全文获取类型
收费全文 | 8004篇 |
免费 | 68篇 |
国内免费 | 7篇 |
专业分类
电工技术 | 27篇 |
综合类 | 3篇 |
化学工业 | 711篇 |
金属工艺 | 55篇 |
机械仪表 | 37篇 |
建筑科学 | 303篇 |
矿业工程 | 72篇 |
能源动力 | 54篇 |
轻工业 | 5289篇 |
水利工程 | 57篇 |
石油天然气 | 1篇 |
无线电 | 196篇 |
一般工业技术 | 408篇 |
冶金工业 | 351篇 |
原子能技术 | 23篇 |
自动化技术 | 492篇 |
出版年
2016年 | 73篇 |
2014年 | 92篇 |
2013年 | 95篇 |
2012年 | 151篇 |
2011年 | 140篇 |
2010年 | 103篇 |
2009年 | 108篇 |
2008年 | 158篇 |
2007年 | 178篇 |
2006年 | 143篇 |
2005年 | 71篇 |
1998年 | 80篇 |
1996年 | 71篇 |
1993年 | 72篇 |
1990年 | 83篇 |
1989年 | 95篇 |
1988年 | 82篇 |
1987年 | 90篇 |
1985年 | 86篇 |
1984年 | 104篇 |
1982年 | 80篇 |
1981年 | 87篇 |
1980年 | 83篇 |
1979年 | 85篇 |
1978年 | 76篇 |
1977年 | 95篇 |
1976年 | 107篇 |
1974年 | 79篇 |
1973年 | 99篇 |
1972年 | 87篇 |
1971年 | 88篇 |
1970年 | 101篇 |
1969年 | 82篇 |
1968年 | 80篇 |
1966年 | 83篇 |
1956年 | 71篇 |
1917年 | 81篇 |
1916年 | 108篇 |
1915年 | 106篇 |
1914年 | 90篇 |
1913年 | 105篇 |
1912年 | 134篇 |
1911年 | 115篇 |
1910年 | 122篇 |
1909年 | 136篇 |
1908年 | 131篇 |
1907年 | 129篇 |
1906年 | 129篇 |
1905年 | 129篇 |
1904年 | 120篇 |
排序方式: 共有8079条查询结果,搜索用时 15 毫秒
51.
52.
City councils hold meetings several times a week. There is a need for computer support at certain meetings. This paper examines the potential for group support systems for use in city council meetings and shows in what ways they can be helpful in pre-meeting and post-meeting activities. The study is based on 17 computer-supported city council meetings, carried out in Stuttgart, Kornwestheim and other cities as part of the Cuparla Project between 1996 and 1998. Three of these meetings are described in the paper as brief case studies. Following this, all 17 meeting sequences are evaluated and analysed. Guidelines have been developed from the results of the study for the introduction of group support systems in city council meetings. 相似文献
53.
Abstract— Coatings of indium tin oxide (ITO) nanoparticles on different flexible polymer substrates were investigated with respect to the achievable sheet resistance and their electrical behavior under oscillatory bending. As substrate materials, polyethyleneterephthalate (PET), polyethylenenaphthalate (PEN), polyetheretherketone (PEEK), and polyimide (PI) were chosen, the surface resistances on the different polymer substrates were compared as a function of annealing temperature and surface topography. The surface topography, which has a strong influence on the surface resistance, was characterized by means of a white‐light confocal (WL‐CF) microscope. On the PET substrate, which exhibits the smoothest surface, the coating of ITO nanoparticles shows the lowest sheet resistance of 2 kΩ/□ for a layer thickness of 3 μm and an annealing temperature of 200°C. Furthermore, the electrical behavior of coatings of ITO nanoparticles under oscillatory bending was investigated using a special device. These coatings show a cyclic change of the conductivity which can be explained by an alternating compression and extension of crack flanks under the applied stress. Due to the growing number of cracks with increasing number of cycles, a decrease of the conductivity is observed in the bent state as well as in the balanced state. For a small bending radii, the decrease of the conductivity is stronger due to more cracks caused by the higher tensile stresses in the layer. The electrical behavior of the coatings of the annealed ITO nanoparticles on PET films under oscillatory bending was compared with commercially available sputtered ITO coatings. The annealed coatings of ITO nanoparticles demonstrate better electrical properties under oscillatory bending than coatings of sputtered ITO. The different electrical behavior under oscillatory bending can be related to differences in crack formation. 相似文献
54.
