全文获取类型
收费全文 | 2267篇 |
免费 | 131篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 19篇 |
综合类 | 11篇 |
化学工业 | 556篇 |
金属工艺 | 63篇 |
机械仪表 | 47篇 |
建筑科学 | 138篇 |
矿业工程 | 24篇 |
能源动力 | 51篇 |
轻工业 | 128篇 |
水利工程 | 10篇 |
无线电 | 189篇 |
一般工业技术 | 471篇 |
冶金工业 | 123篇 |
原子能技术 | 21篇 |
自动化技术 | 553篇 |
出版年
2024年 | 2篇 |
2023年 | 30篇 |
2022年 | 43篇 |
2021年 | 68篇 |
2020年 | 65篇 |
2019年 | 54篇 |
2018年 | 68篇 |
2017年 | 54篇 |
2016年 | 82篇 |
2015年 | 82篇 |
2014年 | 83篇 |
2013年 | 197篇 |
2012年 | 162篇 |
2011年 | 176篇 |
2010年 | 146篇 |
2009年 | 147篇 |
2008年 | 149篇 |
2007年 | 133篇 |
2006年 | 112篇 |
2005年 | 86篇 |
2004年 | 64篇 |
2003年 | 65篇 |
2002年 | 50篇 |
2001年 | 29篇 |
2000年 | 24篇 |
1999年 | 35篇 |
1998年 | 25篇 |
1997年 | 17篇 |
1996年 | 19篇 |
1995年 | 16篇 |
1994年 | 12篇 |
1993年 | 15篇 |
1992年 | 17篇 |
1991年 | 8篇 |
1990年 | 10篇 |
1989年 | 9篇 |
1988年 | 6篇 |
1987年 | 6篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1984年 | 7篇 |
1983年 | 5篇 |
1981年 | 4篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1973年 | 2篇 |
1972年 | 2篇 |
1970年 | 2篇 |
1961年 | 1篇 |
1960年 | 2篇 |
排序方式: 共有2404条查询结果,搜索用时 15 毫秒
41.
Environmental monitoring aware routing: making environmental sensor networks more robust 总被引:2,自引:0,他引:2
Bernd-Ludwig Wenning Dirk Pesch Andreas Timm-Giel Carmelita Görg 《Telecommunication Systems》2010,43(1-2):3-11
Wireless Sensor Networks (WSNs) have a broad application range in the area of monitoring and surveillance tasks. Among these tasks, disaster detection or prevention in environmental scenarios is one typical application for WSN. Disasters may for example be forest fires, volcano outbreaks or flood disasters. Here, the monitored events have the potential to destroy the sensor devices themselves. This has implications for the network lifetime, performance and robustness. While a fairly large body of work addressing routing in WSNs exists, little attention has been paid to the aspect of node failures caused by the sensed phenomena themselves. This paper presents a proactive routing method that is aware of the node’s destruction threat and adapts the routes accordingly, before node failure results in broken routes, delay and power consuming route re-discovery. The performance of the presented routing scheme is evaluated and compared to OLSR based routing in the same scenario. 相似文献
42.
Photoresponsive Fiber Array: Toward Mimicking the Collective Motion of Cilia for Transport Applications 下载免费PDF全文
Anne Helene Gelebart Matthew Mc Bride Albertus P. H. J. Schenning Christopher N. Bowman Dirk J. Broer 《Advanced functional materials》2016,26(29):5322-5327
Remote transport of material is an utmost useful, but challenging, property expanding the design possibilities of many applications such as microfluidics or robotics where species can be carried without interfering with its environment. Nature has solved the problem of transport in e.g., the respiratory system by a concerted motion of cilia. This study addresses a new method to fabricate an array of small parallel fibers acting as cilia placed side by side on a substrate. The fibers consist of a crosslinked liquid crystal main chain polymer functionalized with coreactant azobenzene molecules. The fibers bend toward a light source in a concerted manner. When placed in a liquid, the cooperative bending motion of the fibers creates a flow able to efficiently carry objects. The proposed fabrication process of the fibers is scalable to large area and requires an optimized rheology which is achieved by converting low molecular weight reactive liquid crystal acrylate monomers to oligomers using a multiplication of the monomeric units by the Michael addition reaction with dithiol. The oligomer properties and the elasticity of the fibers are adjusted by changing the thiol spacer leading to optimized manufacturing and maximized optical response. 相似文献
43.
