全文获取类型
收费全文 | 1955篇 |
免费 | 166篇 |
国内免费 | 6篇 |
学科分类
工业技术 | 2127篇 |
出版年
2024年 | 1篇 |
2023年 | 20篇 |
2022年 | 8篇 |
2021年 | 62篇 |
2020年 | 51篇 |
2019年 | 45篇 |
2018年 | 63篇 |
2017年 | 72篇 |
2016年 | 69篇 |
2015年 | 78篇 |
2014年 | 103篇 |
2013年 | 160篇 |
2012年 | 138篇 |
2011年 | 221篇 |
2010年 | 147篇 |
2009年 | 135篇 |
2008年 | 129篇 |
2007年 | 88篇 |
2006年 | 88篇 |
2005年 | 80篇 |
2004年 | 58篇 |
2003年 | 68篇 |
2002年 | 47篇 |
2001年 | 19篇 |
2000年 | 15篇 |
1999年 | 23篇 |
1998年 | 20篇 |
1997年 | 13篇 |
1996年 | 21篇 |
1995年 | 6篇 |
1994年 | 18篇 |
1993年 | 15篇 |
1992年 | 9篇 |
1991年 | 5篇 |
1990年 | 4篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1982年 | 4篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1975年 | 1篇 |
1974年 | 1篇 |
排序方式: 共有2127条查询结果,搜索用时 46 毫秒
61.
The use of glass fibre reinforced polyester composites raises many health and safety and environmental questions. One alternative is the development of high performance bio-based bio-composites with low environmental impact. Improved understanding of interfacial properties is essential to optimise the mechanical properties and durability of these materials, but so far few data are available. The present work describes the interfacial characterization of Flax fibre/Poly(lactic) acid (PLLA) system at the micro-scale using the microbond test. Different thermal treatments have been carried out (cooling rate and annealing) in order to evaluate the influence of matrix and interfacial morphologies as well as residual stress on interfacial properties. Micromechanical models have been used to determine the interfacial shear strength. When cooling rate is slow, improved interfacial properties are observed. 相似文献
62.
Emonds Griet; Declerck Carolyn H.; Boone Christophe; Vandervliet Everhard J. M.; Parizel Paul M. 《Canadian Metallurgical Quarterly》2011,4(1):11
Using functional MRI, we investigate the neural correlates of intrinsic versus extrinsic motivation to cooperate by comparing people who differ in the personality trait Social Value Orientation. Participants (n = 28) played several one-shot prisoner's dilemma games (offering weak cooperative incentives) and coordination games (offering strong cooperative incentives) with anonymous partners while they were under the scanner. Behavioral results indicate that proself individuals adjust their behavior toward more cooperation when extrinsic incentives were present, while prosocials' decisions are not affected by game context. The neurological data is consistent with a priori developed hypotheses regarding different behavioral strategies, and suggest that extrinsically motivated proself strategies are driven by calculation and a situation-by-situation approach. Increased activation was found in dorsolateral prefrontal cortex, posterior superior temporal sulcus (STS), and precuneus. Intrinsically motivated prosocials' strategies reflect norm compliance, routine moral judgment, and social awareness. Increased activation was found in lateral orbitofrontal cortex, anterior STS, and inferior parietal lobule. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
63.
Borchert Elizabeth M. O.; Micheyl Christophe; Oxenham Andrew J. 《Canadian Metallurgical Quarterly》2011,37(1):257
Pitch, the perceptual correlate of fundamental frequency (F0), plays an important role in speech, music, and animal vocalizations. Changes in F0 over time help define musical melodies and speech prosody, while comparisons of simultaneous F0 are important for musical harmony, and for segregating competing sound sources. This study compared listeners' ability to detect differences in F0 between pairs of sequential or simultaneous tones that were filtered into separate, nonoverlapping spectral regions. The timbre differences induced by filtering led to poor F0 discrimination in the sequential, but not the simultaneous, conditions. Temporal overlap of the two tones was not sufficient to produce good performance; instead performance appeared to depend on the two tones being integrated into the same perceptual object. The results confirm the difficulty of comparing the pitches of sequential sounds with different timbres and suggest that, for simultaneous sounds, pitch differences may be detected through a decrease in perceptual fusion rather than an explicit coding and comparison of the underlying F0s. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
64.
