全文获取类型
收费全文 | 3398篇 |
免费 | 211篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 14篇 |
化学工业 | 1368篇 |
金属工艺 | 39篇 |
机械仪表 | 83篇 |
建筑科学 | 90篇 |
矿业工程 | 6篇 |
能源动力 | 79篇 |
轻工业 | 732篇 |
水利工程 | 21篇 |
石油天然气 | 19篇 |
无线电 | 156篇 |
一般工业技术 | 444篇 |
冶金工业 | 160篇 |
原子能技术 | 14篇 |
自动化技术 | 387篇 |
出版年
2024年 | 7篇 |
2023年 | 63篇 |
2022年 | 311篇 |
2021年 | 358篇 |
2020年 | 122篇 |
2019年 | 112篇 |
2018年 | 136篇 |
2017年 | 138篇 |
2016年 | 146篇 |
2015年 | 117篇 |
2014年 | 132篇 |
2013年 | 240篇 |
2012年 | 203篇 |
2011年 | 233篇 |
2010年 | 146篇 |
2009年 | 177篇 |
2008年 | 153篇 |
2007年 | 136篇 |
2006年 | 116篇 |
2005年 | 84篇 |
2004年 | 66篇 |
2003年 | 54篇 |
2002年 | 48篇 |
2001年 | 35篇 |
2000年 | 21篇 |
1999年 | 14篇 |
1998年 | 52篇 |
1997年 | 30篇 |
1996年 | 35篇 |
1995年 | 23篇 |
1994年 | 10篇 |
1993年 | 17篇 |
1992年 | 10篇 |
1991年 | 6篇 |
1990年 | 7篇 |
1989年 | 10篇 |
1988年 | 2篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1980年 | 4篇 |
1977年 | 4篇 |
1976年 | 5篇 |
1973年 | 4篇 |
1965年 | 1篇 |
1934年 | 1篇 |
1933年 | 1篇 |
1932年 | 2篇 |
排序方式: 共有3612条查询结果,搜索用时 0 毫秒
51.
Paulo H. da Rocha Henrique C. Ferreira Michael C. Porsch Roberto M. Sales 《Control Engineering Practice》2009,17(10):1148-1156
Electromagnetic suspension systems are inherently nonlinear and often face hardware limitation when digitally controlled. The main contributions of this paper are: the design of a nonlinear H∞ controller, including dynamic weighting functions, applied to a large gap electromagnetic suspension system and the presentation of a procedure to implement this controller on a fixed-point DSP, through a methodology able to translate a floating-point algorithm into a fixed-point algorithm by using l∞ norm minimization due to conversion error. Experimental results are also presented, in which the performance of the nonlinear controller is evaluated specifically in the initial suspension phase. 相似文献
52.
Filipe Rocha Luís Mateus Urszula Skwara Maíra Aguiar Nico Stollenwerk 《国际计算机数学杂志》2016,93(8):1405-1422
Dengue fever dynamics show seasonality, with the disease transmission being higher during the warmer seasons. In this paper, we analyse seasonally forced epidemic models with and without vector dynamics. We assume small seasonal effects and obtain approximations for the real response of each state variable and also for the corresponding amplitude and phase via decomposition of the sinusoidal forcing into imaginary exponential functions. The analysis begins with the simplest susceptible-infected-susceptible (SIS) model, followed by the simplest model with vector dynamics, susceptible-infected-susceptible for hosts and uninfected-vector (SISUV). Finally, we compare the more complex susceptible-infected-recovered (SIR) and susceptible-infected-recovered for hosts and uninfected-vector (SIRUV) models and conclude that the models give basically the same information when we replace, in the SIR model, the human infectivity by a function of both human and mosquito infectivities. 相似文献
53.
Arce-Urriza Marta Cebollada Javier Tarira María Fernanda 《Information Systems and E-Business Management》2017,15(1):69-87
Information Systems and e-Business Management - This study evaluates the differential effect of price promotions on brand choice across the offline and online channels of a grocery retailer. We use... 相似文献
54.
Rui Rocha Aurélio Campilho Jorge Silva Elsa AzevedoRosa Santos 《Computer methods and programs in biomedicine》2011,101(1):94-106
A new algorithm is proposed for the semi-automatic segmentation of the near-end and the far-end adventitia boundary of the common carotid artery in ultrasound images. It uses the random sample consensus method to estimate the most significant cubic splines fitting the edge map of a longitudinal section. The consensus of the geometric model (a spline) is evaluated through a new gain function, which integrates the responses to different discriminating features of the carotid boundary: the proximity of the geometric model to any edge or to valley shaped edges; the consistency between the orientation of the normal to the geometric model and the intensity gradient; and the distance to a rough estimate of the lumen boundary.A set of 50 longitudinal B-mode images of the common carotid and their manual segmentations performed by two medical experts were used to assess the performance of the method. The image set was taken from 25 different subjects, most of them having plaques of different classes (class II to class IV), sizes and shapes.The quantitative evaluation showed promising results, having detection errors similar to the ones observed in manual segmentations for 95% of the far-end boundaries and 73% of the near-end boundaries. 相似文献
55.
