全文获取类型
收费全文 | 22591篇 |
免费 | 3836篇 |
国内免费 | 2155篇 |
专业分类
电工技术 | 3071篇 |
技术理论 | 1篇 |
综合类 | 2033篇 |
化学工业 | 3523篇 |
金属工艺 | 627篇 |
机械仪表 | 1695篇 |
建筑科学 | 440篇 |
矿业工程 | 303篇 |
能源动力 | 942篇 |
轻工业 | 917篇 |
水利工程 | 255篇 |
石油天然气 | 917篇 |
武器工业 | 422篇 |
无线电 | 3375篇 |
一般工业技术 | 3382篇 |
冶金工业 | 464篇 |
原子能技术 | 392篇 |
自动化技术 | 5823篇 |
出版年
2024年 | 188篇 |
2023年 | 570篇 |
2022年 | 902篇 |
2021年 | 944篇 |
2020年 | 1143篇 |
2019年 | 1004篇 |
2018年 | 1029篇 |
2017年 | 1190篇 |
2016年 | 1292篇 |
2015年 | 1297篇 |
2014年 | 1574篇 |
2013年 | 1725篇 |
2012年 | 1747篇 |
2011年 | 1842篇 |
2010年 | 1202篇 |
2009年 | 1287篇 |
2008年 | 1156篇 |
2007年 | 1313篇 |
2006年 | 1116篇 |
2005年 | 873篇 |
2004年 | 747篇 |
2003年 | 693篇 |
2002年 | 542篇 |
2001年 | 437篇 |
2000年 | 467篇 |
1999年 | 326篇 |
1998年 | 305篇 |
1997年 | 284篇 |
1996年 | 242篇 |
1995年 | 181篇 |
1994年 | 184篇 |
1993年 | 113篇 |
1992年 | 121篇 |
1991年 | 112篇 |
1990年 | 80篇 |
1989年 | 59篇 |
1988年 | 42篇 |
1987年 | 43篇 |
1986年 | 30篇 |
1985年 | 35篇 |
1984年 | 40篇 |
1983年 | 30篇 |
1982年 | 41篇 |
1981年 | 11篇 |
1980年 | 7篇 |
1979年 | 5篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1974年 | 2篇 |
1959年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Jinku Yang Lei Guo Haiku Yang 《IEEJ Transactions on Electrical and Electronic Engineering》2015,10(4):447-452
A multi‐focus image fusion method, which is based on bidimensional empirical mode decomposition (BEMD) and improved local energy algorithm, is presented in this paper. First, the source image is decomposed by BEMD. Then maximum criterion combined with weighted average fusion rule based on local energy is applied to bidimensional intrinsic mode function components of the corresponding frequency segment. If the phase of the bidimensional intrinsic mode function coefficients decomposed by BEMD on two source images is the same, the local energy maximum criterion is used in the frequency coefficients of the fused image; else, if the corresponding phase is opposite, bidimensional intrinsic mode function coefficients of the fused image is determined by a weighted average method based on local energy. Finally, the fusion result is obtained by the inverse BEMD transformation on the fusion coefficient. Simulation shows that the proposed algorithm significantly outperforms traditional methods such as the maximum criterion, weighted average, and wavelet fusion rules. © 2015 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. 相似文献
992.
Xin Guan Min Chen Tomoaki Ohtsuki 《Wireless Communications and Mobile Computing》2015,15(12):1633-1648
In sparse mobile wireless networks, normally, the mobile nodes are carried by people, and the moving activity of nodes always happens in a specific area, which corresponds to some specific community. Between the isolated communities, there is no stable communication link. Therefore, it is difficult to ensure the effective packet transmission among communities, which leads to the higher packet delivery delay and lower successful delivery ratio. Recently, an additional ferry node was introduced to forward packets between the isolated communities. However, most of the existing algorithms are working on how to control the trajectory of only one ferry work in the network. In this paper, we consider multiple ferries working in the network scenario and put our main focus on the optimal packet selection strategy, under the condition of mutual influence between the ferries and the buffer limitation. We introduce a non‐cooperative Bayesian game to achieve the optimal packet selection strategy. By maximizing the individual income of a ferry, we optimize the network performance on packet delivery delay and successful delivery ratio. Simulation results show that our proposed packet selection strategy improves the network performance on packet delivery delay and successful delivery ratio. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
993.
