全文获取类型
收费全文 | 4204篇 |
免费 | 434篇 |
国内免费 | 152篇 |
专业分类
电工技术 | 95篇 |
技术理论 | 2篇 |
综合类 | 157篇 |
化学工业 | 170篇 |
金属工艺 | 21篇 |
机械仪表 | 107篇 |
建筑科学 | 445篇 |
矿业工程 | 48篇 |
能源动力 | 65篇 |
轻工业 | 331篇 |
水利工程 | 53篇 |
石油天然气 | 32篇 |
武器工业 | 26篇 |
无线电 | 362篇 |
一般工业技术 | 425篇 |
冶金工业 | 1098篇 |
原子能技术 | 132篇 |
自动化技术 | 1221篇 |
出版年
2024年 | 46篇 |
2023年 | 118篇 |
2022年 | 177篇 |
2021年 | 227篇 |
2020年 | 196篇 |
2019年 | 166篇 |
2018年 | 108篇 |
2017年 | 142篇 |
2016年 | 163篇 |
2015年 | 149篇 |
2014年 | 269篇 |
2013年 | 243篇 |
2012年 | 267篇 |
2011年 | 318篇 |
2010年 | 255篇 |
2009年 | 256篇 |
2008年 | 219篇 |
2007年 | 207篇 |
2006年 | 176篇 |
2005年 | 132篇 |
2004年 | 133篇 |
2003年 | 120篇 |
2002年 | 98篇 |
2001年 | 118篇 |
2000年 | 31篇 |
1999年 | 44篇 |
1998年 | 28篇 |
1997年 | 20篇 |
1996年 | 26篇 |
1995年 | 19篇 |
1994年 | 16篇 |
1993年 | 20篇 |
1992年 | 9篇 |
1991年 | 8篇 |
1990年 | 12篇 |
1989年 | 13篇 |
1988年 | 9篇 |
1985年 | 12篇 |
1984年 | 8篇 |
1983年 | 8篇 |
1965年 | 7篇 |
1964年 | 22篇 |
1963年 | 20篇 |
1961年 | 13篇 |
1960年 | 16篇 |
1959年 | 13篇 |
1958年 | 10篇 |
1957年 | 14篇 |
1956年 | 7篇 |
1955年 | 18篇 |
排序方式: 共有4790条查询结果,搜索用时 15 毫秒
31.
STUDY ON PHASE PERCEPTION IN SPEECH 总被引:4,自引:0,他引:4
Tong Ming Bian Zhengzhong Li Xiaohui Dai Qijun Chen Yanpu 《电子科学学刊(英文版)》2003,20(5):387-392
The perceptual effect of the phase information in speech has been studied by auditory subjective tests. On the condition that the phase spectrum in speech is changed while amplitude spectrum is unchanged, the tests show that: (1) If the envelop of the reconstructed speech signal is unchanged, there is indistinctive auditory perception between the original speech and the reconstructed speech; (2) The auditory perception effect of the reconstructed speech mainly lies on the amplitude of the derivative of the additive phase; (3) td is the maximum relative time shift between different frequency components of the reconstructed speech signal. The speech quality is excellent while td <10ms; good while 10ms< td <20ms; common while 20ms< td <35ms, and poor while td >35ms. 相似文献
32.
33.
核电厂应急计划中若干问题和概念的讨论 总被引:1,自引:0,他引:1
本文讨论了我国核电厂应急计划和应急准备中新所关心的若干问题,阐述了应急计划中一些基本概念;弄清这些问题和概念,对推动和恰当地进行应急准备可能是重要的。 相似文献
34.
To examine the separate effects of viscosity and sweetness on astringency, aqueous solutions of grape seed tannin (GST) were thickened with carboxymethyl cellulose (CMC) from 2 to 45 cP (experiment 1) or sweetened with 0 to 1.8 g/L aspartame (experiment 2). Trained subjects continuously rated astringency and bitterness in duplicate. Subjects were categorized by the salivary flow induced by citric acid and ability to taste n-propyl thiouracil (PROP). In experiment 1, maximum intensity and total duration of astringency were significantly decreased as viscosity rose, although time to maximum intensity of astringency was not affected. Maximum intensity and total duration of bitterness were not significantly affected by increasing viscosity; however, the onset of bitterness was significantly delayed. In experiment 2, increasing sweetness had no affect on any astringency parameter, although maximum intensity of bitterness was significantly decreased. Neither PROP nor salivary flow-status had any effect on perception of bitterness or astringency in either experiment. 相似文献
35.
