全文获取类型
收费全文 | 407708篇 |
免费 | 35473篇 |
国内免费 | 20835篇 |
专业分类
电工技术 | 27794篇 |
技术理论 | 21篇 |
综合类 | 28928篇 |
化学工业 | 63652篇 |
金属工艺 | 22655篇 |
机械仪表 | 25447篇 |
建筑科学 | 33927篇 |
矿业工程 | 11694篇 |
能源动力 | 11977篇 |
轻工业 | 28437篇 |
水利工程 | 8260篇 |
石油天然气 | 20861篇 |
武器工业 | 3601篇 |
无线电 | 49394篇 |
一般工业技术 | 46069篇 |
冶金工业 | 19130篇 |
原子能技术 | 4496篇 |
自动化技术 | 57673篇 |
出版年
2024年 | 1882篇 |
2023年 | 6366篇 |
2022年 | 12272篇 |
2021年 | 16695篇 |
2020年 | 12372篇 |
2019年 | 10156篇 |
2018年 | 11183篇 |
2017年 | 12987篇 |
2016年 | 11485篇 |
2015年 | 16100篇 |
2014年 | 20577篇 |
2013年 | 25229篇 |
2012年 | 27276篇 |
2011年 | 29527篇 |
2010年 | 26366篇 |
2009年 | 25264篇 |
2008年 | 24567篇 |
2007年 | 23448篇 |
2006年 | 22692篇 |
2005年 | 18966篇 |
2004年 | 13483篇 |
2003年 | 12378篇 |
2002年 | 12504篇 |
2001年 | 11002篇 |
2000年 | 9182篇 |
1999年 | 8946篇 |
1998年 | 7358篇 |
1997年 | 6071篇 |
1996年 | 5576篇 |
1995年 | 4674篇 |
1994年 | 3882篇 |
1993年 | 2900篇 |
1992年 | 2286篇 |
1991年 | 1682篇 |
1990年 | 1353篇 |
1989年 | 1150篇 |
1988年 | 878篇 |
1987年 | 619篇 |
1986年 | 506篇 |
1985年 | 400篇 |
1984年 | 269篇 |
1983年 | 234篇 |
1982年 | 200篇 |
1981年 | 191篇 |
1980年 | 180篇 |
1979年 | 127篇 |
1978年 | 72篇 |
1977年 | 72篇 |
1976年 | 86篇 |
1975年 | 46篇 |
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
991.
ABSTRACTMobile technology has facilitated an emerging form of consumption practices called collaborative consumption. In this study, we investigate one such manifestation whereby merchants send group discount coupons to nearby consumers and encourage them to invite surrounding people to enjoy the discount together. We are interested to know if timing (morning vs. afternoon) and message framing (active vs. passive mutual helping tone) would increase the chance of an individual deciding to invite strangers (and invite a higher proportion of strangers if they did) to participate in the collaborative consumption. Facilitating the participation among strangers can help elevate the reach and influence of collaborative consumption, allowing its potential to be better exploited. Our field experiment findings show that in general people are more likely to invite strangers (and also a higher proportion of strangers in all their invitations) in the morning than in the afternoon. In addition, a message framed to ask the focal individual to actively help others enjoy the deal (active tone) is more effective than a message framed passively, i.e., to let others help him/her (passive tone) in the morning. However, passive tone framing can induce individuals to invite a higher proportion of strangers in the afternoon if they did invite others. These findings have important implications to merchants and app providers on how to more fully tap into the potential of collaborative consumption via mobile technology. 相似文献
992.
提出一种基于B样条整体最小二乘(Total least squares,TLS)的非线性多功能传感器信号重构新方法.该方法利用B样条基函数直接构建描述多功能传感器传递函数反函数的张量积B样条曲面;采用TLS求解超定方程组以获得稳定的控制系数估计.以二输入二输出多功能传感器模型为实验对象,在两种非线性情况下对多功能传感器的输入信号进行了重构,重构相对误差分别为0.162%和1.043%,并与常用重构方法进行了对比分析.理论和实验表明,B样条TLS重构方法对非线性多功能传感器传递函数的反函数具有良好的逼近性能,在信号重构中表现出较好的有效性. 相似文献
993.
