全文获取类型
收费全文 | 829篇 |
免费 | 61篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 3篇 |
综合类 | 4篇 |
化学工业 | 164篇 |
金属工艺 | 16篇 |
机械仪表 | 7篇 |
建筑科学 | 48篇 |
矿业工程 | 3篇 |
能源动力 | 22篇 |
轻工业 | 76篇 |
水利工程 | 4篇 |
武器工业 | 1篇 |
无线电 | 85篇 |
一般工业技术 | 169篇 |
冶金工业 | 83篇 |
原子能技术 | 9篇 |
自动化技术 | 198篇 |
出版年
2024年 | 2篇 |
2023年 | 14篇 |
2022年 | 18篇 |
2021年 | 27篇 |
2020年 | 20篇 |
2019年 | 34篇 |
2018年 | 33篇 |
2017年 | 22篇 |
2016年 | 42篇 |
2015年 | 33篇 |
2014年 | 41篇 |
2013年 | 47篇 |
2012年 | 47篇 |
2011年 | 72篇 |
2010年 | 43篇 |
2009年 | 43篇 |
2008年 | 57篇 |
2007年 | 46篇 |
2006年 | 44篇 |
2005年 | 23篇 |
2004年 | 20篇 |
2003年 | 15篇 |
2002年 | 28篇 |
2001年 | 10篇 |
2000年 | 8篇 |
1999年 | 10篇 |
1998年 | 11篇 |
1997年 | 5篇 |
1996年 | 7篇 |
1995年 | 6篇 |
1994年 | 1篇 |
1993年 | 5篇 |
1992年 | 7篇 |
1991年 | 3篇 |
1990年 | 8篇 |
1989年 | 4篇 |
1988年 | 1篇 |
1987年 | 4篇 |
1986年 | 1篇 |
1985年 | 8篇 |
1984年 | 4篇 |
1983年 | 6篇 |
1982年 | 4篇 |
1981年 | 4篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1976年 | 1篇 |
排序方式: 共有892条查询结果,搜索用时 15 毫秒
41.
Timo Stressler Thomas Eisele Johanna Rost Eva‐Maria Haunschild Prof. Dr. Andreas Kuhn Prof. Dr. Lutz Fischer 《化学,工程师,技术》2013,85(3):318-322
A new isolate of Mortierella alpina, > 98 % identical with M. alpina ATCC 16266, was cultivated in a defined glucose‐based medium with three organic nitrogen sources (glycine, urea and Na‐L‐glutamate) at three different concentrations in shaking flasks at 20 °C. The results were compared to the cultivation in complex medium with yeast extract as nitrogen source. In the defined media, high yields of polyunsaturated fatty acids (PUFAs) and arachidonic acid (ARA), respectively, were obtained with Na‐L‐glutamate. However, the absolute highest yields of PUFA and ARA were measured with the yeast extract medium. An optimized yeast extract complex medium was used for a submerse bioreactor cultivation in a 45‐L scale. Furthermore, M. alpina was cultivated in a solid state fermenter, using an oat bran water mixture as substrate. 相似文献
42.
Taisa Venäläinen Ursula Schwab Jyrki Ågren Vanessa de Mello Virpi Lindi Aino-Maija Eloranta Sanna Kiiskinen David Laaksonen Timo A. Lakka 《Lipids》2014,49(5):467-479
Plasma fatty acid (FA) composition is known to be an indicator of dietary fat quality, but the associations of other dietary factors with plasma FA composition remain unknown in children. We investigated the cross-sectional associations of food consumption with the proportions of FA and estimated desaturase activities in plasma cholesteryl esters (CE) and phospholipids (PL) among children. The subjects were a population sample of 423 children aged 6–8 years examined at baseline of The Physical Activity and Nutrition in Children (PANIC) Study. We assessed food consumption by food records and plasma FA composition by gas chromatography. We used linear regression models adjusted for age, sex, physical activity and total energy intake to analyze the associations. A higher consumption of vegetable oil-based margarine (fat 60–80 %) was associated with a higher proportion of linoleic and α-linolenic acids in plasma CE and PL. A higher consumption of high-fiber grain products was related to a lower proportion of oleic acid in CE and PL. The consumption of candy was directly associated with the proportion of palmitoleic and oleic acid in plasma CE. The consumption of vegetable oil-based margarine was inversely associated with estimated stearoyl-CoA-desaturase activity in plasma CE and PL and the consumption of candy was directly related to it in plasma CE. The results of our study suggest that plasma FA composition is not only a biomarker for dietary fat quality but also reflects the consumption of high-fiber grain products and foods high in sugar among children. 相似文献
43.
Katja M?enp?? Ville Ell? Jari Mauno Minna Kellom?ki Riitta Suuronen Timo Ylikomi Susanna Miettinen 《Journal of the Royal Society Interface》2010,7(42):177-188
There is currently no suitable replacement for damaged temporomandibular joint (TMJ) discs after discectomy. In the present study, we fabricated bilayer biodegradable polylactide (PLA) discs comprising a non-woven mat of poly(L/D)lactide (P(L/D)LA) 96/4 and a P(L/DL)LA 70/30 membrane plate. The PLA disc was examined in combination with adipose stem cells (ASCs) for tissue engineering of the fibrocartilaginous TMJ disc in vitro. ASCs were cultured in parallel in control and chondrogenic medium for a maximum of six weeks. Relative expression of the genes, aggrecan, type I collagen and type II collagen present in the TMJ disc extracellular matrix increased in the ASC-seeded PLA discs in the chondrogenic medium. The hypertrophic marker, type X collagen, was moderately induced. Alcian blue staining showed accumulation of sulphated glycosaminoglycans. ASC differentiation in the PLA discs was close to that observed in pellet cultures. Comparison of the mRNA levels revealed that the degree of ASC differentiation was lower than that in TMJ disc-derived cells and tissue. The pellet format supported the phenotype of the TMJ disc-derived cells under chondrogenic conditions and also enhanced their hyalinization potential, which is considered part of the TMJ disc degeneration process. Accordingly, the combination of ASCs and PLA discs has potential for the development of a tissue-engineered TMJ disc replacement. 相似文献
44.
