全文获取类型
收费全文 | 1133篇 |
免费 | 97篇 |
专业分类
电工技术 | 9篇 |
综合类 | 25篇 |
化学工业 | 386篇 |
金属工艺 | 15篇 |
机械仪表 | 14篇 |
建筑科学 | 56篇 |
矿业工程 | 3篇 |
能源动力 | 19篇 |
轻工业 | 203篇 |
水利工程 | 13篇 |
无线电 | 59篇 |
一般工业技术 | 166篇 |
冶金工业 | 75篇 |
原子能技术 | 4篇 |
自动化技术 | 183篇 |
出版年
2024年 | 2篇 |
2023年 | 12篇 |
2022年 | 37篇 |
2021年 | 42篇 |
2020年 | 33篇 |
2019年 | 39篇 |
2018年 | 31篇 |
2017年 | 37篇 |
2016年 | 40篇 |
2015年 | 47篇 |
2014年 | 46篇 |
2013年 | 71篇 |
2012年 | 65篇 |
2011年 | 78篇 |
2010年 | 90篇 |
2009年 | 50篇 |
2008年 | 88篇 |
2007年 | 60篇 |
2006年 | 46篇 |
2005年 | 32篇 |
2004年 | 35篇 |
2003年 | 32篇 |
2002年 | 27篇 |
2001年 | 17篇 |
2000年 | 16篇 |
1999年 | 21篇 |
1998年 | 16篇 |
1997年 | 19篇 |
1996年 | 7篇 |
1995年 | 8篇 |
1994年 | 15篇 |
1993年 | 12篇 |
1992年 | 10篇 |
1991年 | 11篇 |
1990年 | 3篇 |
1989年 | 3篇 |
1988年 | 5篇 |
1987年 | 5篇 |
1986年 | 2篇 |
1983年 | 4篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1971年 | 1篇 |
1970年 | 1篇 |
排序方式: 共有1230条查询结果,搜索用时 593 毫秒
991.
Philippe Blanchard Claudia Malacrida Clment Cabanetos Jean Roncali Sabine Ludwigs 《Polymer International》2019,68(4):589-606
This review article gives an overview of past and current activities in the Linear Conjugated Systems Group of Angers and in the IPOC – Functional Polymers Group of the Institute of Polymer Chemistry of Stuttgart on the use of triphenylamine (TPA) as versatile building block for organic electronics. In the first part, the properties of TPA itself are introduced including geometrical and energy level considerations. Dimerization of TPA to tetraphenylbenzidine upon electrochemical oxidation is highlighted. The blocking of TPA para‐positions and its implications in terms of electroactivity is further discussed. The second part shows that dimerization of TPA as pendant redox‐active moieties in polymers is a versatile strategy to crosslink polymer films. Coming from redox homopolymers the crosslinking strategy is extended towards conjugated redox polymers based on polythiophenes and block copolymers. Conductivity mechanisms and the influence of doping level on conductivity are probed with cyclic voltammetry coupled with in situ conductance and four‐point probe measurements. The last part is dedicated to the use of TPA as an electron‐donating block in the design of donor‐π‐acceptor chromophores and their use as active material in organic photovoltaics. An overview of some relevant TPA‐based push–pull molecules from the literature and our contribution to this field is presented emphasizing the progress of the photovoltaic performance of organic solar cells made over the last decade. © 2018 Society of Chemical Industry 相似文献
992.
Angelika Lenz Philipp Arnold Reinhold Schneider Sabine Frick Yavuz Caydamli 《材料科学与工程:中英文B版...》2020,(2):74-83
The monitoring of mechanical deformation and damage of composite materials is normally performed by established analytical methods,such as strain gauges and opt... 相似文献
993.
