年 | 12篇 |
1977年 | 16篇 |
1976年 | 26篇 |
1975年 | 13篇 |
1969年 | 11篇 |
排序方式: 共有8799条查询结果,搜索用时 31 毫秒
991.
The present study aimed to assess the effects of aging and awareness on conditional discrimination learning within an eyeblink conditioning procedure by using a consecutive age-groups design (20-35 years, 36-50 years, 51-65 years, 66-80 years). Increasing age was associated with a decline in overall eyeblink conditioned response (CR) frequency and a deficit in conditional discrimination learning in the 2 older groups. Awareness of stimulus contingencies affected discrimination performance but not overall CR rates in younger subjects. Older subjects did not achieve eyeblink conditional discrimination learning, regardless of awareness. Discrimination performance correlated with measures of declarative memory. The pattern of results is discussed with respect to the involvement of hippocampal-cerebellar interactions and awareness in the mediation of age-related conditioning changes. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
992.
Jürgen Hesselbach Hans-Werner Hoffmeister Torsten Loohß Mathias Krefft Christian Armbrecht 《Production Engineering》2007,1(2):205-212
In recent years parallel kinematic machines for wood machining have come into use more frequently. Despite first promising
prototypes, these machines are single solutions for specific applications. To meet the requirements of shorter product life
cycles and higher product diversity, high flexibility is demanded of the machining system. This paper presents a new wood
machining center obtaining both, the reduction of the primary and secondary processing times. The machine concept, based on
a parallel kinematic structure, allows high operating speeds and accelerations not only for workpiece machining but also for
handling. Thus, the machine can be used without any external handling devices. The kinematic structure originates from a plane
closed five-bar chain with two linear drives and additional drive axes for stroke and rotation. In order to increase the useable
workspace a continuous motion between different assembly modes is realized. To guarantee a high feed rate and to minimize
set-up times, an optimized dust exhaustion is included. 相似文献
993.
Admitting banking in emissions trading systems reduces overall compliance costs by allowing for inter-temporal flexibility: cost savings can be traded over time. However, unless individual EU Member States (MS) decide differently, the transfer of unused allowances from the period of 2005–2007 into the first commitment period under the Kyoto Protocol, i.e. 2008–2012, will be prohibited. In this paper, we first explore the implications of such a ban on banking when initial emission targets are lenient. This analysis is based on a simulation which was recently carried out in Germany with companies and with a student control group. The findings suggest that a EU-wide ban on banking would lead to efficiency losses in addition to those losses which arise from the lack of inter-temporal flexibility. Second, we use simple game-theoretic considerations to argue that, under reasonable assumptions, such a EU-wide ban on banking will be the equilibrium outcome. Thus, to avoid a possible prisoners’ dilemma, MS should have co-ordinated their banking decisions. 相似文献
994.
It is an accepted, albeit puzzling finding that negative priming (NP) hinges on the presence of distractors in probe displays. In three experiments without probe distractors, the authors yielded evidence that response-biasing processes based on the contingency between prime and probe displays may have caused this finding. It is argued that it is of help in standard NP experiments to process the distractor in the prime display in order to prepare the response to the probe target. When this contingency was removed (Experiments 2 and 3), NP was reliably observed without probe distractors, whereas no NP emerged if the design contained the typical contingency (Experiment 1). For this reason, the data suggest that the absence of NP, which is usually observed under these conditions, may be due to a contingency-based component. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
995.
The MX-80 bentonite is a reference material for studies in clay barriers. This paper aims to present an investigation of the behaviour of such a material during an infiltration test from the bottom in oedometric conditions. Using dual-energy γ radiation technique, time variations of moisture content are measured at various locations along the clay sample. The transport of water occurring in this experiment can be described by the classical diffusion equation in terms of the Boltzmann variable. A parameter of hydraulic diffusivity is obtained with the Matano's method.Two fluid transport mechanisms govern the phenomena: imbibition of the microporosity in the clay grains and capillary imbibition in the mesoporosity around the grains. The competition between these two mechanisms will be put into relief by modelling the distribution of the water between and inside the bentonite grains. A clogging behaviour of the mesopores during the imbibition process will allow to explain the surprising decrease in hydraulic diffusivity. 相似文献
996.
Smart cards im gesundheitswesen 总被引:2,自引:1,他引:1
Dipl.-Wirt.-Inf. Christian Loos 《WIRTSCHAFTSINFORMATIK》2005,47(3):219-221
997.
Christian Hoymann 《Wireless Personal Communications》2006,36(4):363-385
Advanced antenna technologies and algorithms have been developed during the last years. But until today, advanced antenna algorithms in the physical layer and the modes of operation in medium access layers have not been integrated in modern wireless systems. As one of the first standards the metropolitan area network IEEE 802.16 provides means to support smart antenna techniques.After a detailed introduction of the medium access control layer this article outlines the support of space division multiple access (SDMA) techniques by the wireless metropolitan area network IEEE 802.16. New concepts are introduced that allow and further optimize the use of SDMA techniques brought by intelligent antennas. First, the possibility to enable SDMA in the IEEE 802.16a-2003 protocol is investigated, and second the support of SDMA in the revised 802.16-2004 standard is elaborated in detail. To overcome current limitations of 802.16a-2003, an enhanced control structure is introduced in 802.16-2004 that masters a concurrent transmission and reception of data to/from several different subscriber stations. The approach facilitates a fully flexible structure which significantly improves system capacity.
Christian P. Hoymann received his Diploma degree in electrical engineering from RWTH Aachen University in 2002. Before he served a student internship at SIEMENS Corporate Research, Princeton, USA. Since 2002 he is employed as a Research Assistant at the Chair of Communication Networks (ComNets) of RWTH Aachen University where he is working towards his Ph.D. degree.He worked in the fields of traffic engineering and dimensioning of GSM/GPRS networks together with his project partners at D2 Vodafone. He was actively involved in the IST-STRIKE project where smart antenna systems had been integrated in Metropolitan Area Networks. His current research interests include the optimization of MANs especially in consideration of smart antenna technologies such as SDMA and relaying technologies such as Mesh.Mr. Hoymann has published several conference and journal papers and was actively involved in the standardization of SDMA technologies for IEEE 802.16. 相似文献
998.
Green Melanie C.; Wheeler S. Christian; Hermann Anthony D.; Brock Timothy C. 《Canadian Metallurgical Quarterly》1998,53(9):1078b
Comments on D. Kipnis's (see record 199707781-001) article that critically analyzes social psychology's assumption that psychological states can explain social behavior. The present authors point out that there are many sources in social psychology that, in fact, have revealed a vibrant and rigorous discipline in which, contrary to Kipnis's "caricature," explanations are routinely empirically questioned, variables are directly manipulated and measured, often along with their physiological and neuro-electrical correlates, and multivariate approaches address the separate and joint impact of multiple predictors on multiple dependent variables. It is also noted that Kipnis ignored social psychological research in which experimenters have assessed the physiological correlates of cognitive states. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
999.
1000.
This paper presents the acceleration of minimum-cost covering problems by instance-specific hardware. First, we formulate the minimum-cost covering problem and discuss a branch & bound algorithm to solve it. Then we describe instance-specific hardware architectures that implement branch & bound in 3-valued logic and use reduction techniques similar to those found in software solvers. We further present prototypical accelerator implementations and a corresponding design tool flow. Our experiments reveal significant raw speedups up to five orders of magnitude for a set of smaller unate covering problems. Provided that hardware compilation times can be reduced, we conclude that instance-specific acceleration of hard minimum-cost covering problems will lead to substantial overall speedups. 相似文献