全文获取类型
收费全文 | 68638篇 |
免费 | 5639篇 |
国内免费 | 2978篇 |
专业分类
电工技术 | 3890篇 |
技术理论 | 10篇 |
综合类 | 4535篇 |
化学工业 | 11513篇 |
金属工艺 | 3581篇 |
机械仪表 | 3886篇 |
建筑科学 | 5375篇 |
矿业工程 | 1824篇 |
能源动力 | 1915篇 |
轻工业 | 5306篇 |
水利工程 | 1288篇 |
石油天然气 | 3662篇 |
武器工业 | 526篇 |
无线电 | 8238篇 |
一般工业技术 | 8508篇 |
冶金工业 | 3415篇 |
原子能技术 | 715篇 |
自动化技术 | 9068篇 |
出版年
2024年 | 310篇 |
2023年 | 1175篇 |
2022年 | 2085篇 |
2021年 | 2876篇 |
2020年 | 2245篇 |
2019年 | 1785篇 |
2018年 | 2045篇 |
2017年 | 2132篇 |
2016年 | 2084篇 |
2015年 | 2677篇 |
2014年 | 3337篇 |
2013年 | 3890篇 |
2012年 | 4299篇 |
2011年 | 4704篇 |
2010年 | 3880篇 |
2009年 | 3705篇 |
2008年 | 3680篇 |
2007年 | 3440篇 |
2006年 | 3275篇 |
2005年 | 2855篇 |
2004年 | 2133篇 |
2003年 | 1887篇 |
2002年 | 1729篇 |
2001年 | 1546篇 |
2000年 | 1687篇 |
1999年 | 2004篇 |
1998年 | 1707篇 |
1997年 | 1395篇 |
1996年 | 1378篇 |
1995年 | 1143篇 |
1994年 | 1004篇 |
1993年 | 695篇 |
1992年 | 543篇 |
1991年 | 393篇 |
1990年 | 338篇 |
1989年 | 308篇 |
1988年 | 219篇 |
1987年 | 154篇 |
1986年 | 110篇 |
1985年 | 81篇 |
1984年 | 61篇 |
1983年 | 41篇 |
1982年 | 52篇 |
1981年 | 33篇 |
1980年 | 34篇 |
1979年 | 13篇 |
1977年 | 9篇 |
1976年 | 13篇 |
1974年 | 11篇 |
1973年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
The information overload on the World Wide Web results in the underuse of some existing e‐government services within the business domain. Small‐to‐medium businesses (SMBs), in particular, are seeking “one‐to‐one'' e‐services from government in current highly competitive markets, and there is an imperative need to develop Web personalization techniques to provide business users with information and services specific to their needs, rather than an undifferentiated mass of information. This paper focuses on how e‐governments can support businesses on the problem of selecting a trustworthy business partner to perform reliable business transactions. In the business partner selection process, trust or reputation information is crucial and has significant influence on a business user's decision regarding whether or not to do business with other business entities. For this purpose, an intelligent trust‐enhanced recommendation approach to provide personalized government‐to‐business (G2B) e‐services, and in particular, business partner recommendation e‐services for SMBs is proposed. Accordingly, in this paper, we develop (1) an implicit trust filtering recommendation approach and (2) an enhanced user‐based collaborative filtering (CF) recommendation approach. To further exploit the advantages of the two proposed approaches, we develop (3) a hybrid trust‐enhanced CF recommendation approach (TeCF) that integrates both the proposed implicit trust filtering and the enhanced user‐based CF recommendation approaches. Empirical results demonstrate the effectiveness of the proposed approaches, especially the hybrid TeCF recommendation approach in terms of improving accuracy, as well as in dealing with very sparse data sets and cold‐start users. © 2011 Wiley Periodicals, Inc. 相似文献
112.
Jing Zhao Weinan Wang Yinping Liu Jinming Ma Xiaowei Li Yu Du Geyu Lu Author vitae 《Sensors and actuators. B, Chemical》2011,160(1):604
Ordered mesoporous SnO2 and mesoporous Pd/SnO2 have been successfully synthesized via nanocasting method using the hexagonal mesoporous SBA-15 as template. Two different procedures, impregnation technique and direct synthesis, were utilized for the doping of Pd in the mesoporous SnO2. The results of small angle X-ray diffraction (SAXD), nitrogen adsorption–desorption and transmission electron microscopy (TEM) demonstrate that the SnO2 and Pd/SnO2 display ordered mesoporous structures and high surface areas. Wide angle X-ray diffraction (WAXD) and X-ray photoelectron spectroscopy (XPS) reveal tetragonal structure of SnO2 and the existence of Pd element. The sensing properties of mesoporous SnO2 and mesoporous Pd/SnO2 for H2 were detected. The sensor utilizing mesoporous Pd/SnO2 via direct synthesis method exhibits excellent response and recovery behavior and much higher sensitivity to H2, compared to those using mesoporous SnO2 and mesoporous Pd/SnO2 via impregnation technique. It is believed that its high gas sensing performance is derived from the large surface area, high activity and well dispersion of Pd additive, as well as high porosity, which lead to highly effective surface interaction between the target gas molecules and the surface active sites. 相似文献
113.