Ella Watkins-Dulaney Sabine Straathof Prof. Frances Arnold 《Chembiochem : a European journal of chemical biology》2021,22(1):5-16
Tryptophan synthase (TrpS) has emerged as a paragon of noncanonical amino acid (ncAA) synthesis and is an ideal biocatalyst for synthetic and biological applications. TrpS catalyzes an irreversible, C−C bond-forming reaction between indole and serine to make l -tryptophan; native TrpS complexes possess fairly broad specificity for indole analogues, but are difficult to engineer to extend substrate scope or to confer other useful properties due to allosteric constraints and their heterodimeric structure. Directed evolution freed the catalytically relevant TrpS β-subunit (TrpB) from allosteric regulation by its TrpA partner and has enabled dramatic expansion of the enzyme's substrate scope. This review examines the long and storied career of TrpS from the perspective of its application in ncAA synthesis and biocatalytic cascades. 相似文献
994.
The manifold possibilities to apply coatings made from biopolymers require the design of such membranes with functional properties. The influence of different additives and process parameters on the mechanical stability and penetrability of biopolymer membranes, especially of films based on alginates, is given in this work. Spheres of alginates made by the falling droplet method were used as model system. Besides different effects of additives it turned out that the mechanical stability and the penetrability could be influenced independently. 相似文献
995.
Sabine Wulfkuehler Lisa Kurfiss Dietmar R. Kammerer Agnes Weiss Herbert Schmidt Reinhold Carle 《European Food Research and Technology》2013,236(2):229-241
The objective of this study was to determine the effects of alternative washing procedures on fresh-cut iceberg lettuce and endive, applying warm water (45 °C), warm water with CaCl2 (1 g/L), and chlorinated water (4 °C, 120 ppm), respectively. Processing was conducted on pre-industrial scale, and the produce was subsequently stored in consumer-sized bags (4 °C, 10 days). O2 and CO2 levels in the modified atmosphere, and activities of phenylalanine ammonia-lyase (PAL), peroxidase (POD) and polyphenoloxidase (PPO) of the samples were analyzed. Counts of total aerobic bacteria and pseudomonades were determined on the produce and in the process water. In both commodities, wound-induced PAL activities were significantly reduced by warm water treatment. In iceberg lettuce, adding CaCl2 to warm water resulted in a further reduction of PAL activities. Chlorinated water was less effective than warm water in suppressing wound-induced PAL activity in endive, but proved to be most effective in reducing total microbial cell counts by 1.1 and 2.1 log10 cfu/g in iceberg lettuce and endive, respectively. Warm water treatment exhibited reduction rates of similar magnitudes. For process water, chlorine proved to be the most efficient sanitizer. PPO and POD activities were only marginally affected by the different washing procedures. As indicated by respiration of the fresh-cut produce, warm water treatments applied retained the vitality of both plant species. The results suggest that warm water treatments are suitable measures to improve the quality of iceberg lettuce and endive, but were less efficient in sanitizing the process water. 相似文献
996.
Two ternary systems of fats were studied. In the first system, low-erucic acid rapeseed oil (LERO), hydrogenated lowerucic
acid rapeseed oil (HLERO), and palm oil (PO) were blended. In the second system, hydrogenated palm oil (HPO) was used instead
of PO and was blended with LERO and HLERO. The blends were then studied for their physical properties such as solid fat content
(SFC), melting curves by DSC, and polymorphism (X-ray). HPO showed the highest melting enthalpy after 48 h at 15°C (141±1
J/g), followed by HLERO (131±2 J/g), PO (110±2 J/g), and LERO (65±4 J/g). Binary phase behavior diagrams were constructed
from the DSC and X-ray results. Iso-line diagrams of partial-melting enthalpies were constructed from the DSC results, and
binary and ternary isosolid diagrams were constructed from the NMR results. The isosolid diagrams demonstrated formation of
a eutectic along the binary blend of PO/HLERO. However, no eutectic effect was observed along the binary lines of HPO/HLERO,
PO/LERO, HPO/LERO, or HLERO/LERO. The same results were found with the iso-line diagrams of partial-melting enthalpies. As
expected, addition of PO or HPO increased polymorphic stability in the β′ form of the HLERO/LERO mixture. 相似文献
997.
