全文获取类型
收费全文 | 4023篇 |
免费 | 132篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 80篇 |
综合类 | 6篇 |
化学工业 | 1008篇 |
金属工艺 | 66篇 |
机械仪表 | 68篇 |
建筑科学 | 299篇 |
矿业工程 | 17篇 |
能源动力 | 78篇 |
轻工业 | 610篇 |
水利工程 | 23篇 |
石油天然气 | 11篇 |
无线电 | 259篇 |
一般工业技术 | 530篇 |
冶金工业 | 555篇 |
原子能技术 | 27篇 |
自动化技术 | 522篇 |
出版年
2022年 | 43篇 |
2021年 | 50篇 |
2020年 | 39篇 |
2019年 | 52篇 |
2018年 | 52篇 |
2017年 | 41篇 |
2016年 | 87篇 |
2015年 | 74篇 |
2014年 | 134篇 |
2013年 | 188篇 |
2012年 | 172篇 |
2011年 | 152篇 |
2010年 | 147篇 |
2009年 | 167篇 |
2008年 | 171篇 |
2007年 | 150篇 |
2006年 | 170篇 |
2005年 | 130篇 |
2004年 | 122篇 |
2003年 | 109篇 |
2002年 | 62篇 |
2001年 | 55篇 |
2000年 | 65篇 |
1999年 | 56篇 |
1998年 | 86篇 |
1997年 | 64篇 |
1996年 | 46篇 |
1995年 | 35篇 |
1994年 | 53篇 |
1993年 | 46篇 |
1992年 | 41篇 |
1991年 | 42篇 |
1990年 | 45篇 |
1989年 | 45篇 |
1988年 | 41篇 |
1987年 | 53篇 |
1986年 | 35篇 |
1985年 | 56篇 |
1984年 | 60篇 |
1983年 | 41篇 |
1982年 | 34篇 |
1981年 | 45篇 |
1980年 | 52篇 |
1979年 | 41篇 |
1978年 | 39篇 |
1977年 | 51篇 |
1976年 | 52篇 |
1975年 | 33篇 |
1974年 | 40篇 |
1973年 | 32篇 |
排序方式: 共有4159条查询结果,搜索用时 15 毫秒
31.
Roland Wittmann und Karl Eichner 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1989,188(3):212-220
Zusammenfassung Bei der Maillard-Reaktion reagieren primär reduzierende Zucker mit den freien Aminogruppen der Aminosäuren. Dabei entstehen aus Aldosen als erste stabile Zwischenprodukte die 1-Aminosäure-1-desoxy-ketosen (Amadori-Verbindungen). In Malzen konnten zehn Amadori-Verbindungen quantitativ bestimmt werden. Sie entstehen während des Darrens des Malzes. Aufgrund unterschiedlicher Darrbedingungen unterscheiden sich die Malztypen im Gehalt und im Muster dieser Substanzen. Während der Erhitzungsvorgänge beim Brauprozeß (Maischen, Würzekochung) werden die Amadori-Verbindungen etwa zur Hälfte abgebaut, dagegen sind bei der an schließenden Gärung keine Veränderungen zu beobachten. Aus dem Gehalt und dem Muster der Amadori-Verbindungen im Bier können somit Rückschlüsse auf das verwendete Malz gezogen werden. Bei der Herstellung von Braucouleuren werden Ammoniak bzw. Ammoniumverbindungen als Aminokomponenten eingesetzt. Die Couleure enthalten deshalb keine 1-Aminosäure-l-desoxy-ketosen, dafür aber Desoxyfructosazine, die bei der Reaktion von Zuckern mit Ammoniak entstehen. Diese Pyrazinderivate wurden in Braucouleuren in hohen Mengen (2–6 g/100 g) gefunden. Es wird eine Methode vorgestellt, mit der ein Zusatz von Braucouleuren zum Bier über die Bestimmung der Desoxyfructosazine eindeutig nachgewiesen werden kann.
