全文获取类型
收费全文 | 493篇 |
免费 | 31篇 |
专业分类
化学工业 | 167篇 |
金属工艺 | 3篇 |
机械仪表 | 6篇 |
建筑科学 | 12篇 |
能源动力 | 10篇 |
轻工业 | 144篇 |
水利工程 | 6篇 |
石油天然气 | 8篇 |
无线电 | 17篇 |
一般工业技术 | 61篇 |
冶金工业 | 34篇 |
原子能技术 | 5篇 |
自动化技术 | 51篇 |
出版年
2023年 | 4篇 |
2022年 | 16篇 |
2021年 | 21篇 |
2020年 | 9篇 |
2019年 | 19篇 |
2018年 | 10篇 |
2017年 | 15篇 |
2016年 | 19篇 |
2015年 | 16篇 |
2014年 | 13篇 |
2013年 | 40篇 |
2012年 | 36篇 |
2011年 | 45篇 |
2010年 | 19篇 |
2009年 | 20篇 |
2008年 | 21篇 |
2007年 | 25篇 |
2006年 | 14篇 |
2005年 | 15篇 |
2004年 | 12篇 |
2003年 | 12篇 |
2002年 | 12篇 |
2001年 | 8篇 |
2000年 | 8篇 |
1999年 | 9篇 |
1998年 | 9篇 |
1997年 | 6篇 |
1996年 | 10篇 |
1995年 | 4篇 |
1994年 | 2篇 |
1993年 | 8篇 |
1992年 | 4篇 |
1991年 | 5篇 |
1990年 | 2篇 |
1989年 | 4篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1986年 | 4篇 |
1985年 | 4篇 |
1984年 | 1篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1972年 | 2篇 |
排序方式: 共有524条查询结果,搜索用时 15 毫秒
411.
Le Borgne V Gautier LA Castrucci P Del Gobbo S De Crescenzi M El Khakani MA 《Nanotechnology》2012,23(21):215206
We report on the KrF-laser ablation synthesis, purification and photocurrent generation properties of single-wall carbon nanotubes (SWCNTs). The thermally purified SWCNTs are integrated into hybrid photovoltaic (PV) devices by spin-coating them onto n-Si substrates. These novel SWCNTs/n-Si hybrid devices are shown to generate significant photocurrent (PC) over the entire 250-1050 nm light spectrum with external quantum efficiencies (EQE) reaching up to ~23%. Our SWCNTs/n-Si hybrid devices are not only photoactive in the traditional spectral range of Si solar cells, but generate also significant PC in the UV domain (below 400 nm). This wider spectral response is believed to be the result of PC generation from both the SWCNTs themselves and the tremendous number of local p-n junctions created at the nanotubes/Si interface. To assess the prevalence of these two contributions, the EQE spectra and J-V characteristics of these hybrid devices were investigated in both planar and top-down configurations, as a function of SWCNTs' film thickness. A sizable increase in EQE in the near UV with respect to the silicon is observed in both configurations, with a more pronounced UV photoresponse in the planar mode, confirming thereby the role of SWCNTs in the photogeneration process. The PC generation is found to reach its maximum for an optimal the SWCNT film thickness, which is shown to correspond to the best trade-off between lowest electrical resistance and highest optical transparency. Finally, by analyzing the J-V characteristics of our SWCNTs/n-Si devices with an equivalent circuit model, we were able to point out the contribution of the various electrical components involved in the photogeneration process. The SWCNTs-based devices demonstrated here open up the prospect for their use in highly effective photovoltaics and/or UV-light sensors. 相似文献
412.
The swellability and mass loss of poly(vinyl alcohol)‐graft‐[poly(rac‐lactide)/poly(rac‐lactide‐co‐glycolide)] hydrogels upon hydrolysis are strongly affected by the composition of the hydrogels. Hydrophobic hydrogels remain at a relatively constant mass for a couple of weeks, and the mass decreases dramatically thereafter, whereas more hydrophilic hydrogels lose mass right from the beginning. All hydrogels display water uptake values between 90 and 280% within 8 weeks. For longer periods of degradation, the water uptake increases up to a maximum of about 900%. Studies of the thermal properties of samples upon degradation and their IR measurements have shown that the degradation rate is related to the physical and chemical structure of the hydrogels and hence to the hydrophobic/hydrophilic balance; that is, the degradation increases with the increasing hydrophilicity of the material. As a result, degradation can be engineered through the variation of the composition and structure of the material. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 相似文献
413.