Michael Hävecker Sabine Wrabetz Jutta Kröhnert Lenard-Istvan Csepei Raoul Naumann d’Alnoncourt Yury V. Kolen’ko Frank Girgsdies Robert Schlögl Annette Trunschke 《Journal of Catalysis》2012,285(1):48-60
The surface of a highly crystalline MoVTeNb oxide catalyst for selective oxidation of propane to acrylic acid composed of the M1 phase has been studied by infrared spectroscopy, microcalorimetry, and in situ photoelectron spectroscopy. The acid–base properties of the catalyst have been probed by NH3 adsorption showing mainly Brønsted acidity that is weak with respect to concentration and strength of sites. Adsorption of propane on the activated catalyst reveals the presence of a high number of energetically homogeneous propane adsorption sites, which is evidenced by constant differential heat of propane adsorption qdiff,initial = 57 kJ mol?1 until the monolayer coverage is reached that corresponds to a surface density of approximately 3 propane molecules per nm2 at 313 K. The decrease of the heat to qdiff,initial = 40 kJ mol?1 after catalysis implies that the surface is restructured under reaction conditions. The changes have been analyzed with high-pressure in situ XPS while the catalyst was working applying reaction temperatures between 323 and 693 K, different feed compositions containing 0 mol.% and 40 mol.% steam and prolonged reaction times. The catalytic performance during the XPS experiments measured by mass spectrometry is in good agreement with studies in fixed-bed reactors at atmospheric pressure demonstrating that the XPS results taken under operation show the relevant active surface state. The experiments confirm that the surface composition of the M1 phase differs significantly from the bulk implying that the catalytically active sites are no part of the M1 crystal structure and occur on all terminating planes. Acrylic acid formation correlates with surface depletion in Mo6+ and enrichment in V5+ sites. In the presence of steam in the feed, the active ensemble for acrylic acid formation appears to consist of V5+ oxo-species in close vicinity to Te4+ sites in a Te/V ratio of 1.4. The active sites are formed under propane oxidation conditions and are embedded in a thin layer enriched in V, Te, and Nb on the surface of the structural stable self-supporting M1 phase. 相似文献
998.
Beata Korchowiec Jacek Korchowiec Klaudia Kwieciska Reneta Gevrenova Sabine Bouguet-Bonnet Cheng Deng Max Henry Ewa Rogalska 《International journal of molecular sciences》2022,23(6)
In view of the possible medical applications of saponins, the molecular structure of a GOTCAB saponin from the roots of Gypsophila paniculata L. was determined by NMR. The biological activity of saponins may depend on the interaction with cell membranes. To obtain more insight in the mechanism of membrane-related saponin function, an experimental and theoretical study was conducted. Ternary lipid systems composed of sphingomyelin, 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine, and cholesterol were used as models of mammalian cell membranes. The membrane–saponin interaction was studied experimentally by monitoring surface pressure in the monomolecular films formed at the air–aqueous subphase interface. The behavior of GOTCAB saponin in a water box and model monolayer systems was characterized by molecular dynamics simulations. The results obtained showed that, in the systems used, cholesterol had a decisive effect on the interaction between GOTCAB and phosphocholine or sphingomyelin as well as on its location within the lipid film. 相似文献
999.
Sabine Bernegger Miroslaw Jarzab Silja Wessler Gernot Posselt 《International journal of molecular sciences》2022,23(5)
Gastric cancer is a leading cause of cancer-related death, and a large proportion of cases are inseparably linked to infections with the bacterial pathogen and type I carcinogen Helicobacter pylori. The development of gastric cancer follows a cascade of transformative tissue events in an inflammatory environment. Proteases of host origin as well as H. pylori-derived proteases contribute to disease progression at every stage, from chronic gastritis to gastric cancer. In the present article, we discuss the importance of (metallo-)proteases in colonization, epithelial inflammation, and barrier disruption in tissue transformation, deregulation of cell proliferation and cell death, as well as tumor metastasis and neoangiogenesis. Proteases of the matrix metalloproteinase (MMP) and a disintegrin and metalloproteinase domain-containing protein (ADAM) families, caspases, calpain, and the H. pylori proteases HtrA, Hp1012, and Hp0169 cleave substrates including extracellular matrix molecules, chemokines, and cytokines, as well as their cognate receptors, and thus shape the pathogenic microenvironment. This review aims to summarize the current understanding of how proteases contribute to disease progression in the gastric compartment. 相似文献
1000.