全文获取类型
收费全文 | 321篇 |
免费 | 27篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 8篇 |
综合类 | 1篇 |
化学工业 | 48篇 |
金属工艺 | 10篇 |
机械仪表 | 14篇 |
建筑科学 | 7篇 |
矿业工程 | 3篇 |
能源动力 | 7篇 |
轻工业 | 52篇 |
水利工程 | 2篇 |
无线电 | 22篇 |
一般工业技术 | 63篇 |
冶金工业 | 24篇 |
自动化技术 | 90篇 |
出版年
2024年 | 1篇 |
2023年 | 2篇 |
2022年 | 10篇 |
2021年 | 8篇 |
2020年 | 13篇 |
2019年 | 17篇 |
2018年 | 21篇 |
2017年 | 4篇 |
2016年 | 15篇 |
2015年 | 19篇 |
2014年 | 15篇 |
2013年 | 33篇 |
2012年 | 23篇 |
2011年 | 23篇 |
2010年 | 23篇 |
2009年 | 17篇 |
2008年 | 14篇 |
2007年 | 16篇 |
2006年 | 6篇 |
2005年 | 3篇 |
2004年 | 5篇 |
2003年 | 12篇 |
2002年 | 11篇 |
2001年 | 4篇 |
2000年 | 6篇 |
1999年 | 6篇 |
1998年 | 5篇 |
1997年 | 7篇 |
1996年 | 2篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1982年 | 1篇 |
1980年 | 1篇 |
排序方式: 共有351条查询结果,搜索用时 15 毫秒
341.
342.
Using a scanning near-field optical microscope, we visualize, in three dimensions, the electromagnetic field distribution near an isolated slit aperture in a thin gold film. At the metal-air interface and for a TM incident polarization, we confirm some recently observed results and show that the slit generates two kinds of surface waves: a slowly decaying surface plasmon polariton and a quasi-cylindrical wave that decreases more rapidly when moving away from the slit. These waves are not generated for a TE incident polarization. In a noncontact mode, we also observe how the transmitted light diverges in free space. At a small distance from the slit (< 2 microm), we find that the emerging light spreads in all directions for TM, forming an electromagnetic cloud, whereas it is concentrated above the slit for TE, forming a more directive light jet. The experimental images are in good agreement with the numerical simulations. 相似文献
343.
Julião LM Melo DR Sousa WO Santos MS Fernandes PC Godoy ML 《Radiation protection dosimetry》2007,125(1-4):513-515
In Brazil there are many regions where the extraction mining and processing of ores containing elements of great economical importance as tin, niobium and tantalum. Some of these ores have uranium and thorium natural decay series associated. This study was carried out in a niobium mine, where is obtained concentrates of niobates-tantalates, cassiterite and zirconite. The aim of this study is the evaluation of the occupational exposure to uranium, thorium, niobium and tin through urine bioassay data. In order to have it, 105 urine samples were analysed: 17 samples of exposed workers collected after a working day, 49 samples of exposed workers collected before a working day and 39 samples of local non-exposed people, assigned as a control group. The samples were analysed by mass spectrometry. The obtained results showed that the average concentration of Nb, Sn and U in the exposed group is statistically higher than those found in the control group indicating an occupational exposure. For Th there were no statistically difference between the exposed and the control group. 相似文献
344.
Andrés Julián Aristizábal Daniel Hernán Ospina Mónica Castañeda Sebastián Zapata Edison Banguero 《国际自然能源杂志》2020,41(10):1183-1191
ABSTRACT This article presents the development of an energy management system using fuzzy logic applied to a microgrid that combines photovoltaic solar energy, wind energy and a storage system with batteries. The model was developed using LabVIEW software and allows to obtain performance results of the photovoltaic generator, the wind turbine and the battery bank. The energy management system can be controlled in real time to take advantage of existing weather conditions. The results indicate that the fuzzy logic system guarantees the continuous operation of the load through the energy resources of the microgrid. The designed microgrid allows to generate 63,288?kWh/year of photovoltaic solar energy and 40,175?kWh/year of wind energy. 相似文献
345.