Johan Montagnat Ákos Frohner Daniel Jouvenot Christophe Pera Peter Kunszt Birger Koblitz Nuno Santos Charles Loomis Romain Texier Diane Lingrand Patrick Guio Ricardo Brito Da Rocha Antonio Sobreira de Almeida Zoltán Farkas 《Journal of Grid Computing》2008,6(1):45-59
The medical community is producing and manipulating a tremendous volume of digital data for which computerized archiving,
processing and analysis is needed. Grid infrastructures are promising for dealing with challenges arising in computerized
medicine but the manipulation of medical data on such infrastructures faces both the problem of interconnecting medical information
systems to Grid middlewares and of preserving patients’ privacy in a wide and distributed multi-user system. These constraints
are often limiting the use of Grids for manipulating sensitive medical data. This paper describes our design of a medical
data management system taking advantage of the advanced gLite data management services, developed in the context of the EGEE
project, to fulfill the stringent needs of the medical community. It ensures medical data protection through strict data access
control, anonymization and encryption. The multi-level access control provides the flexibility needed for implementing complex
medical use-cases. Data anonymization prevents the exposure of most sensitive data to unauthorized users, and data encryption
guarantees data protection even when it is stored at remote sites. Moreover, the developed prototype provides a Grid storage
resource manager (SRM) interface to standard medical DICOM servers thereby enabling transparent access to medical data without
interfering with medical practice. 相似文献
56.
Alves RM Pereira BF Pitol DL Senhorini JA Rocha Rde C Caetano FH 《Microscopy research and technique》2012,75(5):615-619
The adipose fin is small, nonpared, and usually located medially between the dorsal and caudal fin. Its taxonomic occurrence is very restrict; thus, it represents an important trace for taxon distinction. As it does not play a known vital physiological roll and it is easily removed, it is commonly used in marking and recapture studies. The present study characterizes the adipose fin of Prochilodus lineatus, as it is poorly explored by the literature. The adipose fin consists basically of a loose connective core, covered by a stratified epithelium supported by collagen fibers. At the epithelium, pigmented cells and alarm substance cells are found. Despite the name, adipocytes or lipid droplets are not observed on the structure of the fin. 相似文献
57.
Effects and interactions of temperature and stress-level related damage on permeability of concrete 总被引:5,自引:0,他引:5
The objective of this study is to investigate damage-temperature-stress level-permeability interactions in structural concrete. The tests are performed on hollow cylindrical concrete specimens, subjected to compressive loading and temperature up to 150 °C. The results emphasize that at stress levels lower than 80% of the peak stress, the variation of permeability is small and it is slightly influenced by the stress. As a matter of fact, the permeability under load is smaller than the permeability measured after unloading. As the load exceeds 80% of the peak stress, micro-cracking increases rapidly, causing an increase of the permeability and a greater sensitivity to the applied load, i.e. a noticeable difference between the permeability measured under load and after unloading, the first becoming greater than the latter. In the post-peak phase the increase of permeability is much larger due to significant crack width growth. The increase of permeability with the applied load seems to be greater with temperature, inducing further alterations of concrete and dilation of the porous structure of the material. Finally, the experimental results seem to agree with the format of coupled evolution of the permeability due to damage and temperature assumed by Gawin et al. [D. Gawin, C.E. Majorana, B.A. Schrefler, Numerical analysis of hygro-thermal behaviour and damage of concrete at high temperature, Mechanics of Cohesive-Frictional Materials 4 (1999) 37-74.]. 相似文献
58.
John J. A. Barry Marta M. C. G. Silva Sarah H. Cartmell Robert E. Guldberg Colin A. Scotchford Steven M. Howdle 《Journal of Materials Science》2006,41(13):4197-4204
Porous scaffold structures are used in tissue engineering to provide structural guidance for regenerating tissues. The use
of carbon dioxide (CO2) to create such scaffolds has received some attention in the past but many researchers believe that although CO2 processing of polymers can lead to porous scaffolds there is limited interconnectivity between the pores. In this study,
highly porous (greater than 85%) and well interconnected scaffolds were obtained in which the size, distribution and number
of pores could be controlled. This control was achieved by altering the rate of venting from polymer discs saturated with
CO2 under modest temperature and pressure. The polymer used is a blend of poly (ethyl methacrylate) and tetrahydrofurfuryl methacrylate
(PEMA/THFMA). This polymer system has shown promise for potential applications in cartilage repair. 相似文献
59.
Thomas K. Hirsch Alexandre Da S. Rocha Fabiano D. Ramos Telmo R. Strohaecker 《Metallurgical and Materials Transactions A》2004,35(11):3523-3530
Plasma nitriding of tool materials is common practice to improve the wear resistance and lifetime of tools. Machining-induced
compressive residual stresses in shallow layers of some tenths of microns are observed accompanied by other characteristic
properties of machined surfaces in these high-strength materials. After plasma nitriding of M2 high-speed steel, previously
induced compressive residual stresses remain stable and the depth of diffusion layers decreases with increasing compressive
residual stresses. This article reports investigations of plasma nitrided samples with different levels of residual stresses
induced prior to the nitriding process. For comparison, experiments with bending load stresses during plasma nitriding have
also been carried out. The plasma nitriding treatment was performed at constant temperature of 500 °C with a gas mixture of
5 vol pct N2 in hydrogen. Nitriding time was varied from 30 to 120 minutes. All samples were characterized before and after plasma nitriding
concerning microstructure, roughness, microhardness, chemical composition, and residual stress states. Experimental results
are compared with analytical calculations on (residual) stress effects in diffusion and show a clear effect of residual and
load stresses in the diffusion of nitrogen in a high-strength M2 tool steel. 相似文献
60.
The aim of this work is to provide a high performance air quality simulation using the sulphur transport Eulerian model 2 (STEM-II) program. First of all we optimize the sequential program with the aim of increasing data locality. Then, the optimized program is parallelized using OpenMP shared-memory directives. Experimental results on a 32-processor SGI Origin 2000 show that the parallel program achieves important reductions in the execution times. 相似文献