全文获取类型
收费全文 | 725篇 |
免费 | 25篇 |
专业分类
电工技术 | 2篇 |
综合类 | 3篇 |
化学工业 | 248篇 |
金属工艺 | 15篇 |
机械仪表 | 11篇 |
建筑科学 | 45篇 |
矿业工程 | 2篇 |
能源动力 | 11篇 |
轻工业 | 78篇 |
水利工程 | 1篇 |
无线电 | 39篇 |
一般工业技术 | 142篇 |
冶金工业 | 45篇 |
原子能技术 | 6篇 |
自动化技术 | 102篇 |
出版年
2023年 | 4篇 |
2022年 | 9篇 |
2021年 | 21篇 |
2020年 | 12篇 |
2019年 | 20篇 |
2018年 | 14篇 |
2017年 | 16篇 |
2016年 | 21篇 |
2015年 | 19篇 |
2014年 | 23篇 |
2013年 | 40篇 |
2012年 | 41篇 |
2011年 | 41篇 |
2010年 | 39篇 |
2009年 | 35篇 |
2008年 | 34篇 |
2007年 | 32篇 |
2006年 | 21篇 |
2005年 | 26篇 |
2004年 | 26篇 |
2003年 | 14篇 |
2002年 | 14篇 |
2001年 | 13篇 |
2000年 | 15篇 |
1999年 | 13篇 |
1998年 | 12篇 |
1997年 | 17篇 |
1996年 | 13篇 |
1995年 | 15篇 |
1994年 | 8篇 |
1993年 | 9篇 |
1992年 | 7篇 |
1991年 | 9篇 |
1990年 | 7篇 |
1989年 | 6篇 |
1988年 | 13篇 |
1987年 | 8篇 |
1985年 | 6篇 |
1984年 | 2篇 |
1983年 | 9篇 |
1982年 | 5篇 |
1981年 | 8篇 |
1980年 | 4篇 |
1979年 | 2篇 |
1976年 | 5篇 |
1975年 | 3篇 |
1974年 | 3篇 |
1972年 | 4篇 |
1970年 | 5篇 |
1969年 | 2篇 |
排序方式: 共有750条查询结果,搜索用时 15 毫秒
701.
702.
Luca Delgrossi Christian Halstrick Dietmar Hehmann Ralf Guido Herrtwich Oliver Krone Jochen Sandvoss Carsten Vogt 《Multimedia Systems》1994,2(4):172-180
HeiTS, the Heidelberg Transport System, is a multimedia communication system for real-time delivery of digital audio and video. HeiTS operates on top of guaranteedperformance networks that apply resource reservation techniques. To make HeiTS also work with networks for which no reservation scheme can be realized (for example, Ethernet or existing internetworks), we implement an extension to HeiTS which performs media scaling at the transport level: The media encoding is modified according to the bandwidth available in the underlying networks. Both transparent and nontransparent scaling methods are examined. HeiTS lends itself to implement transparent temporal and spatial scaling of media streams. At the HeiTS interface, functions are provided which report information on the available resource bandwidth to the application so that nontransparent scaling methods may be used, too. Both a continuous and discrete scaling solution for HeiTS are presented. The continuous solution uses feedback messages to adjust the data flow. The discrete solution also exploits the multipoint network connection mechanism of HeiTS. Whereas the first method is more flexible, the second technique is better suited for multicast scenarios. The combination of resource reservation and media scaling seems to be particularly well suited to meet the varying demands of distributed multimedia applications. 相似文献
703.
704.
705.
A special type of jet loop reactor (JLR), designed for continuous operation and short residence times was investigated with regard to its mass transfer behaviour, described by the volumetric mass transfer coefficient kLa. The jet stream and superficial gas velocities are varied in two JLRs of different sizes, equipped with different nozzles. Fully desalinated water, 0.08 molar NaCI solution and solutions of different concentration of carboxymethyl cellulose (CMC) are used as the liquid phase. A steady-state physical method is employed to determine kLa: air oxygen is purged from the liquid phase by gaseous nitrogen. The measurements show that the reactor is characterized by high power density and high mass transfer performance. No limit of mass transfer capacity was observed in the chosen ranges of volumetric gas and liquid flow rates, i.e. at a given jet stream velocity, the relationship between kLa and the superficial gas velocity is nearly linear. The investigations show that the mass transfer contributed by the jet stream largely depends on liquid phase composition. 相似文献
706.
