全文获取类型
收费全文 | 61711篇 |
免费 | 4773篇 |
国内免费 | 2724篇 |
专业分类
电工技术 | 3266篇 |
技术理论 | 6篇 |
综合类 | 4095篇 |
化学工业 | 10457篇 |
金属工艺 | 3847篇 |
机械仪表 | 3802篇 |
建筑科学 | 4662篇 |
矿业工程 | 2194篇 |
能源动力 | 1952篇 |
轻工业 | 3488篇 |
水利工程 | 1064篇 |
石油天然气 | 4531篇 |
武器工业 | 457篇 |
无线电 | 6453篇 |
一般工业技术 | 7210篇 |
冶金工业 | 3353篇 |
原子能技术 | 720篇 |
自动化技术 | 7651篇 |
出版年
2024年 | 244篇 |
2023年 | 985篇 |
2022年 | 1700篇 |
2021年 | 2424篇 |
2020年 | 1821篇 |
2019年 | 1639篇 |
2018年 | 1827篇 |
2017年 | 2031篇 |
2016年 | 1816篇 |
2015年 | 2339篇 |
2014年 | 2985篇 |
2013年 | 3463篇 |
2012年 | 3646篇 |
2011年 | 4000篇 |
2010年 | 3670篇 |
2009年 | 3290篇 |
2008年 | 3254篇 |
2007年 | 3207篇 |
2006年 | 3189篇 |
2005年 | 2765篇 |
2004年 | 2038篇 |
2003年 | 2145篇 |
2002年 | 2479篇 |
2001年 | 2078篇 |
2000年 | 1611篇 |
1999年 | 1702篇 |
1998年 | 1251篇 |
1997年 | 1067篇 |
1996年 | 1103篇 |
1995年 | 846篇 |
1994年 | 631篇 |
1993年 | 468篇 |
1992年 | 365篇 |
1991年 | 274篇 |
1990年 | 206篇 |
1989年 | 166篇 |
1988年 | 153篇 |
1987年 | 88篇 |
1986年 | 69篇 |
1985年 | 37篇 |
1984年 | 38篇 |
1983年 | 27篇 |
1982年 | 25篇 |
1981年 | 14篇 |
1980年 | 22篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1974年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
This paper proposes an improved semi-fragile speech watermarking scheme by quantization of linear prediction (LP) parameters, i.e., the inverse sine (IS) parameters. The spectral distortion due to watermark embedding is controlled to meet the ‘transparency’ criterion in speech coding. A modified bit allocation algorithm combined with watermarking is developed to determine the quantization step so that the ‘transparency’ requirement is satisfied. Due to the statistical nature, the LP coefficients estimated from the watermarked speech signal are different from the watermarked LP coefficients even in the absence of attacks. This effect is the cause of increase in decoding error and minimum authentication length. To tackle this problem, an Analysis by Synthesis (AbS) scheme is developed to reduce the difference between the estimated LP coefficients and the watermarked ones. The watermark detection threshold and minimum authentication length are then derived according to the probability of error and the signal to noise ratio (SNR) requirements. Experimental results show that the proposed AbS based method can effectively reduce the difference between the watermarked IS parameter and the extracted IS parameter when there is no attacks. In addition, the modified bit allocation algorithm can automatically find the appropriate quantization step used in the odd-even modulation so that the transparency requirement is satisfied. 相似文献
82.
On Controllability of Switched Linear Systems 总被引:1,自引:0,他引:1
Zhijian Ji Long Wang Xiaoxia Guo 《Automatic Control, IEEE Transactions on》2008,53(3):796-801
This paper investigates the number of switchings and design of switching sequences for controllability of switched linear systems. Two related results are established. One is a new constructive approach to designing switching sequences. The controllable state set of each switching sequence designed via the approach coincides with the controllable subspace of switched linear systems. The other is a well-estimated value for the minimum number of switchings required for controllability. Each state in the controllable subspace can be steered to origin within this value of switching times. 相似文献
83.
