全文获取类型
收费全文 | 857篇 |
免费 | 61篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 1篇 |
综合类 | 4篇 |
化学工业 | 339篇 |
金属工艺 | 1篇 |
机械仪表 | 15篇 |
建筑科学 | 18篇 |
矿业工程 | 2篇 |
能源动力 | 18篇 |
轻工业 | 203篇 |
水利工程 | 5篇 |
石油天然气 | 3篇 |
无线电 | 32篇 |
一般工业技术 | 127篇 |
冶金工业 | 85篇 |
原子能技术 | 1篇 |
自动化技术 | 65篇 |
出版年
2024年 | 2篇 |
2023年 | 16篇 |
2022年 | 57篇 |
2021年 | 69篇 |
2020年 | 28篇 |
2019年 | 19篇 |
2018年 | 21篇 |
2017年 | 23篇 |
2016年 | 27篇 |
2015年 | 34篇 |
2014年 | 30篇 |
2013年 | 66篇 |
2012年 | 57篇 |
2011年 | 64篇 |
2010年 | 45篇 |
2009年 | 31篇 |
2008年 | 44篇 |
2007年 | 50篇 |
2006年 | 32篇 |
2005年 | 30篇 |
2004年 | 24篇 |
2003年 | 17篇 |
2002年 | 22篇 |
2001年 | 10篇 |
2000年 | 3篇 |
1999年 | 6篇 |
1998年 | 8篇 |
1997年 | 5篇 |
1996年 | 4篇 |
1995年 | 5篇 |
1994年 | 3篇 |
1993年 | 6篇 |
1992年 | 3篇 |
1990年 | 5篇 |
1989年 | 5篇 |
1988年 | 6篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1984年 | 4篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1975年 | 4篇 |
1974年 | 2篇 |
1968年 | 1篇 |
1967年 | 1篇 |
1965年 | 1篇 |
排序方式: 共有919条查询结果,搜索用时 31 毫秒
781.
Selective Use of News Cues: A Multiple‐Motive Perspective on Information Selection in Social Media Environments
下载免费PDF全文
![点击此处可从《The Journal of communication》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Stephan Winter Miriam J. Metzger Andrew J. Flanagin 《The Journal of communication》2016,66(4):669-693
This study investigated the effects of message and social cues on selective exposure to political information in a social media environment. Based on the heuristic‐systematic model, we hypothesized that readers' selective consideration of specific cues can be explained by situational motivations. In an experiment (N = 137), subjects primed with motivational goals (accuracy, defense, or impression motivations, as well as a control group) were asked to search for information. Participants preferred attitude‐consistent information and balanced information over attitude‐inconsistent information, and also preferred highly recommended articles. Defense‐motivated partisans exhibited a stronger confirmation bias, whereas impression motivation amplified the effects of social recommendations. These findings specify the conditions under which individuals engage in narrow, open‐minded, or social patterns of information selection. 相似文献
782.
Dalton Dittz Cinthia Figueiredo Fernanda O. Lemos Celso T. R. Viana Silvia P. Andrade Elaine M. Souza-Fagundes Ricardo T. Fujiwara Carlos E. Salas Miriam T. P. Lopes 《International journal of molecular sciences》2015,16(4):7027-7044
The proteolytic enzymes from V. cundinamarcensis latex, (P1G10), display healing activity in animal models following various types of lesions. P1G10 or the purified isoforms act as mitogens on fibroblast and epithelial cells by stimulating angiogenesis and wound healing in gastric and cutaneous ulcers models. Based on evidence that plant proteinases act as antitumorals, we verified this effect on a murine melanoma model. The antitumoral effect analyzed mice survival and tumor development after subcutaneous administration of P1G10 into C57BL/6J mice bearing B16F1 low metastatic melanoma. Possible factors involved in the antitumoral action were assessed, i.e., cytotoxicity, cell adhesion and apoptosis in vitro, haemoglobin (Hb), vascular endothelial growth factor (VEGF), tumor growth factor-β (TGF-β), tumor necrosis factor-α (TNF-α) content and N-acetyl-glucosaminidase (NAG) activity. We observed that P1G10 inhibited angiogenesis measured by the decline of Hb and VEGF within the tumor, and TGF-β displayed a non-significant increase and TNF-α showed a minor non-significant reduction. On the other hand, there was an increase in NAG activity. In treated B16F1 cells, apoptosis was induced along with decreased cell binding to extracellular matrix components (ECM) and anchorage, without impairing viability. 相似文献
783.
