全文获取类型
收费全文 | 10443篇 |
免费 | 1737篇 |
国内免费 | 1043篇 |
专业分类
电工技术 | 385篇 |
技术理论 | 1篇 |
综合类 | 1266篇 |
化学工业 | 179篇 |
金属工艺 | 51篇 |
机械仪表 | 448篇 |
建筑科学 | 2893篇 |
矿业工程 | 315篇 |
能源动力 | 164篇 |
轻工业 | 158篇 |
水利工程 | 713篇 |
石油天然气 | 125篇 |
武器工业 | 67篇 |
无线电 | 1566篇 |
一般工业技术 | 757篇 |
冶金工业 | 872篇 |
原子能技术 | 136篇 |
自动化技术 | 3127篇 |
出版年
2024年 | 86篇 |
2023年 | 231篇 |
2022年 | 525篇 |
2021年 | 475篇 |
2020年 | 554篇 |
2019年 | 457篇 |
2018年 | 388篇 |
2017年 | 481篇 |
2016年 | 483篇 |
2015年 | 520篇 |
2014年 | 698篇 |
2013年 | 700篇 |
2012年 | 769篇 |
2011年 | 876篇 |
2010年 | 715篇 |
2009年 | 674篇 |
2008年 | 692篇 |
2007年 | 741篇 |
2006年 | 605篇 |
2005年 | 487篇 |
2004年 | 460篇 |
2003年 | 362篇 |
2002年 | 254篇 |
2001年 | 224篇 |
2000年 | 156篇 |
1999年 | 121篇 |
1998年 | 90篇 |
1997年 | 70篇 |
1996年 | 57篇 |
1995年 | 46篇 |
1994年 | 39篇 |
1993年 | 21篇 |
1992年 | 17篇 |
1991年 | 18篇 |
1990年 | 18篇 |
1989年 | 16篇 |
1988年 | 11篇 |
1987年 | 8篇 |
1986年 | 5篇 |
1985年 | 10篇 |
1984年 | 12篇 |
1983年 | 6篇 |
1982年 | 3篇 |
1966年 | 4篇 |
1965年 | 3篇 |
1964年 | 3篇 |
1963年 | 5篇 |
1959年 | 6篇 |
1957年 | 4篇 |
1956年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
951.
为了降低H.264中模式决定过程的复杂度,提出了一种快速算法。该方法首先检测当前宏块的相邻宏块.当相邻宏块都可用时,使用基于空间相关性的模式决定方法;当相邻宏块并不都为可用时,使用分级模式决定策略.采用以上方法.将空间相关性与分级策略有效地结合起来,减少了计算量,并且对图像质量以及码率没有明显的影响.实验表明.这种新算法平均可以节省的计算时间约为41.7%,同时PSNR下降了约0.12dB,具有一定的现实意义。 相似文献
952.
道路网络中的连续查询是查找在一条路径上满足查询条件的对象。它是空间网络数据库中的一种重要查询类型。现提出了道路网络中基于k阶Voronoi图的连续k近邻查询方法,该查询方法用分枝限界的思想动态地创建局部Voronoi图,降低了查询代价。 相似文献
953.
Dhanushkodi Anandh; Bindu B.; Raju T. R.; Kutty Bindu M. 《Canadian Metallurgical Quarterly》2007,121(3):491
The authors demonstrated the efficacy of enriched housing conditions in promoting the behavioral recovery and neuronal survival following subicular lesion in rats. Chemical lesioning of the ventral subiculum impaired the spatial learning performances in rats. The lesion also induced a significant degree of neurodegeneration in the CA1 and CA3 areas of the hippocampus and entorhinal cortex. Exposure to enriched housing conditions improved the behavioral performance and partially attenuated the neurodegeneration in the hippocampus. The choline acetyl transferase (ChAT) activity in the hippocampus remained unchanged following ventral subicular lesion and also following exposure to an enriched environment. The study implicates the effectiveness of activity-dependent neuronal plasticity induced by environmental enrichment in adulthood following brain insult. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
954.
Sanderson D. J.; Gray A.; Simon A.; Taylor A. M.; Deacon R. M. J.; Seeburg P. H.; Sprengel R.; Good M. A.; Rawlins J. N. P.; Bannerman D. M. 《Canadian Metallurgical Quarterly》2007,121(3):559
Genetically modified mice lacking the glutamate receptor A (GluR-A) subunit of the AMPA receptor (GluR-A-/- mice) display normal spatial reference memory but impaired spatial working memory (SWM). This study tested whether the SWM impairment in these mice could be explained by a greater sensitivity to within-session proactive interference. The SWM performance of GluR-A-/- and wild-type mice was assessed during nonmatching-to-place testing under conditions in which potential proactive interference from previous trials was reduced or eliminated. SWM was impaired in GluR-A-/- mice, both during testing with pseudotrial-unique arm presentations on the radial maze and when conducting each trial on a different 3-arm maze, each in a novel testing room. Experimentally naive GluR-A-/- mice also exhibited chance performance during a single trial of spontaneous alternation. This 1-trial spatial memory deficit was present irrespective of the delay between the sample information and the response choice (0 or 45 min) and the length of the sample phase (0.5 or 5 min). These results imply that the SWM deficit in GluR-A-/- mice is not due to increased susceptibility to proactive interference. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
955.
