全文获取类型
收费全文 | 17797篇 |
免费 | 1418篇 |
国内免费 | 990篇 |
专业分类
电工技术 | 643篇 |
综合类 | 2191篇 |
化学工业 | 2589篇 |
金属工艺 | 811篇 |
机械仪表 | 1316篇 |
建筑科学 | 2089篇 |
矿业工程 | 743篇 |
能源动力 | 573篇 |
轻工业 | 976篇 |
水利工程 | 785篇 |
石油天然气 | 1382篇 |
武器工业 | 286篇 |
无线电 | 1074篇 |
一般工业技术 | 1327篇 |
冶金工业 | 1507篇 |
原子能技术 | 356篇 |
自动化技术 | 1557篇 |
出版年
2024年 | 33篇 |
2023年 | 171篇 |
2022年 | 341篇 |
2021年 | 451篇 |
2020年 | 475篇 |
2019年 | 398篇 |
2018年 | 390篇 |
2017年 | 565篇 |
2016年 | 653篇 |
2015年 | 746篇 |
2014年 | 1071篇 |
2013年 | 953篇 |
2012年 | 1355篇 |
2011年 | 1564篇 |
2010年 | 1194篇 |
2009年 | 1203篇 |
2008年 | 1026篇 |
2007年 | 1274篇 |
2006年 | 1196篇 |
2005年 | 974篇 |
2004年 | 820篇 |
2003年 | 708篇 |
2002年 | 536篇 |
2001年 | 449篇 |
2000年 | 342篇 |
1999年 | 246篇 |
1998年 | 193篇 |
1997年 | 137篇 |
1996年 | 113篇 |
1995年 | 97篇 |
1994年 | 87篇 |
1993年 | 58篇 |
1992年 | 55篇 |
1991年 | 33篇 |
1990年 | 31篇 |
1989年 | 31篇 |
1988年 | 22篇 |
1987年 | 9篇 |
1986年 | 12篇 |
1985年 | 13篇 |
1984年 | 13篇 |
1982年 | 13篇 |
1981年 | 10篇 |
1980年 | 9篇 |
1966年 | 9篇 |
1965年 | 10篇 |
1964年 | 9篇 |
1963年 | 10篇 |
1961年 | 9篇 |
1955年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
51.
Abstract— Recent commercial liquid‐crystal‐display (LCD) televisions are larger and brighter than traditional televisions, thus impacting the viewing conditions in which they are viewed. These changes in viewing conditions may require different electro‐optical transfer functions (EOTFs) for LCD TVs than those for conventional TVs. Here, the way various EOTFs affect the preferred image quality of test images with changes in brightness and surround illumination conditions are examined. The first method used a gain, offset, and gamma (GOG) function with a range of gamma values, and the second method altered the intrinsic EOTFs. Image preference for the simulated EOTFs was determined using a paired‐comparison experiment for ten images. The first experiment took place in a darkened room at two display luminance levels. The results indicated that a gamma of 1.6 was most preferred overall although more so at a lower screen luminance level. In a second experiment, the procedure was repeated with a dim surround of 10% of the display's white point. With this surround, preference for a gamma value of around 1.6 at both screen luminance levels was more enhanced. These results indicated that image preference for different EOTFs is dependent on display luminance and that this dependence is maintained with a dim surround. 相似文献
52.
Since demand for power exhibits great variability the amount of firm energy to be purchased to meet real time demand based on forecasts is usually different from the realized demand for that period. The role of generation reserves is to meet the real time fluctuations of power demand. The predictable part of the demand is met through purchases of firm energy. In this paper a model is presented to determine optimal quantities of firm energy and generation reserves to meet random demands. The model is then parameterized introducing a set of factors to perform a sensitivity study. A full factorial experiment is designed to study the impact of five factors on the response variable (i.e., proportion of generation reserves on the total purchased quantity). An example consisting of 640 simulations corresponding to 25 treatment combinations evaluated over 20 randomly generated mean demands is used to identify significant factors on the response variable. Results from the experiment suggest that generation reserve requirements should be adjusted considering changes in significant factors and in the mean demand over the dispatch interval. 相似文献
53.
