全文获取类型
收费全文 | 666篇 |
免费 | 66篇 |
专业分类
电工技术 | 11篇 |
综合类 | 3篇 |
化学工业 | 240篇 |
金属工艺 | 7篇 |
机械仪表 | 6篇 |
建筑科学 | 34篇 |
矿业工程 | 2篇 |
能源动力 | 16篇 |
轻工业 | 150篇 |
水利工程 | 4篇 |
石油天然气 | 2篇 |
无线电 | 30篇 |
一般工业技术 | 114篇 |
冶金工业 | 44篇 |
原子能技术 | 2篇 |
自动化技术 | 67篇 |
出版年
2024年 | 1篇 |
2023年 | 6篇 |
2022年 | 28篇 |
2021年 | 59篇 |
2020年 | 21篇 |
2019年 | 22篇 |
2018年 | 26篇 |
2017年 | 24篇 |
2016年 | 32篇 |
2015年 | 30篇 |
2014年 | 35篇 |
2013年 | 38篇 |
2012年 | 51篇 |
2011年 | 64篇 |
2010年 | 33篇 |
2009年 | 29篇 |
2008年 | 41篇 |
2007年 | 33篇 |
2006年 | 31篇 |
2005年 | 27篇 |
2004年 | 18篇 |
2003年 | 20篇 |
2002年 | 20篇 |
2001年 | 3篇 |
2000年 | 5篇 |
1999年 | 5篇 |
1998年 | 6篇 |
1997年 | 4篇 |
1996年 | 7篇 |
1995年 | 2篇 |
1994年 | 4篇 |
1993年 | 2篇 |
1992年 | 3篇 |
1988年 | 1篇 |
1982年 | 1篇 |
排序方式: 共有732条查询结果,搜索用时 46 毫秒
631.
Despite the long-term and positive experience with Ecological Tax Reform (ETR), the PETRAS study indicates that awareness about the principles behind ETR is low among both businesses and the general public in Denmark. As well as the lack of awareness of ETR, attitudes towards environmental taxation appear negative. When explaining the political intentions behind ETR, attitudes seem to improve somewhat, but they still remain overall sceptical. 相似文献
632.
Prof. Dr. Andreas Will Dipl.-Medienwiss. Stefan Jazdzejewski Dipl.-Medienwiss. Anja Weber 《Datenschutz und Datensicherheit - DuD》2006,30(2):85-89
Im Wege einer ?konomischen Analyse wird die Kundenfreundlichkeit marktg?ngiger Downloadportale untersucht. Es ergibt sich,
dass — bei zahlreichen Unterschieden im Detail — alle untersuchten Downloadplattformen dem traditionellen Gesch?ftsmodell
der Offline-Welt folgen und Musikstücke gegen Bezahlung anbieten. Verbesserungsm?glichkeiten im Hinblick auf die Kundenfreundlichkeit
konnten bei allen Plattformen gefunden werden. Weitergehende Gestaltungsoptionen des Onlinevertriebs — von innovativen Erl?squellen
bis hin zu einer Abkehr von der Vorstellung, das Datenobjekt sei das ?konomische Gut — bleiben ungenutzt. 相似文献
633.
Stable profit sharing in cooperative investments 总被引:1,自引:1,他引:0
This paper examines profit sharing in cooperative investments where investors bundle their capital endowments to meet the capital requirements of long term investment projects. Furthermore, investors may reinvest intertemporal gains from existing projects into new projects. Focus is on stable allocation schemes as stability is necessary to sustain the long term cooperation of investors. The paper presents sufficient conditions for the existence of stable profit sharing schemes using linear programming techniques.This complete issue was revised and published online in November 2004. The previous version contained a false date.
Correspondence to: Anja De WaegenaereThe authors wish to thank two anonymous referees for comments that helped to improve the paper significantly. The research of J. Suijs is made possible by a fellowship of the Royal Netherlands Academy of Arts and Sciences (KNAW). 相似文献
634.
