全文获取类型
收费全文 | 320篇 |
免费 | 7篇 |
专业分类
电工技术 | 3篇 |
化学工业 | 76篇 |
金属工艺 | 9篇 |
机械仪表 | 5篇 |
建筑科学 | 7篇 |
矿业工程 | 2篇 |
能源动力 | 3篇 |
轻工业 | 65篇 |
水利工程 | 1篇 |
无线电 | 7篇 |
一般工业技术 | 54篇 |
冶金工业 | 70篇 |
原子能技术 | 6篇 |
自动化技术 | 19篇 |
出版年
2021年 | 5篇 |
2019年 | 7篇 |
2016年 | 2篇 |
2015年 | 3篇 |
2014年 | 3篇 |
2013年 | 8篇 |
2012年 | 4篇 |
2011年 | 16篇 |
2010年 | 9篇 |
2009年 | 4篇 |
2008年 | 7篇 |
2007年 | 5篇 |
2006年 | 10篇 |
2005年 | 5篇 |
2004年 | 14篇 |
2003年 | 7篇 |
2002年 | 4篇 |
2001年 | 5篇 |
2000年 | 6篇 |
1999年 | 2篇 |
1998年 | 16篇 |
1997年 | 13篇 |
1996年 | 11篇 |
1995年 | 8篇 |
1994年 | 4篇 |
1993年 | 7篇 |
1992年 | 9篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 8篇 |
1986年 | 5篇 |
1985年 | 8篇 |
1984年 | 12篇 |
1983年 | 5篇 |
1982年 | 11篇 |
1981年 | 2篇 |
1980年 | 9篇 |
1979年 | 3篇 |
1978年 | 9篇 |
1977年 | 8篇 |
1976年 | 8篇 |
1975年 | 2篇 |
1974年 | 3篇 |
1973年 | 4篇 |
1972年 | 4篇 |
1970年 | 5篇 |
1956年 | 2篇 |
1908年 | 2篇 |
排序方式: 共有327条查询结果,搜索用时 15 毫秒
1.
On the suitability of agricultural by-products for the manufacture of granular activated carbon 总被引:1,自引:0,他引:1
An investigation of several agricultural by-products revealed that their suitability for activated carbon production is not determined by general material-specific features (elemental composition) but by type-specific features. A coarse-cellular structure (as in wood), which is indicated by porosities of the raw materials higher than 35% is disadvantageous. A specific change in the properties of cokes (porosity, density, hardness) is possible by varying the conditions of pyrolysis. By rapid heating in the pyrolysis step, for instance, macroporous residues are produced. Temperature and burnoff have the greatest influence on the quality of the activated carbon during the activation step. Of the investigated materials, coconut shells yield granular activated carbon of the highest quality. The following order of suitability of raw materials for activated carbon production was established: coconut shells> peach stones> plum stones> hazelnut shells> walnut shells> cherry stones. 相似文献
2.
Erhard Ueckermann 《Zeitschrift für Jagdwissenschaft》1994,40(1):68
Ohne Zusammenfassung 相似文献
3.
The hydrolytic decomposition of dichlorodifluoromethane (CFC-12) on various modified zirconium oxide surfaces has been studied. The reaction was carried out under flow conditions at 500°C. Complete CFC-12 conversion and long-time stability of the catalysts were achieved accompanied by a limitation of the undesired CFC-13 formation. A maximum CFC-12 conversion was observed on catalysts of sulfated zirconia or zirconia obtained from temperature-controlled calcination of zirconium oxide hydrate. The reaction depends on the presence or in situ formation of Brønsted acid sites. FTIR-photoacoustic measurements were performed on pyridine complexes chemisorbed on the catalyst surface in order to analyze the changes in the catalyst's acidity. The effects of the temperature and water in the reaction gas on the catalyzed decomposition of CFC-12 are examined. 相似文献
4.