Detection of Maillard products in malts, beers, and brewing couleurs
During the Maillard reaction, the reducing sugars first react with the free amino groups of the amino acids. With aldoses, 1-amino-l-deoxyketoses (ketose-amino acids, Amadori compounds) are the first stable intermediates to be formed. In malts ten different Amadori compounds could be determined that formed during the kiln-drying of malt. Dependent on the kiln-drying conditions, the different types of malt contain different amounts and proportions of these compounds. During the brewing process (mashing, mash wort cooking) about half of the Amadori compounds are decomposed, whereas during fermentation no changes can be observed. Therefore the amount and composition of Amadori compounds detected in beer may indicate the type of malt used. During the production of brewing couleurs, ammonia or ammonium compounds react with sugars and deoxyfructosazines are formed. In brewing coleurs, relatively high amount of these pyrazine derivatives (2–6 g/100 g) could be found. An analytical method is described for the quantitative determination of deoxyfructosazines, indicating an addition of brewing couleur to beer.相似文献
32.
Zusammenfassung Der Hg-Gehalt von 16 Speisepilzarten aus verschiedenen geographischen Lagen wurde bestimmt. Die Werte lagen zwischen 18 ppb und 14300 ppb, bezogen auf die Pilztrockensubstanz. Die große Streubreite von über 3 Zehnerpotenzen konnte auf beträchtliche Unterschiede im Quecksilbergehalt zwischen den Pilzarten zurückgeführt werden. Neben anderen Faktoren ist die Hg-Konzentration wesentlich vom Rohproteingehalt der Pilzart abhängig. Zwischen diesen beiden Merkmalen wurde eine hochsignifikante positive Korrelation nachgewiesen.
Mercury-content of Austrian edible mushrooms and its relation to the protein content of the mushrooms
Summary The mercury content of 16 eatable mushroom species from different geographical areas was determined by flameless atomic absorption spectroscopy. Mercury levels lay between 18 and 14300 ppb related to mushroom dry matter. A. great difference in mercury content was found between species.Boletaceae, Lycoperdaceae, Agaricaceae etc. showed constantly high values (> 1000 ppb), but inCantharellaceae a low content (< 100 ppb) was recorded. Besides other factors the mercury concentration is essentially dependent on the protein content. A highly significant positive correlation between the two characteristics was found.相似文献
33.
The flavonol contents of the leaves and pods of peas are influenced particularly by the amount of light irradiation received, while varietal differences appear to be of lesser importance. The seeds contain only traces of flavonols (< 1 part/106). Broad beans on the other hand contain ca 30–70 parts/106 of flavonols, determined as kaempferol, quercetin and myricetin after hydrolysis of the respective glycosides. The flavonols are localised mainly in the skin. No myricetin could be detected in the pods and leaves. 相似文献
34.
Kyung‐Geun Lim Erjuan Guo Axel Fischer Qian Miao Karl Leo Hans Kleemann 《Advanced functional materials》2020,30(27)
Vertical organic transistors are an attractive alternative to realize short channel transistors, which are required for powerful electronic devices and flexible electronic circuits operating at high frequencies. Unfortunately, the vertical device architecture comes along with an increased device fabrication complexity, limiting the potential of this technology for application. A new design of vertical organic field‐effect transistors (VOFETs) with superior electrical performance and simplified processing is reported. By using electrochemical oxidized aluminum oxide (AlOx) as a pseudo self‐aligned charge‐blocking structure in vertical organic transistors, direct leakage current between the source and drain can be effectively suppressed, enabling VOFETs with very low off‐current levels despite the short channel length. The anodization technique is easy to apply and can be surprisingly used on both n‐type and p‐type organic semiconductor thin films with significant signs of degradation. Hence, the anodization technique enables a simplified process of high‐performance p‐type and n‐type VOFETs, paving the road toward complementary circuits made of vertical transistors. 相似文献
35.
36.
Microwave radiometry for cement kiln temperature measurements. 总被引:1,自引:0,他引:1
Karl D Stephan Lingyun Wang Eric Ryza 《The Journal of microwave power and electromagnetic energy》2007,40(3):140-144
The maximum temperature inside a cement kiln is a critical operating parameter, but is often difficult or impossible to measure. We present here the first data that show a correlation between cement kiln temperature measured using a microwave radiometer and product chemistry over an eight-hour period. The microwave radiometer senses radiation in the 12-13 GHz range and has been described previously [Stephan and Pearce (2002), JMPEE 37: 112-124]. 相似文献
37.