Lei Bao Christophe Schuman Jean‐Sébastien Lecomte Marie‐Jeanne Philippe Xiang Zhao Claude Esling 《Advanced Engineering Materials》2011,13(10):928-932
An in depth analysis on twin variant selection and twin growth character during compression by means of “interrupted in situ” EBSD orientation measurement was carried out. An experimental verification and geometrical analysis of the use of Schmid's law as a criterion for selecting twin variants was performed, and proved to be conclusive. Twin variants having Schmid factors higher than 0.4 have a good chance to be activated. The twin growth exhibits two modes: {11–22} twins show a tendency to multiple variants system (MVS) and {10–12} twins show predominant variant system (PVS). The Schmid factor plays an important role in MVS and PVS. 相似文献
65.
Martin Schmid Volker Erckmann Gerd Gantenbein Stefan Illy Stefan Kern Christophe Liévin Andrey Samartsev Andreas Schlaich Thomáz Rzesnicki Manfred Thumm 《Fusion Engineering and Design》2011,86(6-8):518-521
Parasitic beam tunnel oscillations have been discovered on some of the series production gyrotrons for W7-X and also on the coaxial pre-prototype gyrotron for ITER. Solutions to remedy these problems have resulted in a modified beam tunnel design, technologically close to the existing beam tunnel. The new design has successfully been tested on both the coaxial and also the f-step-tunable gyrotrons and has subsequently been implemented on one of the W7-X series-production-tubes presently undergoing factory acceptance tests in Karlsruhe.The ECRH test loads at KIT are operated under normal atmospheric conditions. Several loads have eventually failed in 1 MW long pulse experiments and KIT has therefore started to design its own loads. The first KIT-load is based on a fixed conical mirror and an aluminum cylinder coated with a lossy material for increased absorption. The new load has so far successfully been used during the acceptance tests of two 1-MW CW gyrotrons. Nevertheless a new load based on pure (uncoated) stainless steel absorbers is being developed as a backup solution for the ongoing high priority gyrotron testing.A superconducting magnet capable of rapid field changes between 4.15 and 5.67 T for frequency step-tunable gyrotrons has been procured, has demonstrated a (static) field of 7.2 T and its capability of rapid field-changes. 相似文献
66.
67.
Deendarlianto Christophe Vallée Matthias Beyer Helmar Carl 《Nuclear Engineering and Design》2011,241(8):3359-3372
This paper replaces the paper published in the journal by Deendarlianto et al. (2008). Because of an error in the implementation of the air flow meter some of the data given by Deendarlianto et al. (2008) are wrong. They are corrected within the present paper. The general results and conclusions remain unchanged.An experimental investigation on the air/water counter-current two-phase flow in a horizontal rectangular channel connected to an inclined riser has been conducted. This test-section representing a model of the hot leg of a pressurized water reactor is mounted between two separators in a pressurized experimental vessel. The cross-section and length of the horizontal part of the test-section are (0.25 m × 0.05 m) and 2.59 m, respectively, whereas the inclination angle of the riser is 50°. The flow was captured by a high speed camera in the bended region of the hot leg, delivering a detailed view of the stratified interface as well as of dispersed structures like bubbles and droplets. Counter-current flow limitation (CCFL), or the onset of flooding, was found by analyzing the water levels measured in the separators. The counter-current flow limitation is defined as the maximum air mass flow rate at which the discharged water mass flow rate is equal to the inlet water mass flow rate.From the high-speed observations it was found that the initiation of flooding coincides with the formation of slug flow. Furthermore, a slight hysteresis was noticed between flooding and deflooding. The CCFL data was compared with similar experiments and empirical correlations available in the literature. Therefore, the Wallis-parameter was calculated for the rectangular cross-sections by using the channel height as length, instead of the diameter. The agreement of the CCFL curve is good, but the zero liquid penetration was found at lower values of the Wallis parameter than in most of the previous work. This deviation can be attributed to the special rectangular geometry of the hot leg model of HZDR, since the other investigations were done for pipes. 相似文献
68.
