全文获取类型
收费全文 | 1405篇 |
免费 | 61篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 23篇 |
综合类 | 36篇 |
化学工业 | 306篇 |
金属工艺 | 25篇 |
机械仪表 | 12篇 |
建筑科学 | 125篇 |
矿业工程 | 4篇 |
能源动力 | 45篇 |
轻工业 | 174篇 |
水利工程 | 3篇 |
无线电 | 93篇 |
一般工业技术 | 231篇 |
冶金工业 | 180篇 |
原子能技术 | 5篇 |
自动化技术 | 206篇 |
出版年
2023年 | 13篇 |
2022年 | 23篇 |
2021年 | 39篇 |
2020年 | 35篇 |
2019年 | 26篇 |
2018年 | 26篇 |
2017年 | 31篇 |
2016年 | 56篇 |
2015年 | 35篇 |
2014年 | 47篇 |
2013年 | 75篇 |
2012年 | 46篇 |
2011年 | 87篇 |
2010年 | 74篇 |
2009年 | 73篇 |
2008年 | 87篇 |
2007年 | 75篇 |
2006年 | 76篇 |
2005年 | 65篇 |
2004年 | 35篇 |
2003年 | 38篇 |
2002年 | 21篇 |
2001年 | 27篇 |
2000年 | 19篇 |
1999年 | 35篇 |
1998年 | 56篇 |
1997年 | 39篇 |
1996年 | 16篇 |
1995年 | 16篇 |
1994年 | 15篇 |
1993年 | 19篇 |
1992年 | 11篇 |
1991年 | 18篇 |
1990年 | 5篇 |
1989年 | 10篇 |
1988年 | 8篇 |
1987年 | 6篇 |
1985年 | 6篇 |
1984年 | 8篇 |
1982年 | 4篇 |
1981年 | 5篇 |
1980年 | 5篇 |
1979年 | 8篇 |
1978年 | 5篇 |
1977年 | 8篇 |
1976年 | 9篇 |
1971年 | 4篇 |
1970年 | 3篇 |
1967年 | 3篇 |
1966年 | 3篇 |
排序方式: 共有1468条查询结果,搜索用时 140 毫秒
1.
The objective of this study was to determine the disturbances of urea in serum and urine of endurance trained volunteers during prolonged exposure to hypokinesia (decreased number of km/day). The studies during hypokinesia (HK) were performed for 364 days on twenty long-distance runners in the age of 23 to 26 years, with an average peak oxygen uptake, of 66 ml.kg.min-1. All volunteers were divided into two equal groups: Ten volunteers were placed on a continuous regime of exercise 14.8 km/day and served as control subjects (CS). The remaining volunteers were subjected to continuous HK without the use of any preventive measures and were considered as the hypokinetic subjects (HS). For the simulation of the hypokinetic effect, the HS were kept continuously under an average of 2.7 km/day for the duration of the study. Prior to exposure to HK, the HS were on the same exercise regime as the CS. During a 60 day pre-HK period and during the experimental period, urinary excretion of urea, creatinine, sodium, potassium and calcium and concentrations thereof in serum were measured. In the HS the concentrations of urea, creatinine, sodium, potassium and calcium in serum and the rate of excretion thereof in urine increased significantly when compared to the CS. It was concluded that prolonged restriction of muscular activity induces significant disturbances of urea in serum and urine of endurance trained volunteers. 相似文献
2.
3.
A system for person-independent classification of hand postures against complex backgrounds in video images is presented. The system employs elastic graph matching, which has already been successfully applied for object and face recognition. We use the bunch graph technique to model variance in hand posture appearance between different subjects and variance in backgrounds. Our system does not need a separate segmentation stage but closely integrates finding the object boundaries with posture classification. 相似文献
4.
Matthias Zobel Joachim Denzler Benno Heigl Elmar Nöth Dietrich Paulus Jochen Schmidt Georg Stemmer 《Machine Vision and Applications》2003,14(1):26-34
Abstract. This contribution introduces MOBSY, a fully integrated, autonomous mobile service robot system. It acts as an automatic dialogue-based
receptionist for visitors to our institute. MOBSY incorporates many techniques from different research areas into one working
stand-alone system. The techniques involved range from computer vision over speech understanding to classical robotics.
