全文获取类型
收费全文 | 2726篇 |
免费 | 129篇 |
国内免费 | 22篇 |
专业分类
电工技术 | 64篇 |
综合类 | 8篇 |
化学工业 | 639篇 |
金属工艺 | 78篇 |
机械仪表 | 97篇 |
建筑科学 | 78篇 |
矿业工程 | 8篇 |
能源动力 | 182篇 |
轻工业 | 172篇 |
水利工程 | 24篇 |
石油天然气 | 17篇 |
无线电 | 278篇 |
一般工业技术 | 614篇 |
冶金工业 | 228篇 |
原子能技术 | 24篇 |
自动化技术 | 366篇 |
出版年
2024年 | 11篇 |
2023年 | 40篇 |
2022年 | 87篇 |
2021年 | 126篇 |
2020年 | 100篇 |
2019年 | 76篇 |
2018年 | 130篇 |
2017年 | 109篇 |
2016年 | 95篇 |
2015年 | 69篇 |
2014年 | 124篇 |
2013年 | 201篇 |
2012年 | 123篇 |
2011年 | 141篇 |
2010年 | 150篇 |
2009年 | 122篇 |
2008年 | 130篇 |
2007年 | 123篇 |
2006年 | 86篇 |
2005年 | 76篇 |
2004年 | 54篇 |
2003年 | 60篇 |
2002年 | 38篇 |
2001年 | 41篇 |
2000年 | 26篇 |
1999年 | 37篇 |
1998年 | 47篇 |
1997年 | 35篇 |
1996年 | 36篇 |
1995年 | 31篇 |
1994年 | 28篇 |
1993年 | 26篇 |
1992年 | 25篇 |
1991年 | 22篇 |
1990年 | 17篇 |
1989年 | 21篇 |
1988年 | 12篇 |
1987年 | 20篇 |
1986年 | 15篇 |
1985年 | 20篇 |
1984年 | 18篇 |
1983年 | 15篇 |
1982年 | 14篇 |
1981年 | 13篇 |
1980年 | 14篇 |
1979年 | 15篇 |
1978年 | 9篇 |
1977年 | 14篇 |
1976年 | 12篇 |
1975年 | 4篇 |
排序方式: 共有2877条查询结果,搜索用时 31 毫秒
51.
52.
Design of Barrages with Genetic Algorithm Based Embedded Simulation Optimization Approach 总被引:2,自引:2,他引:0
Raj Mohan Singh 《Water Resources Management》2011,25(2):409-429
Barrages are hydraulic structures constructed across rivers to divert flow into irrigation canals or power generation channels.
The most of these structures are founded on permeable foundation. The optimum cost of these structures is nonlinear function
of factors that cause the seepage forces under the structure. There is, however, no procedure to ascertain the basic barrage
parameters such as depth of sheet piles or cutoffs and the length and thickness of floor in a cost–effective manner. In this
paper, a nonlinear optimization formulation (NLOF), which consists of an objective function of minimizing total cost, is solved
using genetic algorithm (GA). The mathematical model that represents the subsurface flow is embedded in the NLOF. The applicability
of the approach has been illustrated with a typical example of barrage profile. The results obtained in this study shows drastic
cost savings when the proposed NLOF is solved using GA than that of using classical optimization technique and conventional
method. A parametric analysis has also been performed to study the effect of varying soil and hydrological conditions on design
parameters and on over all cost. 相似文献
53.
54.
We advocate the use of quickly‐adjustable, computer‐controlled color spectra in photography, lighting and displays. We present an optical relay system that allows mechanical or electronic color spectrum control and use it to modify a conventional camera and projector. We use a diffraction grating to disperse the rays into different colors, and introduce a mask (or LCD/DMD) in the optical path to modulate the spectrum. We analyze the trade‐offs and limitations of this design, and demonstrate its use in a camera, projector and light source. We propose applications such as adaptive color primaries, metamer detection, scene contrast enhancement, photographing fluorescent objects, and high dynamic range photography using spectrum modulation. 相似文献
55.
Dinh Phung Brett Adams Svetha Venkatesh Mohan Kumar 《Pervasive and Mobile Computing》2009,5(6):714-733
The sensing context plays an important role in many pervasive and mobile computing applications. Continuing from previous work [D. Phung, B. Adams, S. Venkatesh, Computable social patterns from sparse sensor data, in: Proceedings of First International Workshop on Location Web, World Wide Web Conference (WWW), New York, NY, USA, 2008, ACM 69–72.], we present an unsupervised framework for extracting user context in indoor environments with existing wireless infrastructures. Our novel approach casts context detection into an incremental, unsupervised clustering setting. Using WiFi observations consisting of access point identification and signal strengths freely available in office or public spaces, we adapt a density-based clustering technique to recover basic forms of user contexts that include user motion state and significant places the user visits from time to time. High-level user context, termed rhythms, comprising sequences of significant places are derived from the above low-level context by employing probabilistic clustering techniques, latent Dirichlet allocation and its n-gram temporal extension. These user contexts can enable a wide range of context-ware application services. Experimental results with real data in comparison with existing methods are presented to validate the proposed approach. Our motion classification algorithm operates in real-time, and achieves a 10% improvement over an existing method; significant locations are detected with over 90% accuracy and near perfect cluster purity. Richer indoor context and meaningful rhythms, such as typical daily routines or meeting patterns, are also inferred automatically from collected raw WiFi signals. 相似文献
56.
