全文获取类型
收费全文 | 1446篇 |
免费 | 60篇 |
国内免费 | 20篇 |
学科分类
工业技术 | 1526篇 |
出版年
2023年 | 7篇 |
2022年 | 25篇 |
2021年 | 41篇 |
2020年 | 43篇 |
2019年 | 45篇 |
2018年 | 39篇 |
2017年 | 23篇 |
2016年 | 35篇 |
2015年 | 50篇 |
2014年 | 53篇 |
2013年 | 117篇 |
2012年 | 82篇 |
2011年 | 93篇 |
2010年 | 79篇 |
2009年 | 65篇 |
2008年 | 74篇 |
2007年 | 62篇 |
2006年 | 71篇 |
2005年 | 60篇 |
2004年 | 37篇 |
2003年 | 54篇 |
2002年 | 28篇 |
2001年 | 27篇 |
2000年 | 17篇 |
1999年 | 19篇 |
1998年 | 30篇 |
1997年 | 21篇 |
1996年 | 19篇 |
1995年 | 23篇 |
1994年 | 11篇 |
1993年 | 10篇 |
1992年 | 6篇 |
1991年 | 12篇 |
1990年 | 17篇 |
1989年 | 13篇 |
1988年 | 9篇 |
1987年 | 8篇 |
1986年 | 11篇 |
1985年 | 11篇 |
1984年 | 5篇 |
1983年 | 6篇 |
1982年 | 8篇 |
1981年 | 8篇 |
1979年 | 3篇 |
1977年 | 3篇 |
1976年 | 4篇 |
1975年 | 3篇 |
1973年 | 6篇 |
1955年 | 3篇 |
1954年 | 3篇 |
排序方式: 共有1526条查询结果,搜索用时 31 毫秒
1.
Can Ercan S. Esra Safran Artuğ Türkmenoğlu Uğur Karabakal 《Journal of surfactants and detergents》2021,24(1):139-147
Garzan oil field is located at the south east of Turkey. It is a mature oil field and the reservoir is fractured carbonate reservoir. After producing about 1% original oil in place (OOIP) reservoir pressure started to decline. Waterflooding was started in order to support reservoir pressure and also to enhance oil production in 1960. Waterflooding improved the oil recovery but after years of flooding water breakthrough at the production wells was observed. This increased the water/oil ratio at the production wells. In order to enhance oil recovery again different techniques were investigated. Chemical enhanced oil recovery (EOR) methods are gaining attention all over the world for oil recovery. Surfactant injection is an effective way for interfacial tension (IFT) reduction and wettability reversal. In this study, 31 different types of chemicals were studied to specify the effects on oil production. This paper presents solubility of surfactants in brine, IFT and contact angle measurements, imbibition tests, and lastly core flooding experiments. Most of the chemicals were incompatible with Garzan formation water, which has high divalent ion concentration. In this case, the usage of 2-propanol as co-surfactant yielded successful results for stability of the selected chemical solutions. The results of the wettability test indicated that both tested cationic and anionic surfactants altered the wettability of the carbonate rock from oil-wet to intermediate-wet. The maximum oil recovery by imbibition test was reached when core was exposed 1-ethly ionic liquid after imbibition in formation water. Also, after core flooding test, it is concluded that considerable amount of oil can be recovered from Garzan reservoir by waterflooding alone if adverse effects of natural fractures could be eliminated. 相似文献
2.
Emma Layton Anna-Marie Fairhurst Sam Griffiths-Jones Richard K. Grencis Ian S. Roberts 《International journal of molecular sciences》2020,21(23)
In eukaryotes, microRNAs (miRNAs) have roles in development, homeostasis, disease and the immune response. Recent work has shown that plant and mammalian miRNAs also mediate cross-kingdom and cross-domain communications. However, these studies remain controversial and are lacking critical mechanistic explanations. Bacteria do not produce miRNAs themselves, and therefore it is unclear how these eukaryotic RNA molecules could function in the bacterial recipient. In this review, we compare and contrast the biogenesis and functions of regulatory RNAs in eukaryotes and bacteria. As a result, we discovered several conserved features and homologous components in these distinct pathways. These findings enabled us to propose novel mechanisms to explain how eukaryotic miRNAs could function in bacteria. Further understanding in this area is necessary to validate the findings of existing studies and could facilitate the use of miRNAs as novel tools for the directed remodelling of the human microbiota. 相似文献
3.
