全文获取类型
收费全文 | 13016篇 |
免费 | 994篇 |
国内免费 | 571篇 |
专业分类
电工技术 | 676篇 |
技术理论 | 1篇 |
综合类 | 1109篇 |
化学工业 | 2042篇 |
金属工艺 | 819篇 |
机械仪表 | 876篇 |
建筑科学 | 1005篇 |
矿业工程 | 426篇 |
能源动力 | 286篇 |
轻工业 | 847篇 |
水利工程 | 237篇 |
石油天然气 | 845篇 |
武器工业 | 199篇 |
无线电 | 1427篇 |
一般工业技术 | 1336篇 |
冶金工业 | 617篇 |
原子能技术 | 124篇 |
自动化技术 | 1709篇 |
出版年
2024年 | 59篇 |
2023年 | 200篇 |
2022年 | 306篇 |
2021年 | 456篇 |
2020年 | 331篇 |
2019年 | 289篇 |
2018年 | 315篇 |
2017年 | 393篇 |
2016年 | 339篇 |
2015年 | 485篇 |
2014年 | 598篇 |
2013年 | 719篇 |
2012年 | 822篇 |
2011年 | 982篇 |
2010年 | 804篇 |
2009年 | 763篇 |
2008年 | 746篇 |
2007年 | 792篇 |
2006年 | 810篇 |
2005年 | 686篇 |
2004年 | 447篇 |
2003年 | 395篇 |
2002年 | 324篇 |
2001年 | 372篇 |
2000年 | 336篇 |
1999年 | 319篇 |
1998年 | 303篇 |
1997年 | 216篇 |
1996年 | 190篇 |
1995年 | 204篇 |
1994年 | 150篇 |
1993年 | 96篇 |
1992年 | 89篇 |
1991年 | 57篇 |
1990年 | 37篇 |
1989年 | 34篇 |
1988年 | 35篇 |
1987年 | 26篇 |
1986年 | 15篇 |
1985年 | 8篇 |
1984年 | 8篇 |
1983年 | 9篇 |
1982年 | 5篇 |
1981年 | 2篇 |
1980年 | 6篇 |
1979年 | 1篇 |
1972年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
Pricing and inventory management in a system with multiple competing retailers under (r, Q) policies
We consider a multi-retailer system operated on an infinite horizon, in which each retailer faces stochastic demand following a Poisson process and adopts a continuous-review (r, Q) policy for replenishing inventory to satisfy customer demand. The system involves decisions of pricing and inventory management with the goal of maximizing profit, which equals the sales revenue minus the purchase and inventory costs. Taking Cournot competition into account, models are formulated to optimize simultaneously the expected sales volumes and (r, Q) policies of all retailers. An efficient approach is proposed to calculate the approximate inventory cost. Based on this approach, solution methods for centralized and decentralized scenarios are developed. A great number of numerical computations are provided to evaluate the efficiency of the solution methods, and their performance in the two scenarios. Moreover, system performance under sequential decisions (first pricing and then inventory management) is also investigated. 相似文献
72.
Donghai?Guan Weiwei?Yuan Young-Koo?LeeEmail author Sungyoung?Lee 《Applied Intelligence》2011,35(3):345-358
This paper presents a new approach for identifying and eliminating mislabeled training instances for supervised learning algorithms.
The novelty of this approach lies in the using of unlabeled instances to aid the detection of mislabeled training instances.
This is in contrast with existing methods which rely upon only the labeled training instances. Our approach is straightforward
and can be applied to many existing noise detection methods with only marginal modifications on them as required. To assess
the benefit of our approach, we choose two popular noise detection methods: majority filtering (MF) and consensus filtering
(CF). MFAUD/CFAUD is the new proposed variant of MF/CF which relies on our approach and denotes majority/consensus filtering with the aid of unlabeled data. Empirical study validates the superiority of our approach and shows that MFAUD and CFAUD can significantly improve the
performances of MF and CF under different noise ratios and labeled ratios. In addition, the improvement is more remarkable
when the noise ratio is greater. 相似文献
73.
Linggang Guan Chenyang Xue Guojun Zhang Wendong Zhang Panpan Wang 《Microsystem Technologies》2011,17(3):459-467
This paper reports on recent developments to improve the performance of hair vector hydrophone by means of several technological
advancements in the fabrication procedures and corresponding sensor design. With fish’s lateral line organs as prototypes,
NEMS (Nano-Electromechanical System) vector hydrophone with directivity has been designed. This paper describes the meso-piezoresistance
effect of resonant tunneling thin-film, and the NEMS hydrophone based on this effect is highly sensitive and small size. The
application of bionics structure may improve the low-frequency sensitivity of hydrophone. The calibration test shows that
NEMS vector hydrophone’s receiving sensitivity is up to −170 dB (0dB = 1 V/μPa), has a good directional pattern in the form
of “8” shape. The sea test shows that the direction of target can be detected by single NEMS vector hydrophone. In the anechoic
tank, it has been verified that NEMS vector hydrophone can track the trajectory of the moving target. 相似文献
74.