Nishanta Barman Arpita Shome Saurav Kumar Priyam Mondal Karan Jain Mizuki Tenjimbayashi Uttam Manna 《Advanced functional materials》2023,33(22):2214840
Non-sticking droplets wrapped with fine hydrophobic particles, namely liquid marbles, can be transported both on solid and water pool without an undesired spill of the inner encapsulated liquid. While the stimuli-responsive release of the inner liquid in the target area is proposed, the time-programmed release is not yet achieved. Herein, the hydrophobicity of nanoclay is modulated via a catalyst-free 1,4-conjugate addition reaction to form liquid marbles. This nanoclay liquid marble is robust and stable in air but collapses on the liquid pool with a specific lifetime. The lifetime of the liquid marble can be modulated over seconds to hours scale depending on the selection of chemically modulated wettability of the nanoclay. The critical mechanism of lifetime modulation is responsible for controlling the coalescence kinetics between the water pool and inner liquid by nanoclays’ high diffusion length and chemically varied water spreading potential. The NC liquid marble's programmable lifetime to ‘time-bomb’ type drug release and cascade chemical reaction is applied—without requiring any external intervention. 相似文献
57.
Nowadays in the medical field, imaging techniques such as Optical Coherence Tomography (OCT) are mainly used to identify retinal diseases. In this paper, the Central Serous Chorio Retinopathy (CSCR) image is analyzed for various stages and then compares the difference between CSCR before as well as after treatment using different application methods. The first approach, which was focused on image quality, improves medical image accuracy. An enhancement algorithm was implemented to improve the OCT image contrast and denoise purpose called Boosted Anisotropic Diffusion with an Unsharp Masking Filter (BADWUMF). The classifier used here is to figure out whether the OCT image is a CSCR case or not. 150 images are checked for this research work (75 abnormal from Optical Coherence Tomography Image Retinal Database, in-house clinical database, and 75 normal images). This article explicitly decides that the approaches suggested aid the ophthalmologist with the precise retinal analysis and hence the risk factors to be minimized. The total precision is 90 percent obtained from the Two Class Support Vector Machine (TCSVM) classifier and 93.3 percent is obtained from Shallow Neural Network with the Powell-Beale (SNNWPB) classifier using the MATLAB 2019a program. 相似文献
58.
Edge computing is a cloud computing extension where physical computers are installed closer to the device to minimize latency. The task of edge data centers is to include a growing abundance of applications with a small capability in comparison to conventional data centers. Under this framework, Federated Learning was suggested to offer distributed data training strategies by the coordination of many mobile devices for the training of a popular Artificial Intelligence (AI) model without actually revealing the underlying data, which is significantly enhanced in terms of privacy. Federated learning (FL) is a recently developed decentralized profound learning methodology, where customers train their localized neural network models independently using private data, and then combine a global model on the core server together. The models on the edge server use very little time since the edge server is highly calculated. But the amount of time it takes to download data from smartphone users on the edge server has a significant impact on the time it takes to complete a single cycle of FL operations. A machine learning strategic planning system that uses FL in conjunction to minimise model training time and total time utilisation, while recognising mobile appliance energy restrictions, is the focus of this study. To further speed up integration and reduce the amount of data, it implements an optimization agent for the establishment of optimal aggregation policy and asylum architecture with several employees’ shared learners. The main solutions and lessons learnt along with the prospects are discussed. Experiments show that our method is superior in terms of the effective and elastic use of resources. 相似文献
59.
针对直驱风电机组直流电压环和锁相环失稳问题,基于直驱风电机组电流源型线性化模型,分析了电网强度、直流电容输入功率以及控制参数对直驱风电机组稳定性的影响;建立了适用于直流电压环和锁相环稳定性分析的电流源型阻尼转矩模型,通过阻尼转矩法揭示了直驱风电机组失稳机理;进一步地将阻尼转矩法拓展至多机并联系统。研究结果表明:电网强度的减小、直流电容输入功率的增加、控制参数(直流电压环比例参数、锁相环比例参数)的减小会降低直驱风电机组低频振荡模式(直流电压环模式、锁相环模式)的阻尼系数,当阻尼系数小于0时,该模式下系统失稳,表现为直驱风电机组发生低频振荡。 相似文献
60.
Tripathi Kuldeep Narayan Yadav Ashish Mohan Sharma S. C. 《Wireless Personal Communications》2022,124(3):2475-2504
Wireless Personal Communications - This work aims to implement a clustering scheme to separate vehicles into a cluster that is based on various parameters, such as the total number of relay nodes,... 相似文献