全文获取类型
收费全文 | 75篇 |
免费 | 1篇 |
专业分类
电工技术 | 1篇 |
化学工业 | 28篇 |
金属工艺 | 4篇 |
机械仪表 | 2篇 |
建筑科学 | 1篇 |
能源动力 | 1篇 |
轻工业 | 14篇 |
水利工程 | 1篇 |
无线电 | 2篇 |
一般工业技术 | 9篇 |
冶金工业 | 5篇 |
自动化技术 | 8篇 |
出版年
2023年 | 1篇 |
2022年 | 8篇 |
2021年 | 2篇 |
2019年 | 1篇 |
2018年 | 4篇 |
2017年 | 4篇 |
2016年 | 4篇 |
2015年 | 1篇 |
2014年 | 3篇 |
2013年 | 3篇 |
2012年 | 4篇 |
2011年 | 3篇 |
2010年 | 2篇 |
2009年 | 9篇 |
2008年 | 2篇 |
2007年 | 3篇 |
2006年 | 1篇 |
2004年 | 4篇 |
2000年 | 3篇 |
1998年 | 3篇 |
1997年 | 1篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1991年 | 1篇 |
1989年 | 1篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有76条查询结果,搜索用时 15 毫秒
61.
Diego B. Silva Vanda H. P. Bueno Joop J. A. Van Loon Maria Fernanda G. V. Peñaflor José Maurício S. Bento Joop C. Van Lenteren 《Journal of chemical ecology》2018,44(1):29-39
Plants emit volatile compounds in response to insect herbivory, which may play multiple roles as defensive compounds and mediators of interactions with other plants, microorganisms and animals. Herbivore-induced plant volatiles (HIPVs) may act as indirect plant defenses by attracting natural enemies of the attacking herbivore. We report here the first evidence of the attraction of three Neotropical mirid predators (Macrolophus basicornis, Engytatus varians and Campyloneuropsis infumatus) toward plants emitting volatiles induced upon feeding by two tomato pests, the leaf miner Tuta absoluta and the phloem feeder Bemisia tabaci, in olfactometer bioassays. Subsequently, we compared the composition of volatile blends emitted by insect-infested tomato plants by collecting headspace samples and analyzing them with GC-FID and GC-MS. Egg deposition by T. absoluta did not make tomato plants more attractive to the mirid predators than uninfested tomato plants. Macrolophus basicornis is attracted to tomato plants infested with either T. absoluta larvae or by a mixture of B. tabaci eggs, nymphs and adults. Engytatus varians and C. infumatus responded to volatile blends released by tomato plants infested with T. absoluta larvae over uninfested plants. Also, multiple herbivory by T. absoluta and B. tabaci did not increase the attraction of the mirids compared to infestation with T. absoluta alone. Terpenoids represented the most important class of compounds in the volatile blends and there were significant differences between the volatile blends emitted by tomato plants in response to attack by T. absoluta, B. tabaci, or by both insects. We, therefore, conclude that all three mirids use tomato plant volatiles to find T. absoluta larvae. Multiple herbivory did neither increase, nor decrease attraction of C. infumatus, E. varians and M. basicornis. By breeding for higher rates of emission of selected terpenes, increased attractiveness of tomato plants to natural enemies may improve the effectiveness of biological control. 相似文献
62.
Mariana C. S. Vallejo Nuno M. M. Moura Ana T. P. C. Gomes Ana S. M. Joaquinito Maria Amparo F. Faustino Adelaide Almeida Idalina Gonalves Vanda Vaz Serra Maria Graa P. M. S. Neves 《International journal of molecular sciences》2021,22(8)
Microorganisms, usually bacteria and fungi, grow and spread in skin wounds, causing infections. These infections trigger the immune system and cause inflammation and tissue damage within the skin or wound, slowing down the healing process. The use of photodynamic therapy (PDT) to eradicate microorganisms has been regarded as a promising alternative to anti-infective therapies, such as those based on antibiotics, and more recently, is being considered for skin wound-healing, namely for infected wounds. Among the several molecules exploited as photosensitizers (PS), porphyrinoids exhibit suitable features for achieving those goals efficiently. The capability that these macrocycles display to generate reactive oxygen species (ROS) gives a significant contribution to the regenerative process. ROS are responsible for avoiding the development of infections by inactivating microorganisms such as bacteria but also by promoting cell proliferation through the activation of stem cells which regulates inflammatory factors and collagen remodeling. The PS can act solo or combined with several materials, such as polymers, hydrogels, nanotubes, or metal-organic frameworks (MOF), keeping both the microbial photoinactivation and healing/regenerative processes’ effectiveness. This review highlights the developments on the combination of PDT approach and skin wound healing using natural and synthetic porphyrinoids, such as porphyrins, chlorins and phthalocyanines, as PS, as well as the prodrug 5-aminolevulinic acid (5-ALA), the natural precursor of protoporphyrin-IX (PP-IX). 相似文献
63.
