全文获取类型
收费全文 | 811篇 |
免费 | 44篇 |
国内免费 | 2篇 |
学科分类
工业技术 | 857篇 |
出版年
2023年 | 2篇 |
2022年 | 6篇 |
2021年 | 11篇 |
2020年 | 13篇 |
2019年 | 22篇 |
2018年 | 28篇 |
2017年 | 19篇 |
2016年 | 22篇 |
2015年 | 11篇 |
2014年 | 22篇 |
2013年 | 60篇 |
2012年 | 28篇 |
2011年 | 44篇 |
2010年 | 43篇 |
2009年 | 25篇 |
2008年 | 47篇 |
2007年 | 29篇 |
2006年 | 32篇 |
2005年 | 33篇 |
2004年 | 24篇 |
2003年 | 25篇 |
2002年 | 22篇 |
2001年 | 14篇 |
2000年 | 13篇 |
1999年 | 27篇 |
1998年 | 44篇 |
1997年 | 33篇 |
1996年 | 19篇 |
1995年 | 11篇 |
1994年 | 13篇 |
1993年 | 12篇 |
1992年 | 5篇 |
1991年 | 7篇 |
1990年 | 4篇 |
1989年 | 2篇 |
1988年 | 4篇 |
1987年 | 9篇 |
1986年 | 11篇 |
1985年 | 11篇 |
1984年 | 4篇 |
1983年 | 4篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1978年 | 4篇 |
1977年 | 3篇 |
1976年 | 11篇 |
1975年 | 4篇 |
1974年 | 2篇 |
排序方式: 共有857条查询结果,搜索用时 15 毫秒
21.
22.
Matt Jones Steve Jones Gareth Bradley Nigel Warren David Bainbridge Geoff Holmes 《Personal and Ubiquitous Computing》2008,12(7):513-525
Listening to music on personal, digital devices whilst mobile is an enjoyable, everyday activity. We explore a scheme for
exploiting this practice to immerse listeners in navigation cues. Our prototype, ONTRACK, continuously adapts audio, modifying
the spatial balance and volume to lead listeners to their target destination. First we report on an initial lab-based evaluation
that demonstrated the approach’s efficacy: users were able to complete tasks within a reasonable time and their subjective
feedback was positive. Encouraged by these results we constructed a handheld prototype. Here, we discuss this implementation
and the results of field-trials. These indicate that even with a low-fidelity realisation of the concept, users can quite
effectively navigate complicated routes.
相似文献
Matt Jones (Corresponding author)Email: |
Steve JonesEmail: |
Gareth BradleyEmail: |
Nigel WarrenEmail: |
David BainbridgeEmail: |
Geoff HolmesEmail: |
23.
J Zhuang T Droma S Sun C Janes RE McCullough RG McCullough A Cymerman SY Huang JT Reeves LG Moore 《Canadian Metallurgical Quarterly》1993,74(1):303-311
Lifelong high-altitude residents of North and South America acquire blunted hypoxic ventilatory responses and exhibit decreased ventilation compared with acclimatized newcomers. The ventilatory characteristics of Himalayan high-altitude residents are of interest in the light of their reportedly lower hemoglobin levels and legendary exercise performance. Until recently, Sherpas have been the only Himalayan population available for study. To determine whether Tibetans exhibited levels of ventilation and hypoxic ventilatory drives that were as great as acclimatized newcomers, we compared 27 lifelong Tibetan residents of Lhasa, Tibet, China (3,658 m) with 30 acclimatized Han ("Chinese") newcomers matched for age, body size, and extent of exercise training. During room air breathing, minute ventilation was greater in the Tibetan than in the Han young men because of an increased respiratory frequency, but arterial O2 saturation and end-tidal PCO2 did not differ, indicating similar levels of effective alveolar ventilation. The Tibetan subjects had higher hypoxic ventilatory response shape parameter A values and hypercapnic ventilatory responsiveness than the Han subjects. Among the Han subjects, duration of high-altitude residence correlated with the degree of blunting of the hypoxic ventilatory drive. Paradoxically, hyperoxia (inspired O2 fraction 0.70) increased minute ventilation and decreased end-tidal PCO2 in the Tibetan but not in the Han men. We concluded that lifelong Tibetan residents of high altitude neither hypoventilated nor exhibited blunted hypoxic ventilatory responses compared with acclimatized Han newcomers, suggesting that the effects of lifelong high-altitude residence on ventilation and ventilatory response to hypoxia differ in Tibetan compared with other high-altitude populations. 相似文献
24.