Little is known about whether personality characteristics influence initial attraction. Because adult attachment differences influence a broad range of relationship processes, the authors examined their role in 3 experimental attraction studies. The authors tested four major attraction hypotheses--self similarity, ideal-self similarity, complementarity, and attachment security--and examined both actual and perceptual factors. Replicated analyses across samples, designs, and manipulations showed that actual security and self similarity predicted attraction. With regard to perceptual factors, ideal similarity, self similarity, and security all were significant predictors. Whereas perceptual ideal and self similarity had incremental predictive power, perceptual security's effects were subsumed by perceptual ideal similarity. Perceptual self similarity fully mediated actual attachment similarity effects, whereas ideal similarity was only a partial mediator. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
36.
The authors hypothesize that depressed states evolved to minimize risk in social interactions in which individuals perceive that the ratio of their social value to others, and their social burden on others, is at a critically low level. When this ratio reaches a point where social value and social burden are approaching equivalence, the individual is in danger of exclusion from social contexts that, over the course of evolution, have been critical to fitness. Many features of depressed states can be understood in relation to mechanisms that reduce social risk in such circumstances, including (a) hyper-sensitivity to signals of social threat from others, (b) sending signals to others that reduce social risks, and (c) inhibiting risk-seeking (e.g., confident, acquisitive) behaviors. These features are discussed in terms of psychosocial and neurobiological research on depressive phenomena. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
37.
Scheduling emergency medicine residents (EMRs) is a complex task, which considers a large number of rules (often conflicting) related to various aspects such as limits on the number of consecutive work hours, number of day and night shifts that should be worked by each resident, resident staffing requirements according to seniority levels for the day and night shifts, restrictions on the number of consecutive day and night shifts assigned, vacation periods, weekend off requests, and fair distribution of responsibilities among the residents. Emergency rooms (ERs) are stressful workplaces, and in addition shift work is well-known to be more demanding than regular daytime work. For this reason, preparing schedules that suit the working rules for EMRs is especially important for reducing the negative impact on shift workers physiologically, psychologically, and socially. In this paper, we present a goal programming (GP) model that accommodates both hard and soft constraints for a monthly planning horizon. The hard constraints should be adhered to strictly, whereas the soft constraints can be violated when necessary. The relative importance values of the soft constraints have been computed by the analytical hierarchy process (AHP), which are used as coefficients of the deviations from the soft constraints in the objective function. The model has been tested in the ER of a major local university hospital. The main conclusions of the study are that problems of realistic size can be solved quickly and the generated schedules have very high qualities compared to the manually prepared schedules, which require a lot of effort and time from the chief resident who is responsible for this duty. 相似文献
38.
Becker D. Vaughn; Kenrick Douglas T.; Neuberg Steven L.; Blackwell K. C.; Smith Dylan M. 《Canadian Metallurgical Quarterly》2007,92(2):179
Findings of 7 studies suggested that decisions about the sex of a face and the emotional expressions of anger or happiness are not independent: Participants were faster and more accurate at detecting angry expressions on male faces and at detecting happy expressions on female faces. These findings were robust across different stimulus sets and judgment tasks and indicated bottom-up perceptual processes rather than just top-down conceptually driven ones. Results from additional studies in which neutrally expressive faces were used suggested that the connections between masculine features and angry expressions and between feminine features and happy expressions might be a property of the sexual dimorphism of the face itself and not merely a result of gender stereotypes biasing the perception. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
39.
Michael H. Brill 《Color research and application》1994,19(1):34-36
Metelli's theory of the perception of translucency models the effective reflectance of a translucent sheet on a background as a partitive mixture of the color of the sheet and the color of the background. In the achromatic case, the usable (that is, scale-invariant) rules governing the apparent reflectances are the same as those that would emerge from the Kubelka-Munk theory. For chromatic translucency, the relationships are more complex, but a set of rules still emerge from the partitive-mixture theory that are invariant to tradeoffs between illuminant and reflectances. This column sets forth the rules in the hopes that they will have graphical applications, both on computer VDUs and in hardcopy. 相似文献
40.
Frischen Alexandra; Bayliss Andrew P.; Tipper Steven P. 《Canadian Metallurgical Quarterly》2007,133(4):694
During social interactions, people's eyes convey a wealth of information about their direction of attention and their emotional and mental states. This review aims to provide a comprehensive overview of past and current research into the perception of gaze behavior and its effect on the observer. This encompasses the perception of gaze direction and its influence on perception of the other person, as well as gaze-following behavior such as joint attention, in infant, adult, and clinical populations. Particular focus is given to the gaze-cueing paradigm that has been used to investigate the mechanisms of joint attention. The contribution of this paradigm has been significant and will likely continue to advance knowledge across diverse fields within psychology and neuroscience. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献