Helmut Neukirchen Benjamin Zeiss Jens Grabowski 《International Journal on Software Tools for Technology Transfer (STTT)》2008,10(4):309-326
Experience with the development and maintenance of large test suites specified using the Testing and Test Control Notation (TTCN-3) has shown that it is difficult to construct tests that are concise with respect to quality aspects such as maintainability
or usability. The ISO/IEC standard 9126 defines a general software quality model that substantiates the term “quality” with
characteristics and subcharacteristics. The domain of test specifications, however, requires an adaption of this general model.
To apply it to specific languages such as TTCN-3, it needs to be instantiated. In this paper, we present an instantiation
of this model as well as an approach to assess and improve test specifications. The assessment is based on metrics and the
identification of code smells. The quality improvement is based on refactoring. Example measurements using our TTCN-3 tool
TRex demonstrate how this procedure is applied in practise.
B. Zeiss is supported by a Ph.D. scholarship from Siemens AG, Corporate Technology. 相似文献
55.
Helmut Reimer 《Datenschutz und Datensicherheit - DuD》2008,32(11):766-767
Ohne Zusammenfassung 相似文献
56.
57.
Lawrence E. Matson Helmut Erhart Moonyong Lee Robert A. Rapp 《Metallurgical and Materials Transactions A》1984,15(12):2241-2246
In situ oxidation of polycrystalline iron at 1200 °C and
atm has revealed symmetrical square growth pits in the wustite scale. The pit walls are nominally oriented with the {110}
planes of the wustite lattice but are dissociated into macro- and microledges consisting of {100}-type planes. Such growth
pits intrude into the wustite scale at the gas/oxide interface, and at the oxide/metal interface small oxide nodules intrude
into the metal. After sufficiently long oxidation times at 1200 °C, rate control should shift from oxidant arrival to cation
volume diffusion, and pits are then destabilized and a planar morphology is achieved. 相似文献
58.
Herbert Wieser Wolfgang Stempfl Werner Grosch und Hans-Dieter Belitz 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1984,179(6):447-449
Zusammenfassung Achtzehn Fettsäuren, Fettsäuremethylester und Fettalkohole, emulgiert in Wasser mit Sucrosepalmitatstearat, wurden auf ihre Geschmacksqualität untersucht; bei bitterschmeckenden Verbindungen wurden die Schwellenwerte bestimmt. Die Intensität des Bittergeschmacks von Fettsäuren und Fettalkoholen hängt von der Länge des Alkylrestes sowie von der Anzahl, der Konfiguration und der Position der Doppelbindungen ab. Linol- und Linolensäuremethylester schmecken nicht bitter. -Linolenylalkohol und -Linolensäure haben die niedrigsten Schwellenwerte (0,2–0,5 bzw. 0,6–1,2 mmol/l) und liegen etwa im gleichen Bereich wie Coffein (0,8–1,2 mmol/l).
Studies of the bitter taste of fatty acid emulsions
Summary Eighteen fatty acids, methyl esters of fatty acids and fatty alcohols emulsified in water with sucrose palmitate stearate were tested for taste quality. In the case of bitter tasting compounds the taste thresholds were determined. The intensity of bitter taste of fatty acids and fatty alcohols is dependent on the length of the hydrocarbon chain and on the number, the configuration and the positions of double bonds. The methyl esters of linoleic and linolenic acid are not bitter. Gamma-linolenyl alcohol and alphalinolenic acid have the lowest threshold values (0.2–0.5 and 0.6–1.2 mmol/l), similar to that of caffeine (0.8–1.2 mmol/l).相似文献
59.