Removal of excess fluoride from groundwater using natural coagulant Moringa oleifera Lam and microfiltration
下载免费PDF全文
![点击此处可从《加拿大化工杂志》网站下载免费的PDF全文](/ch/ext_images/free.gif)
784.
Alvin C. K. Lai Miriam A. Byrne Antony J. H. Goddard 《Aerosol science and technology》2013,47(10):973-982
Understanding the fate of particles indoors is important for human health assessment because deposited particles, unless resuspended, cannot be inhaled. To complement studies in real buildings, where control of variables is often difficult, an experimental test chamber facility (8 m 3 ) was designed to study particle deposition under well-stirred conditions using monodisperse tracer aerosol particles in the range of 0.7 to 5.4 w m. The use of neutron-activatable tracers facilitated simultaneous surface sampling and aerosol concentration decay measurements. Aerosol deposition on both smooth surfaces and regular arrays of three-dimensional roughness elements under 3 different airflow speeds was investigated in the test chamber.It was expected that the texture of the chamber surface would significantly influence particle deposition, but some counterintuitive results were observed: under the lowest airflow condition and for the smallest particle size, particle deposition onto rough samples was found to be less than on the corresponding smooth surfaces. The ratio of particle deposition on rough surfaces relative to smooth surfaces increased with particle size and magnitude of airflow. For the largest particle size and airflow speed, particle deposition on the rough surfaces exceeded that on the smooth surfaces by a factor of 3. 相似文献
785.
Dr. Sunil V. Sharma Miriam Arbach Dr. Alexandra A. Roberts Dr. Colin J. Macdonald Dr. Murree Groom Dr. Chris J. Hamilton 《Chembiochem : a European journal of chemical biology》2013,14(16):2160-2168
Bacillithiol (BSH) is the major low‐molecular‐weight (LMW) thiol in many low‐G+C Gram‐positive bacteria (Firmicutes). Evidence now emerging suggests that BSH functions as an important LMW thiol in redox regulation and xenobiotic detoxification, analogous to what is already known for glutathione and mycothiol in other microorganisms. The biophysical properties and cellular concentrations of such LMW thiols are important determinants of their biochemical efficiency both as biochemical nucleophiles and as redox buffers. Here, BSH has been characterised and compared with other LMW thiols in terms of its thiol pKa, redox potential and thiol–disulfide exchange reactivity. Both the thiol pKa and the standard thiol redox potential of BSH are shown to be significantly lower than those of glutathione whereas the reactivities of the two compounds in thiol–disulfide reactions are comparable. The cellular concentration of BSH in Bacillus subtilis varied over different growth phases and reached up to 5 mM , which is significantly greater than previously observed from single measurements taken during mid‐exponential growth. These results demonstrate that the biophysical characteristics of BSH are distinctively different from those of GSH and that its cellular concentrations can reach levels much higher than previously reported. 相似文献
786.
Copper hollow spheres were created on porous iron particles by electro-less deposition. The consequent Ni plating was applied to improve the mechanical properties of copper hollow micro-particles. Corrosion properties of coated hollow spheres were investigated using potentiodynamic polarisation method in 1 mol dm−3 NaCl solution. Surface morphology and composition were studied by scanning electron microscopy (SEM), light microscopy (LM) and energy-dispersive X-ray spectroscopy (EDX). Original iron particles, uncoated copper spheres and iron particles coated with nickel were studied as the reference materials. The effect of particle composition, particularly Ni content on the corrosion potential value was investigated. The results indicated that an increase in the amount of Ni coating layer deteriorated corrosion resistivity of coated copper spheres. Amount of Ni coating layer depended on conditions of Ni electrolysis, mainly on electrolysis time and current intensity. Corrosion behaviour of sintered particles was also explored by potentiodynamic polarisation experiments for the sake of comparison. Formation of iron rich micro-volumes on the particle surface during sintering caused the corrosion potential shift towards more negative values. A detailed study of the morphological changes between non-sintered and sintered micro-particles provided explanation of differences in corrosion potential (Ecorr). 相似文献
787.