This paper first develops architecture for a multiprocessor job scheduling system with an embedded simulation technique. The architecture provides a shell for applications that are characterized by two scheduling policies, a heuristic algorithm policy and a First-In-First-Out (FIFO) policy. These policies are implemented in the simulation model by using the embedded technique. The paper evaluates these two policies using the queue length, waiting time and flow time as the criteria to compare the performance of these two scheduling policies. Next we designed two simulation situations using two different real world applications. The purpose is to examine the performances of multiprocessor systems with and without inspection operations and two different scheduling policies. The two applications, berth allocation for the container terminal operations and production scheduling arrangement in an Original Equipment Manufacturer (OEM) power supply factory, are studied. The final results show that a proper scheduling policy will perform better than the traditional FIFO approach for a multiprocessor system. Our study also provides guidelines on balancing a system with the addition of a final inspection activity. 相似文献
75.
Xiaoxu Guan C.J. Noble O. Zatsarinny K. Bartschat B.I. Schneider 《Computer Physics Communications》2009,180(12):2401-2409
We describe a general ab initio and non-perturbative method to solve the time-dependent Schrödinger equation (TDSE) for the interaction of a strong attosecond laser pulse with a general atom. While the field-free Hamiltonian and the dipole matrices may be generated using an arbitrary primitive basis, they are assumed to have been transformed to the eigenbasis of the problem before the solution of the TDSE is propagated in time using the Arnoldi–Lanczos method. Probabilities for survival of the ground state, excitation, and single ionization can be extracted from the propagated wavefunction.
Program summary
Program title: ALTDSECatalogue identifier: AEDM_v1_0Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEDM_v1_0.htmlProgram obtainable from: CPC Program Library, Queen's University, Belfast, N. IrelandLicensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.htmlNo. of lines in distributed program, including test data, etc.: 2154No. of bytes in distributed program, including test data, etc.: 30 827Distribution format: tar.gzProgramming language: Fortran 95. [A Fortran 2003 call to “flush” is used to simplify monitoring the output file during execution. If this function is not available, these statements should be commented out.].Computer: Shared-memory machinesOperating system: Linux, OpenMPHas the code been vectorized or parallelized?: YesRAM: Several Gb, depending on matrix size and number of processorsSupplementary material: To facilitate the execution of the program, Hamiltonian field-free and dipole matrix files are provided.Classification: 2.5External routines: LAPACK, BLASNature of problem: We describe a computer program for a general ab initio and non-perturbative method to solve the time-dependent Schrödinger equation (TDSE) for the interaction of a strong attosecond laser pulse with a general atom [1,2]. The probabilities for survival of the initial state, excitation of discrete states, and single ionization due to multi-photon processes can be obtained.Solution method: The solution of the TDSE is propagated in time using the Arnoldi–Lanczos method. The field-free Hamiltonian and the dipole matrices, originally generated in an arbitrary basis (e.g., the flexible B-spline R-matrix (BSR) method with non-orthogonal orbitals [3]), must be provided in the eigenbasis of the problem as input.Restrictions: The present program is restricted to a 1Se initial state and linearly polarized light. This is the most common situation experimentally, but a generalization is straightforward.Running time: Several hours, depending on the number of threads used.References: [1] X. Guan, O. Zatsarinny, K. Bartschat, B.I. Schneider, J. Feist, C.J. Noble, Phys. Rev. A 76 (2007) 053411. [2] X. Guan, C.J. Noble, O. Zatsarinny, K. Bartschat, B.I. Schneider, Phys. Rev. A 78 (2008) 053402. [3] O. Zatsarinny, Comput. Phys. Comm. 174 (2006) 273. 相似文献76.
