全文获取类型
收费全文 | 6153篇 |
免费 | 683篇 |
国内免费 | 138篇 |
专业分类
电工技术 | 59篇 |
技术理论 | 1篇 |
综合类 | 215篇 |
化学工业 | 777篇 |
金属工艺 | 16篇 |
机械仪表 | 84篇 |
建筑科学 | 312篇 |
矿业工程 | 30篇 |
能源动力 | 47篇 |
轻工业 | 2619篇 |
水利工程 | 28篇 |
石油天然气 | 20篇 |
武器工业 | 19篇 |
无线电 | 306篇 |
一般工业技术 | 365篇 |
冶金工业 | 1097篇 |
原子能技术 | 8篇 |
自动化技术 | 971篇 |
出版年
2024年 | 63篇 |
2023年 | 173篇 |
2022年 | 272篇 |
2021年 | 346篇 |
2020年 | 264篇 |
2019年 | 283篇 |
2018年 | 239篇 |
2017年 | 258篇 |
2016年 | 231篇 |
2015年 | 208篇 |
2014年 | 324篇 |
2013年 | 359篇 |
2012年 | 339篇 |
2011年 | 377篇 |
2010年 | 310篇 |
2009年 | 324篇 |
2008年 | 293篇 |
2007年 | 258篇 |
2006年 | 236篇 |
2005年 | 228篇 |
2004年 | 190篇 |
2003年 | 187篇 |
2002年 | 170篇 |
2001年 | 158篇 |
2000年 | 78篇 |
1999年 | 83篇 |
1998年 | 70篇 |
1997年 | 57篇 |
1996年 | 63篇 |
1995年 | 66篇 |
1994年 | 59篇 |
1993年 | 42篇 |
1992年 | 47篇 |
1991年 | 22篇 |
1990年 | 16篇 |
1989年 | 16篇 |
1988年 | 10篇 |
1987年 | 14篇 |
1986年 | 11篇 |
1985年 | 17篇 |
1984年 | 9篇 |
1983年 | 8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 |
1955年 | 18篇 |
排序方式: 共有6974条查询结果,搜索用时 15 毫秒
21.
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
22.
Phoneme identification with audiovisually discrepant stimuli is influenced hy information in the visual signal (the McGurk effect). Additionally, lexical status affects identification of auditorily presented phonemes. The present study tested for lexical influences on the McGurk effect. Participants identified phonemes in audiovisually discrepant stimuli in which lexical status of the auditory component and of a visually influenced percept was independently varied. Visually influenced (McGurk) responses were more frequent when they formed a word and when the auditory signal was a nonword (Experiment 1). Lexical effects were larger for slow than for fast responses (Experiment 2), as with auditory speech, and were replicated with stimuli matched on physical properties (Experiment 3). These results are consistent with models in which lexical processing of speech is modality independent. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
23.
Being perceptive is a trait highly valued in scientific and engineering professions. What a scientist or engineer notices while considering a problem, evaluating alternatives, or interpreting data has a profound impact on how a problem is viewed and solved. This paper focuses on processes we believe underlie being perceptive: firstly, preparation—becoming attuned to salient or important features; secondly, assimilation-detection and exploration of patterns (invariants) as well as anomalies; and thirdly, strategic control-heuristic strategies for exploring the implications of what has been observed. These processes play an integral role in characteristic activities within creative design, including problem reformulation, the emergence of properties and constraints on the solution, and the ability to incorporate into the design experimental feedback from the environment and from experiences with prototypes and previous designs. The paper presents a computational model incorporating these ideas, implemented in a system called IMPROVISER. 相似文献
24.
Kammrath Lara K.; Mendoza-Denton Rodolfo; Mischel Walter 《Canadian Metallurgical Quarterly》2005,88(4):605
Three studies investigated conditions in which perceivers view dispositions and situations as interactive, rather than independent, causal forces when making judgments about another's personality. Study 1 showed that perceivers associated 5 common trait terms (e.g., friendly and shy) with characteristic if...then... (if situation a, then the person does x, but if situation b, then the person does y) personality signatures. Study 2 demonstrated that perceivers used information about a target's stable if...then... signature to infer the target's motives and traits; dispositional judgments were mediated by inferences about the target's motivations. Study 3 tested whether perceivers draw on if...then... signatures when making judgments about Big Five trait dimensions. Together, the findings indicate that perceivers take account of person-situation interactions (reflected in if...then... signatures) in everyday explanations of social behavior and personality dispositions. Boundary conditions are also discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
25.