Volatile phenols in virgin olive oils: Influence of olive variety on their formation during fruits storage 总被引:1,自引:0,他引:1
Stefania Vichi Agustí Romero Joan Gallardo-Chacón Joan Tous Elvira López-Tamames Susana Buxaderas 《Food chemistry》2009
The potential significance as odorants and markers of olive fruits degradation has been recently pointed out for volatile phenols in virgin olive oil (VOO) and related to the appearance of VOO sensory defects. The few studies carried out in order to elucidate the factors affecting their formation in olive fruits or VOOs, indicated that they could be considered as analytical indices of olive fruits degradation during storage, likely reflecting the microbiological activity. In the present study, the effect of the olive variety (‘Arbequina’, ‘Arbosana’ and ‘Leccino’) on the production of volatile phenols during twelve days of storage in closed plastic bags was evaluated. The different resistance of each variety to the microbiological attach was observed during olive fruit storage, and it was reflected by the evolution of guaiacol, 4-ethylphenol and 4-ethylguaiacol, and related to free acidity values. On the contrary, a scarce dependence on the microbial growth or varietal factors was observed for 4-vinyl derivatives, which appeared more directly related to the time of olives storage. The evolution of volatile phenols found certain correspondence in the sensory characteristics of the resulting VOOs, while the rest of VOO chemical quality indices did not show major variations during fruits storage. 相似文献
414.
The reduction of the alcoholic degree of a white model wine by means of membrane separation technology was studied in this work. Reverse osmosis and nanofiltration are the most promising processes for the production of wines with low alcohol content, because they can operate at low temperature and thereby preserve the aromatic profile of wine. Assuming that the rejection of the main wine compounds (i.e. acids, sugars and tannins) is very high, the aim of this research was to study the permeation of several characteristic aroma compounds in the white model wine. Permeation was conducted in batch retentate-recycling mode with two reverse osmosis and one nanofiltration membranes previously conditioned with a 12 ml/100 ml aqueous ethanol solution. Aroma compounds were identified by gas chromatography coupled to quadrupolar mass selective spectrometry. A mathematical model allowed calculation of the aroma compound concentrations in the retentate and permeate streams as a function of permeate volume and the concentration of solutes in the diluted final wine at 8 ml/100 ml ethanol concentration. 相似文献
415.
A review of the potential of pretreated solids to improve gas biofuels production in the context of an OFMSW biorefinery
下载免费PDF全文
![点击此处可从《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Leticia Romero‐Cedillo Hector M Poggi‐Varaldo Teresa Ponce‐Noyola Elvira Ríos‐Leal Ana C Ramos‐Valdivia Carlos M Cerda‐García Rojas José Tapia‐Ramírez 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2017,92(5):937-958
The organic fraction of municipal solid waste (OFMSW), mainly composed of lignocellulosic polymers, is extremely complex. Therefore, it is necessary to apply pretreatments to remove the lignin content and decrease the cellulose crystallinity in order to use the OFMSW for gas biofuels production in the context of biorefineries from waste. This work focused on critically reviewing the conventional pretreatments applied to OFMSW, with the goal of improving the H2 production, as well as other biofuels in modern biorefineries. There are a wide variety of pretreatments that have successfully been used, mainly alkaline, milling and dilute acid. In addition, some research has focused on the recovery and reutilization of the alkali, acid or solvents after the pretreatment, to be incorporated into new cycles of production, minimizing the environmental impacts. Moreover, it would be necessary to incorporate analytical tools, in order to determine the sustainability of the biorefinery project. It is concluded that waste pretreatments could significantly contribute to increased yields of biogas fuels in organic waste‐based biorefineries. Therefore, establishing preliminary stages for conditioning biomass or wastes is essential to improve the degradation of wastes and bio‐product generation. © 2016 Society of Chemical Industry 相似文献
416.
Consumer discrimination of Chemlali and Arbequina olive oil cultivars according to their cultivar,geographical origin,and processing system
下载免费PDF全文
![点击此处可从《European Journal of Lipid Science and Technology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Kaouther Ben Hassine Milad El Riachy Amani Taamalli Dhafer Malouche Mohamed Ayadi Khouloud Talmoudi Maroua Aouini Yosra Jlassi Cinzia Benincasa Elvira Romano Enzo Perri Apostolos Kiristakis Mokhtar Hamdi Naziha Grati‐Kammoun Mohamed Hammami 《European Journal of Lipid Science and Technology》2014,116(7):812-824
417.