In order to determine chemically the amino end groups present in a polyamide, the polymer was treated with a solution of 1-fluoro-2,4-dinitrobenzene (FDNB) in 2,2,2-trifluoroethanol (TFE). The resulting Nω-[2,4-dinitrophenyl-(1)]-(DNP-) polyamide was precipitated in water at pH 3, washed free of excess reagent, redissolved in TFE, and the optical density of the solution measured at λmax = 350 nm (ε350: 17300 [1000 cm2/mole]). Both the primary and secondary amino groups could be simultaneously determined by this method, since the absorption maximum of dinitrophenylated secondary amino groups is shifted to 390 nm (ε390: 18000 [1000 cm2/mole]). Using this spectroscopic phenomenon a two-component analytical procedure was developed. With known concentrations of dinitrophenylated primary amines, secondary amines, and nylon-6 and nylon-6,6 oligomers, the following analytical equations were derived: (c1: concentration of primary amino groups in mole/l; c2: concentration of secondary amino groups in mole/l; D350, D390: optical density at 350 nm and 390 nm resp.). The coefficients of variation for four different commercially available nylon-6 fibres (unmodified and modified for dyeability) were in the range of 2.7 to 6.0%. The limiting concentration detectable was 6 × 10?7 mole DNP-amino groups/l TFE. A kinetic analysis was performed for the reaction of FDNB with nylon-6 and with a model compound, ε-aminocaproic acid. Using the “absolute rate theory of Eyring”, it was found that the polymer and monomer both fulfilled the “principle of equal reactivity”. The activation parameters for the reaction were: ΔH≠ : 15.9 ± 0.9 kcal/mole, ΔG≠: 22.9 ±0.3 kcal/mole, and ΔS≠: ?22.1 ± 1.9 e.u./mole. 相似文献
707.
Stefan Wiemann Hartmut Voss Christian Schwager Thomas Rupp Joseph Stegemann Jürgen Zimmermann Dietmar Grothues Christoph Sensen Holger Erfle Neil Hewitt Andrea Banrevi Wilhelm Ansorge 《Yeast (Chichester, England)》1993,9(12):1343-1348
We have sequenced two segments containing a total of 51·6 kb of the left arm from chromosome XI of Saccharomyces cerevisiae. The first segment of 38·5 kb contains 18 open reading frames (ORFs) of more than 100 amino acid residues. Five ORFs encode known yeast genes, including the fatty acid synthase gene (FAS1). Three new yeast genes were discovered with homologies to non-yeast genes and ten new genes without homologies to any known sequences. The second segment of 13 kb contains five ORFs with two known yeast genes and three unknown genes. The sequences from cosmid pUKG041 were obtained entirely with the walking primer strategy resulting in a very low overall sequence redundancy of 2·8 and an average reading length of 443 bases. 相似文献
708.
709.
Prof. dr.-Ing. Kurt Nixdorff Dipl.-Ing. Dietmar Hämisch 《Forschung im Ingenieurwesen》1981,47(5):147-148
Zusammenfassung In den bisherigen Arbeiten über Schwingungen von Rohren mit einem freien und einem eingespannten Ende nahm man an, da? das
feste Ende starr eingespannt sei. Es wird gezeigt, da? diese ungenaue Annahme (die zu auff?lligen Unterschieden zwischen berechneten
und gemessenen Werten führt) unn?tig ist und ersetzt werden kann durch die Annahme einer “linearen” Einspannung (verallgemeinerten
elastischen Einspannung), deren Koeffizienten aus gemessenen Frequenzen der freien Schwingungen des Rohrs bestimmt werden
k?nnen.
Herrn Prof. Dr. rer. nat.F. Weidenhammer zur Vollendung des 60. Lebensjahres in Verehrung und Dankbarkeit gewidmet 相似文献
710.
Jost Engert Jörn Beyer Dietmar Drung Alexander Kirste Margret Peters 《International Journal of Thermophysics》2007,28(6):1800-1811
The application of a magnetic-field-fluctuation thermometer (MFFT) is described for practical thermometry in the low-temperature
range. The MFFT inductively measures the magnetic noise generated by Johnson noise currents in a metallic temperature sensor.
The temperature of the sensor is deduced from its thermal magnetic noise spectrum by applying the Nyquist theorem, making
the thermometer in principle linear over a wide range of temperatures. In this setup, a niobium-based dc SQUID gradiometer
detects the magnetic field fluctuations. The gradiometer design optimizes the inductive coupling to the metallic temperature
sensor, yet equally ensures sufficient insensitivity to external magnetic interference. In order to obtain a highly sensitive
and fast thermometer, the SQUID chip is placed directly onto the surface of the temperature sensor. The compact setup of the
gradiometer/temperature sensor unit ensures good conditions for thermal equilibration of the sensor with the temperature to
be measured, a factor that becomes increasingly important in the temperature range below 1 K. The first direct comparison
measurements of the MFFT with a high-accuracy realization of the Provisional Low Temperature Scale of 2000 (PLTS-2000) are
presented. Special emphasis is given to the investigation of the linearity, speed, and accuracy of the MFFT. 相似文献