Gilja V Chestek CA Diester I Henderson JM Deisseroth K Shenoy KV 《IEEE transactions on bio-medical engineering》2011,58(7):1891-1899
Neural prosthetic systems aim to help disabled patients by translating neural signals from the brain into control signals for guiding computer cursors, prosthetic arms, and other assistive devices. Intracortical electrode arrays measure action potentials and local field potentials from individual neurons, or small populations of neurons, in the motor cortices and can provide considerable information for controlling prostheses. Despite several compelling proof-of-concept laboratory animal experiments and an initial human clinical trial, at least three key challenges remain which, if left unaddressed, may hamper the translation of these systems into widespread clinical use. We review these challenges: achieving able-bodied levels of performance across tasks and across environments, achieving robustness across multiple decades, and restoring able-bodied quality proprioception and somatosensation. We also describe some emerging opportunities for meeting these challenges. If these challenges can be largely or fully met, intracortically based neural prostheses may achieve true clinical viability and help increasing numbers of disabled patients. 相似文献
38.
Stijn F. L. Mertens Matthew Gara Alla S. Sologubenko Joachim Mayer Sönke Szidat Karl W. Krämer Timo Jacob David J. Schiffrin Thomas Wandlowski 《Advanced functional materials》2011,21(17):3259-3267
Dynamic core–shell nanoparticles have received increasing attention in recent years. This paper presents a detailed study of Au–Hg nanoalloys, whose composing elements show a large difference in cohesive energy. A simple method to prepare Au@Hg particles with precise control over the composition up to 15 atom% mercury is introduced, based on reacting a citrate stabilized gold sol with elemental mercury. Transmission electron microscopy shows an increase of particle size with increasing mercury content and, together with X‐ray powder diffraction, points towards the presence of a core–shell structure with a gold core surrounded by an Au–Hg solid solution layer. The amalgamation process is described by pseudo‐zero‐order reaction kinetics, which indicates slow dissolution of mercury in water as the rate determining step, followed by fast scavenging by nanoparticles in solution. Once adsorbed at the surface, slow diffusion of Hg into the particle lattice occurs, to a depth of ca. 3 nm, independent of Hg concentration. Discrete dipole approximation calculations relate the UV–vis spectra to the microscopic details of the nanoalloy structure. Segregation energies and metal distribution in the nanoalloys were modeled by density functional theory calculations. The results indicate slow metal interdiffusion at the nanoscale, which has important implications for synthetic methods aimed at core–shell particles. 相似文献
39.
Doug Williams Marian F. Ursu Joshan Meenowa Pablo Cesar Ian Kegel Karl Bergström 《Telematics and Informatics》2011
This paper discusses results from research related to the use of television as a device that supports social interaction between close-knit groups in settings that include more than two locations, each location being potentially equipped with more than one camera. The paper introduces the notion of a framing experience, as a specific scenario or situation within which social communication takes place. It reports on the evaluation of some of the key attributes of social communication through semi-structured interviews, with 16 families across four European countries. The inferences drawn from this study are reduced to four system capabilities including the ability to support: excitement, engagement and entertainment; high quality, reliable audiovisual communications; flexibility and adaptability sufficient to support the unpredictable and reactive nature of human interaction and discourse. These system requirements are, in turn, reduced to a number of technology challenges which if solved will help enable effective social communications between groups, mediated by the television. These technology challenges include: high quality reliable audio visual communication; interaction orchestration, multimedia interpretation and multimedia composition. Finally the paper reflects on the impact the use of framing experiences, such as those described here, could have on strategy and policy for service providers and regulators. 相似文献
40.
Christian Pacha Oliver Kessler Peter Glo¨seko¨tter Karl F. Goser Werner Prost Andreas Brennemann Uwe Auer Franz J. Tegude 《Analog Integrated Circuits and Signal Processing》2000,24(1):7-25
Quantum-effect devices utilizing resonant tunneling are promising candidates for future nano-scale integration. Originating from the technological progress of semiconductor technology, circuit architectures with reduced complexity are investigated by exploiting the negative-differential resistance of resonant tunneling devices. In this paper a resonant tunneling device threshold logic family based on the Monostable-Bistable Transition Logic Element (MOBILE) is proposed and applied to different parallel adder designs, such as ripple carry and binary carry lookahead adders. The basic device is a resonant tunneling transistor (RTT) composed of a resonant tunneling diode monolithically integrated on the drain contact layer of a heterostructure field effect transistor. On the circuit level the key components are a programmable NAND/NOR logic gate, threshold logic gates, and parallel counters. The special properties of MOBILE logic gates are considered by a bit-level pipelined circuit style. Experimental results are presented for the NAND/NOR logic gate. 相似文献