Kubie John L.; Fenton Andre; Novikov Nicolay; Touretzky David; Muller Robert U. 《Canadian Metallurgical Quarterly》2007,121(4):751
In the cognitive mapping theory of hippocampal function, currently active place cells represent a rat's spatial location (J. O'Keefe & L. Nadel, 1978). A systematic shift of firing field locations should therefore produce a similar shift in a rat's judgment of its location. A. A. Fenton, G. Csizmadia, and R. U. Muller (2000a) recorded place cells in cylinders with 2 cue cards separated by 135°. When the separation was changed, firing fields moved systematically, as described by a vector-field equation (A. A. Fenton, G. Csizmadia, & R. U. Muller, 2000b). Given this cohesive movement of firing fields, the mapping theory predicts that a rat's decisions about the location of an unmarked goal should move after card separation changes, as described by the vector-field equation. The authors tested this reasoning with a task in which the rat earned a food reward by pausing in a small, unmarked goal zone. When cues were shifted in the absence of reward, goal choice shifts were accurately predicted by the vector-field equation, providing strong support for the notion that a rat's judgment of its spatial location is intimately related to the across-cell discharge pattern of simultaneously active place cells. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
956.
Jones Peter M.; Pearce John M.; Davies Vanessa J.; Good Mark A.; McGregor Anthony 《Canadian Metallurgical Quarterly》2007,121(6):1258
Hippocampal damage impairs navigation with respect to information provided by the shape of an arena. Recent evidence has suggested that normal rats use local geometric information, as opposed to a global geometric representation, to navigate to a correct corner. One implication of this pattern of results is that hippocampal lesions may impair processing of 1 or more of the local geometric features of an environment. The authors therefore investigated the effects of hippocampal cell loss in rats on navigation to a hidden goal with respect to a variety of local cues in an environment with a distinctive shape. Rats with lesions of the hippocampus were impaired in discriminating a right-angled corner from its mirror image. However, they were able to use cues provided by an acute-angled corner (Experiment 1) or a local polarizing cue (Experiment 2). In contrast, lesioned rats were impaired in discriminating long versus short walls (Experiment 3). Results indicate that the hippocampus plays a role in disambiguating locations by processing (metric) information related to the distance between corners. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
957.
Cheng Ken; Shettleworth Sara J.; Huttenlocher Janellen; Rieser John J. 《Canadian Metallurgical Quarterly》2007,133(4):625
Spatial judgments and actions are often based on multiple cues. The authors review a multitude of phenomena on the integration of spatial cues in diverse species to consider how nearly optimally animals combine the cues. Under the banner of Bayesian perception, cues are sometimes combined and weighted in a near optimal fashion. In other instances when cues are combined, how optimal the integration is might be unclear. Only 1 cue may be relied on, or cues may seem to compete with one another. The authors attempt to bring some order to the diversity by taking into account the subjective discrepancy in the dictates of multiple cues. When cues are too discrepant, it may be best to rely on 1 cue source. When cues are not too discrepant, it may be advantageous to combine cues. Such a dual principle provides an extended Bayesian framework for understanding the functional reasons for the integration of spatial cues. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
958.
Perceived awareness and caring, or beliefs about how much parents and peers know and care about students' behavior, was assessed in relation to students' drinking patterns. Prior to and at the end of the first semester at college, participants completed Web-based surveys assessing alcohol use, family and social motives, and perceived awareness and caring from parents and peers. Family motives moderated the effect of perceived parental awareness and caring on the quantity of high school alcohol use, whereas social motives moderated the effect of perceived peer awareness and caring on frequency and quantity of college drinking. Longitudinally, college alcohol use was predicted by perceived awareness and caring from parents. Perceived awareness and caring may affect alcohol use whereby parents exert influence during high school but peers are more influential in college. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
959.
Hourihan Kathleen L.; Goldberg Samantha; Taylor Tracy L. 《Canadian Metallurgical Quarterly》2007,61(2):91
This study examined whether spatial location mediates intentional forgetting of peripherally presented words. Using an item-method directed forgetting paradigm, words were presented in peripheral locations at study. A recognition test presented all words at either the same or a different location relative to study. Results showed that while recognition of Remember words was unaffected by test location, when Forget words were presented in the same location at test as at study, recognition accuracy was significantly greater than when presented in a different location. Experiment 2 showed that the speed to localize a previously studied word was faster when it was presented in the same rather than a different study-test location but that the magnitude of this spatial priming was unaffected by memory instruction. We suggest that the location of peripherally presented words is represented in memory and can aid the retrieval of poorly encoded words. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
960.
Fouriezos George; Capstick Gary; Monette Fran?ois; Bellemare Christine; Parkinson Matthew; Dumoulin Angela 《Canadian Metallurgical Quarterly》2007,61(4):277
The flash-lag effect is a visual illusion wherein intermittently flashed, stationary stimuli seem to trail after a moving visual stimulus despite being flashed synchronously. We tested hypotheses that the flash-lag effect is due to spatial extrapolation, shortened perceptual lags, or accelerated acquisition of moving stimuli, all of which call for an earlier awareness of moving visual stimuli over stationary ones. Participants judged synchrony of a click either to a stationary flash of light or to a series of adjacent flashes that seemingly bounced off or bumped into the edge of the visual display. To be judged synchronous with a stationary flash, audio clicks had to be presented earlier--not later--than clicks that went with events, like a simulated bounce (Experiment 1) or crash (Experiments 2-4), of a moving visual target. Click synchrony to the initial appearance of a moving stimulus was no different than to a flash, but clicks had to be delayed by 30-40 ms to seem synchronous with the final (crash) positions (Experiment 2). The temporal difference was constant over a wide range of motion velocity (Experiment 3). Interrupting the apparent motion by omitting two illumination positions before the last one did not alter subjective synchrony, nor did their occlusion, so the shift in subjective synchrony seems not to be due to brightness contrast (Experiment 4). Click synchrony to the offset of a long duration stationary illumination was also delayed relative to its onset (Experiment 5). Visual stimuli in motion enter awareness no sooner than do stationary flashes, so motion extrapolation, latency difference, and motion acceleration cannot explain the flash-lag effect. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献