全文获取类型
收费全文 | 6601篇 |
免费 | 1088篇 |
国内免费 | 800篇 |
学科分类
工业技术 | 8489篇 |
出版年
2024年 | 12篇 |
2023年 | 73篇 |
2022年 | 185篇 |
2021年 | 204篇 |
2020年 | 239篇 |
2019年 | 159篇 |
2018年 | 160篇 |
2017年 | 194篇 |
2016年 | 274篇 |
2015年 | 310篇 |
2014年 | 471篇 |
2013年 | 454篇 |
2012年 | 543篇 |
2011年 | 690篇 |
2010年 | 546篇 |
2009年 | 538篇 |
2008年 | 606篇 |
2007年 | 660篇 |
2006年 | 514篇 |
2005年 | 449篇 |
2004年 | 353篇 |
2003年 | 263篇 |
2002年 | 183篇 |
2001年 | 130篇 |
2000年 | 78篇 |
1999年 | 47篇 |
1998年 | 30篇 |
1997年 | 27篇 |
1996年 | 18篇 |
1995年 | 6篇 |
1994年 | 13篇 |
1993年 | 11篇 |
1992年 | 2篇 |
1991年 | 8篇 |
1990年 | 3篇 |
1989年 | 4篇 |
1988年 | 3篇 |
1986年 | 3篇 |
1985年 | 5篇 |
1982年 | 1篇 |
1981年 | 3篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 1篇 |
1976年 | 7篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有8489条查询结果,搜索用时 15 毫秒
991.
Steganalysis attack is to statistically estimate the embedded watermark in the watermarked multimedia,and the estimated watermark may be destroyed by the attacker.The existing methods of false negative probability,however,do not consider the influence of steganalysis attack.This paper proposed the game theory based false negative probability to estimate the impacts of steganalysis attack,as well as unintentional attack.Specifically,game theory was used to model the collision between the embedment and steganalysis attack,and derive the optimal building embedding/attacking strategy.Such optimal playing strategies devote to calculating the attacker destructed watermark,used for calculation of the game theory based false negative probability.The experimental results show that watermark detection reliability measured using our proposed method,in comparison,can better reflect the real scenario in which the embedded watermark undergoes unintentional attack and the attacker using steganalysis attack.This paper provides a foundation for investigating countermeasures of digital watermarking community against steganalysis attack. 相似文献
992.
A lossless digital watermarking scheme,which was zero- perturbation on the content and graphics for the digital image maps,is proposed.During the simulation,the scheme has been utilized to model the copyright protection program as a commerce application.Compared to the traditional digital watermarking schemes,our scheme operates in redundancy areas of maps and is scalable to topology changes.Experimental results show that,with respect to the geometric attacks and image transformed,the performance of our scheme is better than the classical algorithms based space or frequency domain with much lower complexity.. 相似文献
993.
Despite that existing data sharing systems in online social networks(OSNs)propose to encrypt data before sharing,the multiparty access control of encrypted data has become a challenging issue.In this paper,we propose a secure data sharing scheme in OSNs based on ciphertext-policy attributebased proxy re-encryption and secret sharing.In order to protect users' sensitive data,our scheme allows users to customize access policies of their data and then outsource encrypted data to the OSNs service provider.Our scheme presents a multiparty access control model,which enables the disseminator to update the access policy of ciphertext if their attributes satisfy the existing access policy.Further,we present a partial decryption construction in which the computation overhead of user is largely reduced by delegating most of the decryption operations to the OSNs service provider.We also provide checkability on the results returned from the OSNs service provider to guarantee the correctness of partial decrypted ciphertext.Moreover,our scheme presents an efficient attribute revocation method that achieves both forward and backward secrecy.The security and performance analysis results indicate that the proposed scheme is secure and efficient in OSNs. 相似文献
994.
Zero-watermark technique,embedding watermark without modifying carriers,has been broadly applied for copyright protection of images.However,there is little research on audio zerowatermark.This paper proposes an audio zero-watermark scheme based on energy relationship between adjacent audio sections.Taking use of discrete wavelet transformation(DWT),it gets power approximations,or energies,of audio segments.Then,it extracts the audio profile,i.e.the zero-watermark,according to the relative size of energies of consecutive fragments.The experimental results demonstrate that the proposed scheme is robust against general malicious attacks including noise addition,resampling,low-pass filtering,etc.,and this approach effectively solves the contradiction between inaudibility and robustness. 相似文献
995.