Serap Safran 《Ceramics International》2019,45(8):10243-10249
In this study, the critical current density and mechanical performance of MgB2 superconductors prepared using different magnesium sources (Mg and MgH2 with 99.9% and 96.5% purities, respectively) were analyzed. When the samples were characterized structurally and electrically, we found that the grain sizes were about 40?nm and transition temperature was around 30?K being lower than the literature. Critical current densities of all samples were calculated using Bean's model and our calculations yielded critical current density values higher than 106?A?cm?2 in self-field. The highest critical transition temperature value belongs to M800 (Mg with 99.9% purity) sample and when the critical current density and transition temperature values of this sample are considered, this sample appears to have the potential for practical use. Vicker's microhardness measurements were performed and yield stress (Y), elastic modulus (E), brittleness (Bi), ductility (D) and fracture toughness (KIC) were calculated. All samples exhibited Indentation Size Effect (ISE) and microhardness measurements were compared with some microhardness models with were compatible with ISE behavior. 相似文献
4.
5.
Xunwang Shi Xiuhan Yu Caiwen Nie Fengji Li Sam Zhang 《Ceramics International》2021,47(15):21546-21553
Color films are widely used for visual effect as well as for their functional properties. To date, however, synthesizing thin films with desired color remains challenging. In this work, AlN color films are deposited on Si wafers by precise control of the deposition time for different thickness during reactive magnetron sputtering from an Al target in Ar/N2 atmosphere. The thickness, morphology, structure, composition and color index are carefully examined by field emission scanning electron microscopy, atomic force microscopy, grazing incidence X-ray diffraction, X-ray photoelectron spectrometry and colorimeter, respectively. As the film thickness changes from 57 nm to 165 nm, the film exhibits purple, indigo, blue, green, yellow, orange and red in color. These colors repeat in the same order when the thickness goes over 165 nm. Once the thickness exceeds 467 nm, overlapping of colors takes place. The mechanisms are elucidated. 相似文献
6.
Selvasundarasekar Sam Sankar Arumugam Rathishkumar Kathiresan Geetha Subrata Kundu 《International Journal of Hydrogen Energy》2021,46(17):10366-10376
Electrospinning (ES) is a most reliable method for synthesizing one dimensional (1D) fibrous material. Fibrous materials are having peculiar interest owing to their fascinating properties. For efficient hydrogen fuel generation, electrocatalytic water splitting is one of the finest way of producing hydrogen in a pure form. But it is encountered by the counter oxygen evolution reaction (OER) in more often. As of now, noble metal based catalysts are utilized in the commercial sector. Some of the disadvantages associated with the noble materials are restrict their usage commercially. To address this issue, herein, we have synthesized One dimensional (1D), hydrated porous cobalt phosphate fibrous network by an ES method and act as an electrocatalyst for OER in both alkaline and neutral media for the first time, which exhibits an overpotential of 245 and 457 mV respectively at a current density of 10 mAcm?2 with astonishing stability. 相似文献
7.
8.
Sam Safran 《Israel journal of chemistry》2015,55(11-12):1160-1163
9.
10.
Sam Van Wassenbergh Nuno Zavattieri Potes Dominique Adriaens 《Journal of the Royal Society Interface》2015,12(109)
Presumably as an adaptation for mouthbrooding, many cichlid fish species have evolved a prominent sexual dimorphism in the adult head. Since the head of fishes serves as a bow during locomotion, an evolutionary increase in head volume to brood more eggs can trade-off with the hydrodynamic efficiency of swimming. Here, the differences between males and females in three-dimensional shape and size of the external head surfaces and the effect thereof on drag force during locomotion was analysed for the Nile tilapia (Oreochromis niloticus), a maternal mouthbrooder. To do so, three-dimensional body surface reconstructions from laser scans and computational fluid dynamics simulations were performed. After scaling the scanned specimens to post-cranial body volume, in order to theoretically equalize propulsive power, the external volume of the head of females was 27% larger than that of males (head length + 14%; head width + 9%). These differences resulted in an approximate 15% increase in drag force. Yet, hydrodynamics imposed important constraints on the adaptation for mouthbrooding as a much more drastic drop in swimming efficiency seems avoided by mainly enlarging the head along the swimming direction. 相似文献