Alfredo Iranzo Antonio Salva Pierre Boillat Johannes Biesdorf Elvira Tapia Felipe Rosa 《International Journal of Hydrogen Energy》2017,42(19):13839-13849
A commercial 50 cm2 PEM fuel cell with serpentine flow fields was operated at 2.0 bar (a) and 60 °C with different relative humidity (RH) values for the inlet reactants (a matrix of 3 RH for anode and 3 RH for cathode). Between each test the cell was decompressed and liquid water was thus flushed out. The liquid water build-up and the time evolution during each experiment were recorded by means of Neutron Imaging. A qualitative and quantitative analysis of the results is presented in this work. It was observed that the dynamics of water build-up comprises three main stages, where the major difference is the liquid water accumulation rate. The onset location for the water appearance in the flow field channels was found to be determined by the flow field design, gravity and gas flow direction along the serpentine path. The time evolution of the water progressive accumulation along the flow field channels and cell active area is discussed. 相似文献
418.
“Electro‐Typing” on a Carbon‐Nanoparticles‐Filled Polymeric Film using Conducting Atomic Force Microscopy
下载免费PDF全文
![点击此处可从《Advanced materials (Deerfield Beach, Fla.)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Sumita Goswami Suman Nandy Arghya Narayan Banerjee Asal Kiazadeh Gowra Raghupathy Dillip Joana V. Pinto Sang Woo Joo Rodrigo Martins Elvira Fortunato 《Advanced materials (Deerfield Beach, Fla.)》2017,29(47)
Next‐generation electrical nanoimprinting of a polymeric data sheet based on charge trapping phenomena is reported here. Carbon nanoparticles (CNPs) (waste carbon product) are deployed into a polymeric matrix (polyaniline) (PANI) as a charge trapping layer. The data are recorded on the CNPs‐filled polyaniline device layer by “electro‐typing” under a voltage pulse (VET, from ±1 to ±7 V), which is applied to the device layer through a localized charge‐injection method. The core idea of this device is to make an electrical image through the charge trapping mechanism, which can be “read” further by the subsequent electrical mapping. The density of stored charges at the carbon–polyaniline layer, near the metal/polymer interface, is found to depend on the voltage amplitude, i.e., the number of injected charge carriers. The relaxation of the stored charges is studied by different probe voltages and for different devices, depending on the percolation of the CNPs into the PANI. The polymeric data sheet retains the recorded data for more than 6 h, which can be refreshed or erased at will. Also, a write–read–erase–read cycle is performed for the smallest “bit” of stored information through a single contact between the probe and the device layer. 相似文献
419.
Rachele Macirella Antonello Guardia Daniela Pellegrino Ilaria Bernabò Valentina Tronci Lars O. E. Ebbesson Settimio Sesti Sandro Tripepi Elvira Brunelli 《International journal of molecular sciences》2016,17(3)
Mercury (Hg) is a highly hazardous pollutant widely used in industrial, pharmaceutical and agricultural fields. Mercury is found in the environment in several forms, elemental, inorganic (iHg) and organic, all of which are toxic. Considering that the liver is the organ primarily involved in the regulation of metabolic pathways, homeostasis and detoxification we investigated the morphological and ultrastructural effects in Danio rerio liver after 96 h exposure to two low HgCl2 concentrations (7.7 and 38.5 μg/L). We showed that a short-term exposure to very low concentrations of iHg severely affects liver morphology and ultrastructure. The main effects recorded in this work were: cytoplasm vacuolization, decrease in both lipid droplets and glycogen granules, increase in number of mitochondria, increase of rough endoplasmic reticulum and pyknotic nuclei. Pathological alterations observed were dose dependent. Trough immunohistochemistry, in situ hybridization and real-time PCR analysis, the induction of metallothionein (MT) under stressor conditions was also evaluated. Some of observed alterations could be considered as a general response of tissue to heavy metals, whereas others (such as increased number of mitochondria and increase of RER) may be considered as an adaptive response to mercury. 相似文献
420.
Salinity source‐induced changes in yield,mineral composition,phenolic acids and flavonoids in leaves of artichoke and cardoon grown in floating system
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)