Nearest neighbor editing aided by unlabeled data 总被引:1,自引:0,他引:1
This paper proposes a novel method for nearest neighbor editing. Nearest neighbor editing aims to increase the classifier’s generalization ability by removing noisy instances from the training set. Traditionally nearest neighbor editing edits (removes/retains) each instance by the voting of the instances in the training set (labeled instances). However, motivated by semi-supervised learning, we propose a novel editing methodology which edits each training instance by the voting of all the available instances (both labeled and unlabeled instances). We expect that the editing performance could be boosted by appropriately using unlabeled data. Our idea relies on the fact that in many applications, in addition to the training instances, many unlabeled instances are also available since they do not need human annotation effort. Three popular data editing methods, including edited nearest neighbor, repeated edited nearest neighbor and All k-NN are adopted to verify our idea. They are tested on a set of UCI data sets. Experimental results indicate that all the three editing methods can achieve improved performance with the aid of unlabeled data. Moreover, the improvement is more remarkable when the ratio of training data to unlabeled data is small. 相似文献
77.
Automatic human face detection from video sequences is an important component of intelligent human computer interaction systems for video surveillance, face recognition, emotion recognition and face database management. This paper proposes an automatic and robust method to detect human faces from video sequences that combines feature extraction and face detection based on local normalization, Gabor wavelets transform and Adaboost algorithm. The key step and the main contribution of this work is the incorporation of a normalization technique based on local histograms with optimal adaptive correlation (OAC) technique to alleviate a common problem in conventional face detection methods: inconsistent performance due to sensitivity to variation illuminations such as local shadowing, noise and occlusion. The approach uses a cascade of classifiers to adopt a coarse-to-fine strategy for achieving higher detection rates with lower false positives. The experimental results demonstrate a significant performance improvement gains and achieved by local normalization over methods without normalizations in real video sequences with a wide range of facial variations in color, position, scale, and varying lighting conditions. 相似文献
78.
Jianfeng Guan Hongbin Luo Hongke Zhang Han-Chieh Chao Jong Hyuk Park 《Computer Communications》2009,32(3):552-559
Mobile multicast is a research hotspot and can provide many applications. Some mobile multicast schemes have been proposed, but most of them introduce new entities and study construction algorithms of the dynamic multicast delivery structure which is heavyweight for wireless devices. In this paper, we propose a light-weight mobile multicast (LMM) scheme for Fast Mobile IPv6 which reduces the redundant operational overhead by simplifying multicast listener discovery (MLD) proxying. The LMM scheme implements simplified MLD proxying function on home agent to reduce the complicated multicast routing protocol and modifies MLD host part function on mobile node to reduce the multicast membership messages interaction. In order to solve the tunnel convergence problem, LMM also introduces a multicast tunnel combination and reconstruction algorithm. We set up a test-bed to evaluate the performance of LMM, and compare it with other mobile multicast schemes. The experimental results show that LMM reduces the multicast disruption time at handover. Based on the experimental results, we analyze the cost of LMM, and the results show that it has lower protocol cost than other schemes. 相似文献
79.
Wen-Shiung Lee Gwo-Hshiung Tzeng Jyh-Liang Guan Kuo-Ting Chien Juan-Ming Huang 《Expert systems with applications》2009,36(3):6421-6430
Basing on the Gordon model perspective and applying multiple criteria decision making (MCDM), this research explores the influential factors and relative weight of dividend, discount rate, and dividend growth rate. The purpose is to establish an investment decision model and provides investors with a reference/selection of stocks most suitable for investing effects to achieve the greatest returns. Taking full consideration of the interrelation effect among variables of the decision model, this paper introduced analytical network process (ANP) and examined leading electronics companies spanning the hottest sectors of lens, solar, and handset by experts. Empirical findings indicated that dividend was affected by industry outlook, earnings, operating cash flow, and dividend payout rate; discount rate was affected by market β and risk-free rate; and dividend growth rate was affected by earnings growth rate and dividend payout growth rate. Also, according to literatures, discount rate possessed a self-effect relationship. Among the eight evaluation criteria, market β was the most important factor influencing investment decisions, followed by dividend growth rate and risk-free rate. In stock evaluations, leadership companies in the solar industry outperformed those in handset and lens, becoming investors’ favorite stock group at the time that this research was conducted. 相似文献
80.
安钢中板厂的炉号跟踪系统中,冷金属检测器CMD用来检测冷床区钢坯的运动,但是CMD只能检测出辊道上是否有钢坯经过,而不能判断钢坯在冷床区具体上到哪个冷床,因此,目前冷床部分的钢坯跟踪是靠人工手动完成的.针对该问题,提出一种新的运用数字图像处理技术完成冷床区钢坯自动跟踪的方法.该方法利用运动目标检测方法检测出辊道上有钢坯运动,然后经过最佳阈值分割、改进的区域生长算法、质心标记、数据库程序等步骤完成钢坯运动轨迹的标记,实现自动跟踪. 相似文献