Alexandra Lauw Vanda Oliveira Fernando Lopes Helena Pereira 《Holz als Roh- und Werkstoff》2018,76(1):123-132
Cork production and technological quality were characterized following a field sampling covering the whole area of cork oaks in Portugal (six regions), with one site per 20,000 ha of cork oak area (30 sites), using samples taken from the tree at the time of cork stripping (20 trees per site). The following quality parameters were determined: thickness of the raw cork planks, calliper of the cork planks after boiling, cork growth index, i.e., growth of the first 8 complete years, density and porosity. The cork growth index was 28.6 mm, with significant differences between regions and sites within regions. A production cycle of 9 years was applied to 51% of the trees with annual productivity of 0.93 kg m?2 year?1 of debarked surface, 30.3 mm raw cork plank thickness, 33.9 mm corkboard calliper, 251 kg m?3 density and a porosity coefficient of 5.8%. For all the cork quality parameters analysed, the regions and sites within regions were a significant factor of variation. This research covers the natural variability of cork production features for industrial processing, namely for the production of wine stoppers. It is the most extensive work characterizing the geographical variation of cork as an industrial raw-material. The results are useful for optimizing the production cycle and for improving management practices and regulations. 相似文献
64.
Vanda B Galazka Eric Dickinson Dave A Ledward 《Journal of the science of food and agriculture》2000,80(8):1219-1229
The influence of sulphated polysaccharides (dextran sulphate (DS), ι‐carrageenan (ι‐CAR) and κ‐carrageenan (κ‐CAR)) on the emulsifying properties of ovalbumin (OVA) has been investigated over a range of pressures and temperatures. Oil‐in‐water emulsions (10 g l−1 protein, 200 ml l−1 n‐tetradecane, pH 6.2) prepared with heat‐treated (80 °C for 10 min) mixtures of OVA + DS (1:0.25 by weight) had increased creaming stability but unchanged average droplet size compared to those made with untreated OVA and OVA + DS. Emulsions made with pressure‐processed (600 MPa for 20 min) OVA + DS (1:0.25 or 1:0.5 by weight) mixtures had the best emulsifying efficiency and stability. Under similar experimental conditions, replacement of DS with either ι‐ or κ‐CAR gave emulsions with larger droplets and more rapid serum separation, probably owing to depletion flocculation. High‐pressure treatment (600 MPa) of the OVA and mixed biopolymer solutions at pH 6.2 in the presence of salt (>0.04 M ) led to unstable emulsions, and so the protective effect of DS was lost. High‐pressure treatment (600 MPa) of emulsions prepared with native OVA or OVA + DS mixtures induced significant levels of flocculation, as indicated by changes in the average droplet size and creaming behaviour. © 2000 Society of Chemical Industry 相似文献
65.
P. Zhang M. Karimpour D. Balint J. Lin 《International journal for numerical methods in engineering》2012,92(8):715-733
A novel scheme is presented for incorporating finite thickness cohesive interfaces in virtual grain structures for crystal plasticity finite element (CPFE) analyses of intergranular crack initiation and propagation. A Voronoi tessellation model is used to define the virtual grain structure, with automatically generated nonzero thickness cohesive zones (CZs) representing the grain boundaries and multiple junctions. An efficient grain boundary offsetting algorithm is presented, and issues related to automatically partitioning multiple junctions are discussed. Two feasible junction partitioning schemes are presented, the second of which has the advantage of partitioning junctions using uniform quadrilateral elements and naturally defining their normal and tangential directions. For the second scheme, a rule‐based method is presented that carries out the preliminary meshing of CZ junctions, including data representation, edge event processing, and cut and trim operations. A virtual grain structure modelling system, VGRAIN, is introduced to implement the proposed CZ junction partitioning method and directly generate meshed virtual grain structures with CZ grain boundaries for CPFE studies. To demonstrate the proposed junction partitioning and CZ representation schemes, two finite strain CPFE simulations are presented for plane strain uniaxial tension and three‐point bending, demonstrating large‐scale crack initiation and propagation under shear and opening modes. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
66.