This article presents a low coordination overhead cooperative Automatic Repeat reQuest (ARQ) scheme with an integrated frame
combiner, which exploits space diversity and cooperation between neighbouring nodes. A comparison between cooperation with
and without frame combiner is also performed. In channels with a strong Line of Sight (LOS) component and low Signal-to-Noise
ratio (SNR), the efficiency of the proposed protocol is many times higher than for other ARQ schemes. For non-LOS scenarios,
the cooperative ARQ without frame combiner achieves the best efficiency results, and the overhead introduced by the frame
combiner mechanism leads to results that can be even below the classical ARQ mechanism. In AWGN channels, the saturation throughput
of the proposed scheme integrated into a IEEE 802.11 DCF based MAC is also studied. When the number of active stations is
high, the cooperative ARQ without frame combiner shows to be the best option, while for light network loads, the presented
scheme performs better. 相似文献
346.
为了研究工艺参量对光纤激光切割切口质量的影响,进行了切割T4003不锈钢试验,分析了工艺参量与切口质量之间的关系。采用基于误差反向传播算法的人工神经网络,建立了激光功率、切割速率、辅助气体压力等工艺参量与切口粗糙度之间的预测模型。对切割试验采集的训练样本进行了网络训练,并利用测试样本对训练模型进行验证。结果表明,随着激光功率增加,切口粗糙度增大;随着切割速率和辅助气体压力增加,切口粗糙度减小。神经网络预测模型精度较高,网络训练效果良好,预测值与试验样本值间的最大相对误差为2.4%。训练后检验精度较高,检验样本最大相对误差仅为6.23%。该模型可有效预测激光切割切口表面粗糙度,同时为合理选择及优化工艺参量,提高激光切割质量提供试验依据。 相似文献
347.
C. Ancín Belén Ayestarán Asunción García Julián Garrido 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1998,206(2):143-147
The evolution of fatty acids during the fermentation of Vitis vinífera var. Garnacha and var. Viura musts as well as during the aging of the rosé and white wines produced from the said musts was studied. In Garnacha
must, practically all the fatty acids were consumed, with the exception of the medium-chain fatty acids, by the time that
50% of the sugar was used up. During the second half of fermentation 80.1% of the fatty acids were consumed, with 28.8% of
the remaining fatty acids being used up during aging. In Viura must, the total fatty acid concentration declined 46.9% during
the first half of fermentation (first 50% of sugar), most noteworthy was the high consumption of unsaturated large-chain fatty
acids (72.3%); during the second half of fermentation, 77.2% of the fatty acids were used, with high consumption of the large-chain
saturated and unsaturated acids. During the aging of wine, medium-chain fatty acids were excreted and a small amount of unsaturated
acids was consumed.
Received: 3 March 1997 / Revised version: 21 July 1997 相似文献
348.
Díaz MT Alvarez I De la Fuente J Sañudo C Campo MM Oliver MA Font I Furnols M Montossi F San Julián R Nute GR Cañeque V 《Meat science》2005,71(2):256-263
The fatty acid composition of commercial lambs from different production systems of Spain, Germany, United Kingdom and of two types of Uruguayan lambs (heavy and light) was studied. Concentrate fed lambs, as Spanish lambs, displayed the highest proportions of linoleic acid (C18:2), while Uruguayan lambs, reared under extensive grazing conditions, showed the highest proportions of linolenic acid (C18:3), due to the great concentration of this fatty acid in grass. German and British lambs, which were fed grass and concentrate, displayed intermediate proportions of linolenic acid (C18:3). Heavy Uruguayan lambs had higher intramuscular fat content (5.92%) than German (4.25%) and British (4.32%) lambs, and this content was twofold higher than light lambs (Spanish (2.41%) and light Uruguayan (3.05%)). Heavy Uruguayan, German and British lambs had a low polyunsaturated/saturated (P/S) ratio due to their high saturated fatty acid (SFA) content and proportion. Principal component analysis was performed to study the relationship between fatty acids. Spanish lambs were clearly separated from the other types and were situated close to the proportions of short chain and n-6 fatty acids and n-6/n-3 ratio in the data plot for fatty acid proportions. Light Uruguayan lambs were located close to long chain fatty acids, and heavy Uruguayan and British lambs were placed near the antithrombotic potential (ATT), stearic acid (C18:0), SFA and conjugated linoleic acid (CLA) proportions. German lambs were located between Spanish lambs and the other types. 相似文献
349.
350.