全文获取类型
收费全文 | 749篇 |
免费 | 65篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 16篇 |
综合类 | 2篇 |
化学工业 | 228篇 |
金属工艺 | 13篇 |
机械仪表 | 16篇 |
建筑科学 | 30篇 |
能源动力 | 23篇 |
轻工业 | 121篇 |
水利工程 | 1篇 |
石油天然气 | 2篇 |
无线电 | 51篇 |
一般工业技术 | 100篇 |
冶金工业 | 38篇 |
原子能技术 | 6篇 |
自动化技术 | 168篇 |
出版年
2024年 | 1篇 |
2023年 | 15篇 |
2022年 | 27篇 |
2021年 | 46篇 |
2020年 | 25篇 |
2019年 | 34篇 |
2018年 | 42篇 |
2017年 | 37篇 |
2016年 | 45篇 |
2015年 | 32篇 |
2014年 | 47篇 |
2013年 | 58篇 |
2012年 | 42篇 |
2011年 | 58篇 |
2010年 | 39篇 |
2009年 | 46篇 |
2008年 | 24篇 |
2007年 | 28篇 |
2006年 | 25篇 |
2005年 | 16篇 |
2004年 | 13篇 |
2003年 | 8篇 |
2002年 | 13篇 |
2001年 | 5篇 |
2000年 | 9篇 |
1999年 | 12篇 |
1998年 | 9篇 |
1997年 | 5篇 |
1996年 | 7篇 |
1995年 | 6篇 |
1994年 | 4篇 |
1993年 | 6篇 |
1992年 | 6篇 |
1991年 | 4篇 |
1990年 | 4篇 |
1989年 | 3篇 |
1988年 | 4篇 |
1986年 | 3篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1974年 | 1篇 |
排序方式: 共有815条查询结果,搜索用时 15 毫秒
801.
Wesley Pacheco Calixto Jesus Carlos da Mota Bernardo Pinheiro de Alvarenga 《International Journal of Numerical Modelling》2011,24(6):568-582
This paper presents a method for calculating the parameters of the Schwarz–Christoffel inverse transformation using the Genetic Algorithm. It is shown that for problems involving a polygonal geometry with axial symmetry, the number of estimated parameters is reduced by half. Simulations are performed with polygonal figures with several different geometries and with up to 27 sides. A four‐sided polygon is inversely mapped in order to verify the accuracy of the method. The method is also applied for calculating the induction lines and the flux lines in the region of a doubly slotted airgap of an electrical machine. Finally, based on the length of the midline of induction in the airgap, a new and very simple formula to calculate the Carter factor of an electrical machine is presented, which takes into account the actual geometry of the airgap. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
802.
Paulo Henrique Março Ronei Jesus Poppi Ieda Spacino Scarminio Romà Tauler 《Food chemistry》2011,125(3):1020-1027
The major anthocyanin pigments extracted from Hibiscus acetosella flower were investigated by UV–Vis spectroscopy and multivariate curve resolution-alternating least squares (MCR-ALS). Pure spectra and kinetic of the species present at different pH values were recovered for anthocyanins transformation and degradation products, found with and without UV radiation exposure. In the absence of UV radiation, up to seven different species were detected and by UV radiation exposure, this number increased to up to nine. The species detected in the absence of radiation were also detected when pigments samples were exposed to UV radiation, where degradation occurred faster and two new species appear. The kinetic profiles obtained at different pH values allowed the proposal of a reaction mechanism and pathway. 相似文献
803.
Capillary electrophoresis (CE) with capacitively coupled contactless conductivity detection (C4D) was used for simple, rapid, and simultaneous determination of aspartame, cyclamate, saccharin and acesulfame-K in commercial samples of soft drinks and tabletop sweetener formulations. A buffer solution containing 100 mmol L−1 tris(hydroxymethyl)aminomethane (TRIS) and 10 mmol L−1 histidine (His) was used as background electrolyte (BGE). A complete separation of the analytes could be attained in less than 6 min. The limits of detection (LOD) and quantification (LOQ) were considered better than those usually obtained by CE with photometric detection. Recoveries ranging from 94% to 108% were obtained for samples spiked with standard solutions of the sweeteners. The relative standard deviation (RSD) for the analysis of the samples with the CE-C4D method varied in the range of 1.5%–6.5%. 相似文献
804.
