全文获取类型
收费全文 | 9631篇 |
免费 | 632篇 |
国内免费 | 492篇 |
专业分类
电工技术 | 441篇 |
综合类 | 790篇 |
化学工业 | 143篇 |
金属工艺 | 105篇 |
机械仪表 | 509篇 |
建筑科学 | 170篇 |
矿业工程 | 57篇 |
能源动力 | 149篇 |
轻工业 | 50篇 |
水利工程 | 70篇 |
石油天然气 | 41篇 |
武器工业 | 47篇 |
无线电 | 827篇 |
一般工业技术 | 703篇 |
冶金工业 | 41篇 |
原子能技术 | 26篇 |
自动化技术 | 6586篇 |
出版年
2024年 | 16篇 |
2023年 | 57篇 |
2022年 | 90篇 |
2021年 | 92篇 |
2020年 | 154篇 |
2019年 | 142篇 |
2018年 | 112篇 |
2017年 | 216篇 |
2016年 | 228篇 |
2015年 | 308篇 |
2014年 | 426篇 |
2013年 | 640篇 |
2012年 | 535篇 |
2011年 | 653篇 |
2010年 | 431篇 |
2009年 | 668篇 |
2008年 | 714篇 |
2007年 | 744篇 |
2006年 | 671篇 |
2005年 | 539篇 |
2004年 | 496篇 |
2003年 | 456篇 |
2002年 | 386篇 |
2001年 | 301篇 |
2000年 | 255篇 |
1999年 | 193篇 |
1998年 | 191篇 |
1997年 | 180篇 |
1996年 | 112篇 |
1995年 | 99篇 |
1994年 | 93篇 |
1993年 | 70篇 |
1992年 | 70篇 |
1991年 | 42篇 |
1990年 | 33篇 |
1989年 | 39篇 |
1988年 | 44篇 |
1987年 | 25篇 |
1986年 | 22篇 |
1985年 | 32篇 |
1984年 | 47篇 |
1983年 | 27篇 |
1982年 | 21篇 |
1981年 | 20篇 |
1980年 | 18篇 |
1979年 | 12篇 |
1978年 | 7篇 |
1977年 | 11篇 |
1976年 | 9篇 |
1975年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
1.
Efficient electricity price forecasting plays a significant role in our society. In this paper, a novel influencer-defaulter mutation (IDM) mutation operator has been proposed. The IDM operator has been combined with six well-known optimization algorithms to create mutated optimization algorithms whose performance has been tested on twenty-four standard benchmark functions. Further, the artificial neural network is integrated with mutated optimization algorithms to solve the electricity price prediction problem. The policymakers can identify appropriate variables based on the predicted prices to help future market planning. The statistical results prove the efficacy of the IDM operator on the recent optimization algorithms. 相似文献
2.
Gehad Abo-Lila Taha Sokkar Eman Seisa Emam Omar 《Microscopy research and technique》2022,85(2):667-684
In this article, an adaptive denoising method is suggested to accurate investigate the optical and structural features of polymeric fibers from noisy phase shifting microinterferograms. The mixed class of noise that may produce in the phase-shifting interferometric techniques is established. To our knowledge, this is an early study considered the mixing noises that may occur in microinterferograms. The suggested method utilized the convolution neural networks to detect the noise class and then denoising, it according to its class. Four convolution neural networks (Googlenet, VGG-19, Alexnet, and Alexnet–SVM) are refined to perform the automatic classification process for the noise class in the established data set. The network with the highest validation and testing accuracy of these networks is considered to apply the suggested method on realistic noisy microinterferograms for polymeric fibers, polypropylene and antimicrobial polyethylene terephthalate)/titanium dioxide, recoded using interference microscope. Also, the suggested method is applied on noisy microinterferograms include crazing and nanocomposite material. The demodulated phase maps and the three-dimensional birefringence profiles are calculated for tested fibers according to the suggested method. The obtained results are compared with the published data for these fibers and found to be in good agreements. 相似文献
3.
Replenishment policy for a purchase-to-order seller: a tradeoff between ordering cost and delay cost
Guanqun Ni 《国际生产研究杂志》2020,58(4):1239-1254
We consider replenishment decisions on when and how many goods to purchase for a seller under a purchase-to-order mode where there is no inventory and the seller purchases goods to fulfil orders already placed. For each purchase, there is a constant ordering cost. For each order, delay cost will be incurred if it is not fulfilled timely. Generally, the more frequent the replenishment, the higher the ordering cost but the lower the delay cost. Consequently, there is a tradeoff between the ordering cost and the delay cost for the seller to make replenishment decisions minimising the total cost. In this paper, we study three cases of the problem and investigate both offline versions and online versions according to the seller's knowledge about information of future orders. For offline versions with perfect information, we either develop an optimal policy, or prove it is NP-hard and develop an approximation policy. For online versions without any information about future orders, from the perspective of competitive analysis we prove the lower bound of competitive ratio for any possible online policy and present a 10-competitive online policy for the general case and a 2-competitive online policy for each of two special cases. 相似文献
4.
5.
