全文获取类型
收费全文 | 554篇 |
免费 | 29篇 |
专业分类
电工技术 | 6篇 |
综合类 | 3篇 |
化学工业 | 208篇 |
金属工艺 | 12篇 |
机械仪表 | 7篇 |
建筑科学 | 27篇 |
矿业工程 | 3篇 |
能源动力 | 6篇 |
轻工业 | 83篇 |
水利工程 | 3篇 |
无线电 | 19篇 |
一般工业技术 | 78篇 |
冶金工业 | 29篇 |
原子能技术 | 2篇 |
自动化技术 | 97篇 |
出版年
2024年 | 2篇 |
2023年 | 9篇 |
2022年 | 24篇 |
2021年 | 29篇 |
2020年 | 11篇 |
2019年 | 16篇 |
2018年 | 8篇 |
2017年 | 11篇 |
2016年 | 22篇 |
2015年 | 17篇 |
2014年 | 17篇 |
2013年 | 35篇 |
2012年 | 31篇 |
2011年 | 36篇 |
2010年 | 31篇 |
2009年 | 46篇 |
2008年 | 38篇 |
2007年 | 28篇 |
2006年 | 35篇 |
2005年 | 19篇 |
2004年 | 23篇 |
2003年 | 23篇 |
2002年 | 14篇 |
2001年 | 9篇 |
2000年 | 6篇 |
1999年 | 9篇 |
1998年 | 3篇 |
1996年 | 2篇 |
1995年 | 4篇 |
1994年 | 6篇 |
1993年 | 2篇 |
1992年 | 4篇 |
1991年 | 2篇 |
1989年 | 3篇 |
1988年 | 3篇 |
1984年 | 1篇 |
1981年 | 2篇 |
1978年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有583条查询结果,搜索用时 15 毫秒
51.
Which objects and animals are children willing to accept as referents for words they know? To answer this question, the authors assessed early word comprehension using the preferential looking task. Children were shown 2 stimuli side by side (a target and a distractor) and heard the target stimulus named. The target stimulus was either a typical or an atypical exemplar of the named category. It was predicted that children first connect typical examples with the target name and broaden the extension of the name as they get older to include less typical examples. Experiment 1 shows that when targets are named, 12-month-olds display an increase in target looking for typical but not atypical targets whereas 24-month-olds display an increase for both. Experiment 2 shows that 18-month-olds display a pattern similar to that of 24-month-olds. Implications for the early development of word comprehension are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
52.
53.
Kerstin Hannemann Volker Puchta Ernst Simon Herta Ziegler Gunter Ziegler Gerhard Spiteller 《Lipids》1989,24(4):296-298
The observation that F-acids (1) occur in rat chow initiated a search for F-acids in human diet. We observed that the amount
of F-acids with a pentyl side chain in α-position taken up with a one-day diet correlates well with the amount of excreted
degradation products, the pentyl urofuran acids (2), (3) and (4). Therefore it can be concluded that F-acids with a pentyl
side chain are not produced in the human body but are introduced through the diet. The origin of F-acids carrying an α-propyl
side chain is less clear. The amount of propyl-urofuran acids (2) and (3) excreted in urine was found in one case out of three
to be five times higher than the amount of F-acids carrying a propyl group in α-position taken up by the diet. Therefore,
it can presently not be excluded that a portion of the propyl F-acids is produced by the body.
F-acids found in human food are mainly introduced into the body by vegetables and fruits. F-acids were found also in birch
leaves in considerable amounts, as well as in grasses, dandelion and clover leaves. Thus, we can conclude that F-acids are
common constituents of plants. 相似文献
54.
55.
Matt Harrington Michael Lin Kerstin N. Nordstrom Wolfgang Losert 《Granular Matter》2014,16(2):185-191
Many recent advances in the study of granular media have stemmed from the improved capability to image and track individual grains in two and three dimensions. While two-dimensional systems readily yield both translational and rotational motion, a challenge in three-dimensional experiments is the tracking of rotational motion of isotropic particles. We propose an extension of the refractive index matched scanning technique as a method of measuring individual particle rotation. Initial measurements indicate that shear-driven rotational motion may stem from gear-like motion within the shear zone. 相似文献
56.