Madan G. Sood Jagjit Singh 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1985,35(1):11-13
Cladosporium herbarum grown as a surface culture in a chemically defined medium of sucrose and inorganic salts gave a high yield of fat (29.2%). The component acids of this fat have been found to be palmitic (34.2%); oleic (15.9%); linoleic (34.2%) and linolenic (15.7%). The combined proportion of linoleic and linolenic acids being about 50 per cent, the fat will be of great value for the manufacture of oil-modified resins as the films produced by such resins do not become yellow with age. 相似文献
26.
水库大坝安全监测是工程安全的重要保障措施,亟需结合新一代信息技术,提升大坝安全监测能力。系统总结了长江科学院近年来在大坝安全监测智能感知与智慧管理技术方面的研究及应用工作,通过研发系列化智能传感器、智能采集单元和物联网感知平台,建设统一的大坝安全监测数据资源池,开发通用化安全监测云服务系统,搭建专业数据挖掘平台和综合可视化应用,实现了大坝安全监测数据感知、传输、管理、分析及展示全链路应用,形成了大坝安全监测全生命周期智慧解决方案。研究成果已在乌东德、溪洛渡、向家坝、大藤峡等100余项水利水电工程中成功应用,为保障工程建设及运行安全发挥了重要的支撑作用,具有很好的推广应用前景。 相似文献
27.
为探究不同洪水预报智能模型在我国半干旱半湿润区的应用效果,选用决策树、多层感知器、随机森林和支持向量机4种模型在陕西省3个典型流域进行逐时洪水预报;选择相关系数、纳什效率系数、均方根误差、平均绝对误差和相对误差等评价指标,比较不同预见期下4种模型在半干旱半湿润典型流域洪水预报的适用性。结果表明:在短预见期预报中,4种模型在半湿润区典型流域均可获得较高的预报结果,在半干旱典型流域模拟精度相对偏低,仅支持向量机模型满足预报要求;随着预见期延长,不同模型性能变化差异大,支持向量机模型整体稳定,在小流域实时洪水预报中具有明显优势;随机森林模型与决策树模型精度随预见期延长而缓慢下降,前者适应性更好;多层感知器模型精度随预见期延长而骤减,模型稳定性较差。 相似文献
28.
The results of two experiments showed that an illusion of memory can be produced by unconscious perception. In a first phase of those experiments, a long list of words was presented for study. For the test of recognition memory given in the second phase of each experiment, presentation of a "context" word preceded that of most recognition test words. Ss were to judge whether or not the test words had been presented during the earlier study phase of the experiment. Effects of a context word on this recognition memory decision were opposite when Ss were aware vs. unaware of its presentation. For example, as compared to a condition in which no context word was presented, the probability of false recognition was increased when Ss were unaware but decreased when Ss were aware of the presentation of a context word that matched the recognition test word. Results are discussed in terms of unconscious influences on an attribution process. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
29.
未知环境下地面的不平坦性和机器人相对障碍物位姿的不确定性会造成障碍物特征提取困难,为了准确检测障碍物特征,采用3维相机获取机器人周围环境的灰度图像和距离信息。在此基础上,提出基于灰度信息和3维信息的"阈值法"进行障碍物区域的提取,并针对3维信息"阈值法"剔除的地面与障碍物过渡区域过多,以及机器人相对斜坡方位的不确定性引起的障碍物特征检测不准确,提出区域的恢复算法和表面法线坡度计算。实验结果表明,所提出的算法具有简单、有效、准确和鲁棒性强的优点。 相似文献
30.
在Weber定律的启发下提出一种基于"恰可识别差异"的尺度空间自适应构建方法。Weber定律认为人类感知模式不仅与刺激的变化有关,而且与原刺激强度有关。基于此观点,在图像尺度空间的构建过程中,首先以Marr视觉理论的屋脊型边缘和阶梯型边缘的特征之和计算图像的信息量,再通过实验获得人类视觉能感知到"恰可识别差异"时的图像信息量变化,最后通过曲线拟合自适应构建图像的尺度空间。实验结果表明,该方法充分体现了人类视觉感知特性,与其他尺度空间构建方法相比,在目标匹配实验中,匹配数目提升了25%以上;在去噪实验中,本算法的去噪效果良好。 相似文献