全文获取类型
收费全文 | 6389篇 |
免费 | 1222篇 |
国内免费 | 1228篇 |
学科分类
工业技术 | 8839篇 |
出版年
2024年 | 25篇 |
2023年 | 116篇 |
2022年 | 227篇 |
2021年 | 303篇 |
2020年 | 326篇 |
2019年 | 286篇 |
2018年 | 288篇 |
2017年 | 338篇 |
2016年 | 408篇 |
2015年 | 368篇 |
2014年 | 548篇 |
2013年 | 478篇 |
2012年 | 573篇 |
2011年 | 634篇 |
2010年 | 561篇 |
2009年 | 512篇 |
2008年 | 515篇 |
2007年 | 496篇 |
2006年 | 408篇 |
2005年 | 315篇 |
2004年 | 234篇 |
2003年 | 183篇 |
2002年 | 142篇 |
2001年 | 86篇 |
2000年 | 88篇 |
1999年 | 63篇 |
1998年 | 41篇 |
1997年 | 37篇 |
1996年 | 35篇 |
1995年 | 30篇 |
1994年 | 25篇 |
1993年 | 22篇 |
1992年 | 14篇 |
1991年 | 20篇 |
1990年 | 18篇 |
1989年 | 7篇 |
1988年 | 6篇 |
1987年 | 5篇 |
1985年 | 4篇 |
1984年 | 3篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 5篇 |
1976年 | 3篇 |
1963年 | 4篇 |
1961年 | 2篇 |
1960年 | 5篇 |
1959年 | 6篇 |
1958年 | 2篇 |
排序方式: 共有8839条查询结果,搜索用时 15 毫秒
1.
2.
It is important to verify assumptions and methods of image retrieval against actual human behavior. A study was conducted to compare similarity methods of color histograms against human assessment of similarity. The similarity methods tested include basic histogram intersection, center histogram matching, locality histogram matching, and size-weighted histogram matching. 161 subjects participated in the empirical study. The findings, based on Spearman correlation analysis, showed that both the basic histogram intersection method and size-weighted histogram are very close to human assessment of similarity (Spearman correlation coefficient of 0.915). The other two are not close to human judgment on similarity. This study illustrates an alternative approach to evaluating matching algorithms. Unlike the usual measures of recall and precision, this approach emphasizes human validation. Fewer images are required with the use of statistical testing. 相似文献
3.
Wiltrout Charles; Dogra Samriti; Linster Christiane 《Canadian Metallurgical Quarterly》2003,117(2):236
Studies on odor mixture perception suggest that although odor components can often be identified in mixtures, mixtures can also give rise to novel perceptual qualities that are not present in the components. Using an olfactory habituation task, the authors evaluated how the perceptual similarity between components in a mixture affects the perceptual quality of the mixture itself. Rats perceived binary mixtures composed of similar components as different from their 2 components, whereas binary mixtures composed of dissimilar components were perceived as very similar to their components. Results show that for both types of mixtures, pretraining to Component A reduces subsequent learning about Component B in rats trained in the presence of A. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
4.
Qing Li 《Computer Standards & Interfaces》1991,13(1-3):99-103
The term ‘object-oriented database’ has been used to refer to different characteristics and mechanisms supported by semantic databases and (behaviorally) object-oriented ones. While this indicates the current confusion due to the lack of a common model, it also suggests the potential desirability of combining these two kinds of modeling facilities into the same nutshell. This paper summarizes from these two paradigms the features common to both, the features influenced/adopted by each other, and the features which are presented in one paradigm but missing from the other. After a brief analysis and discussion of these features, we conclude this paper by proposing our major theme: a complete object data model should take the union of the facilities offered by these two kinds of models. 相似文献
5.
Yoon Carolyn; Feinberg Fred; Hu Ping; Gutchess Angela Hall; Hedden Trey; Chen Hiu-Ying Mary; Jing Qicheng; Cui Yao; Park Denise C. 《Canadian Metallurgical Quarterly》2004,19(3):379
Understanding how aging influences cognition across different cultures has been hindered by a lack of standardized, cross-referenced verbal stimuli. This study introduces a database of such item-level stimuli for both younger and older adults, in China and the United States, and makes 3 distinct contributions. First, the authors specify which item categories generalize across age and/or cultural groups, rigorously quantifying differences among them. Second, they introduce novel, powerful methods to measure between-group differences in freely generated ranked data, the rank-ordered logit model and Hellinger Affinity. Finally, a broad archive of tested, cross-linguistic stimuli is now freely available to researchers: data, similarity measures, and all stimulus materials for 105 categories and 4 culture-by-age groups, comprising over 10,000 fully translated unique item responses. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
6.
7.
Zhang Sheng-ming Yangtze River Scientific Research Institute Wuhan Hubei P. R. China 《水动力学研究与进展(B辑)》1992,(2)
Through a series of model tests of five scales for 2-D free hydraulic jump, the da-ta of fluctuating pressure acting on the floor level within the hydraulic jump were obtained. Dur-ing the experiments, Froude number varied from 2.94 to 8.61, and Reynolds number rangedfrom 2×10~4 to 6×10~5. Experiment results indicate that the amplitude scale of fluctuating pres-sure is the length scale of model, i. e. P'=L, which agrees with gravity similarity law: Thefrequency scale of the fluctuating pressure is a unity i. e., f=1, which does not satisfy thegravity similarity law. 相似文献
8.
1. Introduction Seismic physical modeling technology is an important method for the research on seismic exploration theory and methods. In seismic physical experiments, the earth, mantle or field site are scaled down to physical models according to the similarity principle, and then the seismic field and its variation are observed in the laboratory for the research work on the theories and methods of the earth structure, earthquake forecasting, energy and mineral resource exploration, and engi… 相似文献
9.
自治Agents的面向服务的协商模型 总被引:3,自引:0,他引:3
提出了一个基于自治Agents的面向服务的协商模型。模型主要包括两大模块:首先定义了一系列的战略和战术过程,使得Agents可以产生初始建议,评价对方的建议,以及在此基础上做出反建议;其次,定义了两个层次的Agent通信机制。二者相辅相成,实现了Agents间合作的动态形成和随机协调,使得Agents可以承担因环境的不确定性而需动态协作的复杂任务。 相似文献
10.