Experiments have been performed to investigate the mechanical response of unfilled polycarbonate vis‐à‐vis the influence of prior deformation on stress relaxation and creep. Piecewise linear deformation histories, which involve strain‐controlled tensile loading of a specimen to a maximum load and partial unloading to a target strain/stress point as prologue to a relaxation test, have been shown to qualitatively influence the recorded stress‐time behavior. In particular, the stress magnitude during relaxation first increases and is then followed by a decrease. Analogously, in creep tests during unloading, the strain might decrease and then increase. Time characteristics for this U‐turn in the deformation response are influenced by the placement of the test. The influence of prior specimen conditioning on this phenomenon is investigated by comparing test data from virgin samples to that of specimens having high (~85%) inelastic strain from prior tensile elongation. Findings suggest that the observed persistence in the occurrence of this reversal effect for both types of specimens is evidence of the need to incorporate this behavior into the fold of material modeling. Additionally, this novel relaxation and creep behavior has been observed in other amorphous (poly(phenylene oxide)) and crystalline (high‐density polyethylene) polymers. Polym. Eng. Sci. 44:1783–1791, 2004. © 2004 Society of Plastics Engineers. 相似文献
5.
The porosity of -alumina-based materials is an important parameter affecting the extent of fluorination (aerogels > commercial -Al2O3 > xerogels) and, consequently, also the textural, acidic and catalytic properties of the final fluorinated materials. Only the highly fiuorinated aluminas having strong Lewis acidic sites catalyse the isomerisation of CHF2CHF2 to CF3CH2F. 相似文献
6.
A survey of approaches to automatic schema matching 总被引:76,自引:1,他引:75
Erhard Rahm Philip A. Bernstein 《The VLDB Journal The International Journal on Very Large Data Bases》2001,10(4):334-350
Schema matching is a basic problem in many database application domains, such as data integration, E-business, data warehousing,
and semantic query processing. In current implementations, schema matching is typically performed manually, which has significant
limitations. On the other hand, previous research papers have proposed many techniques to achieve a partial automation of
the match operation for specific application domains. We present a taxonomy that covers many of these existing approaches,
and we describe the approaches in some detail. In particular, we distinguish between schema-level and instance-level, element-level
and structure-level, and language-based and constraint-based matchers. Based on our classification we review some previous
match implementations thereby indicating which part of the solution space they cover. We intend our taxonomy and review of
past work to be useful when comparing different approaches to schema matching, when developing a new match algorithm, and
when implementing a schema matching component.
Received: 5 February 2001 / Accepted: 6 September 2001 Published online: 21 November 2001 相似文献
7.
8.
9.
Shaomin Xiong Na Wang Robert Smith Dongbo Li Erhard Schreck Qing Dai 《Tribology Letters》2017,65(2):74
Heat assisted magnetic recording (HAMR) promises to deliver higher storage areal density than the current perpendicular magnetic recording products. Laser heating is implemented in HAMR to achieve magnetic writing of the very high coercivity media. However, the high temperature environment creates several reliability challenges for the head disk interface (HDI). In this paper, material transfer within the HDI under HAMR recording conditions is studied. The mechanisms of material transfer are explored via experiments and modeling. This study revealed that temperature difference and mechanical interaction between the head and media are the main mechanisms for material transfer inside the HDI. Possible methods to remove the material are also discussed in this paper. 相似文献
10.
Streckel W Wolff AC Prager R Tietze E Tschäpe H 《Molecular nutrition & food research》2004,48(7):496-503
The presence and expression of sopB, sopD1, sopE1, and avrA genes encoding virulence associated effector proteins were studied comparatively in 405 Salmonella enterica strains. They belong to different serovars and clonal types (genotypes, phage types) and originated from different clinical (systemic infection, focal enteritis, enterocolitis) and epidemic sources (epidemics, sporadic cases). The sopB and sopD1 determinants were commonly prevalent, but sopE1 and avrA genes only in 55% and 80%, respectively. A correlation of this pattern of absence and presence of the respective genes to the epidemic and clinical origin could not be detected. In contrast, the expression of the respective genes appeared differently: SopB and SopE1 proteins are well produced, but SopD1 and AvrA proteins only rarely under the applied standard culture conditions. However, using a range of different environmental signals (temperature, pH, cations, etc.) some of the S. enterica nonproducer strains (e. g., S. Agona, S. Bovismorbificans, S. Virchow, etc.) begin to produce AvrA and SopD1. They turned now into an expression profile which was found typically for the epidemic strains of S. Typhimurium and S. Enteritidis. Also S. enterica strains from systemic infections could be characterized by their strong SopB and SopE1 expression while SopD1 and AvrA proteins were missing. Although it is premature to outline generally a correlation of these expression profiles and the clinical and epidemiological potency of Salmonellae, the reported results allow a first understanding how a fine tuning of their virulence will take place. 相似文献