Ana Maria P. dos Santos Adriana Caires Oliveira Anderson Santos Souza Robson Mota de Jesus S��rgio L. C. Ferreira 《Food Analytical Methods》2011,4(4):567-573
Inductively coupled plasma optical emission spectrometry was used to determine the elements present in Chinese cabbage (Beta vulgaris). The accuracy of the method was confirmed by analysis of a certified reference material of spinach leaves. The study involved
57 samples that were collected in 13 Brazilian cities. Average concentrations of elements found per gram of Chinese cabbage
were as follows: 3.44 mg g−1 sodium, 5.09 mg g−1 potassium, 1.25 mg g−1 phosphorous, 0.85 mg g−1 calcium, 0.49 mg g−1 magnesium, 2.79 μg g−1 manganese, 9.50 μg g−1 iron, 0.74 μg g−1 copper, 14.28 μg g−1 zinc, and 6.44 μg g−1 strontium. Principal component analysis and hierarchical cluster analysis demonstrated that there is no systematic difference
in the mineral composition between the cabbage samples that were analyzed. 相似文献
805.
Olivero-Verbel J Duarte D Echenique M Guette J Johnson-Restrepo B Parsons PJ 《The Science of the total environment》2007,372(2-3):707-716
During June-August 2004, blood lead (BPb) levels and various hematological parameters were evaluated in children aged 5-9 years old at ten primary schools located in eight neighborhoods in Cartagena, Colombia. The schools selected for this study are attended mainly by children from families of low income. A total of 189 subjects participated in the survey. The arithmetic mean+/-standard error BPb level was 5.49+/-0.23 microg/dL (range<1.0-21.0 microg/dL). The geometric mean was 4.74 microg/dL (95% CI: 4.29-5.18). A proportion of the children (7.4%) had BPb levels above the US Centers for Disease Control and Prevention's threshold of concern (10 microg Pb/dL). BPb levels were correlated weakly, but significantly and positively, with red blood cell count (RBC), and negatively with child body size, age, mean corpuscular volume (MCV), and mean corpuscular hemoglobin (MCH). BPb levels did not differ significantly between boys and girls but significant differences were observed between neighborhoods (P<0.001). Activities such as metal melting-related processes and fishing net sinker production are the main sources of Pb exposure in Cartagena. 相似文献
806.
Yanan Cao Christopher L. E. Swartz Jesus Flores‐Cerrillo Jingran Ma 《American Institute of Chemical Engineers》2016,62(5):1602-1615
High purity distillation columns and multi‐stream heat exchangers (MSHXs) are critical units in cryogenic air separation plants. This article focuses on modeling approaches for the primary section of a super‐staged argon plant. A full‐order stage‐wise model for distillation columns in air separation units (ASUs) that considers key process phenomena is presented, followed by a reduced‐order model using a collocation approach. The extent of model reduction that can be achieved without losing significant prediction accuracy is demonstrated. A novel moving boundary model is proposed to handle MSHXs with phase change. Simulation results demonstrate the capability of the proposed model for tracking the phase change occurrence along the length of the heat exchanger. Dynamic simulation studies of the integrated plant show that the thermal integration between the feed and product streams captured in the primary heat exchanger is critical to accurately capture the behavior of ASUs. © 2016 American Institute of Chemical Engineers AIChE J, 62: 1602–1615, 2016 相似文献
807.
Clícia Maria de Jesus Benevides Márcia Cristina da Cunha Veloso Pedro Afonso de Paula Pereira Jailson Bittencourt de Andrade 《Food chemistry》2011
Carotenoids are present in many foods. Due to their polyenic chains, they undergo oxidation reactions which may give several compounds. Ozone, a powerful antimicrobial agent, is applied in the food industry due to its high reactivity and penetrability. This work presents a chemical study of the degradation of β-carotene in solutions, under the influence of ozone. The experiments were carried out at ozone concentrations ranging from 0.8 to 2.5 ppm and the β-carotene solutions were sampled and analysed from zero to seven hours of reaction. The oxidation products were collected in C18 cartridges coated with dinitrophenylhydrazine and the hydrazones formed were analysed by LC-MS. The oxidation reaction was found to follow a zero order kinetic model and the β-carotene decay ranged between 17.2% and 99.8%. Fourteen oxidation products were tentatively identified, amongst them eight which had not been cited yet in the literature as oxidation products of β-carotene. 相似文献
808.
809.
810.
Francisco Rafael Campos de Macedo Rômulo Ribeiro Magalhães de Sousa José Wellinton Nogueira Junior Cleânio Luz-Lima Maxwell Santana Libório Anderson de Oliveira Lobo Vladimir Jesus Trava-Airoldi Fernanda Roberto Marciano Michelle Cequeira Feitor Thércio Henrique de Carvalho Costa Rubens Maribondo do Nascimento 《国际钢铁研究》2023,94(6):2200760