Microelectronics has revolutionized the architecture and design concepts of telecommunications products dramatically. Its strength is based on the combination of three different disciplines: technology, design automation and device architecture. The evolution in all these topics will be described and illustrated with several examples of telecommunications applications. At present vlsi circuits are used in three important business segments of the telecommunications market: switching, transmission and end-user systems. The technology requirements for these applications are followed by a brief discussion on reliability requirements and future technology trends. 相似文献
44.
A time series analysis of the development of bitterness units (BU) of a collective of 1,202 Pilsner beer samples analysed between 1983 and 2013 shows a small but statistically significant decline from values of around 30 BU in the 1980s to values of around 27 in the last years. The results confirm a trend to lower hopped Pilsner beers, which could derive from economic pressures on the breweries combined with a lack of regulations, or a change in consumer preference. So–called Pilsner beers with extremely low BU values are judged as a being misleading to the consumer, which is an offence against European food law. Copyright © 2015 The Institute of Brewing & Distilling 相似文献
45.
Dirk W. Lachenmeier Helmut Reusch Constanze Sproll Kerstin Schoeberl Thomas Kuballa 《Food additives & contaminants. Part A, Chemistry, analysis, control, exposure & risk assessment》2013,30(10):1216-1224
A survey of benzene contamination of 451 beverage samples, using headspace sampling combined with gas chromatography and mass spectrometry (HS-GC/MS) with a quantification limit of 0.13 µg l?1, was conducted. Artefactual benzene formation during headspace sampling was excluded by gentle heating at 50°C only and adjustment of sample pH to 10. The incidence of benzene contamination in soft drinks, beverages for babies, alcopops and beer-mixed drinks was relatively low, with average concentrations below the EU drinking-water limit of 1 µg l?1. Significantly higher concentrations were only found in carrot juice, with the highest levels in carrot juice specifically intended for infants. About 94% of 33 carrot juice for infants had detectable benzene levels, with an average concentration of 1.86?±?1.05 µg l?1. Benzene contamination of beverages was significantly correlated to iron and copper concentrations, which act as catalyst in benzene formation. The formation of benzene in carrot juice was predominantly caused by a heat-induced mechanism, which explains the higher levels in infant carrot juices that are subject to higher heat-treatment to exclude microbiological contamination. 相似文献
46.
Antioxidants, preferentially those of dietary origin, have for a long time been considered to help against diseases that are presumably aggravated by oxidative stress, such as cardiovascular diseases, cancer, and neurodegenerative disorders. The outcome of clinical trials undertaken to corroborate this hypothesis, however, remained largely inconclusive. Evidence is now emerging that some dietary "antioxidants" influence signaling pathways and the expression of genes relevant in atherosclerosis by mechanisms other than antioxidative ones. By concrete examples we show that (1) vitamin E has gene regulatory functions which might be more important than acting as an antioxidant in vivo, (2) selenium itself is not an antioxidant at all, and even not in general when incorporated into glutathione peroxidases, and (3) a moderate oxidative stress is beneficial rather than detrimental since it can induce defense mechanisms counteracting xenobiotic and oxidative stress. Thus, there is only a future for antioxidants in the prevention of any disease if their real mechanism of action is considered and suitable read-outs and biomarkers are established. 相似文献
47.
文章介绍了搭载人类自体干细胞的纤维支架技术及其在软组织再生中的应用优势。选用藻酸盐材料结合人体干细胞搭载关键技术制成的纤维支架,同时具有促进血管再生和触发成脂分化的能力。 相似文献
48.
