全文获取类型
收费全文 | 1039篇 |
免费 | 31篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 24篇 |
综合类 | 1篇 |
化学工业 | 263篇 |
金属工艺 | 14篇 |
机械仪表 | 20篇 |
建筑科学 | 71篇 |
矿业工程 | 1篇 |
能源动力 | 32篇 |
轻工业 | 185篇 |
水利工程 | 3篇 |
石油天然气 | 4篇 |
无线电 | 56篇 |
一般工业技术 | 174篇 |
冶金工业 | 78篇 |
原子能技术 | 5篇 |
自动化技术 | 140篇 |
出版年
2023年 | 5篇 |
2022年 | 17篇 |
2021年 | 21篇 |
2020年 | 10篇 |
2019年 | 10篇 |
2018年 | 13篇 |
2017年 | 26篇 |
2016年 | 18篇 |
2015年 | 16篇 |
2014年 | 17篇 |
2013年 | 26篇 |
2012年 | 42篇 |
2011年 | 71篇 |
2010年 | 52篇 |
2009年 | 47篇 |
2008年 | 58篇 |
2007年 | 71篇 |
2006年 | 39篇 |
2005年 | 48篇 |
2004年 | 31篇 |
2003年 | 30篇 |
2002年 | 26篇 |
2001年 | 25篇 |
2000年 | 33篇 |
1999年 | 19篇 |
1998年 | 36篇 |
1997年 | 23篇 |
1996年 | 17篇 |
1995年 | 26篇 |
1994年 | 19篇 |
1993年 | 9篇 |
1992年 | 13篇 |
1991年 | 7篇 |
1990年 | 13篇 |
1989年 | 12篇 |
1988年 | 9篇 |
1987年 | 6篇 |
1985年 | 6篇 |
1984年 | 8篇 |
1983年 | 11篇 |
1982年 | 9篇 |
1980年 | 11篇 |
1978年 | 5篇 |
1976年 | 10篇 |
1975年 | 4篇 |
1974年 | 4篇 |
1969年 | 3篇 |
1967年 | 3篇 |
1925年 | 4篇 |
1904年 | 3篇 |
排序方式: 共有1071条查询结果,搜索用时 31 毫秒
101.
The ability of nonproteolytic Clostridium botulinum type B spores to grow and produce toxin in cooked, uncured turkey packaged under modified atmospheres was investigated at refrigeration and mild to moderate abuse temperatures. Cook-in-bag turkey breast was carved into small chunks, surface-inoculated with a mixture of nonproteolytic C. botulinum type B spores, packaged in O2-impermeable bags under two modified atmospheres (100% N2 and 30% CO2:70% N2), and stored at 4, 10, and 15 degrees C. Samples were analyzed for botulinal toxin and indigenous microorganisms, as well as subjected to sensory evaluation, on days 0, 7, 14, 28, 42, and 60. Given sufficient incubation time, nonproteolytic C. botulinum type B grew and produced toxin in all temperature and modified atmosphere treatment combinations. At moderate temperature abuse (15 degrees C), toxin was detected by day 7, independent of packaging atmosphere. At mild temperature abuse (10 degrees C), toxin was detected by day 14, also independent of packaging atmosphere. At refrigeration temperature (4 degrees C), toxin was detected by day 14 in product packaged under 100% N2 and by day 28 in product packaged under 30% CO2:70% N2. Reduced storage temperature significantly delayed toxin production and extended the period of sensory acceptability of cooked turkey, but even strict refrigeration did not prevent growth and toxigenesis by nonproteolytic C. botulinum. At all three storage temperatures, toxin detection preceded or coincided with development of sensory characteristics of spoilage, demonstrating the potential for consumption of toxic product when spoilage-signaling sensory cues are absent. 相似文献
102.
Raphael Geiger Rainer Perren Roland Kuenzli Felix Escher 《Journal of food science》2005,70(2):E124-E130
ABSTRACT: Evolution of carbon dioxide and water vapor during roasting of coffee was followed in an isothermal high-temperature short-time and a low-temperature long-time roasting process. In addition, CO2 release during storage of roasted beans was followed. CO2 and water vapor concentration were assayed in the exhaust air by nondispersive infrared gas analysis. Although CO2 evolution rates differed in the 2 processes, the final total amount of CO2 released after 63 d of storage remained equal. CO2 evolution and differentiation between evaporation of initial water and chemically formed water showed that chemical reactions leading to relevant amounts of CO2 and water start at ap -proximately 180°C. A mass balance established on the present measurements was able to account fairly well for the gravimetrically measured roast loss. 相似文献
103.
Matthias Jger Claus Jordan Alwin Luttmann Wolfgang Laurig DOLLY Group 《International Journal of Industrial Ergonomics》2000,25(6):644-571
The load on the lumbar spine during occupational manual materials handling was previously investigated with respect to short activity sections or to specified load-handling types such as lifting or carrying. Within the so-called Dortmund Lumbar Load Study, analysis of the occupationally induced load on the lumbar spine during total working shifts in the field of surface construction, drop forge, industrial meat processing, and refuse collection was performed on the shop-floor. The body postures adopted, the action forces applied at the hands, and the resultant lumbar load for all load-handling tasks were analysed for 2 shifts in each field on the basis of video evaluations. Via a newly developed detailed classification procedure, the spatial position of the body segments as well as amplitude and direction of the action forces were described in a detailed manner. Consecutive biomechanical model calculations lead, for total shifts, to time courses of various measures for the load on the lumbar spine, such as flexion or torsional moments of force as well as compression and shear forces at the lumbosacral disc. In relation to recommended limits for the maximal disc compression provided in the literature, lumbar load is exceeded in numerous situations during a shift, in particular, with regard to persons of higher age. In a “dose model” applied in this study, the cumulative effect of single-task exposures was considered by superproportional weighting of the compressive force with respect to the corresponding duration of a working task.
