全文获取类型
收费全文 | 9984篇 |
免费 | 666篇 |
国内免费 | 24篇 |
专业分类
电工技术 | 124篇 |
综合类 | 4篇 |
化学工业 | 2590篇 |
金属工艺 | 233篇 |
机械仪表 | 318篇 |
建筑科学 | 374篇 |
矿业工程 | 19篇 |
能源动力 | 379篇 |
轻工业 | 1722篇 |
水利工程 | 119篇 |
石油天然气 | 77篇 |
无线电 | 622篇 |
一般工业技术 | 1565篇 |
冶金工业 | 653篇 |
原子能技术 | 56篇 |
自动化技术 | 1819篇 |
出版年
2024年 | 36篇 |
2023年 | 115篇 |
2022年 | 323篇 |
2021年 | 502篇 |
2020年 | 317篇 |
2019年 | 419篇 |
2018年 | 449篇 |
2017年 | 400篇 |
2016年 | 459篇 |
2015年 | 293篇 |
2014年 | 460篇 |
2013年 | 794篇 |
2012年 | 675篇 |
2011年 | 803篇 |
2010年 | 545篇 |
2009年 | 582篇 |
2008年 | 506篇 |
2007年 | 425篇 |
2006年 | 323篇 |
2005年 | 253篇 |
2004年 | 221篇 |
2003年 | 198篇 |
2002年 | 174篇 |
2001年 | 125篇 |
2000年 | 110篇 |
1999年 | 108篇 |
1998年 | 203篇 |
1997年 | 145篇 |
1996年 | 109篇 |
1995年 | 91篇 |
1994年 | 80篇 |
1993年 | 50篇 |
1992年 | 50篇 |
1991年 | 32篇 |
1990年 | 28篇 |
1989年 | 46篇 |
1988年 | 31篇 |
1987年 | 19篇 |
1986年 | 20篇 |
1985年 | 20篇 |
1984年 | 24篇 |
1983年 | 11篇 |
1982年 | 6篇 |
1981年 | 13篇 |
1980年 | 16篇 |
1979年 | 7篇 |
1978年 | 5篇 |
1977年 | 12篇 |
1976年 | 22篇 |
1975年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Eduardo M. R. Fairbairn Iuri A. Ferreira Guilherme C. Cordeiro Marcos M. Silvoso Romildo D. Toledo Filho Fernando L. B. Ribeiro 《Materials and Structures》2010,43(8):1061-1074
Cement production gives rise to CO2 emissions generated by the calcination of CaCO3 and by the combustion of fossil fuels, being responsible for about 5% of the global CO2 emissions. These emissions can be substantially reduced if cement replacement materials are used. In this paper two residual
ashes that can be used as mineral additions are considered: sugar cane bagasse ash and rice husk ash. A case study of the
construction of a dam with a blended material composed by cement and these two ashes is presented, indicating the potentiality
of its use for civil engineering applications. The analyses were performed using experimental and numerical tools developed
on the basis of a thermo-chemo-mechanical model. This model considers the coupling, within the theory of thermodynamics, of
the several phenomena that intervene in the hydration process, namely, exothermicity, thermo-activation, chemo-plasticity,
evolution of thermal and mechanical properties with the hydration reaction, which includes creep and relaxation. 相似文献
992.
993.
Daniela de Oliveira Ribeiro Bianca Waruar Lobo Nádia Maria Volpato Venício Féo da Veiga Mendes Lúcio Cabral Valeria Pereira de Sousa 《Nutrition journal》2009,8(1):51-13
Background
Preterm infants need high amounts of calcium and phosphorus for bone mineralization, which is difficult to obtain with parenteral feeding due to the low solubility of these salts. The objective of this study was to evaluate the physicochemical compatibility of high concentrations of calcium associated with organic phosphate and its influence on the stability of AIO admixtures for neonatal use. 相似文献994.
Fernando H. Cristovan Fernando R. de Paula Sherlan G. Lemos Adilson J.A. De Oliveira Ernesto C. Pereira 《Synthetic Metals》2009,159(21-22):2188-2190
In this study, conducting blends of poly(acrylonitrile-butadiene-styrene) and polyaniline doped with dodecylbenzene sulfonic acid were prepared by solution blending. In order to understand the electrical conduction mechanism of the samples, DC electrical conductivity measurements of the blends were carried out in the temperature range of 80–320 K. The experimental results fit well with Mott's model of three-dimensional variable range hopping conduction. The values of Mott's temperature, density of states at the Fermi energy, average hopping distance and barrier height for the composites were calculated and presented. 相似文献
995.
The catalytic activity of single‐wall carbon nanohorns (SWNH) as counter electrodes (CE) of dye‐sensitized solar cells (DSC) was studied for the iodide/triiodide redox reaction. The catalytic activities of SWNH and high surface SWNH (HS‐SWNH) obtained by partial oxidation of SWNH were assessed based on charge‐transfer resistances (Rct) and current–voltage curves. A half‐cell configuration was used, and CE performances were compared to CEs made of carbon black (CB) and Pt. A CE assembled with HS‐SWNH and mixed with 10 wt.% of hydroxyethyl cellulose (HEC) ‐ HS‐SWNH/HEC was found to have the highest electrocatalytic activity (lowest Rct) among all the carbon‐based CEs tested when annealed at 180 °C (Rct = 141 Ω cm2); however, a very thick film (several tens of µm) would be required in order to perform comparably to a Pt CE. The annealing of such CE at higher temperatures (above 400 °C) did not improve its catalytic activity, contrary to the other studied carbonaceous CEs. The redox catalytic activity of SWNH and HS‐SWNH decorated with Pt was also studied on a half‐cell configuration and compared to that of Pt/CB and pristine Pt. The Pt/SWNH/HEC CE showed the highest electrocatalytic activity per mass of Pt, needing just 50% of Pt load to yield the same electrocatalytic activity of a DSC equipped with a Pt CE, but having half of its transparency. Additionally, applications in temperature‐sensitive substrates are envisioned for the Pt/SWNH/HEC CE due to the use of lower annealing temperatures. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
996.
