全文获取类型
收费全文 | 1465篇 |
免费 | 44篇 |
专业分类
电工技术 | 34篇 |
综合类 | 4篇 |
化学工业 | 359篇 |
金属工艺 | 19篇 |
机械仪表 | 18篇 |
建筑科学 | 63篇 |
矿业工程 | 1篇 |
能源动力 | 35篇 |
轻工业 | 145篇 |
水利工程 | 2篇 |
石油天然气 | 1篇 |
无线电 | 103篇 |
一般工业技术 | 188篇 |
冶金工业 | 333篇 |
原子能技术 | 12篇 |
自动化技术 | 192篇 |
出版年
2021年 | 26篇 |
2020年 | 16篇 |
2019年 | 13篇 |
2018年 | 23篇 |
2017年 | 14篇 |
2016年 | 23篇 |
2015年 | 22篇 |
2014年 | 28篇 |
2013年 | 49篇 |
2012年 | 68篇 |
2011年 | 64篇 |
2010年 | 48篇 |
2009年 | 55篇 |
2008年 | 51篇 |
2007年 | 49篇 |
2006年 | 45篇 |
2005年 | 38篇 |
2004年 | 39篇 |
2003年 | 33篇 |
2002年 | 28篇 |
2001年 | 19篇 |
2000年 | 26篇 |
1999年 | 31篇 |
1998年 | 56篇 |
1997年 | 35篇 |
1996年 | 37篇 |
1995年 | 32篇 |
1994年 | 25篇 |
1993年 | 21篇 |
1992年 | 17篇 |
1990年 | 13篇 |
1989年 | 18篇 |
1988年 | 18篇 |
1987年 | 14篇 |
1984年 | 13篇 |
1982年 | 13篇 |
1981年 | 20篇 |
1979年 | 20篇 |
1978年 | 11篇 |
1977年 | 16篇 |
1976年 | 15篇 |
1975年 | 12篇 |
1974年 | 18篇 |
1973年 | 19篇 |
1971年 | 12篇 |
1970年 | 15篇 |
1969年 | 22篇 |
1968年 | 17篇 |
1967年 | 12篇 |
1966年 | 22篇 |
排序方式: 共有1509条查询结果,搜索用时 31 毫秒
41.
Forschung im Ingenieurwesen - Nasslaufende Lamellenkupplungen weisen zu Betriebsbeginn eine Phase des Einlaufens auf, in der sich das Reibungsverhalten durch Anpassung der Reibflächen... 相似文献
42.
Behnam Mohammadi Robert Raudner Mohsin Shafiq Edgar Ahn Hermann C. Altmeppen Markus Glatzel 《European Journal of Lipid Science and Technology》2020,122(9)
Prion‐reduction in standard biodiesel processes is caused by acidic and alkaline conditions. In the alternative RepCat biodiesel process, efficient prion‐reduction can be achieved by high‐temperature/pressure. However, a possible increase in thermostability of prions in the presence of methanol during these conditions has not previously been investigated, and is verified in this work. Samples are spiked with prions, treated with methanol, and incubated at 220 °C at 80 bar for 30 min. No traces of protease‐resistant prion protein (as proxy for prions) are detected in tallow or glycerine (as the final by‐product) after treatment. Serial dilutions of spiked prions show at least 6 log10 prion reduction. More importantly, similar effects are detected using milder conditions of 200 °C at 70 bar for 15 min, representing the worst‐case conditions of the process. In conclusion, this study shows that methanol does not increase the thermostability of prions and the RepCat process can efficiently eliminate prions and is therefore safe for the usage of category 1 tallow. Practical Applications: The study further supports the applicability of RepCat process in reducing prion‐contamination in the presence of methanol. Furthermore, the conditions leads to a considerable reduction of prions in glycerine obtained as by‐product. 相似文献
43.
Zafer Defne Kevin A. Haas Hermann M. Fritz Lide Jiang Steven P. French Xuan Shi Brennan T. Smith Vincent S. Neary Kevin M. Stewart 《Renewable & Sustainable Energy Reviews》2012,16(5):3326-3338
A geodatabase of tidal constituents is developed to present the regional assessment of tidal stream power resource in the USA. Tidal currents are numerically modeled with the Regional Ocean Modeling System (ROMS) and calibrated with the available measurements of tidal current speeds and water level surfaces. The performance of the numerical model in predicting the tidal currents and water levels is assessed by an independent validation. The geodatabase is published on a public domain via a spatial database engine with interactive tools to select, query and download the data. Regions with the maximum average kinetic power density exceeding 500 W/m2 (corresponding to a current speed of ~1 m/s), total surface area larger than 0.5 km2 and depth greater than 5 m are defined as hotspots and documented. The regional assessment indicates that the state of Alaska (AK) has the largest number of locations with considerably high kinetic power density, followed by, Maine (ME), Washington (WA), Oregon (OR), California (CA), New Hampshire (NH), Massachusetts (MA), New York (NY), New Jersey (NJ), North and South Carolina (NC, SC), Georgia (GA), and Florida (FL). 相似文献
44.
45.
46.
