全文获取类型
收费全文 | 1346篇 |
免费 | 66篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 24篇 |
综合类 | 1篇 |
化学工业 | 312篇 |
金属工艺 | 23篇 |
机械仪表 | 40篇 |
建筑科学 | 73篇 |
矿业工程 | 6篇 |
能源动力 | 41篇 |
轻工业 | 218篇 |
水利工程 | 8篇 |
石油天然气 | 1篇 |
无线电 | 79篇 |
一般工业技术 | 240篇 |
冶金工业 | 116篇 |
原子能技术 | 11篇 |
自动化技术 | 222篇 |
出版年
2023年 | 22篇 |
2022年 | 31篇 |
2021年 | 57篇 |
2020年 | 29篇 |
2019年 | 47篇 |
2018年 | 35篇 |
2017年 | 32篇 |
2016年 | 44篇 |
2015年 | 35篇 |
2014年 | 55篇 |
2013年 | 67篇 |
2012年 | 72篇 |
2011年 | 94篇 |
2010年 | 79篇 |
2009年 | 62篇 |
2008年 | 85篇 |
2007年 | 63篇 |
2006年 | 54篇 |
2005年 | 32篇 |
2004年 | 29篇 |
2003年 | 30篇 |
2002年 | 31篇 |
2001年 | 26篇 |
2000年 | 18篇 |
1999年 | 14篇 |
1998年 | 16篇 |
1997年 | 14篇 |
1996年 | 13篇 |
1995年 | 12篇 |
1994年 | 6篇 |
1993年 | 11篇 |
1992年 | 14篇 |
1991年 | 15篇 |
1990年 | 10篇 |
1989年 | 14篇 |
1988年 | 7篇 |
1987年 | 6篇 |
1985年 | 5篇 |
1983年 | 5篇 |
1978年 | 5篇 |
1977年 | 6篇 |
1976年 | 6篇 |
1975年 | 5篇 |
1974年 | 5篇 |
1973年 | 6篇 |
1971年 | 4篇 |
1905年 | 15篇 |
1904年 | 17篇 |
1903年 | 13篇 |
1902年 | 11篇 |
排序方式: 共有1415条查询结果,搜索用时 15 毫秒
11.
Sviatlana Kalinina Christian Freymueller Nilanjon Naskar Bjoern von Einem Kirsten Reess Ronald Sroka Angelika Rueck 《International journal of molecular sciences》2021,22(11)
Metabolic FLIM (fluorescence lifetime imaging) is used to image bioenergetic status in cells and tissue. Whereas an attribution of the fluorescence lifetime of coenzymes as an indicator for cell metabolism is mainly accepted, it is debated whether this is valid for the redox state of cells. In this regard, an innovative algorithm using the lifetime characteristics of nicotinamide adenine dinucleotide (phosphate) (NAD(P)H) and flavin adenine dinucleotide (FAD) to calculate the fluorescence lifetime induced redox ratio (FLIRR) has been reported so far. We extended the FLIRR approach and present new results, which includes FLIM data of the various enzymes, such as NAD(P)H, FAD, as well as flavin mononucleotide (FMN). Our algorithm uses a two-exponential fitting procedure for the NAD(P)H autofluorescence and a three-exponential fit of the flavin signal. By extending the FLIRR approach, we introduced FLIRR1 as protein-bound NAD(P)H related to protein-bound FAD, FLIRR2 as protein-bound NAD(P)H related to free (unbound) FAD and FLIRR3 as protein-bound NAD(P)H related to protein-bound FMN. We compared the significance of extended FLIRR to the metabolic index, defined as the ratio of protein-bound NAD(P)H to free NAD(P)H. The statistically significant difference for tumor and normal cells was found to be highest for FLIRR1. 相似文献
12.
Berchtold von Steiger Armin Keller Rainer Schulin 《Nutrient Cycling in Agroecosystems》1998,50(1-3):303-306
Extraction of heavy metals by accumulating plants is a method which is currently in development for the "gentle" remediation of contaminated agricultural soils (phytoremediation, see [2]). Areal contaminant mass flux balances are basic criteria for the design of such remediations and their control. A framework for the integration of contaminant balances relating the field scale of remediation with the regional scale of soil monitoring networks is provided by the recently developed method PROTERRA [3]. The objective of the study presented in this paper was to test the suitability of PROTERRA for planning and monitoring gentle soil remediations. For this purpose we applied the PROTERRA method to the contaminated agricultural land in and around Dornach, Switzerland, to assess copper flux balances.The calculations showed that atmospheric deposition and the application of pesticides and manure are important pathways for the inputs of copper. The copper export with a special maize cultivar accumulating heavy metals would be about three times higher than the average metal export with crops. A moderate increase of sewage sludge application would lead to a substantial increase of the copper input. Decisions to remediate the soil should take the uncertainty of mass flux balances both on field scale as well as on regional scale into account. Therefore, an important need of further development of the PROTERRA method is the integration of uncertainty analysis on both scales. 相似文献
13.
