全文获取类型
收费全文 | 26131篇 |
免费 | 4531篇 |
国内免费 | 2900篇 |
专业分类
电工技术 | 1094篇 |
综合类 | 2532篇 |
化学工业 | 1113篇 |
金属工艺 | 499篇 |
机械仪表 | 1624篇 |
建筑科学 | 579篇 |
矿业工程 | 2999篇 |
能源动力 | 261篇 |
轻工业 | 419篇 |
水利工程 | 640篇 |
石油天然气 | 477篇 |
武器工业 | 296篇 |
无线电 | 4492篇 |
一般工业技术 | 1409篇 |
冶金工业 | 1139篇 |
原子能技术 | 48篇 |
自动化技术 | 13941篇 |
出版年
2024年 | 186篇 |
2023年 | 487篇 |
2022年 | 1095篇 |
2021年 | 1300篇 |
2020年 | 1358篇 |
2019年 | 896篇 |
2018年 | 783篇 |
2017年 | 870篇 |
2016年 | 1012篇 |
2015年 | 1123篇 |
2014年 | 1701篇 |
2013年 | 1475篇 |
2012年 | 2030篇 |
2011年 | 2106篇 |
2010年 | 1667篇 |
2009年 | 1685篇 |
2008年 | 1797篇 |
2007年 | 1948篇 |
2006年 | 1694篇 |
2005年 | 1420篇 |
2004年 | 1173篇 |
2003年 | 1053篇 |
2002年 | 887篇 |
2001年 | 624篇 |
2000年 | 529篇 |
1999年 | 481篇 |
1998年 | 381篇 |
1997年 | 292篇 |
1996年 | 223篇 |
1995年 | 207篇 |
1994年 | 166篇 |
1993年 | 153篇 |
1992年 | 118篇 |
1991年 | 61篇 |
1990年 | 54篇 |
1989年 | 72篇 |
1988年 | 44篇 |
1987年 | 26篇 |
1986年 | 25篇 |
1985年 | 34篇 |
1984年 | 33篇 |
1983年 | 43篇 |
1982年 | 38篇 |
1981年 | 34篇 |
1980年 | 27篇 |
1979年 | 23篇 |
1978年 | 23篇 |
1977年 | 26篇 |
1976年 | 23篇 |
1974年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
992.
On the Sequential Accumulation of Evidence 总被引:1,自引:0,他引:1
In this paper, we introduce a method for sequentially accumulating evidence as it pertains to an active observer seeking to identify an object in a known environment. We develop a probabilistic framework, based on a generalized inverse theory, where assertions are represented by conditional probability density functions. This leads to a sequential recognition strategy in which evidence is accumulated over successive viewpoints using Bayesian chaining until a definitive assertion can be made. To illustrate the theory we show how the characteristics of belief distributions can be exploited in a model-based recognition problem, where the task is to identify an unknown model from a database of known objects on the basis of parameter estimates. We illustrate the robustness of the algorithm through recognition experiments in two very different contexts: (1) a highly structured recognition context where 3-D parametric models can be estimated directly from range data, (2) a complex environment, where the relationship between the data and the model is learned through an appearance-based strategy. Specifically, the flow fields computed through the object's motion are used as structural signatures for recognition. 相似文献
993.
Emotions should play an important role in the design of interfaces because people interact with machines as if they were social actors. This paper presents a literature review on affective expressions through speech, music and body language. It summarizes the quality and quantity of their parameters and successful examples of synthesis. Moreover, a model for the convincingness of affective expressions, based on Fogg and Hsiang Tseng (1999), was developed and tested. The empirical data did not support the original model and therefore this paper proposes a new model, which is based on appropriateness and intensity of the expressions. Furthermore, the experiment investigated if the type of emotion (happiness, sadness, anger, surprise, fear and disgust), knowledge about the source (human or machine), the level of abstraction (natural face, computer rendered face and matrix face) and medium of presentation (visual, audio/visual, audio) of an affective expression influences its convincingness and distinctness. Only the type of emotion and multimedia presentations had an effect on convincingness. The distinctness of an expression depends on the abstraction and the media through which it is presented. 相似文献
994.