Alexander Pyattaev Jiri Hosek Kerstin Johnsson Radko Krkos Mikhail Gerasimenko Pavel Masek Aleksandr Ometov Sergey Andreev Jakub Sedy Vit Novotny Yevgeni Koucheryavy 《ETRI Journal》2015,37(5):877-887
This paper is a first‐hand summary on our comprehensive live trial of cellular‐assisted device‐to‐device (D2D) communications currently being ratified by the standards community for next‐generation mobile broadband networks. In our test implementation, we employ a full‐featured 3GPP LTE network deployment and augment it with all necessary support to provide real‐time D2D connectivity over emerging Wi‐Fi‐Direct (WFD) technology. As a result, our LTE‐assisted WFD D2D system enjoys the required flexibility while meeting the existing standards in every feasible detail. Further, this paper provides an account on the extensive measurement campaign conducted with our implementation. The resulting real‐world measurements from this campaign quantify the numerical effects of D2D functionality on the resultant system performance. Consequently, they shed light on the general applicability of LTE‐assisted WFD solutions and associated operational ranges. 相似文献
57.
Sven Thiele Kerstin Sempf Klaus Jaenicke-Roessler Lutz-Michael Berger Jörg Spatzier 《Journal of Thermal Spray Technology》2011,20(1-2):358-365
The development of new hardmetal coating applications such as fatigue-loaded parts, structural components, and tools for metal forming is connected with improvement of their performance and reliability. For modelling purposes, the knowledge of thermophysical, mechanical, and other material data is required. However, this information is still missing today. In this study, the thermophysical data of a WC-17Co coating sprayed with a liquid-fuelled HVOF-process from a commercial agglomerated and sintered feedstock powder from room temperature up to 700 °C was determined as an example. The dependence of the heat conductivity on temperature was obtained through measurement of the coefficient of thermal expansion, the specific heat capacity, and the thermal diffusivity. Heat conductivities ranging from 29.2 W/(mK) at 50 °C to 35.4 W/(mK) at 700 °C were determined. All measurements were performed twice (as-sprayed and after the first thermal cycle) to take into account the structural and compositional changes. Extensive XRD and FESEM studies were performed to characterize the phase compositions and microstructures in the as-sprayed and heat-treated states. Bulk samples obtained by spark plasma sintering from the feedstock powder were studied for comparison. 相似文献
58.
59.
A large dataset comprising output from an automatic milking (AM) system between 1999 and 2006 was examined and a total of 172 cow lactation curves and 68 heifer lactation curves were identified for further analysis. Relationships between milking frequency at different stages of lactation and lactation persistency and total lactation yield were determined. Cows had higher peak and total milk yields than heifers, but heifers had higher persistency (defined as the rate of decline in milk yield between days 100 and 300 post calving). Milking frequency did not differ significantly between cows and heifers in early lactation, but thereafter decreased significantly more in cows than in heifers. The effect of milking frequency on yield characteristics was analysed by comparing the highest and lowest quartiles for milking frequency. High milking frequency in early lactation was consistently associated with increased peak yield. High milking frequency averaged across the whole lactation was associated with increased peak yield in both cows and heifers, and with improved lactation persistency in cows only. This resulted in total lactation yield that was 21% greater in the high quartile cows compared with the low. 相似文献
60.
Kerstin Büchner Nadja Ehrhardt Brian P. Cahill Christian Hoffmann 《Thin solid films》2011,519(19):6480-6485
Internal reflection ellipsometry was used for detection of the consecutive coating of two polyelectrolytes, poly(allylamine hydrochloride) (PAH) and poly(acrylic acid) (PAA), onto a tantalum pentoxide (Ta2O5) substrate until the 10th bilayer. The UV patterned PAH-PAA-multilayer was characterized in air via ellipsometry and atomic force microscopy. Suited optical models enabled the determination of the layer thicknesses in wet and dry states. Linear multilayer formation could be proved by Attenuated Total Reflection — Fourier Transformed Infrared Spectroscopy measurements following the increase of the ν(C=O) band depending on the adsorption of the PAA. Streaming potential measurements after each layer deposition step indicated a change in surface charge after each layer deposition due to the consecutive coating of PAH and PAA. In this article the internal reflection ellipsometry is shown to be a convenient possibility to analyze the modification of a thin transparent Ta2O5 substrate. 相似文献