Diane M. Markoff Vince Cianciolo Chuck L. Britton Ronald G. Cooper Geoff L. Greene 《Journal of research of the National Institute of Standards and Technology》2005,110(4):449-452
We are developing a high-efficiency neutron detector with 1 cm position resolution and coarse energy resolution for use at high-flux neutron source facilities currently proposed or under construction. The detector concept integrates a segmented 3He ionization chamber with the position sensitive, charged particle collection methods of a MicroMegas detector. Neutron absorption on the helium produces protons and tritons that ionize the fill gas. The charge is amplified in the field region around a wire mesh and subsequently detected in current mode by wire strips mounted on a substrate. One module consisting of a high-voltage plate, a field-shaping high-voltage plate, a grid and wire strips defines a detection region. For 100 % efficiency, detector modules are consecutively placed along the beam axis. Analysis over several regions with alternating wire strip orientation provides a two-dimensional beam profile. By using 3He, a 1/v absorption gas, each axial region captures neutrons of a different energy range, providing an energy-sensitive detection scheme especially useful at continuous beam sources. 相似文献
25.
Transporting QoS adaptive flows 总被引:4,自引:0,他引:4
Distributed audio and video applications need to adapt to fluctuations in delivered quality of service (QoS). By trading
off temporal and spatial quality to available bandwidth, or manipulating the playout time of continuous media in response
to variation in delay, audio and video flows can be made to adapt to fluctuating QoS with minimal perceptual distortion. In
this paper, we extend our previous work on a QoS Architecture (QoS-A) by populating the QoS management planes of our architecture
with a framework for the control and management of multilayer coded flows operating in heterogeneous multimedia networking
environments. Two key techniques are proposed: i) an end-to-end rate-shaping scheme which adapts the rate of MPEG-coded flows
to the available network resources while minimizing the distortion observed at the receiver; and ii) an adaptive network service,
which offers “hard” guarantees to the base layer of multilayer coded flows and “fairness” guarantees to the enhancement layers
based on a bandwidth allocation technique called Weighted Fair Sharing. 相似文献
26.
The single bootstrap already is popular in economics, though the double bootstrap has better convergence properties. We discuss the theory and implementation of the double bootstrap, both with and without the pivotal transformation, and give detailed examples of each. One example is a nonlinear double bootstrap of a Cobb-Douglas production function, and explains the use of Gauss-Newton Regressions as a device to decrease computational time. Another example is double bootstrapping elasticities from a translog production function. 相似文献
27.
In 3 experiments, the authors investigated the effects of to-be-remembered (TBR) and intervening list length on free recall to determine whether selective rehearsal could explain the previous finding that recall was affected only by TBR list length. In Experiments 1 (covert rehearsal) and 2 (overt rehearsal), participants saw 5- and 20-word lists and had to recall the list prior to that last presented list. In Experiment 3, either 1 or 2 lists were presented, and recall of TBR list was postcued. Recall proportion decreased with increased TBR list length. Moreover, the authors found extended recency effects when recall was replotted by when words were last rehearsed (Experiments 2 and 3) and an effect of intervening list length when rehearsal was reduced (Experiment 3). (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
28.
Karl Fraser Scott J. Harrison Geoff A. Lane Don E. Otter Yacine Hemar Siew-Young Quek Susanne Rasmussen 《Food chemistry》2012
Tea is the second most consumed beverage in the world and its consumption has been associated with numerous potential health benefits. Factors such as fermentation methods, geographical origin and season can affect the primary and secondary metabolite composition of tea. In this study, a hydrophilic interaction liquid chromatography (HILIC) method coupled to high resolution mass spectrometry in both positive and negative ionisation modes was developed and optimised. The method when combined with principal component analysis to analyse three different types of tea, successfully distinguished samples into different categories, and provided evidence of the metabolites which differed between them. The accurate mass and high resolution attributes of the mass spectrometric data were utilised and relative quantification data were extracted post-data acquisition on 18 amino acids, showing significant differences in amino acid concentrations between tea types and countries. This study highlights the potential of HILIC chromatography combined with non-targeted mass spectrometric methods to provide a comprehensive understanding of polar metabolites in plant extracts. 相似文献
29.
30.