Significant emergency measures should be taken until an emergency event occurs. It is understood that the emergency is characterized by limited time and information, harmfulness and uncertainty, and decision-makers are always critically bound by uncertainty and risk. This paper introduces many novel approaches to addressing the emergency situation of COVID-19 under spherical fuzzy environment. Fundamentally, the paper includes six main sections to achieve appropriate and accurate measures to address the situation of emergency decision-making. As the spherical fuzzy set (FS) is a generalized framework of fuzzy structure to handle more uncertainty and ambiguity in decision-making problems (DMPs). First, we discuss basic algebraic operational laws (AOLs) under spherical FS. In addition, elaborate on the deficiency of existing AOLs and present three cases to address the validity of the proposed novel AOLs under spherical fuzzy settings. Second, we present a list of Einstein aggregation operators (AgOp) based on the Einstein norm to aggregate uncertain information in DMPs. Thirdly, we are introducing two techniques to demonstrate the unknown weight of the criteria. Fourthly, we develop extended TOPSIS and Gray relational analysis approaches based on AgOp with unknown weight information of the criteria. In fifth, we design three algorithms to address the uncertainty and ambiguity information in emergency DMPs. Finally, the numerical case study of the novel carnivorous (COVID-19) situation is provided as an application for emergency decision-making based on the proposed three algorithms. Results explore the effectiveness of our proposed methodologies and provide accurate emergency measures to address the global uncertainty of COVID-19. 相似文献
6.
Yuanbo LI 《等离子体科学和技术》2019,21(9):95601-131
To implement on-line, real-time monitoring for the surface morphology of Plasma-Facing Materials (PFMs) in tokamak, we developed a Laser Speckle Interferometry measurement approach. A laser ablation method was used to simulate the erosion process during Plasma-Wall Interactions in a tokamak. In the present investigation, we evaluated the results of laser ablation morphology changes on the surface of Mo material reconstructed by four different approaches (Flood-fill, Quality-guided, Discrete Cosine Transform (DCT) and Weighted-DCT). The morphology results measured by the weighted-DCT approach are very close to the measurement results from confocal microscopy with an average error rate within 7%. It is verified that the weighted-DCT algorithm has high accuracy and can efficiently reduce the influence of noise pollution coming from laser ablation, which is used as a proxy for erosion from plasma wall interaction. Additionally, the CPU computer time has been shortened. This is of great significance for the real-time monitoring of PFMs’ morphology in the Experimental Advanced Superconducting Tokamak (EAST) in the future. 相似文献
7.
针对移动机器人在海水环境中的三维路径规划问题容易陷入局部最优和收敛慢等瑕疵,根据三维环境全局信息来改进蚁群算法以提高实时性和收敛速度。改进蚁群算法的启发函数,采用局部信息和全局信息结合动态地改进信息素更新方式,以及根据三维空间中路径的平坦程度和光滑度二阶微分分别增加了一阶微分和二阶微分来再次修改信息素更新规则。仿真对比实验结果显示改进后的蚁群算法克服了收敛速度慢、容易陷入局部最优的缺点。 相似文献
8.
9.
随着个性化推荐技术的发展,推荐系统面临着越来越多的挑战。传统的推荐算法通常存在数据稀疏性和推荐精度低等问题。针对以上问题,提出了一种融合时间隐语义填充和子群划分的推荐算法[K]-TLFM(Time Based Latent Factor Model Integrated with [k]-means)。该算法利用融合时间因素的隐语义模型对原始用户物品评分矩阵缺失项进行填充,避免了用全局平均值或者用户/物品平均值补全矩阵带来的误差,有效缓解了数据稀疏性问题,同时融合时间因素有效地刻画了用户偏好随时间的变化;完成评分矩阵缺失项填充后,基于二分[k]-means聚类算法将偏好、兴趣特征相似的对象划分到同一个子群中,在目标用户所属的子群中基于选定的协同过滤算法为用户产生推荐列表,提高了推荐效率和准确性。在MovieLens和Netflix数据集上对该算法的推荐性能进行了对比实验,结果表明该算法具有更高的推荐精度。 相似文献
10.
Mariame Amine Abdellatif Kobbane Jalel Ben‐Othman Abdellaziz Walid 《International Journal of Communication Systems》2020,33(8)
Recently, academic and industrial research communities are paying more explicit attention to the 5G multiple radio access technology ultra‐dense networks (5G multi‐RAT UDNs) for boosting network capacity, especially in UD urban zones. To this aim, in this paper, we intend to tackle the user association problem in 5G multi‐RAT UDNs. By considering the decoupled uplink/downlink access (DUDA), we divide our user association problem into two distinct subproblems representing, respectively, the uplink and the downlink channels. Next, we formulated each one as a nonlinear optimization problem with binary variables. Then, to solve them, we were restricted by the hard complexity, as well as the hard feasibility of centralized user association schemes. Thus, to resolve our user association problem in a reasonable time and distributed manner, we formulated each subproblem as a many‐to‐one matching game based on matching theory. Next, we provide two fully distributed association algorithms to compute the uplink and downlink stable matching among user equipments (UEs) and base stations (BSs). Simulation results corroborate our theoretical model and show the effectiveness and improvement of our achieved results in terms of the overall network performance, quality of service (QoS), and energy efficiency (EE) of UEs. 相似文献