全文获取类型
收费全文 | 2230篇 |
免费 | 64篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 21篇 |
综合类 | 19篇 |
化学工业 | 823篇 |
金属工艺 | 36篇 |
机械仪表 | 35篇 |
建筑科学 | 137篇 |
矿业工程 | 4篇 |
能源动力 | 52篇 |
轻工业 | 111篇 |
水利工程 | 4篇 |
石油天然气 | 3篇 |
无线电 | 87篇 |
一般工业技术 | 414篇 |
冶金工业 | 254篇 |
原子能技术 | 24篇 |
自动化技术 | 272篇 |
出版年
2021年 | 22篇 |
2019年 | 31篇 |
2018年 | 26篇 |
2017年 | 23篇 |
2016年 | 40篇 |
2015年 | 49篇 |
2014年 | 58篇 |
2013年 | 87篇 |
2012年 | 102篇 |
2011年 | 103篇 |
2010年 | 90篇 |
2009年 | 85篇 |
2008年 | 103篇 |
2007年 | 87篇 |
2006年 | 78篇 |
2005年 | 68篇 |
2004年 | 68篇 |
2003年 | 45篇 |
2002年 | 53篇 |
2001年 | 53篇 |
2000年 | 49篇 |
1999年 | 56篇 |
1998年 | 48篇 |
1997年 | 38篇 |
1996年 | 40篇 |
1995年 | 39篇 |
1994年 | 35篇 |
1993年 | 23篇 |
1992年 | 36篇 |
1991年 | 40篇 |
1990年 | 32篇 |
1989年 | 47篇 |
1988年 | 27篇 |
1987年 | 31篇 |
1986年 | 17篇 |
1985年 | 18篇 |
1984年 | 19篇 |
1983年 | 27篇 |
1982年 | 26篇 |
1981年 | 22篇 |
1980年 | 25篇 |
1979年 | 20篇 |
1978年 | 35篇 |
1977年 | 27篇 |
1976年 | 25篇 |
1975年 | 31篇 |
1974年 | 33篇 |
1973年 | 32篇 |
1971年 | 17篇 |
1970年 | 21篇 |
排序方式: 共有2296条查询结果,搜索用时 8 毫秒
1.
The local chemistry and structure of α-iron/molybdenum nitride heterophase interfaces is studied on a subnanometer scale by atom-probe field-ion microscopy (APFIM),
three-dimensional atom-probe microscopy (3DAPM) and both conventional transmission electron microscopy (CTEM) and highresolution
electron microscopy (HREM). Molybdenum nitride precipitates are generated by annealing Fe-2 at. pct Mo-X, where X=0.4 at.
pct Sb or 0.5 at. pct Sn, at 550 °C or 600 °C, in an ammonia/hydrogen mixture. Internal nitridation at 550 °C produces thin,
coherent platelet-shaped molybdenum nitride precipitates. Nitridation at 600 °C generates a much coarser structure with semicoherent
thick plate-shaped and spheroidal precipitates in addition to the thin-platelet structure. The APFIM and 3DAPM analyses of
the heterophase interfaces show substantial segregation of the solute species Sn and Sb only at the coarse precipitates, with
Gibbsian interfacial excesses of up to 7±3 nm−2, whereas the broad faces of the thin platelets have no detectable segregation. The TEM and HREM analyses show that the coarse
precipitates are semicoherent, whereas the thin platelets are either coherent or have much fewer misfit dislocations than
geometrically necessary. This demonstrates that Sn and Sb segregation is related to the presence of misfit dislocations at
the interfaces of the coarse precipitates.
This article is based on a presentation made at the symposium entitled “The Mechanisms of the Massive Transformation,” a part
of the Fall 2000 TMS Meeting held October 16–19, 2000, in St. Louis, Missouri, under the auspices of the ASM Phase Transformations
Committee. 相似文献
2.
The evaporation kinetics of Zn and Pb from liquid iron at 1600°C were studied under argon pressure 0.1 to 50 bar in an induction furnace. It was found that the limiting step of evaporation under pAr < 1 bar is diffusion in the melt. Diffusion in the gas phase becomes rate-determining with increasing argon pressure. The phase boundary reaction has no effect on the evaporation of Zn and Pb. The evaporation of Zn can evidently be reduced by increasing argon pressure above 1 bar, while the evaporation of Pb is not significantly effected by changes of argon pressure. 相似文献
3.
Dieter Oswald 《真空研究与实践》1996,8(2):88-91
All vacuumpummps which use a liquid as a sealing-agent have to take care of their specific demands. In this paper liquid-ring-vacuum-pumps will be short mentioned, because the user is familiar with this pumps and alternative fluids. Using other fluids in other mecanical vacuumpumps are not in operation in the field of the various applications frequently. You will find some ideas for using other fluids which are possibly used in rotary-vane vacuum-pumps to find more consideration in the future. 相似文献
4.