Guan Gui Abolfazl Mehbodniya Fumiyuki Adachi 《Wireless Communications and Mobile Computing》2015,15(12):1649-1658
Standard least mean square/fourth (LMS/F) is a classical adaptive algorithm that combined the advantages of both least mean square (LMS) and least mean fourth (LMF). The advantage of LMS is fast convergence speed while its shortcoming is suboptimal solution in low signal‐to‐noise ratio (SNR) environment. On the contrary, the advantage of LMF algorithm is robust in low SNR while its drawback is slow convergence speed in high SNR case. Many finite impulse response systems are modeled as sparse rather than traditionally dense. To take advantage of system sparsity, different sparse LMS algorithms with lp‐LMS and l0‐LMS have been proposed to improve adaptive identification performance. However, sparse LMS algorithms have the same drawback as standard LMS. Different from LMS filter, standard LMS/F filter can achieve better performance. Hence, the aim of this paper is to introduce sparse penalties to the LMS/F algorithm so that it can further improve identification performance. We propose two sparse LMS/F algorithms using two sparse constraints to improve adaptive identification performance. Two experiments are performed to show the effectiveness of the proposed algorithms by computer simulation. In the first experiment, the number of nonzero coefficients is changing, and the proposed algorithms can achieve better mean square deviation performance than sparse LMS algorithms. In the second experiment, the number of nonzero coefficient is fixed, and mean square deviation performance of sparse LMS/F algorithms is still better than that of sparse LMS algorithms. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
994.
This paper investigates three major issues regarding the elicitation of expert knowledge for economic risk analysis: (1) recognition of some of the implicit assumptions and beliefs; (2) development of an approach to elicit expert knowledge as accurate, calibrated and coherent subjective probabilities; and (3)a study to explore human ability to predict future events and the validity of the implicit assumptions and beliefs in the context of the expert judgements. The proposed elicitation approach combines the theoretical requirements for valid subjective probabilities with a practical process. The recognition that some of the implicit assumptions and beliefs in engineering risk analysis should be explored when dealing with the human ability to predict future events, and the inherent difficulties in developing experiments and methods to test such beliefs arc some of the benefits of the study. Directions for future work are suggested. 相似文献
995.
996.
Covariance‐based hardware selection part IV: Solution using the generalized benders decomposition 下载免费PDF全文
Jin Zhang Xiaoxi Wang Donald J. Chmielewski 《American Institute of Chemical Engineers》2016,62(10):3628-3638
Recently the covariance based hardware selection problem has been shown to be of the mixed integer convex programming (MICP) class. While such a formulation provides a route to global optimality, use of the branch and bound search procedure has limited application to fairly small systems. The particular bottleneck is that during each iteration of the branch and bound search, a fairly slow semi‐definite programming (SDP) problem must be solved to its global optimum. In this work, we illustrate that a simple reformulation of the MICP and subsequent application of the generalized Benders decomposition algorithm will result in massive reductions in computational effort. While the resulting algorithm must solve multiple mixed integer linear programs, this increase in computational effort is significantly outweighed by the reduction in the number of SDP problems that must be solved. © 2016 American Institute of Chemical Engineers AIChE J, 62: 3628–3638, 2016 相似文献
997.
998.
Fenton技术中残余组分对COD测定的干扰和消除研究 总被引:1,自引:0,他引:1
Fenton试剂与水样中难降解有机物反应后,残余组分会对后续水样COD测定产生干扰。实验表明,Fenton试剂残余组分中H_2O_2对COD测定产生的干扰较大,其对水样COD测定产生的影响值与H_2O_2浓度成良好的线性关系,而残余组分Fe~(2+)对COD测定产生的干扰与H_2O_2相比,影响值较小,可忽略其影响。通过对比分析掩蔽剂法、催化分解法对H_2O_2干扰消除试验得出,掩蔽剂Na_2SO_3能够迅速的与H_2O_2发生反应,消除H_2O_2的干扰,但掩蔽剂Na_2SO_3也会对水样COD产生一定的干扰,测量结果偏差较大;MnO_2催化分解H_2O_2的效率较高,很好的消除H_2O_2的干扰,但MnO_2分解后水样COD测定值需乘以折减系数0.89,满足试验精度的要求;过氧化氢酶可以将H_2O_2完全分解,分解效率较高,干扰消除效果较好。 相似文献
999.
1000.