Lei Guo Xingwei Wang Qingyang Song Weigang Hou Fei Yang 《Information Sciences》2008,178(18):3635-3644
With the development of intelligent optical networks and the general multi-protocol label switching (GMPLS) technique, the seamless convergence between IP network and optical network is no longer be a dream but a practical reality. Similar to the Internet, current optical networks have been divided into multiple domains each of which has its own network provider and management policy. Therefore, the development of multi-domain optical networks will be the trend of new-generation intelligent optical networks, and GMPLS-based survivability for multi-domain optical networks will become a hot topic of research in the future. This paper provides a comprehensive review of the existing survivable schemes in multi-domain optical networks and analyzes the shortcomings of current research. Based on previous studies, we present possible challenges and propose new ideas to design efficient survivable schemes to guide the future work of researchers in multi-domain optical networks. 相似文献
84.
面向业务问题求解的知识供应过程模型 总被引:1,自引:0,他引:1
为了满足企业在业务问题求解方面的实际需求,提出了一个面向业务问题求解的知识供应过程模型。该模型提出了知识供应过程中的问题空间、知识空间和流程空间的概念及其关联关系,并进一步给出了包含知识的获取、评价、存储和重用的知识供应过程的有关算法。该模型与算法将业务问题求解过程与知识供应过程进行了融合,通过关联关系实现了知识的主动供应,在优化了业务问题求解过程的同时,提高了知识积累的质量和知识重用的效率。基于该模型建立了知识管理问题求解的原型系统KMPSS,并得到了初步应用验证。 相似文献
85.
将常规的数字温度仪与压力计通过串行口和计算机连接,构建基于LabVIEW 8.0测定纯液体蒸发焓的虚拟仪器,实现实验数据的动态采集、实时显示、自动绘制p~T曲线并显示曲线方程、自动数据处理和写成结果报告等。应用结果表明:基于LabVIEW构建的测定纯液体蒸发焓的虚拟仪器,免除人工操作的繁琐和人为误差,测定乙醇和苯蒸发焓的相对误差分别为0.86%、-2.97%,提高了测量结果的准确度,且具有界面友好,操作简便和功能易扩展等诸多优点。 相似文献
86.
Mao-Zu Guo Jun Wang Chun-yu Wang Yang Liu 《Soft Computing - A Fusion of Foundations, Methodologies and Applications》2009,13(12):1143-1151
TagSNP selection, which aims to select a small subset of informative single nucleotide polymorphisms (SNPs) to represent the
whole large SNP set, has played an important role in current genomic research. Not only can this cut down the cost of genotyping
by filtering a large number of redundant SNPs, but also it can accelerate the study of genome-wide disease association. In
this paper, we propose a new hybrid method called CMDStagger that combines the ideas of the clustering and the graph algorithm,
to find the minimum set of tagSNPs. The proposed algorithm uses the information of the linkage disequilibrium association
and the haplotype diversity to reduce the information loss in tagSNP selection, and has no limit of block partition. The approach
is tested on eight benchmark datasets from Hapmap and chromosome 5q31. Experimental results show that the algorithm in this
paper can reduce the selection time and obtain less tagSNPs with high prediction accuracy. It indicates that this method has
better performance than previous ones. 相似文献
87.
Control of frictional forces is required in many applications of tribology. While the problem is approached by chemical means traditionally, a recent approach was proposed to control the system mechanically to tune frictional responses. We design feedback control laws for a one-dimensional particle array sliding on a surface subject to friction. The Frenkel-Kontorova model describing the dynamics is a nonlinear interconnected system and the accessible control elements are average quantities only. We prove local stability of equilibrium points of the un-controlled system in the presence of linear and nonlinear particle interactions, respectively. We then formulate a tracking control problem, whose control objective is for the average system to reach a designated targeted velocity using accessible elements. Sufficient stabilization conditions are explicitly derived for the closed-loop error systems using the Lyapunov theory based methods. Simulation results show satisfactory performances. The results can be applied to other physical systems whose dynamics is described by the Frenkel-Kontorova model. 相似文献
88.
Yin Lifeng Kong Yanggang Guo Mingkang Zhang Xingyu Yan Wenlong Zhang Hua 《Magma (New York, N.Y.)》2023,36(4):651-658
Magnetic Resonance Materials in Physics, Biology and Medicine - This study aims to present a radiomic application in diagnosing the long head of biceps (LHB) tendinitis. Moreover, we evaluated... 相似文献
89.
90.
The Journal of Supercomputing - We argue the agent’s low generalization problem for searching target object in challenging visual navigation could be solved by "how" and... 相似文献