全文获取类型
收费全文 | 1069篇 |
免费 | 68篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 15篇 |
化学工业 | 245篇 |
金属工艺 | 14篇 |
机械仪表 | 25篇 |
建筑科学 | 48篇 |
矿业工程 | 1篇 |
能源动力 | 51篇 |
轻工业 | 131篇 |
水利工程 | 10篇 |
石油天然气 | 2篇 |
无线电 | 77篇 |
一般工业技术 | 185篇 |
冶金工业 | 95篇 |
原子能技术 | 5篇 |
自动化技术 | 234篇 |
出版年
2023年 | 10篇 |
2022年 | 26篇 |
2021年 | 38篇 |
2020年 | 21篇 |
2019年 | 33篇 |
2018年 | 40篇 |
2017年 | 26篇 |
2016年 | 37篇 |
2015年 | 33篇 |
2014年 | 67篇 |
2013年 | 89篇 |
2012年 | 71篇 |
2011年 | 77篇 |
2010年 | 42篇 |
2009年 | 69篇 |
2008年 | 64篇 |
2007年 | 60篇 |
2006年 | 26篇 |
2005年 | 35篇 |
2004年 | 26篇 |
2003年 | 30篇 |
2002年 | 28篇 |
2001年 | 15篇 |
2000年 | 11篇 |
1999年 | 12篇 |
1998年 | 33篇 |
1997年 | 20篇 |
1996年 | 15篇 |
1995年 | 10篇 |
1994年 | 7篇 |
1993年 | 12篇 |
1992年 | 5篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 3篇 |
1986年 | 5篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 7篇 |
1981年 | 6篇 |
1980年 | 4篇 |
1979年 | 2篇 |
1977年 | 4篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1970年 | 1篇 |
1968年 | 2篇 |
排序方式: 共有1138条查询结果,搜索用时 15 毫秒
1.
In this paper, the space-vector transformation used in machine vector control is applied to power system analysis. The proposed method is used to model electric machines, power electronic converters, transformers, and transmission lines and to analyze power sources and loads with different connections (delta and wye). This method can also be applied to analyze steady-state (or transient phenomena) and unbalanced sources, including harmonics. Models obtained with this method are as simple as those of the per-phase approach. With the space-vector transformation, instantaneous active and reactive power concepts can be generalized, and new power system control strategies can be developed when power electronic converters are used. Steady-state, transient behavior, and harmonic analyses examples and applications are presented to illustrate the performance and advantages of the proposed method. This method can be extended to unbalanced systems (e.g., unsymmetric faults) using instantaneous symmetrical components in polyphase balanced circuits. 相似文献
2.
Journal of Low Temperature Physics - We have investigated disorder phenomena in solid 4He near megting in presence of vacancies by means of Quantum Monte Carlo (MC) simulations using the Shadow... 相似文献
3.
Fiber cross sections for use in textiles and composites are becoming more and more complex. Shape impacts fiber or filaments properties and therefore the yarn and fabric characteristics. This paper presents the influence of the fiber cross section on the fabric surface characteristics. The material used was polyester staple fibers, of four different shapes: round, scalloped oval, cruciform and hexachannel. All fibers had the same cut length with different fineness. Yarns obtained from these fibers had nominally the same yarn count, torsion value and structure. Plain jersey fabrics were knitted from each of the yarns under identical conditions and then relaxed prior to testing. Friction behavior was evaluated and a roughness-friction criterion developed. An indirect measurement of the real area of contact was obtained in order to provide roughness and friction properties. The influence of fiber cross section on yarn bending rigidity and on the state of the knitted fabric surface was characterized. 相似文献
4.
MC Bueno Jayme Gallani RC Rodrigues Colombo E de Araújo Cintra S Brunelli Rigacci 《Canadian Metallurgical Quarterly》1996,4(2):179-199
The overall purpose of this study was to explore nurses' feelings about the applicability and adequacy of a pilot model of nursing assessment (PMNA) developed for coronary care units (CCU) in order to obtain data that could help in establishing a definitive model. The evaluation, performed by 11 CCU nurses, showed that they considered the development and implementation of PMNA as valuable, and that its design was adequate for interviewing cardiac patients. These results will be employed in the elaboration of a definitive model of nursing assessment. 相似文献
5.
CJ Moerman HB Bueno de Mesquita FW Smeets S Runia 《Canadian Metallurgical Quarterly》1995,24(6):591-602
BACKGROUND: Gallstones and obesity have been suggested as risk factors for cancer of the biliary tract. Since both factors are related to diet, we studied the relationship between dietary intake and the cancer of interest in a population-based case-control study. METHODS: The study population comprised 111 patients and 480 controls. Food intake was assessed by means of a semiquantitative food frequency questionnaire. Estimates of the intake of foods and micronutrients were obtained from cases and controls themselves (direct respondents) or from relatives (indirect respondents). Participants were categorized into tertiles of intake. Risk ratios were estimated by logistic regression analysis. RESULTS: The major findings are a monotonic decrease in risk associated with the consumption of vegetables (ORs 1.0, 0.7, 0.4, P value trend < 0.01) and a monotonic increase in risk associated with sugar added to drinks and desserts (ORs 1.0, 1.3, 2.5; P value trend < 0.01). CONCLUSIONS: The finding on added sugar corresponds to our earlier report that the group monosaccharides and disaccharides is a potential risk factor for this cancer. Sugar may influence bile composition through lipoprotein metabolism. The protective effect of vegetables is in accordance with the reported inverse relationship between vegetables and many epithelial cancers of the alimentary tract. 相似文献
6.