788.
Carlo Morasso Miriam Colombo Silvia Ronchi Laura Polito Serena Mazzucchelli Diego Monti Marco Buscaglia Tommaso Bellini Davide Prosperi 《Advanced functional materials》2010,20(22):3932-3940
Highly fluorinated materials are being widely investigated due to a number of peculiar properties, which are potentially useful for various applications, including use as lubricants, anti‐adhesive films, and substitutes for biological fluids for biomedical utilization. However, at present such potential is still poorly exploited. One of the major drawbacks that hampers the rapid development of nanoscale fluoro‐hybrid devices is the remarkable inertness of perfluoropolymeric materials that lack reactive functionalities, as they do not offer any functional groups that can be employed to covalently anchor organic molecules on their surface. In this paper, a convenient method for the stable biofunctionalization of strongly unreactive perfluoropolymer nanoparticles (PnPs) is reported. PnPs are easily coated with newly synthesized asymmetric diacetylenic monomer compounds (ADMs), thanks to PnP’s high propensity to interact with hydrophobic moieties. Once monomerically adsorbed onto PnPs, such suitably designed ADMs enable the formation of a robust polymeric shell around the perfluoroelastomer core via a clean UV‐promoted localized photopolymerization. Given the peculiar optical characteristics of PnPs, the coating of the particles can be monitored step by step using light scattering, which also allows estimation of the fraction of reacted monomers by competitive adsorption with smaller particles. The potential of this method for the biofunctionalization of PnPs is demonstrated with representative proteins and carbohydrates. Among them, the extension to avidin–biotin technology may broaden the scope and applicability of this strategy to potentially a large number of molecules of biomedical interest. 相似文献
789.
Miriam Gálová Renáta Orináková Tomáš Grygar Ladislav Lux Mária Heželová 《Particulate Science and Technology》2013,31(1):85-94
ABSTRACT The importance of the passivation layer on Fe powder surfaces formed by oxides, hydroxides, and/or salts and water molecules is pointed out for both electrochemical oxidative dissolution of iron powder and electrodeposition of Ni layer on it. This layer behaves as ohmic contact resistance. The layer thickness affects the surface reactivity of the powder and is influenced by the way of preactivation the powder prior to the electrochemical process. A reliable voltammetric method reflecting the surface reactivity was found, theoretically treated, and experimentally verified by measuring the rate of electrochemical dissolution of Fe powder. The efficiency of Ni electrodeposition on this powder was determined in a series of independent electrolyses. The correlation between both later mentioned parameters was satisfying for small powder particle fractions as well as for activation procedures which include chemical step. 相似文献
790.
Beatriz C.B.S. Mello José Carlos Cunha Petrus Miriam Dupas Hubinger 《Journal of food engineering》2010
Propolis has a variable and complex chemical composition with high concentration of flavonoids and phenolic compounds present in the extract. The extract varies with the solvent used in extraction. Ethanol extracts more phenolic acid and polar compounds than water. Before their use in industry, extracts must be concentrated but the use of high temperatures can degrade some compounds. Membrane processes is an option that allows concentration at low temperatures. Nanofiltration was carried out with aqueous and ethanolic extracts and each extract results in two distinct fractions: permeate and retentate. The capacity of the membrane to retain the compounds was verified by spectrophotometric analysis: for aqueous solution, the membrane retained around 94% of the phenolic compounds and 99% of the flavonoids, while for the ethanolic solution these values were 53% and 90%, respectively. Ferulic acid retention index was 1.00 and 0.88 to aqueous and ethanolic solutions, respectively. Thus, the nanofiltration process showed high efficiency in the concentration of propolis extracts. 相似文献