Aurel Prstić Zagorka Aćimović‐Pavlović Anja Terzić Ljubica Pavlović Snežana Grujić 《International Journal of Applied Ceramic Technology》2014,11(2):321-331
In this study, new refractory coatings based on synthesized cordierite for the casting applications were developed. The investigation included starting raw materials characterization, synthesis of the cordierite, design of the refractory coating as final product, and its application testing. The obtained results pointed out that coating suspension sediment stability was crucial quality parameter. Design and optimization of the coatings composition, with controlled rheological properties included, were achieved by application of different coating components, namely different suspension agents and by alteration of the coating production procedure. Cordierite, used as filler, was obtained by means of synthesis in the solid‐state reaction on the basis of talc, kaolin, and alumina. The investigation showed that the application of these particular types of water/alcohol‐based coatings has positive influence on surface quality and structural and mechanical properties of the castings of aluminum alloys obtained by casting into sand molds by means of evaporable models method, that is, evaporate pattern casting process. 相似文献
635.
Anja S. Goldmann Damien Quémener Pierre-Eric Millard Thomas P. Davis Martina H. Stenzel Christopher Barner-Kowollik Axel H.E. Müller 《Polymer》2008,49(9):2274-2281
The coupling of the reversible addition fragmentation chain transfer (RAFT) polymerization technique with the copper-catalyzed Huisgen 1,3-dipolar cycloaddition (“click chemistry”) as a simple and effective way to generate polystyrene (PS) macrocycles is presented. The novel strategy entails the synthesis of linear PS backbones followed by endgroup modification to facilitate click chemistry for the formation of ring shaped polymers. An azido group modified 4-cyanopentanoic acid dithiobenzoate is employed as the chain transfer agent in the RAFT mediated polymerization of styrene to form PS with Mn from 2000 g mol?1 to 6000 g mol?1 and PDI < 1.2. To facilitate the cyclization of the polystyrene chains by click coupling, the thiocarbonylthio endgroup is removed and concomitantly replaced by an alkyne bearing function. This is carried out via the radical decomposition of excess azobis(4-cyano valeric acid) (ACVA) modified with an alkyne endgroup in the presence of the thiocarbonylthio-capped PS. The successful click endgroup modifications of several polystyrenes along with the results from the cyclization of a PS with Mn = 4300 g mol?1 are discussed in detail. This improved method avoids the presence of thiocarbonylthio functions in the macrocycle, thus considerably increasing the chemical stability of these polymers. 相似文献
636.
Bernhardt A Lode A Boxberger S Pompe W Gelinsky M 《Journal of materials science. Materials in medicine》2008,19(1):269-275
In the field of bone tissue engineering there is a high demand on bone graft materials which promote bone formation. By combination
of collagen type I with nanocrystalline hydroxyapatite (HA) we generated a resorbable material which structure and composition
is close to those of the extracellular bone matrix. This nanocomposit material was produced in a biomimetic process in which
collagen fibril assembly and mineralisation with hydroxyapatite occur simultaneously. In this study the proliferation and
osteogenic differentiation of human bone marrow-derived stromal cells (hBMSC) on membranes of biomimetically mineralised collagen
type I was investigated. To this end, we optimised biochemical assays for determination of cell number and alkaline phosphatase
activity corresponding to the special properties of this biomaterial. For cell experiments hBMSC were seeded on the mineralised
collagen membranes and cultivated over 35 days, both in static and perfusion culture, in the presence and absence of dexamethasone,
β-glycerophosphate and ascorbate. Compared to cells grown on tissue culture polystyrene we found attenuated proliferation
rates, but markedly increased activity of alkaline phosphatase on the mineralised collagen indicating its promoting effect
on the osteogenic differentiation of hBMSC. Therefore this bone-like material may act as a suitable artificial extracellular
matrix for bone tissue engineering. Perfusion of the 2D cell matrix constructs with cell culture medium did not improve proliferation
and osteogenic differentiation of the hBMSC.
Anne Bernhardt and Anja Lode contributed equally to this paper 相似文献
637.