Diego B. Silva Berhane T. Weldegergis Joop J.A. Van Loon Vanda H. P. Bueno 《Journal of chemical ecology》2017,43(1):53-65
Plants release a variety of volatile organic compounds that play multiple roles in the interactions with other plants and animals. Natural enemies of plant-feeding insects use these volatiles as cues to find their prey or host. Here, we report differences between the volatile blends of tomato plants infested with the whitefly Bemisia tabaci or the tomato borer Tuta absoluta. We compared the volatile emission of: (1) clean tomato plants; (2) tomato plants infested with T. absoluta larvae; and (3) tomato plants infested with B. tabaci adults, nymphs, and eggs. A total of 80 volatiles were recorded of which 10 occurred consistently only in the headspace of T. absoluta-infested plants. Many of the compounds detected in the headspace of the two herbivory treatments were emitted at different rates. Plants damaged by T. absoluta emitted at least 10 times higher levels of many compounds compared to plants damaged by B. tabaci and intact plants. The multivariate separation of T. absoluta-infested plants from those infested with B. tabaci was due largely to the chorismate-derived compounds as well as volatile metabolites of C18-fatty acids and branched chain amino acids that had higher emission rates from T. absoluta-infested plants, whereas the cyclic sesquiterpenes α- and β-copaene, valencene, and aristolochene were emitted at significantly higher levels from B. tabaci-infested plants. Our findings imply that feeding by T. absoluta and B. tabaci induced emission of volatile blends that differ quantitatively and qualitatively, providing a chemical basis for the recently documented behavioral discrimination by two generalist predatory mirid species, natural enemies of T. absoluta and B. tabaci employed in biological control. 相似文献
67.
Smectite clay samples from the Amazon region, Brazil, were pillarized by intercalating the species obtained from the chemical reactions: (i) AlCl3·6H2O/NaOH, (ii) titanium ethoxide in hydrochloric acid and (iii) direct use of ZrOCl2·8H2O solution. The natural matrices and the pillaring solutions were maintained under vigorous stirring at 298 K for 3 h and then subjected to calcination at temperatures of 723 and 873 K. Natural and pillared matrices were characterized by XRD, FTIR, TG–DTG and nitrogen adsorption–desorption isotherms. The resulting materials were used for zinc adsorption from aqueous solution at room temperature. The Langmuir, Freundlich and Temkin adsorption isotherm models have been applied to fit the experimental data and the Freundlich model is limited for higher concentrations. The pillaring process increases the thermal stability, the basal spacing of the natural clay sample (A1) from 1.55 to 2.06 nm and the surface area from 44.30 to 223.73 m2 g−1. Kinetic studies demonstrated an equilibrium time of 180 min for zinc adsorption on the pillared matrices. Pseudo-first-order, Lagergren pseudo-second-order and Elovich equations demonstrated a better agreement with second-order kinetics was obtained with K2 = 4.17–10.43 × 10−3 g mg−1 min−1 for the A1 sample. 相似文献
68.
George Rozvany Vanda Pomezanski Tomasz Sokół 《Structural and Multidisciplinary Optimization》2014,50(2):193-205
The main aim of this paper is to present a general theory of exact compliance-based, multi-load truss topology optimization, including an illustrative example and its numerical verifications. A minor aim is to provide background material for an Authors’ Reply to a Discussion by Logo of a paper by Rozvany and Maute. 相似文献
69.
A stable and convex static meniscus is appropriate for the growth of a single crystal ribbon of given half thickness, if the upper half thickness of the meniscus is equal to the ribbon half thickness and the angle between the tangent line to the meniscus and the vertical is equal to the growth angle. In this paper the material parameters, the shaper half thickness, the gas pressure above the meniscus and the half thickness of the ribbon, which has to be grown, are considered prior given. The problem that is solved is the determination of the melt column height (between the horizontal crucible melt level and the shaper top level) such that the resulting meniscus is convex, is static stable and is appropriate for the growth of the desired ribbon. The determination is numerically illustrated for silicon sheet and the dependence of the melt column height on the shaper half thickness is discussed. 相似文献
70.
Paulo Cartaxana Carlos R. Mendes Vanda Brotas 《Lakes & Reservoirs: Research and Management》2009,14(3):221-230
Phytoplankton biomass and composition were monitored for four coastal lagoons of the Algarve, Portugal, from February to November 2006. The phytoplankton community in the freshwater lagoons – Dunas Douradas (FW1) and Garrão (FW2) – as determined by biomarker pigment concentration using high-performance liquid chromatography and the program chemtax , was dominated by diatoms and chlorophytes. For the brackish lagoons – Salgados (BW1) and Almargem (BW2) – cyanophytes and diatoms were the most important groups respectively. The trophic state indices, based on algal biomass, classify FW1, FW2 and BW1 lagoons as hypertrophic, whereas BW2 is classified as mesotrophic. Signs of eutrophication in the former lagoons include large phytoplankton biomass (chlorophyll- a ) fluctuations, the presence of phytoplankton taxa that usually thrive under nutrient-enriched conditions and high concentrations of chlorophyll- a -degradation products. Chemotaxonomic analyses derived from high-performance liquid chromatography data might constitute a valuable tool for achieving Water Framework Directive requirements for an evaluation system based on phytoplankton taxonomic composition. 相似文献