Relevance to industry
A comprehensive evaluation of lumbar load for complete shifts is presented considering the real shop-floor conditions. Analyses for dustbin removal, surface construction and industrial meat processing have discovered numerous exceedings of lumbar-load limits. Such tasks should not be performed by older persons from the preventive point of view. 相似文献
104.
105.
Zusammenfassung Ziel dieses Artikels ist es, einen überblick über technische Sicherheitsl?sungen für Intranets zu geben. Ein Modell, das
die Anforderungen an ein Sicherheitssystem in Form von abstrakten Diensten abbildet, dient dazu, verschiedene L?sungsalternativen
zur Realisierung der unterschiedlichen Dienste auf Basis offener Standards oder generalisierter Produktklassen beurteilen
zu k?nnen. Darauf aufbauend wird eine beispielhafte Referenzarchitektur für Unternehmen auf Basis einer X.509 Public-Key-Infrastruktur
entworfen.
相似文献
106.
Supported gold catalysts, e.g., Au on Al2O3, Fe2O3, CeO2, MnO2, TiO2, ZrO2, activated carbon, titanium silicalite TS‐1, were prepared and used for the isomerization of linoleic acid (cis‐9,cis‐12‐octadecadienoic acid) to conjugated linoleic acids (CLA) in the presence of hydrogen at 165 °C in a batch reactor. The best results were obtained using a catalyst with 2 wt % Au on TS‐1, which exhibits a high selectivity (78 %) towards CLA. The two biologically active target CLA isomers, i.e., cis‐9,trans‐11‐CLA and trans‐10,cis‐12‐CLA, were the main products. During the isomerization of linoleic acid to CLA, consecutive reactions also took place. These were the hydrogenation of linoleic acid and CLA to monounsaturated octadecenoic acids and the further hydrogenation of monounsaturated acids to stearic acid. Thus, gold catalysts are capable of isomerizing linoleic acid to CLA and hydrogenating their double bonds to an extent that depends on the Au catalyst used. 相似文献
107.
Detlef Stiller Birgit Gaschler-Markefski Frank Baumgart Frank Schindler Claus Tempelmann Hans-Jochen Heinze henning Scheich 《Magma (New York, N.Y.)》1997,5(4):275-284
Prosodic modulation of speech provides information about emotional states of speakers (affective prosodies) or serves as syntactic
markers to change linguistic aspects of speech (linguistic prosodies). Previous electrophysiological investigations and studies
on patients with right or left hemisphere damage showed nonuniform results with respect to lateralization of prosodic processing.
In this study 20 healthy right-handed volunteers were investigated with functional magnetic resonance imaging of the acoustically
responsive areas on the supratemporal plane while detecting phonemes as control targets or prosodies in strings of nonsense
syllables and adjectives, the latter randomly intonated in a declarative, interrogative, commanding, happy, or sad fashion.
In control task A the phoneme /a/ was detected in the syllables. In control task B the phoneme /a/ was detected in the adjectives,
and in the experimental task C the sad intonations (affective) and in the experimental task D the interrogative intonations
(linguistic) had to be detected in the same material. In task A intensity-weighted volumes of activated voxels were not different
in the two hemispheres (laterality index 0). In task B with an irrelevant phoneme detection with respect to prosodic material,
the population split into two subgroups with similar right or left hemispheric lateralization of activity leading to an absolute
laterality index of 26.8 across all subjects. During detection of affective prosodies (task C), lateralization was maintained
yet the absolute laterality index reduced to 14.5, while there was no lateralization during detection of linguistic prosodies.
The sum of activations in the two hemispheres was the same across all tasks and subgroups, which suggests that the lateralizations
occurring with presentation and detection of prosodic material depend on a redistribution of activity between hemispheres. 相似文献
108.
Volker Claus 《Informatik-Spektrum》2005,28(2):124-128
Ein Ranking beruht meist auf einer Abbildung einer endlichen Menge von (hochkomplexen) Strukturen auf die reelle Achse. 相似文献
109.
Simplified counter-current distribution procedures are described which allow correct analysis of the α acids and iso α acids content of hop extracts. 相似文献
110.
Masoud Kayhanian Amardeep Singh Claus Suverkropp Steve Borroum 《Canadian Metallurgical Quarterly》2003,129(11):975-990
The objective of this study was to evaluate correlations between annual average daily traffic (AADT) and storm water runoff pollutant concentrations generated from California Department of Transportation (Caltrans) highway sites. Analyses of data collected from the Caltrans four-year (1997–2001) highway runoff characterization program revealed that, in general, pollutant concentrations from urban highways were higher than those found from nonurban highways. For a limited number of pollutants, however, the concentrations from nonurban highways were found to be higher than the concentrations from urban highways. No direct linear correlation was found between highway runoff pollutant event mean concentrations and AADT. However, through multiple regression analyses, it was shown that AADT has an influence on most highway runoff constituent concentrations, in conjunction with factors associated with watershed characteristics and pollutant build-up and wash off. The other noticeable factors shown to influence the accumulation of pollutants on highways were antecedent dry period, drainage area, maximum rain intensity, and land use. 相似文献