Klara Insulander Björk Valentin Fhager Christophe Demazière 《Progress in Nuclear Energy》2011,53(6):618-625
With the aim of investigating the technical feasibility of fuelling a conventional BWR (Boiling Water Reactor) with thorium-based fuel, computer simulations were carried out in a 2D infinite lattice model using CASMO-5. Four different fissile components were each homogenously combined with thorium to form mixed oxide pellets: Uranium enriched to 20% U-235 (LEU), plutonium recovered from spent LWR fuel (RGPu), pure U-233 and a mixture of RGPu and uranium recovered from spent thorium-based fuel. Based on these fuel types, four BWR nuclear fuel assembly designs were formed, using a conventional assembly geometry (GE14-N). The fissile content was chosen to give a total energy release equivalent to that of a UOX fuel bundle reaching a discharge burnup of about 55 MWd/kgHM. The radial distribution of fissile material was optimized to achieve low bundle internal radial power peaking. Reactor physical parameters were computed, and the results were compared to those of reference LEU and MOX bundle designs. It was concluded that a viable thorium-based BWR nuclear fuel assembly design, based on any of the fissile components, can be achieved. Neutronic parameters that are essential for reactor safety, like reactivity coefficients and control rod worths, are in most cases similar to those of LEU and MOX fuel. This is also true for the decay heat produced in irradiated fuel. However when Th is mixed with U-233, the void coefficient (calculated in 2D) can be positive under some conditions. It was concluded that it is very difficult to make savings of natural uranium by mixing LEU (20% U-235) homogenously with thorium and that mixing RGPu with thorium leads to more efficient consumption of Pu compared to MOX fuel. 相似文献
69.
Navin Michael A. P. Vinod Christophe Moy Jacques Palicot 《Circuits, Systems, and Signal Processing》2011,30(4):799-821
Emerging communication paradigms like the cognitive radio require extremely flexible physical layer functional units that
can be parameterized at runtime for supporting multiple modes. Parameterizing the hardware accelerators in the cognitive radio
baseband incurs a latency penalty, which is a function of the amount of reconfiguration data required by the accelerators.
In an opportunistic spectrum access scenario, the cumulative latency required to reconfigure all the physical layer units
when switching to a new channel reduces the useful time available for transmission, leading to a lower system throughput.
Against this background, this paper gives an overview of the amount of reconfiguration data required by different candidate
accelerator architectures for performing the computationally intensive channelization function, in the digital front-end of
the cognitive radio terminal. The paper also identifies opportunities for reusing hardwired stages of a channelization accelerator
across multiple modes, while minimizing the reconfiguration overhead. 相似文献
70.
Rami Khazaka Etienne Moulin Mathieu Boccard Loïc Garcia Simon Hnni Franz‐Josef Haug Fanny Meillaud Christophe Ballif 《Progress in Photovoltaics: Research and Applications》2015,23(9):1182-1189
We compare the performance of two back reflector designs on the optoelectrical properties of microcrystalline silicon solar cells. The first one consists of a 5‐µm‐thick low‐pressure chemical vapor deposition (LPCVD)‐ZnO electrode combined with a white sheet; the second one incorporates an Ag reflector deposited on a thin LPCVD‐ZnO layer (with thickness below 200 nm). For this latter design, the optical loss in the nano‐rough Ag reflector can be strongly reduced by smoothing the surface of the thin underlying ZnO layer, by means of an Ar‐plasma treatment. Because of its superior lateral conductivity, the thin‐ZnO/Ag back reflector design provides a higher fill factor than the dielectric back reflector design. When decreasing the roughness of the front electrode with respect to our standard front LPCVD‐ZnO layer, the electrical cell performance is improved; in addition, the implementation of the thin‐ZnO/Ag back reflector leads to a significant relative gain in light trapping. Applying this newly optimized combination of front and back electrodes, the conversion efficiency is improved from 8.9% up to 9.4%, for cells with an active‐layer thickness of only 1.1 µm. We thereby highlight the necessity to optimize simultaneously the front and back electrodes. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献