针对并联不间断电源(UPS)系统的均流控制问题,设计了一种新的并联UPS系统自主控制策略.新方案可用于多个三相在线UPS模块的并联电流分配控制.每台UPS控制器将滤波电容的电压参考设计为其自身输出电流的函数进行调节,无需逆变器之间信息交换即可实现自主均流控制.同时,控制器还保证了负载电压的控制精度以及负载扰动下的动态性能.利用两台UPS为主体构成的实验平台对所设计的新型自主控制方案进行了测试.实验结果表明,在不同负载条件下,包括阶跃负载和非线性负载工况下控制器均具有较好的控制效果. 相似文献
996.
面向第六代移动通信系统(6G),感知通信一体化技术作为6G的关键技术之一,将助力实现6G的数字化、网络化、智能化的发展需求. 通信感知一体化系统中的干扰管理面临诸多挑战,其内涵不仅包括感知子系统和通信子系统协同实现通信感知一体化功能时的互干扰消除,还包括更加灵活高效的干扰避免和干扰利用办法,体现了绿色通信的发展理念. 首先概述了通信感知一体化系统中干扰管理的必要性,然后从一体化系统实现的三种模式分别讨论了干扰消除办法,接着列举了实现干扰避免和干扰利用的可行方法,最后总结全文并给出了该领域的若干开放性问题.避免和干扰利用的可行方法,最后总结全文并给出了该领域的若干开放性问题. 相似文献
997.
Gad Rabinowitz Abraham Mehrez Subhashish Samaddar 《International Journal of Flexible Manufacturing Systems》1991,3(2):149-180
We propose a mixed 0–1 linear programming model for repetitive scheduling of multirobot assembly and machining cells. The approach adopted is monolithic as opposed to hierarchical to avoid system suboptimization. The model permits any number of alternative ways (or modes) to perform each operation. A mode of an operation is determined by the required resources (facilities) and the duration of their use. The model incorporates facility changeover times. Robot collisions are avoided. Several objective functions are formulated to support different purposes. The scheduling problem of a multirobot assembly cell is formulated and solved by using commercially available mathematical programming software. Solutions under four different objective functions are reported.Acknowledging the complexity and considerable size of the formulation required, we prescribe and illustrate specific methods to achieve size reduction. Finally, for successful use of our model, an information processing schema is offered as a general guidance to help data management needed by the model. 相似文献
998.
Fortin Claudette; Bédard Marie-Claude; Champagne Julie 《Canadian Metallurgical Quarterly》2005,31(2):276
Duration and location of breaks in time interval production were manipulated in various conditions of stimulus presentation (Experiments 1-4). Produced intervals shortened and then stabilized as break duration lengthened, suggesting that participants used the break as a preparatory period to restart timing as quickly as possible at the end of the break. This interpretation was supported in Experiment 5, in which similar results were obtained with a reaction time response executed at the end of the break. In all experiments, produced intervals lengthened as the break occurred later during the interval. The authors conclude that varying break location and duration reveal, respectively, the influence of attentional time-sharing before the interruption and of preparatory processes taking place during the break. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
999.
At the 1992 World Administrative Radio Conference (WARC), spectrum was allocated, on a primary basis, to the broadcast satellite service (sound). The allocations were not, however, uniform worldwide, nor will the BSS(S) have sole use of these allocations. In addition, many countries have reserved primary use of the spectrum for existing services until 2007, with the BSS(S) permitted only on a noninterference basis. This situation will impose serious constraints on the proposed ESA S-DAB service, to be radiated from the ‘Archimedes’ constellation of satellites. The launch date for this service may be before the end of the century, and sharing with other spectrum users will therefore be necessary. Such users include fixed telephony links, broadcast links and mobile aeronautical telemetry. This paper reviews current spectrum usage in Europe and elsewhere, and investigates the restrictions thus imposed on the ESA S-DAB service. Numerical examples based on real-world systems are given, and demonstrate the feasibility, in many cases, of spectrum sharing. 相似文献
1000.
数字水印作为数字媒体版权保护的有效手段。受到极大关注,钽却没有一个良好的衡量手段来对数字水印算法作出合理的评测,本文总结了目前比较流行的数字水印算法衡量手段以及几种有效的数字水印的攻击手段,旨在帮助全面评测水印算法的性能,进而帮助改进数字水印算法,使数字水印算法具有更好的隐形性、稳健性、安全性,以促进数字水印走向实用化。 相似文献