45.
Heinonen Johanna; Aro Tuija; Ahonen Timo; Poikkeus Anna-Maija 《Canadian Metallurgical Quarterly》2011,23(1):184
Test-taking behaviors (i.e., task focus, maintenance of attention, and cooperation) affect children's cognitive test performance, and, thus, it is critical to take test-taking behavior into account when drawing conclusions and making recommendations. Prior studies have evaluated test-taking behaviors at the end of the assessment; the present study focused on the fluctuation of cooperation and attention during a neuropsychological assessment. We examined the attention and cooperation of 5-year-old children in a test-taking situation; the associations between these aspects of their test-taking behavior and the children's concurrent neurocognitive test performance, IQ, and parent-rated behavior; and the associations with their IQ, behavioral outcomes, and academic achievement at 8 years of age. The data (for 76 boys and 63 girls) were drawn from the Jyv?skyl? Longitudinal Study of Dyslexia (Lyytinen et al., 2001, 2004). All the children were Caucasian and spoke Finnish as their native language. As a whole, the 5-year-old children showed high cooperation and attention, but a slight decrement in test-taking behavior toward the end of the session was rather common. Three subgroups of children with different levels of cooperation and attention were identified. Children in the subgroup with nonoptimal attention and cooperation showed decreasing neurocognitive test performance toward the end of the assessment session. They also showed more inattentive behavior 3 years later. The findings imply that the examiner's observations of waning attention and cooperation during the assessment session are highly relevant, as these provide stable and clinically meaningful information about the child's behavioral tendencies. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
46.
Investigations on metal-cutting machining processes that were conducted since the second half of the twentieth century have
considerably contributed to disclosing the principles underlying the cutting process. Although numerous studies have been
carried out on this subject, a generally valid model of the cutting process and the interactions in the separating processes
does not exist yet. Such a model could guarantee the disclosure of the principles of thermodynamic interactions between the
cutting process and the involved machine structure. This contribution is twofold and presents an experimental setup used to
determine cutting forces and temperatures in orthogonal cutting processes. The results are then used as a reference for simulations
made with the Discrete Element Method (DEM). The DEM is due to its meshless nature well suited to capture large deformations
and rupture of material which is included very naturally. It is examined to which extent the measured results can be captured
with the DEM model. 相似文献
47.
Mika Kettunen Adnan S Abu‐Surrah Timo Repo Markku Leskel 《Polymer International》2001,50(11):1223-1227
Synthesis of functional aliphatic polyketones was achieved by co‐ and terpolymerization of the strained exo‐methylenecycloalkane, methylenecyclopropane (MCP), and also the dienes 1,5‐hexadiene, 1,7‐octadiene and 1,6‐heptadien‐4‐ol, with carbon monoxide and propene, using the dicationic palladium(II) phosphine complex [Pd(dppp) (NCCH3)2](BF4)2 (I) (dppp is 1,3‐bis(diphenyl‐phosphino)propane) as the catalyst precursor. The resulting MCP/CO copolymer contains both ring‐opened and cyclic microstructures. Ring‐opening copolymerization yields exo‐methylene functionalized polyketone. In contrast to hexadiene/carbon monoxide copolymer (Hx/CO), no ring structures were observed in the alternating octadiene/carbon monoxide (Oc/CO) and heptadien‐4‐ol/carbon monoxide (Hp‐ol/CO) copolymers. The remaining double bonds were left intact to yield polymers with olefinic functionalities in the side chains. © 2001 Society of Chemical Industry 相似文献
48.
Process plants are typically divided into different process parts having specific processing tasks with possibly different ownership. Heat integration between these processes can increase the energy- and economic efficiency for both the overall plant and the individual processes. In this paper we present a heat exchanger network synthesis MINLP-model that allows simultaneous heat integration directly between streams in the same process and both directly and indirectly between streams in different processes. The indirect heat transfer is accomplished by using intermediate streams. Two examples, one small explanatory one and one from the literature, are optimized. The results verify that the model works logically. 相似文献
49.
50.
Role of microbes in controlling the speciation of arsenic and production of arsines in contaminated soils 总被引:7,自引:0,他引:7
Turpeinen R Pantsar-Kallio M Kairesalo T 《The Science of the total environment》2002,285(1-3):133-145
The influence of microbes on the speciation of arsenic and production of arsines in contaminated soils was investigated under laboratory conditions. Microbes were able to carry out reactions that resulted in changes in the speciation of arsenic in soil. The transformation of soil dominating species, arsenate [As(V)], under both aerobic and anaerobic conditions to arsenite [As(III)], monomethylarsonic acid [MMAA], dimethylarsinic acid [DMAA] and to volatile trimethylarsine [TMA] was, however, less than 0.5%, of which the production of TMA represented 0.02-0.3%. The volatilization process was also verified in the field, in the soil of a dumping area. The 'life-time' of arsines in air was, however, short and they were rapidly converted back to water soluble species, As(V) and trimethyl arsine oxide (TMAO). 相似文献