Armin Salsani Jahanbakhsh Daneshian Shahram Shariati Abdolreza Yazdani-Chamzini Mehdi Taheri 《Neural computing & applications》2014,24(7-8):1823-1831
With growing use of roadheaders in the world and its significant role in the successful accomplishment of a tunneling project, it is a necessity to accurately predict performance of this machine in different ground conditions. On the other hand, the existence of some shortcomings in the prediction models has made it necessary to perform more research on the development of the new models. This paper makes an attempt to model the rate of roadheader performance based on the geotechnical and geological site conditions. For achieving the aim, an artificial neural network (ANN), a powerful tool for modeling and recognizing the sophisticated structures involved in data, is employed to model the relationship between the roadheader performance and the parameters influencing the tunneling operations with a high correlation. The database used in modeling is compiled from laboratory studies conducted at Azad University at Science and Research Branch, Tehran, Iran. A model with architecture 4-10-1 trained by back-propagation algorithm is found to be optimum. A multiple variable regression (MVR) analysis is also applied to compare performance of the neural network. The results demonstrate that predictive capability of the ANN model is better than that of the MVR model. It is concluded that roadheader performance could be accurately predicted as a function of unconfined compressive strength, Brazilian tensile strength, rock quality designation, and alpha angle R 2 = 0.987. Sensitivity analysis reveals that the most effective parameter on roadheader performance is the unconfined compressive strength. 相似文献
14.
Naoufal Bahlawane Edgar Fischer Rivera Katharina Kohse-Hinghaus Armin Brechling Ulf Kleineberg 《Applied catalysis. B, Environmental》2004,53(4):245-255
The chemical vapor deposition method was used to deposit thin films of cobalt oxide starting with cobalt (II) acetylacetonate and oxygen. The deposition process was investigated and the obtained films were identified as a cubic spinel-type polycrystalline Co3O4 with a crystallite size of 30–40 nm. The coating was carbon-free and the surface oxygen concentration was measured to be 66 at.% with AES analysis. Smooth and highly uniform thin films were deposited on planar stainless steel substrates and subjected to TPR and catalysis tests that show positive correlation. The apparent activation energy of Co3O4 reduction to CoO was measured to be (33±5) kJ/mol. The catalytic activity of Co3O4 was investigated toward the conversion of both propane and ethanol to carbon dioxide. Though the catalytic action was registered at the same temperature, the deactivation process was seen to be different. The catalytic conversion of ethanol induces a fast deactivation process, which was linked to its high ability to reduce Co3O4. 相似文献
15.
Armin Mosandl und Ursula Palm 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1991,193(2):109-114
Zusammenfassung Die Synthese von acht verschiedenen 2-Alkoxy-5-alkyl-tetrahydrofuranen und ihren Stereoisomeren wird vorgestellt, sieben von ihnen sind als Aromastoffe der Wassermelone bekannt. Alle Stereoisomeren werden, ausgehend von optisch reinen-Nonalacton-Enantiomeren, synthetisiert und mit Diisobutylaluminiumhydrid selektiv zu den entsprechenden Lactolen reduziert. Die Lactole werden mit den gewünschten Alkoholen in schwach saurer Lösung zucis/trans-Diastereomeren umgesetzt und durch Flüssigchromatographie in optisch reine Stereoisomere getrennt. Die sensorische Charakteristik aller Stereoisomeren der sieben Verbindungen wird aufgezeigt. Die Trennung dercis/trans-Diastereomeren an DB-210 wird vorgestellt und die chirospezifische Differenzierung der acht Verbindungen diskutiert.
Stereoisomeric flavour compounds L. Optically pure 2-alkoxy-5-alkyl-tetrahydrofurans — structures and properties
Summary The synthesis of eight different 2-alkoxy-5-alkyltetrahydrofurans and their stereoisomers is presented, seven of which are known to be flavour compounds of water melons. All stereoisomers were synthesized from optically pure-lactone enantiomers, which were selectively reduced by diisobutylaluminium hydride to the corresponding lactols. The lactols were treated with the desired alcohol component in weakly acidic media to yield thecis/trans diastereoisomers, which were separated into optically pure stereoisomers by liquid chromatography. The sensory characteristics of all four stereoisomers of the seven compounds are given. The Stereodifferentiation of thesecis/trans diastereoisomers on DB-210 is demonstrated and the direct chirospecific differentiation of all eight compounds discussed.相似文献
16.
Tröger Armin Svensson Glenn P. Galbrecht Hans-Martin Twele Robert Patt Joseph M. Bartram Stefan Zarbin Paulo H. G. Segraves Kari A. Althoff David M. von Reuss Stephan Raguso Robert A. Francke Wittko 《Journal of chemical ecology》2021,47(12):1025-1041
Journal of Chemical Ecology - The obligate pollination mutualism between Yucca and yucca moths is a classical example of coevolution. Oviposition and active pollination by female yucca moths occur... 相似文献
17.
Chaudry Oliver Friedberger Andreas Grimm Alexandra Uder Michael Nagel Armin Michael Kemmler Wolfgang Engelke Klaus 《Magma (New York, N.Y.)》2021,34(3):367-376
Magnetic Resonance Materials in Physics, Biology and Medicine - To develop a precise semi-automated segmentation of the fascia lata (FL) of the thigh to quantify IMAT volume in T1w MR images and... 相似文献
18.
Mischa Schmidt Jan Seedorf Stefano Napolitano Rosario G. Garroppo Andrea Cavaliere Thilo Ewald Armin Jahanpanah Zbigniew Kopertowski Marcin Pilarski Pawel Grochocki 《Peer-to-Peer Networking and Applications》2013,6(2):134-154
Application Layer Traffic Optimization (ALTO) has recently gained attention in the research and standardisation community as a way for a network operator to guide the peer selection process of distributed applications by providing network layer topology information. In particular P2P applications are expected to gain from ALTO, due to the many connections peers form among each other, often without taking network layer topology information into account. In this paper, we present results of an extensive intra-ISP trial with an ALTO-enhanced P2P filesharing software. In summary, our results show that—depending on the concrete setting and on the distribution of upload capacity in the network—ALTO enables an ISP to save operational costs significantly while not degrading application layer performance noticeably. In addition, based on our experience we are able to give advice to operators on how to save costs with ALTO while not sacrificing application layer performance at all. 相似文献
19.
20.