网络机器人(Web Robo)t是一种自动化获取网页数据的程序。实践中使用对特定主题感兴趣的网络机器人获取数据,与数据库中数据进行比对,得出有用的结果。 相似文献
994.
995.
996.
Series expansions of fundamental solutions are essential to algorithms and analysis of the null field method (NFM) and to analysis of the method of fundamental solutions (MFS). For linear elastostatics, new Fourier series expansions of FS are derived, directly from integration. The new expansions of the FS are simpler than those in Chen et?al. (J Mech 26(3):393?C401, 2010), thus facile to application in NFM and MFS. The new series expansions of FS in this paper are important to both theory and computation of linear elastostatics. Some computation of the MFS for linear elastostatics is provided, where the expansions of fundamental solutions are a basis tool in analysis. Numerical results of a simple example are reported, accompanied with error analysis. 相似文献
997.
Xiaofeng Chen Qianhong Wu Haibo Tian Byoungcheon Lee Kwangjo Kim 《Information Sciences》2011,181(8):1493-1502
It is considered to be the most suitable solution for large scale elections to design an electronic voting scheme using blind signatures and anonymous channels. Based on this framework, Okamoto first proposed a receipt-free voting scheme [30] for large scale elections. However, in the following paper, Okamoto [31] proved that the scheme [30] was not receipt-free and presented two improved schemes. One scheme requires the help of the parameter registration committee and the other needs a stronger physical assumption of the voting booth. In this paper, we utilize the double-trapdoor commitment to propose a new receipt-free voting scheme based on blind signatures for large scale elections. Neither the parameter registration committee nor the voting booth is required in our scheme. We also present a more efficient zero-knowledge proof for secret permutation. Therefore, our scheme is much more efficient than Okamoto’s schemes [30] and [31] with the weaker physical assumptions. Moreover, we prove that our scheme can achieve the desired security properties. 相似文献
998.
Active worms have posed a major security threat to the Internet and many research efforts have focused on them. However, defending against them remains challenging due to their continuous evolution. In this paper, we study a new class of defense-oriented evolved worms, the Varying Scan Rate worm (the VSR worm in short). In order to circumvent detection by existing worm detection schemes, the VSR worm deliberately varies its scan rate according to these schemes’ weaknesses. To counteract the VSR worm, we design a new worm-detection scheme, the attack-target Distribution Entropy-based Dynamic detection scheme (DED detection for short). DED detection utilizes the attack-target distribution and robust statistical feature in conjunction with dynamic decision adaptation to distinguish worm-scan traffic from non-worm-scan traffic. We present a comparatively complete space of detection schemes and conduct extensive performance evaluations on the DED detection scheme compared with other schemes, using real-world Internet traces as background scan traffic. Our data clearly demonstrate the effectiveness of the DED detection scheme in detecting both the VSR worm and the traditional worm. 相似文献
999.
Barycentric coordinates are very popular for interpolating data values on polyhedral domains. It has been recently shown that expressing them as complex functions has various advantages when interpolating two‐dimensional data in the plane, and in particular for holomorphic maps. We extend and generalize these results by investigating the complex representation of real‐valued barycentric coordinates, when applied to planar domains. We show how the construction for generating real‐valued barycentric coordinates from a given weight function can be applied to generating complex‐valued coordinates, thus deriving complex expressions for the classical barycentric coordinates: Wachspress, mean value, and discrete harmonic. Furthermore, we show that a complex barycentric map admits the intuitive interpretation as a complex‐weighted combination of edge‐to‐edge similarity transformations, allowing the design of “home‐made” barycentric maps with desirable properties. Thus, using the tools of complex analysis, we provide a methodology for analyzing existing barycentric mappings, as well as designing new ones. 相似文献
1000.
Collision and intersection detection of surfaces is an important problem in computer graphics and robotic engineering. A key idea of our paper is to use the bracket method to derive the necessary and sufficient conditions for the collision of two ruled surfaces. Then the numerical intersection curve can be characterized. The cases for two bounded ruled surfaces are also discussed. 相似文献