Physiological relevance of food grade microcapsules: Impact of milk protein based microcapsules on inflammation in mouse models for inflammatory bowel diseases 下载免费PDF全文
Rebecca Würth Ilias Lagkouvardos Thomas Clavel Julia Wilke Petra Foerst Ulrich Kulozik Dirk Haller Gabriele Hörmannsperger 《Molecular nutrition & food research》2015,59(8):1629-1634
In order to increase beneficial effects of bioactive compounds in functional food and dietary supplements, enormous efforts are put in the technological development of microcapsules. Although these products are often tailor‐made for disease susceptible consumer, the physiological impact of microcapsule uptake on the respective target consumer has never been addressed. The present study aimed to assess the relevance of this aspect by analyzing the impact of milk protein based microcapsules on experimental inflammatory bowel disease. Long‐term feeding of sodium caseinate or rennet gel microcapsules resulted in significant alterations in the intestinal microbiota of healthy mice. In TNFΔARE/wt mice, a model for chronic ileal inflammation, rennet gel microcapsules resulted in further increased splenomegaly, whereas ileal inflammation was unchanged. In IL10?/? mice, a model for chronic colitis, both types of microcapsules induced a local increase of the intestinal inflammation. The present study is the first to demonstrate that, independent of their cargo, microcapsules have the potential to affect the intestinal microbiota and to exert unprecedented detrimental effects on disease‐susceptible individuals. In conclusion, the impact of microcapsule uptake on the respective target consumer groups should be thoroughly investigated in advance to their commercial use in functional food or dietary supplements. 相似文献
49.
Innovations in beef production systems that enhance the nutritional and health value of beef lipids and their relationship with meat quality 总被引:3,自引:0,他引:3
Scollan N Hocquette JF Nuernberg K Dannenberger D Richardson I Moloney A 《Meat science》2006,74(1):17-33
Consumers are becoming more aware of the relationships between diet and health and this has increased consumer interest in the nutritional value of foods. This is impacting on the demand for foods which contain functional components that play important roles in health maintenance and disease prevention. For beef, much attention has been given to lipids. This paper reviews strategies for increasing the content of beneficial omega-3 polyunsaturated fatty acids (PUFA) and conjugated linoleic acid (CLA) and reducing saturated fatty acids (SFA) in beef. Particular attention is given to intramuscular fat (IMF) and the relationships between fatty acid composition and key meat quality parameters including colour shelf life and sensory attributes. Despite the high levels of ruminal biohydrogenation of dietary PUFA, nutrition is the major route for increasing the content of beneficial fatty acids in beef. Feeding grass or concentrates containing linseed (rich in α-linolenic acid, 18:3n-3) in the diet increases the content of 18:3n-3 and its longer chain derivative eicosapentaenoic acid (EPA, 20:5n-3) in beef muscle and adipose tissue, resulting in a lower n-6:n-3 ratio. Grass feeding also increases docasahexaenoic acid (DHA, 22:6n-3). Feeding PUFA rich lipids which are protected from ruminal biohydrogenation result in further enhancement of the PUFA in meat with concomitant beneficial improvements in the ratio of polyunsaturated:saturated fatty acids (P:S ratio) and n-6:n-3 ratio. The main CLA isomer in beef is CLA cis-9, trans-11 and it is mainly associated with the triacylglycerol lipid fraction and therefore is positively correlated with level of fatness. The level of CLA cis-9, trans-11 in beef is related to (1) the amount of this isomer produced in the rumen and (2) synthesis in the tissue, by delta-9 desaturase, from ruminally produced trans vaccenic acid (18:1 trans-11; TVA). Feeding PUFA-rich diets increases the content of CLA cis-9, trans-11 in beef. Trans-fatty acids in foods are of rising importance and knowledge of the differential effects of the individual trans isomers is increasing. TVA is the major trans 18:1 isomer in beef and as the precursor for tissue CLA in both animals and man should be considered as a neutral or beneficial trans-isomer. Increasing the content of n-3 PUFA in beef can influence colour shelf life and sensory attributes of the meat. As the content of n-3 PUFA increases then sensory attributes such as "greasy" and "fishy" score higher and colour shelf life may be reduced. Under these situations, high levels of vitamin E are necessary to help stabilise the effects of incorporating high levels of long chain PUFA into meat. However, grass feeding not only increases n-3 PUFA and CLA but, due to its high content of vitamin E, colour shelf life is improved. It is evident that opportunities exist to enhance the content of health promoting fatty acids in beef and beef products offering opportunities to add value and contribute to market differentiation. However, it is imperative that these approaches to deliver "functional" attributes do not compromise on the health value (lipoperoxidation) or the taste of beef products. 相似文献
50.
描述了生物聚合物的创新应用.探索了两种趋势的原因.首先,最近三年中,原油价格猛涨,各种衍生物的价格也随之上涨,促使人们寻找其他可能的原料.其次,欧洲农业处于重大变革的前夜,环境法律的实施,向世界经济的开放以及补贴的减少,促使农业寻找新的市场.玉米和糖用甜菜可能是未来的出路. 相似文献