Ulrich Schoch Jürg Lüthy und Christian Schlatter 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1984,178(5):351-355
Zusammenfassung In Rohextrakten von 18Penicillium camemberti- und 6P. roqueforti-Stämmen, die als Reifungsorganismen bei der Schimmelkäseproduktion in Schweizer Käsereien eingesetzt werden, wurde das mutagene Potential mit Hilfe des Ames-Testes bestimmt. In keinem der geprüften Extrakte konnte eine mutagene Aktivität festgestellt werden. Roquefortin, ein in Blauschimmelkäsen nachweisbares Mykotoxin vonP. roqueforti, erwies sich im Ames-Test als nicht mutagen. Die ermittelten Resultate ergaben keine Anhaltspunkte für genotoxische Effekte durch die Konsumation von schimmelgereiftem Käse.
Auszug aus der Dissertation von U. Schoch, Mykotoxine in schimmelgereiften Käsen, Diss. ETH Nr. 7278, ETH Zürich, 1983 相似文献
Mutagenicity testing of commercialP. Camemberti- andP. roqueforti-strains
Summary We tested the mutagenic potential of crude extracts of 18 strains ofPenicillium camemberti- and 6 strains ofP. roqueforti, which are used commercially in the production of mould ripened cheese in Switzerland. No mutagenic activity could be detected in any of the extracts. Roquefortine, a mycotoxin ofP. roqueforti, often found in Blue cheese, was negative in the Amestest. The results obtained do not lead reasons for experting undesired long term effects from the consumption of mould ripened cheese.
Auszug aus der Dissertation von U. Schoch, Mykotoxine in schimmelgereiften Käsen, Diss. ETH Nr. 7278, ETH Zürich, 1983 相似文献
60.
Wolfgang Sümmermann Hans Rohleder und Friedhelm Korte 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1978,166(3):137-144
Zusammenfassung Im Rahmen eines koordinierten Forschungsprogramms des BMFT wurde eine orientierende Studie an möglichst repräsentativen Stichproben durchgeführt. Trotz relativ großer Streubreiten zeichnen sich die Bereiche der wichtigsten Lebensmittelgruppen deutlich voneinander ab mit Mittelwerten um 0,005 /g für fettarme pflanzliche Grundnahrungsmittel, um 0,05 /g für pflanzliche Nahrungsfette, um 0,3 /g für Milch-, Käse und Butterfette, um 0,15 /g für sonstige Nahrungsfette von Landtieren, um 0,03 /g für Hühnereier und um 10 /g für Fischfett. Wichtet man die Gehalte entsprechend der durchschnittlichen Diät in der BRD, so ergibt sich eine tägliche PCB-Aufnahme von rund 29 aus tierischen Fetten und rund 6 aus den übrigen Lebensmitteln. Die Gesamtaufnahme von ca. 35 g pro Tag und capita entspricht etwa dem Wert, der von der WHO als ADI-Wert für HCB (Hexachlorbenzol) in Aussicht genommen wurde.
Polychlorinated biphenyls (PCB) in foodThe situation in the Federal Republic of Germany
Summary In a coordinated research program of the Federal Ministry of Research and Technology (BMFT), a screening study was carried out with representative samples. In spite of rather large ranges of PCB concentrations, the most important food-stuffs show clearly defined clusters with mean values of approx. 0.005 /g in low fat food components of plant origin such as cereals or potatoes, approx. 0.05 /g in vegetable fats, approx. 0.3 /g in fat from milk, butter and cheese, approx. 0.15 gg/g in animal fat, approx. 0.03 in chicken eggs and approx. 10 /g in fish fat. Considering the mean diet in the FRG, a daily PCB intake of about 29 g from animal fat and of 6 from the other food-stuffs results. The total intake of about 35 g per day and capita is almost the same as the figure conditionally suggested by the WHO as the acceptable daily HCB (hexachlorobenzene) intake.相似文献