Michael Z. Levy Fernando S. Malaga Chavez Juan G. Cornejo del Carpio Daril A. Vilhena F. Ellis McKenzie Joshua B. Plotkin 《Journal of the Royal Society Interface》2010,7(48):1061-1070
The rational design of interventions is critical to controlling communicable diseases, especially in urban environments. In the case of the Chagas disease vector Triatoma infestans, successful control is stymied by the return of the insect after the effectiveness of the insecticide wanes. Here, we adapt a genetic algorithm, originally developed for the travelling salesman problem, to improve the spatio-temporal design of insecticide campaigns against T. infestans, in a complex urban environment. We find a strategy that reduces the expected instances of vector return 34-fold compared with the current strategy of sequential insecticide application to spatially contiguous communities. The relative success of alternative control strategies depends upon the duration of the effectiveness of the insecticide, and it shows chaotic fluctuations in response to unforeseen delays in a control campaign. We use simplified models to analyse the outcomes of qualitatively different spatio-temporal strategies. Our results provide a detailed procedure to improve control efforts for an urban Chagas disease vector, as well as general guidelines for improving the design of interventions against other disease agents in complex environments. 相似文献
997.
Cristina M. Rosell Eva Santos Concha Collar 《European Food Research and Technology》2010,231(4):535-544
Dietary fiber incorporation into bread dough systems greatly interferes with protein association and behavior during heating and cooling. The objective of this study was to understand the individual and combined effects of dietary fibers on dough behavior during mixing, overmixing, pasting and gelling using the Mixolab® device. Impact of different commercial dietary fibers (inulin, sugar beet fiber, pea cell wall fiber and pea hull fiber) on wheat dough mixing, pasting and gelling profiles has been investigated. Mixolab® plots indicate that the incorporation of sugar beet fiber into the dough matrix induces the disruption of the viscoelastic system yielding weaker doughs, and it greatly competes for water with starch affecting pasting and gelling. Conversely, inulin in the range tested seems to integrate into the dough increasing its stability. Additionally, the responses acquired with this device were compared with those obtained with other available methodologies, such as the Brabender Farinograph and the Rapid Visco Analyser, to explore its use as a suitable technique for studying fiber-enriched bread dough physical properties. A broad range of correlation between Mixolab® and traditional devices were found. 相似文献
998.
José M. Campiña Hiléia K.S. Souza Maria Pilar Gonçalves Fernando Silva 《Electrochimica acta》2010,55(28):8779-8790
Chitosan ultrathin films have been formed on polycrystalline Au substrates using the LbL technique with the purpose of studying its interaction with bovine β-lactoglobulin (β-LG) at the solid-liquid interface. The immobilization of chitosan was followed by Quartz Crystal Microbalance with energy dissipation (QCM-D), Cyclic Voltammetry (CV) and Electrochemical Impedance Spectroscopy (EIS). The behavior of the chitosan films in the presence of β-LG solutions with different bulk concentrations ([β-LG]), ionic strength (I), and pH has been investigated using the same techniques plus Atomic Force Microscopy (AFM). The results showed that for pHs lower than protein's pI, weak intermolecular forces (H bonding, Van der Waals, hydrophobic, etc.) are established between β-LG and chitosan (especially close to the pI) leading to low coverage nonspecific adsorption. On the contrary when pH > pI, strong ionic bonding through attractive electrostatic interactions lead to high coverage adsorbed phases composed of large β-LG aggregates. The adsorption process was shown to consist of a relatively fast step (in which these interactions are predominant) which is followed, once the β-LG monolayer is exceeded, by the slow formation of thicker and increasingly viscoelastic films through β-LG self-aggregation. QCM-D and AFM experiments unveiled the role of [β-LG] and I on the formation of these aggregates. The adsorption isotherm built from impedance data in the medium-low [β-LG] range (0.001-0.3 mg mL−1), showed good fitting to the Langmuir model confirming that the formation of one β-LG monolayer is achieved in this concentration range. 相似文献
999.
1000.
The behavior of Pt/C and Pt–RuOx/C electrodes subjected to a larger number of potential scans and constant potential for prolonged time periods was investigated in the absence and presence of methanol. The structural changes were analyzed on the basis of the modifications observed in the X-ray diffraction pattern of the catalysts. Carbon monoxide stripping experiments were performed before and after the potential scans, thus enabling analysis of the behavior of the electrochemically active surface area. The resulting solutions were examined by inductively coupled plasma mass spectrometry (ICP-MS). There was reduction in the electrochemically active surface area, as well as increase in crystallite size and dissolution of catalyst components after the potential scan tests. Catalyst degradation was more pronounced in the presence of methanol, and cyclic potential conditions accelerate the degradation mechanisms. 相似文献