WANG Kai WANG Bei WU Rui-zhi 《国际设备工程与管理》2007,12(3):154-159
In order to reduce the vibration on a machine tool, more orthogonal experiment schemes have been designed, which are based on the steel balls vibration reducing principle. After experiments the optimal reducing vibration scheme was determined. This kind of vibration reducing scheme is used in steel balls vibration absorber, which can be used to reduce vibration magnitudes of a machine tools under the working conditions, whereby improving machining precision. The suggested experiment method is of useful reference in reducing vibrations on other machine tools too. 相似文献
54.
This article reports research intended to assess and extend a recent theory of peer responses to low-performing team members (J. A. LePine & L. Van Dyne, 2001a). An instrument that assesses 4 types of peer responses to low performers (compensating for, training, motivating, and rejecting) was developed and then cross-validated in a subsequent study. Results of the study supported the validity of the peer responses measure and were generally consistent with the attributional theory of peer responses. Low-performer characteristics influenced the peer responses. These effects were mediated in part by peer attributions, affect, and cognitions, which explained variance in the peer responses over and above the variance explained by respondents' personality characteristics (i.e., The Big Five). (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
55.
Withdrawal from an escalating-dose, bingelike regimen of cocaine administration in rats produced significantly depressed levels of locomotor activity during the nocturnal portion of the day-night cycle. This effect was observed during the first 48 hrs of testing. Extracellular single-unit recordings of ventral tegmental area (VTA) dopamine (DA) neurons revealed no differences between saline- and cocaine-treated rats with respect to basal firing rates. However, significantly fewer spontaneously active VTA DA neurons were encountered in rats withdrawn from binge cocaine. As with the nocturnal hypoactivity, this effect was observed only during the first 48 hrs of withdrawal. These findings suggest that short-term DA neuron dysfunction during cocaine withdrawal temporally corresponds to behavioral disruptions that are similar to those described in human addicts. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
56.
Whereas there exists a vast literature investigating consumer satisfaction ratings of various behavioral interventions, the majority of these studies have been limited to analogue conditions, which may compromise utility and generalization. Additionally, most research has failed to explore multiple-source, multiple-setting data in the investigation of treatment acceptability. This study investigated parent, teacher, and child treatment acceptability ratings derived from field-based conjoint behavioral consultation cases. Data indicate that overall, 67 parents (aged 23-54 yrs), 67 teachers (aged 22-57 yrs), and 67 children (aged 5-15 yrs) rated conjoint behavioral consultation-based behavioral interventions as very to highly acceptable. For parents, interventions with a reductive component were rated as more acceptable than interventions using both positive and negative components; no significant differences were found among teacher and child group ratings. For teachers, there was a positive relationship between (a) intervention complexity and treatment acceptability ratings and (b) problem severity ratings and treatment acceptability ratings... (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
57.
本文针对美孚油回收液与兰炼8#油混合利用进行可行性实验研究,经过重度、粘度、可燃性等方面的实验研究,表明美孚油回收液与兰炼8#油混合可以用在电动轮上并且获得良好的效果。 相似文献
58.
Salinger Walter L.; Ladrow Pamela; Wheeler Catherine 《Canadian Metallurgical Quarterly》2003,117(6):1257
Reeler (rl/rl) and reeler/wild-type (+/rl) mice synthesize Reln at subnormal rates, as do patients with schizophrenia, bipolar disorder, and autism, thereby forming the basis for a Reln hypothesis for vulnerability to these psychopathologies and justifying attention to the behavioral phenotypes of Reln-deficient mice. Tests of gait, emotionality, social aggression, spatial working memory, novel-object detection, fear conditioning, and sensorimotor reflex modulation revealed the behavioral phenotype of rl/rl, but not +/rl, mice to be different from that of wild-type (+/+) mice. These results reveal no effect of Reln gene dosage and provide significant challenges to both the Reln and the neurodevelopmental hypotheses of the etiology of major psychopathologies. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
59.
60.
星间激光通信技术进展与趋势 总被引:3,自引:3,他引:0
较详细地评述了目前国外卫星间光通信技术研究的现状.根据关键单元技术的进展情况,总结了未来星间光通信系统的发展趋势。 相似文献