全文获取类型
收费全文 | 309篇 |
免费 | 28篇 |
专业分类
电工技术 | 1篇 |
综合类 | 1篇 |
化学工业 | 89篇 |
金属工艺 | 2篇 |
机械仪表 | 14篇 |
建筑科学 | 11篇 |
矿业工程 | 2篇 |
能源动力 | 6篇 |
轻工业 | 54篇 |
水利工程 | 7篇 |
无线电 | 14篇 |
一般工业技术 | 47篇 |
冶金工业 | 9篇 |
原子能技术 | 1篇 |
自动化技术 | 79篇 |
出版年
2024年 | 1篇 |
2023年 | 6篇 |
2022年 | 4篇 |
2021年 | 7篇 |
2020年 | 8篇 |
2019年 | 4篇 |
2018年 | 13篇 |
2017年 | 14篇 |
2016年 | 16篇 |
2015年 | 15篇 |
2014年 | 18篇 |
2013年 | 31篇 |
2012年 | 26篇 |
2011年 | 24篇 |
2010年 | 29篇 |
2009年 | 16篇 |
2008年 | 23篇 |
2007年 | 18篇 |
2006年 | 14篇 |
2005年 | 7篇 |
2004年 | 11篇 |
2003年 | 8篇 |
2002年 | 8篇 |
2001年 | 2篇 |
2000年 | 4篇 |
1999年 | 2篇 |
1998年 | 2篇 |
1997年 | 1篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1989年 | 1篇 |
1984年 | 1篇 |
排序方式: 共有337条查询结果,搜索用时 33 毫秒
61.
Inés García‐Benito Iwan Zimmermann Javier Urieta‐Mora Juan Aragó Joaquín Calbo Josefina Perles Alvaro Serrano Agustín Molina‐Ontoria Enrique Ortí Nazario Martín Mohammad Khaja Nazeeruddin 《Advanced functional materials》2018,28(31)
Three new star‐shaped hole‐transporting materials (HTMs) incorporating benzotripyrrole, benzotrifuran, and benzotriselenophene central cores endowed with three‐armed triphenylamine moieties ( BTP‐1 , BTF‐1 , and BTSe‐1 , respectively) are designed, synthesized, and implemented in perovskite solar cells (PSCs). The impact that the heteroatom‐containing central scaffold has on the electrochemical and photophysical properties, as well as on the photovoltaic performance, is systematically investigated and compared with their sulfur‐rich analogue ( BTT‐3 ). The new HTMs exhibit suitable highest‐occupied molecular orbitals (HOMO) levels regarding the valence band of the perovskite, which ensure efficient hole extraction at the perovskite/HTM interface. The molecular structures of BTF‐1 , BTT‐3 , and BTSe‐1 are fully elucidated by single‐crystal X‐ray crystallography as toluene solvates. The optimized (FAPbI3)0.85(MAPbBr3)0.15‐based perovskite solar cells employing the tailor‐made, chalcogenide‐based HTMs exhibit remarkable power conversion efficiencies up to 18.5%, which are comparable to the devices based on the benchmark spiro‐OMeTAD. PSCs with BTP‐1 exhibit a more limited power conversion efficiency of 15.5%, with noticeable hysteresis. This systematic study indicates that chalcogenide‐based derivatives are promising HTM candidates to compete efficiently with spiro‐OMeTAD. 相似文献
62.
ASCE and FAO-56 standardized reference evapotranspiration (ET0) equations were compared using data from 31 meteorological stations in Andalusia, Southern Spain. Comparisons were made between daily ET0 obtained by summing hourly standardized ASCE–Penman–Monteith estimations and calculated from the addition of hourly FAO56–Penman–Monteith estimations, daily ET0 estimated on a daily basis, and calculated by the Hargreaves equation. On an hourly basis, the FAO-56 version estimated lower than the ASCE version as 6% in some locations, with a difference of 4% on the average, mainly due to the higher surface resistance (70?s?m?1) used in the FAO-56 version during daytime periods, as opposed to the 50?s?m?1 rs value used by the ASCE version. Differences between both estimates were higher when evaporative demand increases. The level of agreement improved when the two computational time steps were compared, because differences were lower (2% on the average) and did not depend on the wind speed or ET0 values. The Hargreaves equation showed a higher spatial variability. At coastal areas, the equation generally underpredicted ASCE Penman–Monteith ET0 and provided good estimations for inland locations. Accuracy of the equation was affected by annual averages of evaporative demand and wind speed. 相似文献
63.
The principal component analysis is used to identify and quantify spatial distributions of relative photoresponse as a function of the exposure time for a visible CCD array. The analysis shows a simple way to define an invariant photoresponse nonuniformity and compare it with the definition of this invariant pattern as the one obtained for long exposure times. Experimental data of radiant exposure from levels of irradiance obtained in a stable and well-controlled environment are used. 相似文献
64.
Joaquín M. Azagra-Caro 《Scientometrics》2012,91(3):671-691
Access to public knowledge is a prerequisite for the good functioning of developed economies. Universities strive and are
also requested to contribute to this knowledge both locally and internationally. Traditional studies on the geography of knowledge
flows have identified a localisation effect; however, these studies do not use the country as the unit of observation and
hence do not explore national patterns. In this paper, we hypothesise that the localisation of university knowledge flows
is directly related to share of firm expenditure on research and development. To test this hypothesis, we use references to
universities in patent documents as indicators based on a data set of around 20,000 university references, for 37 countries
in the period 1990–2007, resulting in panels of around 300–500 observations. We build indicators for the university knowledge
flows both inside and outside the applicant country, which we explain as a function of some proxies for national size and
research structure based on econometric estimations. We draw some conclusions as to the importance of national business scientific
strength for fostering increased domestic university knowledge flows. 相似文献
65.