Frank S. Barnes John Price Allen Hermann Zhihang Zhang Huey-Daw Wu David Galt 《组合铁电体》2013,141(1-2):171-184
Abstract The group at the University of Colorado has been working on the applications of BaSrTiO3 and high temperature superconductors to microwave circuits and systems with support from Superconducting Core Technologies, NASA and ONR. This work has included the development of a voltage tunable oscillator, a phase shifter, and a voltage tunable phased array antenna system. An important aspect of this program is the lattice match between the high temperature superconductor and the ferroelectric materials which enables us to grow thin films of either material on each other. By choosing the appropriate barium stronium ratio we are able to obtain changes in the dielectric constant of 5 to 1 in bulk capacitors at 77 K, the liquid nitrogen boiling temperature. Phase shifts of a little less than 126° at 10 Ghz have been obtained by applying 5 volts on a one centimeter coplanar line. The proposed phased array systems should enable us to point the beam radiated from the antenna in an arbitrary direction using two control voltages of less than 50 volts. We believe this approach leads to the possibility of inexpensive electronically scannable antenna systems which could be used for mobile communications with satellites and cellular systems. 相似文献
47.
In cake filtration processes with an air-blowing step, cracking is an undesirable phenomenon as it leads to deterioration of the filtration process by highly increasing gas throughput. This leads to higher residual moisture if the pressure difference cannot be maintained and an increase in overall cost. Crack formation can be avoided by compacting the filter cake before desaturation. While this action will make the separation process applicable by highly reducing gas consumption, there are also potential negative effects. Compaction increases filter cake resistance and might therefore slow down desaturation kinetics. Therefore, the authors investigated how the filter cake characteristics governing desaturation change from the nonconsolidated to the consolidated state of the filter cake and compared these findings to the actual dewatering kinetics. The results showed that for the case where cracking could be oppressed, dewatering kinetics of the consolidated cake are actually faster than for the nonconsolidated cake, despite higher resistance of the consolidated cake. Thus, compaction is an appropriate action when dealing with filter cake cracking. 相似文献
48.
Two organosilicone-modified polyurethanes are investigated as potential materials for the conservation and consolidation of natural stones. The materials are low molecular weight oligomers at the application stage and react with the humidity of the air to give polymers, forming continuous microlayers. The two differ in the length of the organosilicone chain, resulting in pronounced differences in their physical state: one forms a brittle glassy material (Tg ≈ 70°C). and the other, a soft rubbery material (Tg ≈ −100°C). The rate of the polymerization of the prepolymers was investigated at different conditions, showing a strong dependence on the presence of a catalyst and air humidity. Both these favorable conditions exist probably in the natural stone pores, enhancing the formation of the protective hydrophobic internal microlayer. © 1996 John Wiley & Sons, Inc. 相似文献
49.
Flavins and Chinamoyl Derivatives in Relation to the Light-induced Leaf Opening in Albizia julibrissin In search of blue-light photoreceptors for light-induced leaf opening we isolated from the aqueous extract of Albizia julibrissin Durazz. two flavins by adsorption on XAD-4 and separation with HPLC. One sample was identified as riboflavin 1a. In the hydrolysate of the second flavin fraction we found another dimethylisoalloxazine with a C5-side chain. Furthermore we isolated the cinnamoyl derivatives 3-O-(4-hydroxy-trans-cinnamoyl) quinic acid 2 and 3-O-(3,4-dihydroxy-trans-cinnamoyl)-4-O-malonyl-quinic acid 3 which formed charge transfer complexes with the flavins in the XAD-fraction. As a model complex we examined the absorption behaviour of the complex between riboflavin and chlorogenic acid. Using the association constant, we calculated the absorption spectrum and could show that a complex between a flavin and a phenolic compound is a possible blue-light photoreceptor for the light-induced leaf opening in Albizia julibrissin. 相似文献
50.
Séverine Goscinny Hermann Unterluggauer Jasmin Aldrian Vincent Hanot Sonja Masselter 《Food Analytical Methods》2012,5(5):1177-1185
A straightforward analytical method has been developed for the determination of glyphosate and aminomethylphosphonic acid (AMPA), its major metabolite in cereals. This method entails a rapid extraction and derivatization with 9-fluorenylmethyl chloroformate followed by separation with a conventional reversed-phase rapid chromatography used in daily routine analysis and detection by electrospray ionization tandem mass spectrometry. To overcome matrix effects and compensate for any analyte losses during sample treatment, an isotopic dilution approach was used. Since 2010, the monitoring of cereals for the widely used herbicide glyphosate is obligatory to all European Union (EU)-member states, laid down in Commission Regulation (EC) No. 1213/2008. Hence, there is definitively a need for a reliable and easy-to-handle analytical method for monitoring of this compound. The proposed method can be run without having to make time-consuming changes on the equipment used for daily routine analysis. The analytical performance of the method was evaluated according to SANCO/10684/2009 criteria and demonstrated that this method is rugged and cost-effective, therefore suitable for monitoring purposes as well as legislative enforcements within the EU. The apparent recoveries of both analytes were between 97% and 113% with relative standard deviations less than 20%. The limits of quantification of glyphosate and AMPA were 0.02 mg/kg in cereal matrices. Finally, the accuracy of the method was assessed by analyzing a proficiency test material which was available from a previous round (EUPT-C4). 相似文献