This paper informs about an evaluation of Spanish educational research journals using the modality of reputation inferred
from survey data. Univariate and multivariate patterns are offered. Specifically cluster analysis and non-parametric multidimensional
scaling reveal themselves as useful methods to inquire the complexity of this scientometric question which is the evaluation
of periodical series.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
7.
Feng Ning Damien Delhomme Yann LeCun Fabio Piano Léon Bottou Paolo Emilio Barbano 《IEEE transactions on image processing》2005,14(9):1360-1371
We describe a trainable system for analyzing videos of developing C. elegans embryos. The system automatically detects, segments, and locates cells and nuclei in microscopic images. The system was designed as the central component of a fully automated phenotyping system. The system contains three modules 1) a convolutional network trained to classify each pixel into five categories: cell wall, cytoplasm, nucleus membrane, nucleus, outside medium; 2) an energy-based model, which cleans up the output of the convolutional network by learning local consistency constraints that must be satisfied by label images; 3) a set of elastic models of the embryo at various stages of development that are matched to the label images. 相似文献
8.
Neiva Maria Almeida Maria Regina Bueno Franco 《Journal of the science of food and agriculture》2007,87(14):2596-2603
BACKGROUND: The chemical composition of Amazonian fish is extremely variable, being influenced by the season and the type and amount of food. A special interest in the fish oil composition has been developed owing to the presence of essential fatty acids, since this is directly related to human health. This study aimed to investigate the fatty acid composition (FAC) of the total lipid (TL), neutral lipid (NL) and phospholipid (PL) fractions of the dorsal muscle and orbital cavity of farmed and wild matrinxã in the Amazon area captured in different seasons. RESULTS: Fatty acids (FA) were analysed by high‐resolution gas chromatography/mass spectrometry. Sixty‐five FA were detected in the TL, 66 in the NL and 55 in the PL. The main FA found in farmed and wild fish were oleic, palmitic, stearic and linoleic acids. No distinctions in the quality or quantity of these fractions between dorsal muscle and orbital cavity were found. CONCLUSION: The season had a significant influence on the TL and FAC. Fish captured during the dry season showed lower levels of lipid and a higher percentage of long‐chain polyunsaturated fatty acids. Matrinxã farmed in a semi‐intensive system showed a nutritional quality comparable to that of wild matrinxã captured in the wet season. Copyright © 2007 Society of Chemical Industry 相似文献
9.
Emilio Marengo Valentina Longo Elisa Robotti Marco Bobba Fabio Gosetti Orfeo Zerbinati Silvana Di Martino 《应用聚合物科学杂志》2008,109(6):3975-3982
Principal component regression (PCR), partial least squares (PLS), StepWise ordinary least squares regression (OLS), and back‐propagation artificial neural network (BP‐ANN) are applied here for the determination of the propylene concentration of a set of 83 production samples of ethylene–propylene copolymers from their infrared spectra. The set of available samples was split into (a) a training set, for models calculation; (b) a test set, for selecting the correct number of latent variables in PCR and PLS and the end point of the training phase of BP‐ANN; (c) a production set, for evaluating the predictive ability of the models. The predictive ability of the models is thus evaluated by genuine predictions. The model obtained by StepWise OLS turned out to be the best one, both in fitting and prediction. The study of the breakdown number of samples to be included in the training set showed that at least 52 experiments are necessary to build a reliable and predictive calibration model. It can be concluded that FTIR spectroscopy and OLS can be properly employed for monitoring the synthesis or the final product of ethylene–propylene copolymers, by predicting the concentration of propylene directly along the process line. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
10.
Fabrication of alumina-aluminium titanate laminates that combine high strength external layers with flaw tolerant internal
layers is limited by the difficulty of the co-sintering of layers with large differences in the green state. This work describes
a new method to obtain alumina-aluminium titanate layered materials constituted by layers with large differences in terms
of grain size starting from green bodies with similar microstructures. The approach is based on the effect of small amounts
of titania (TiO2) as agents for alumina grain growth enhancement. Starting from a fine grained green body that combined alumina layers with
composite layers made of mixtures of alumina and titania, a two step sintering schedule led to a layered structure with external
layers of small grain sized alumina combined with internal alumina layers with large grain size due to the diffusion of titanium.
The large grain sized alumina layers conferred flaw tolerant behaviour to the laminate due to crack branching and bridging. 相似文献