Rahul Singh Richard M. Voyles David Littau Nikolaos P. Papanikolopoulos 《Autonomous Robots》2001,10(3):317-338
We present an approach for controlling robotic interactions with objects, using synthetic images generated by morphing shapes. In particular, we attempt the problem of positioning an eye-in-hand robotic system with respect to objects in the workspace for grasping and manipulation. In our formulation, the grasp position (and consequently the approach trajectory of the manipulator), varies with each object. The proposed solution to the problem consists of two parts. First, based on a model-based object recognition framework, images of the objects taken at the desired grasp pose are stored in a database. The recognition and identification of the grasp position for an unknown input object (selected from the family of recognizable objects) occurs by morphing its contour to the templates in the database and using the virtual energy spent during the morph as a dissimilarity measure. In the second step, the images synthesized during the morph are used to guide the eye-in-hand system and execute the grasp. The proposed method requires minimal calibration of the system. Furthermore, it conjoins techniques from shape recognition, computer graphics, and vision-based robot control in a unified engineering amework. Potential applications range from recognition and positioning with respect to partially-occluded or deformable objects to planning robotic grasping based on human demonstration. 相似文献
995.
A model-based hand gesture recognition system 总被引:2,自引:0,他引:2
This paper introduces a model-based hand gesture recognition system, which consists of three phases: feature extraction,
training, and recognition. In the feature extraction phase, a hybrid technique combines the spatial (edge) and the temporal
(motion) information of each frame to extract the feature images. Then, in the training phase, we use the principal component
analysis (PCA) to characterize spatial shape variations and the hidden Markov models (HMM) to describe the temporal shape
variations. A modified Hausdorff distance measurement is also applied to measure the similarity between the feature images
and the pre-stored PCA models. The similarity measures are referred to as the possible observations for each frame. Finally,
in recognition phase, with the pre-trained PCA models and HMM, we can generate the observation patterns from the input sequences,
and then apply the Viterbi algorithm to identify the gesture. In the experiments, we prove that our method can recognize 18
different continuous gestures effectively.
Received: 19 May 1999 / Accepted: 4 September 2000 相似文献
996.
Mitsuyoshi Nagao Masahito Yamamoto Keiji Suzuki & Azuma Ohuchi 《International Transactions in Operational Research》2001,8(1):31-45
In this paper, we propose a face identification system based on the Mahalanobis–Taguchi System (MTS). The MTS is one of the pattern recognition methods frequently used in quality engineering, and can perform robust pattern recognition by using training data, including noise. It is likely that this advantage will allow the effective implementation of a robust face identification system against lighting and face position fluctuations. Moreover, the MTS can optimize the number of attributes required for identification by using the orthogonal array and the signal/noise (SN) ratio. The face identification system has to deal with many users and the amount of data in a facial image is large. Therefore, the time required for identification can be decreased and the amount of data in the facial image database can be reduced by performing the optimization. We confirmed the effectiveness of the proposed system through practical experiments. The experimental results revealed that the MTS was an effective method for robust face identification, and could effectively reduce the number of attributes required for identification. 相似文献
997.
998.
基于联合时频分析的混合神经系统在信号分类与模式识别中的应用 总被引:3,自引:0,他引:3
介绍了一种基于STFT,WVD和Wavelet变换的混合神经系统在特征提取和信号分类中的应用.它运用时频信号处理技术与混合神经网络结构以及高级训练算法相结合的设计思想,辅之以主元分析和全局决策融合策略,对传统的模式识别技术进行了有效地改进.本文将所述基于WT,STFT和WVD的混合神经系统信号分类器(WSWHNS)的算法程序嵌入一汽车实时智能故障诊断软件包中做了现场实验,获得了非常满意的诊断效果. 相似文献
999.
1000.
Detecting and tracking human faces in video sequences is useful in a number of applications such as gesture recognition and
human-machine interaction. In this paper, we show that online appearance models (holistic approaches) can be used for simultaneously
tracking the head, the lips, the eyebrows, and the eyelids in monocular video sequences. Unlike previous approaches to eyelid
tracking, we show that the online appearance models can be used for this purpose. Neither color information nor intensity
edges are used by our proposed approach. More precisely, we show how the classical appearance-based trackers can be upgraded
in order to deal with fast eyelid movements. The proposed eyelid tracking is made robust by avoiding eye feature extraction.
Experiments on real videos show the usefulness of the proposed tracking schemes as well as their enhancement to our previous
approach.
相似文献
Javier OrozcoEmail: |