Along with the two main aspects of vision and speech, we also focus on the integration aspect, both on the methodological
and on the technical level. We describe the task and the techniques involved. Finally, we discuss the experiences that we
gained with MOBSY during a live performance at our institute. 相似文献
5.
It is well recognized that performance changes over time. However, the effect of these changes on overall assessments of performance is largely unknown. In a laboratory experiment, we examined the influence of salient Gestalt characteristics of a dynamic performance profile on supervisory ratings. We manipulated performance trend (flat, linear-improving, linear-deteriorating, U-shaped, and ∩-shaped), performance variation (small, large), and performance mean (negative, zero, positive) within subjects and display format (graphic, tabular) between subjects. Participants received and evaluated information about the weekly performance of different employees over a simulated 26-week period. Results showed strong main effects on performance ratings of both performance mean and performance trend, as well as interactions with display format. Theoretical and practical implications of the results are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
6.
Awareness of the construction environment can be improved by automatic three-dimensional (3D) sensing and modeling of job sites in real time. Commercially available 3D modeling approaches based on range scanning techniques are capable of modeling static objects only, and thus cannot model dynamic objects in real time in an environment comprised of moving humans, equipment, and materials. Emerging prototype video range cameras offer an alternative by facilitating affordable, wide field of view, dynamic object tracking at frame rates better than 1?Hz (real time). This paper describes a methodology to model, detect, and track the position of static and moving objects in real time, based on data obtained from video range cameras. Experiments with this technology have produced results that indicate that video rate 3D data acquisition and analysis of construction environments can support effective modeling, detection, and tracking of project resources. This approach to job site awareness has inherent value and broad application. In combination with effective management practices and other sensing techniques, this technology has the potential to significantly improve safety on construction job sites. 相似文献
7.
The paper deals with a physical model for the calculation of the strip temperature in a hot rolling mill. Beside the heat transfer from the strip to the environment in the different mill sections a sub‐model for the material properties of steel including phase transitions is introduced. For the application in a process automation system an online adaptation of the model to the current state of the mill is indispensable. The adaptation is explained in detail. 相似文献
8.
9.
Weight-loss kinetics were studied for 10 industrial extruded samples of poly(vinyl chloride) (PVC) plasticized by 20–30% by weight of didecylphtalate at 85, 95, 105, 110, and 120deg;C. For the most unstable samples, which contained a light coplasticizer, the weight-loss rate obeyed Fick's law. In the other cases, it was constant in the early period of exposure. The apparent Arrhenius parameters (i.e., preexponential factor and activation energy) were intercorrelated and varied strongly from one sample to another. This was explained by the existence of two distinct kinetic regimes corresponding, respectively, to diffusion or evaporation, the whole process being controlled by the slowest step, and a transition between both regimes occurring in the temperature range of exposure. In the proposed model, small changes of the preexponential factor of diffusion from one sample to another are sufficient to take into account the observed behavior. 相似文献
10.
F Petersen H Z?hner JW Metzger S Freund RP Hummel 《Canadian Metallurgical Quarterly》1993,46(7):1126-1138
During germination spores of Streptomyces viridochromogenes NRRL B-1551 excrete a compound, germicidin, which has an inhibitory effect on the germination of its own arthrospores at a concentration as low as 200 pM (40 pg/ml). At higher concentrations germicidin inhibits porcine Na+/K(+)-activated ATPase and retards the germination of the cress Lepidium sativum. Germicidin is the first known autoregulative inhibitor of spore germination in the genus Streptomyces and was isolated from the supernatant of germinated spores, but also from the supernatant of the submerged culture. Spectroscopic analysis and derivatization reactions revealed germicidin to be 6-(2-butyl)-3-ethyl-4-hydroxy-2-pyrone (C11H16O3). Crude isolates of germicidin from the supernatant of submerged culture, but not from the spores, contained a second, structurally very similar compound (C10H14O3), in which in contrast to germicidin a 2-propyl instead of the 2-butyl chain was bound to C-6 and which did not show any activity in the germination and ATPase assay. The germination assay was evaluated as a new screening model for specifically active compounds. 相似文献