Maurus Biedermann Konrad Grob Dieter Fr?hlich Werner Meier 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1992,195(5):409-416
Summary On-line coupled liquid chromatography-gas chromatography-flame ionisation detection (LC-GC-FID) enables efficient and unambiguous determination of irradiation for some fat-containing foods (e.g. meat). Other products, however, contain interfering components or are contaminated, e.g., with mineral oil. Since more selective detection by mass spectrometry has limited success, the determination was improved by a more selective isolation of some key components among the fat degradation products, e.g. the dienes or trienes, by LC-LC-GC-FID. Applications are shown for soup mixes, some spices, fish, and shrimps.
Nachweis der Bestrahlung fetthaltiger Lebensmittel durch direkt gekoppelte LC-GC und LC-LC-GC
Zusammenfassung Die Bestrahlung einiger fetthaltiger Lebensmittel, z. B. Fleisch, kann mit direkt gekoppelter LC-GC-FID rationell und eindeutig nachgewiesen werden. In anderen Proben wird die Analyse aber durch Inhaltsstoffe des Produktes oder durch Verunreinigungen (z. B. mit Mineralöl) gestört. Da selektivere Detektion durch Massenspektrqmetrie wenig verspricht, wurde der Nachweis durch selektivere Isolierung von Schlüsselkomponenten unter den Bestrahlungsprodukten, z. B. der Diene oder Triene, mittels LC-LC-GC yerbessert. Anwendungen werden gezeigt für Suppenpulver, einige Gewürze, Fisch und Garnelen.相似文献
5.
A dielectric model comprising band gap transitions and free electron excitations (Drude model) is successfully applied to simulate transmittance spectra of ZnO films doped with 0.5%, 1% and 2% Al. The Drude formula contains a frequency-dependent damping term in order to get a good fit in the visible spectral region. Useful physical parameters obtained from the fit are electron density and mobility within the grains, film thickness, band gap and refractive index. The optically determined film thickness agrees with that obtained with the stylus method within 2%. The optically determined electronic parameters are compared with those obtained by electrical measurements. Contrary to thin In2O3:Sn films, the Drude mobility inside the grains is similar to the direct current Hall mobility indicating more perfect film growth without forming pronounced grain boundaries. Maximum value is 35 cm2/V s. The effective electron mass is estimated to be about 0.6 of the free electron mass. The refractive index at 550 nm decreases with increasing electron density. 相似文献
6.
Dieter Ullmann 《NTM》2006,14(1):1-8
A lot of publications on the acoustics of theatres and churches were published around the turn of the 18th to the 19th century.The
authors were architects who were interested in acoustical problems. Chladni was the first physicist who published on the acoustics
of rooms, he introduced the term “reverberation” into this field. His publications on this subject are reviewed. They have
been the basis for the great progress of room acoustics since 1900.
Zum 250. Geburtstag des Gelehrten 相似文献
Zum 250. Geburtstag des Gelehrten 相似文献
7.
Slab casting for hot rolled steel and strip casting using the twin roll casting (TRC) method are compared in terms of inclusions evolution. There are differences of the processes, mainly the use of casting flux in CC of slabs, or pool shapes and sizes in terms of TRC, particularly when roll diameters vary. The inclusion evolution of alumina in a low carbon steel grade was estimated. By modelling particle growth rate, coagulation and deposition, an ‘agglomeration index’ was created to describe the probability of clogging in the SEN. Similarly the growth of secondary alumina precipitation during cooling of the melt in the pool by Stokes collision and turbulent collision was estimated in terms of forming large particles which are able to float‐up. Influences of melt superheat or caster size were taken into account. 相似文献
8.
Alexander Babich Konstantinos Mavrommatis Dieter Senk Heinrich Wilhelm Gudenau 《国际钢铁研究》2004,75(7):428-432
This contribution deals with advanced educational technologies needed to equip customers from higher education institutions, research and industry with efficient tools supporting their work and operating new skills‐training methods. The challenges are reducing the training costs, improving quality and increasing the number of graduates in engineering departments. The concept of a Virtual Lab based on the combination of various teaching methods and tools is presented. Principles of mathematisation in metallurgical education and training are discussed. An example of online course designed in the form of Virtual Lab is demonstrated. 相似文献
9.
10.
Dieter Braun Manfred Rtzsch Peter Fiedler Günter Weber Heinz Hofmann Bernd Gutschalk 《大分子材料与工程》1991,187(1):101-121
Based on the example of PE-LD grades and on model substances obtained by preparative fractionation (fractions in the molecular weight range M?w = 1.2 ? 390·104 g/mol), comprehensive investigations regarding the problems of structure/properties have been carried out. The correlations of M?w with 15 physical and application technological perameters have been investigated taking into account the reaction mechanism during the manufacturing of PE-LD in the tubular and agitated autoclave reactor, resulting in the formation of so-called primary structure perameters M?n, M?w, molar mass distribution, short chain branching and long chain branching. For the interpretation of the results, among other factors, also the morphological conditions have been taken into consideration, which in connection with the molecular parameters reveal — for specific M?w-ranges — strong changes and saturation ranges, resp., for the physical and application technological properties. 相似文献