Graefe A Stanca SE Nietzsche S Kubicova L Beckert R Biskup C Mohr GJ 《Analytical chemistry》2008,80(17):6526-6531
In this study, we describe the preparation and evaluation of new fluorescent sensor nanoparticles for the ratiometric measurement of chloride concentrations. Both a chloride-sensitive dye (lucigenin) and a reference dye (sulforhodamine derivative) were incorporated into polyacrylamide nanoparticles via inverse microemulsion polymerization and investigated for their response to chloride ions in buffered suspension as well as in living cells. The fluorescence intensity of lucigenin reversibly decreased in the presence of chloride ions due to a collisional quenching process, which can be described with the Stern-Volmer equation. The determined Stern-Volmer constant K SV for the quenching of lucigenin incorporated into particles was found to be 53 M (-1) and is considerably smaller than the Stern-Volmer constant for quenching of free lucigenin ( K SV = 250 M (-1)) under the same conditions. To test the nanosensors in living cells, we incorporated them into Chinese hamster ovary cells and mouse fibroblasts by using the conventional lipofectamin technique and monitored the response to changing chloride concentrations in the cell. 相似文献
638.
Assessing the impact of changes in landuse and management practices on the diffuse pollution and retention of nitrate in a riparian floodplain 总被引:2,自引:0,他引:2
Krause S Jacobs J Voss A Bronstert A Zehe E 《The Science of the total environment》2008,389(1):149-164
In many European lowland rivers and riparian floodplains diffuse nutrient pollution is causing a major risk for the surface waters and groundwater to not achieve a good status as demanded by the European Water Framework Directive. In order to delimit the impact of diffuse nutrient pollution substantial and often controversial changes in landuse and management are under discussion. In this study we investigate the impact of two complex scenarios considering changes in landuse and land management practices on the nitrate loads of a typical lowland stream and the riparian groundwater in the North German Plains. Therefore the impacts of both scenarios on the nitrate dynamics, the attenuation efficiency and the nitrate exchange between groundwater and surface water were investigated for a 998.1 km(2) riparian floodplain of the Lower and Central Havel River and compared with the current conditions. Both scenarios target a substantial improvement of the ecological conditions and the water quality in the research area but promote different typical riparian landscape functions and consider a different grade of economical and legal feasibility of the proposed measures. Scenario 1 focuses on the optimisation of conservation measures for all natural resources of the riparian floodplain, scenario 2 considers measures in order to restore a good status of the water bodies mainly. The IWAN model was setup for the simulation of water balance and nitrate dynamics of the floodplain for a perennial simulation period of the current landuse and management conditions and of the scenario assumptions. The proposed landuse and management changes result in reduced rates of nitrate leaching from the root zone into the riparian groundwater (85% for scenario 1, 43% for scenario 2). The net contributions of nitrate from the floodplain can be reduced substantially for both scenarios. In case of scenario 2 a decrease by 70% can be obtained. For scenario 1 the nitrate exfiltration rates to the river drop even below the infiltration rates from the river, the riparian floodplain in that scenario represents a net sink for river derived nitrate. As the nitrate contributions from the investigated riparian floodplain represent only a small proportion of the total nitrate loads within the river (1% p.a.) the overall impact of the scenario measures on the nitrate loads at the river outlet remains small. However, during the ecologically most sensitive summer periods under current conditions nitrate contributions from the riparian groundwater of the Lower and Central Havel River (which covers only 5% of the area of the Havel catchment) represent more than 20% of the river loads. By the implementation of the investigated landuse changes within the research area the groundwater derived nitrate contributions could be halved to only 10% during summer baseflow conditions. 相似文献
639.
Anna Evans Anja Bieberle-HütterLorenz J. Bonderer Stefanie StuckenholzLudwig J. Gauckler 《Journal of power sources》2011,196(23):10069-10073
Ultrathin 3 mol.% yttria-stabilised-tetragonal-zirconia-polycrystal (Y-TZP) foils with thicknesses of 1-10 μm are fabricated by a new wet-chemical processing route. The foils are free-standing, semi-transparent and flexible. The in-plane electrical conductivity of the Y-TZP foil is 0.03 S m−1 at 500 °C. Cross-plane impedance measurements with sputtered Pt electrodes yield two arcs, of which the high-frequency arc is attributed to the ohmic resistance of the electrolyte and the low-frequency arc to the electrode-electrolyte interface. A symmetrical micro-solid oxide fuel cell (SOFC) is designed using this ultrathin free-standing Y-TZP foil as the electrolyte and sputtered Pt electrodes. An open-circuit voltage of 0.98 V and a maximum power density of 12 mW cm−2 are measured at 500 °C. These results prove the feasibility of this approach to the fabrication of miniaturised planar SOFCs without the need for microfabrication. 相似文献