Concentrates of triterpenic acids obtained from crude olive pomace oils: characterization and evaluation of their potential antioxidant activity
下载免费PDF全文
![点击此处可从《Journal of the science of food and agriculture》网站下载免费的PDF全文](/ch/ext_images/free.gif)
66.
Preservation of different fig cultivars (Ficus carica L.) under modified atmosphere packaging during cold storage
下载免费PDF全文
![点击此处可从《Journal of the science of food and agriculture》网站下载免费的PDF全文](/ch/ext_images/free.gif)
67.
Biofilm formation on abiotic and biotic surfaces during Spanish style green table olive fermentation
Domínguez-Manzano J Olmo-Ruiz C Bautista-Gallego J Arroyo-López FN Garrido-Fernández A Jiménez-Díaz R 《International journal of food microbiology》2012,157(2):230-238
In this work, the establishment of polymicrobial communities on the surfaces which come into contact with the brine during Spanish style Gordal cv. green olive fermentation when subjected to spontaneous or controlled processes (inoculated with Lactobacillus pentosus LPCO10 or 128/2) was studied. Scanning electron microscopy showed that L. pentosus and yeast populations were able to form mixed biofilms throughout the fermentation process on both abiotic (glass slide) and biotic (olive skin) surfaces. The biofilm architectures in both supports were completely different: on the glass slides only aggregates of L. pentosus and yeasts without any polymeric matrix surrounding them were found while on the skin of the fruits, true mature biofilms were observed. During fermentation, the lactic acid bacteria (LAB) population on the olives remained similar while that of yeasts increased progressively to reach similar levels at the end of the process (8-9 log CFU/cm(2)). Molecular analysis showed that different populations of L. pentosus and yeasts were the only microbial members of the biofilm formed during fermentation, regardless of inoculation. Hence, the green olive surface provides an appropriate environmental condition for the suitable development and formation of complex biofilms during controlled or natural table olive processing. 相似文献
68.
María Moreno-Baquero J Bautista-Gallego J Garrido-Fernández A López-López A 《Journal of food science》2012,77(2):S107-S114
This work studies the effects of the initial brine concentrations of NaCl, KCl, and CaCl(2) on the mineral content and gustatory and kinaesthetic sensations of fermented green table olives, using a simplex centroid mixture design augmented with interior points. The sodium in the flesh was linearly related to the mixture concentrations while potassium and calcium were linked by quadratic and special cubic models respectively. Acidity, saltiness, hardness, fibrousness, and crunchiness were expressed as linear funtions of the NaCl, KCl, and CaCl(2) initial brine contents but bitterness required quadratic equations. The models can be used to produce table olives with specific mineral contents in the flesh and to predict their corresponding sensory characteristics. PRACTICAL APPLICATION: The study provides the industry with models to estimate the Na, K, and Ca mineral contents in the flesh of fermented Gordal green table olives as well as their sensory characteristics as a function of the NaCl, KCl, and CaCl(2) initial compositions in the brining solution. Therefore, the paper provides tools which are able to support the production of commercial presentations which not only satisfy consumer demand for low Na, but are also K and Ca fortified table olive presentations with specific sensory profiles. 相似文献
69.
Arturo Morales Susana Marmesat M. Carmen Dobarganes Gloria Márquez-Ruiz Joaquín Velasco 《Journal of the American Oil Chemists' Society》2012,89(4):675-684
The influence of temperature (40, 60 and 80 °C) and addition of α-tocopherol (0, 500 mg/kg) on the formation and distribution
of the main oxidation products of linoleic acid, i.e. hydroperoxy-, keto- and hydroxy-dienes, were studied in samples of fatty
acid methyl esters (FAME) derived from high-linoleic (HL) and high-oleic (HO) sunflower oils. In the range of temperatures
studied, the formation of hydroperoxydienes showed monomolecular and bimolecular rate constants that ranged from 0.01 to 1 mmol1/2kg−1/2h−1 and from 0.02 to 0.9 h−1, respectively. The overall activation energies involved were similar for both samples and for the monomolecular and bimolecular
periods (63–68 kJ/mol). The relative oxidation of methyl linoleate, which depended on the fatty acid composition of the FAME
sample, was unaffected by temperature. At the three temperatures assayed, hydroperoxydienes constituted approximately 90 and
50% of total hydroperoxides in the HL and HO samples, respectively. Formation of keto- and hydroxy-dienes was influenced by
temperature in a similar way to hydroperoxydienes and, consequently, changes in the distribution of compounds were not observed.
The addition of α-tocopherol not only decreased the overall oxidation rate, but also affected the distribution of compounds.
The content of hydroperoxydienes relative to that of total hydroperoxides was not affected by the presence of the antioxidant
in the HL sample, whereas a significant increase (75%) was found in the HO sample compared with the control (50%). The addition
of α-tocopherol in both samples also resulted in a slight increase of keto- and hydroxy-dienes in relation to hydroperoxydienes. 相似文献
70.
A simple and nonexpensive adapted dip-coating technique is presented and used to fabricate arrays of magnetic nanowires with a linear varying height profile. This approach allows controlling the wire height from tenths of nanometers up to several micrometers. Furthermore, the main parameters of this height gradient can be controlled, such as the maximum wire height and the lateral span of the wire array, which can be predicted with excellent accuracy using a proposed analytical model. Moreover, we show that by sequential electrodeposition with dip-coating, arrays of these height varying wires can be grown. This technique represents a novel method to fill porous templates with controlled spatial growth, leading to the fabrication of novel structures and providing control over structural features on the nanoscale level. In particular, the use of these asymmetrically loaded magnetic nanowired substrates to obtain improved microwave nonreciprocal behavior is shown for a microwave phase shifter. 相似文献