Zhe-Ming Lu Author Vitae Jun-Xiang Wang Author Vitae Bei-Bei Liu Author Vitae 《Journal of Systems and Software》2009,82(6):1016-1024
Copyright protection and information security have become serious problems due to the ever growing amount of digital data over the Internet. Reversible data hiding is a special type of data hiding technique that guarantees not only the secret data but also the cover media can be reconstructed without any distortion. Traditional schemes are based on spatial, discrete cosine transformation (DCT) and discrete wavelet transformation (DWT) domains. Recently, some vector quantization (VQ) based reversible data hiding schemes have been proposed. This paper proposes an improved reversible data hiding scheme based on VQ-index residual value coding. Experimental results show that our scheme outperforms two recently proposed schemes, namely side-match vector quantization (SMVQ)-based data hiding and modified fast correlation vector quantization (MFCVQ)-based data hiding. 相似文献
114.
Since color recording and color representing abilities of various media are very different, color information is often lost or misrepresented in the process of image transmission and reproduction. A Color Management System (CMS) based on iCAM color appearance model is presented in this paper. It can be used either in computer operation system software or application software for obtaining color consistency across different software applications, imaging devices, imaging media and viewing conditions. 相似文献
115.
Hu Changhui Lu Xiaobo Ye Mengjun Zeng Weili Du Yijun 《Multimedia Tools and Applications》2017,76(24):26523-26550
Multimedia Tools and Applications - The extended sparse representation classifier (ESRC) is one of the state-of-the-art solutions for single sample face recognition, but it performs... 相似文献
116.
Lu Gui-Fu Zou Jian Wang Yong Wang Zhongqun 《Multimedia Tools and Applications》2017,76(14):15801-15816
Multimedia Tools and Applications - Null space based linear discriminant analysis (NSLDA) is a well-known feature extraction method, which can make use of the most discriminant information in the... 相似文献
117.
Lu Zhao Lin Yu-Ru Huang Xiaoxia Xiong Naixue Fang Zhijun 《Multimedia Tools and Applications》2017,76(8):10855-10879
Multimedia Tools and Applications - Nowadays, microblogging has become popular, with hundreds of millions of short messages being posted and shared every minute on a variety of topics in social... 相似文献
118.
Zeming Lu Fusaomi Nagata Keigo Watanabe Maki K. Habib 《Artificial Life and Robotics》2017,22(3):374-379
With the progress of electronics technology, the development of civilian UAV (unmanned aerial vehicle) applications becomes possible. In addition, smartphones have rapidly gained popularity and become very important due to the simple operability and mobility. Hence, there is a need to have an easy and flexible way to control a UAV using such technology. In this study, a remote controller using an iOS device is developed for a quadrotor to enable remote control with easy operations. Four basic programs for obtaining compass information, controlling a gimbal, autopilot function for return, and video preview function are developed and implemented for an iOS device. The basic functionalities of the programs are evaluated and confirmed through experiments using a quadrotor and an iOS device. 相似文献
119.
This paper aims to reduce the problems of incomplete data in computed tomography, which happens frequently in medical image process and analysis, e.g., when the high-density region of objects can only be penetrated by X-rays at a limited angular range. As the projection data are available only in an angular range, the incomplete data problem can be attributed to the limited angle problem, which is an ill-posed inverse problem. Image reconstruction based on total variation (TV) reduces the problem and gives better performance on edge-preserving reconstruction; however, the artificial parameter can only be determined through considerable experimentation. In this paper, an effective TV objective function is proposed to reduce the inverse problem in the limited angle tomography. This novel objective function provides a robust and effective reconstruction without any artificial parameter in the iterative processes, using the TV as a multiplicative constraint. The results demonstrate that this reconstruction strategy outperforms some previous ones. 相似文献
120.
提出了一种查找化合物中立体中心的算法 ,通过该算法可以找到和确认化合物中由于不对称碳和碳碳双键等产生的所有的立体中心。 相似文献