全文获取类型
收费全文 | 252篇 |
免费 | 7篇 |
学科分类
工业技术 | 259篇 |
出版年
2022年 | 4篇 |
2021年 | 4篇 |
2020年 | 2篇 |
2019年 | 2篇 |
2018年 | 4篇 |
2017年 | 3篇 |
2016年 | 5篇 |
2015年 | 8篇 |
2014年 | 10篇 |
2013年 | 20篇 |
2012年 | 15篇 |
2011年 | 21篇 |
2010年 | 14篇 |
2009年 | 13篇 |
2008年 | 17篇 |
2007年 | 8篇 |
2006年 | 13篇 |
2005年 | 11篇 |
2004年 | 7篇 |
2003年 | 8篇 |
2002年 | 2篇 |
2001年 | 4篇 |
2000年 | 5篇 |
1999年 | 5篇 |
1998年 | 5篇 |
1997年 | 6篇 |
1996年 | 3篇 |
1995年 | 3篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1991年 | 3篇 |
1990年 | 3篇 |
1989年 | 1篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 11篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1972年 | 1篇 |
1971年 | 2篇 |
1964年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有259条查询结果,搜索用时 15 毫秒
1.
K Bj?ro JP Blomhoff E Schrumpf F Brosstad A Bergan T Egge 《Canadian Metallurgical Quarterly》1997,117(9):1274-1276
Budd Chiari syndrome (liver vein thrombosis) may be a diagnostic and therapeutic problem. On the basis of four different cases we review the major diagnostic and therapeutic principles involved. Imaging techniques are necessary in order to establish the diagnosis. Ultrasound examination with Duplex doppler is usually sufficient, but MR angiography is also useful. Treatment options are thrombolysis, surgery or liver transplantation. What treatment is selected will depend on the clinical situation and the prognosis. 相似文献
2.
Bone grafts are used to lengthen the dorsum and elevate the tip of the nose in patients with Binder's syndrome. Disappointing long-term results in some patients generally have been assumed to be a result of resorption and/or displacement of the grafts. Treatment outcome was studied in 11 patients with the use of serial profile roentgenograms. At 40 months, the mean values after surgery were reduction of the initial transplant length by 28 percent and reduction of the transplant angle by 4 degrees. The initial nose length was increased by 1 mm, and nose tip projection was increased by 2 mm. Although the mean changes of nose length and nose tip projection seemed small, treatment outcome varied considerably between patients. In contrast with earlier assumptions, no correlation could be found between the degree of transplant resorption and/or displacement and the effect of surgery on nose length and nose tip projection. 相似文献
3.
Comparison of a contactor catalytic membrane reactor with a conventional reactor: example of wet air oxidation 总被引:1,自引:0,他引:1
Sylvain Miachon Victor Perez Gabriel Crehan Eddy Torp Henrik R der Rune Bredesen J. -A. Dalmon 《Catalysis Today》2003,82(1-4):75-81
A wet air oxidation reaction was carried out in a gas/liquid catalytic membrane reactor of the contactor type. The oxidation of formic acid was used as a model reaction. The mesoporous top-layer of a ceramic tubular membrane was used as catalyst (Pt) support, and was placed at the interface of the gas (air) and liquid (HCOOH solution) phases.
A similar reaction was carried out in a conventional batch reactor, using a steering rate high enough to avoid gas-diffusion limitations, and exactly identical conditions than for the CMR (amount of catalyst, pressure, etc.). At room temperature, the CMR showed an initial activity three to six times higher than the conventional reactor. This activity increase was attributed to an easier oxygen access to the catalytic sites. Nevertheless, the catalytic membrane gradually deactivated after a few hours of operation. Different deactivation mechanisms are presented. 相似文献
4.
Stangegaard M Frøslev TG Frank-Hansen R Hansen AJ Morling N 《Journal of laboratory automation》2011,16(2):134-140
We have implemented and validated automated protocols for DNA extraction and PCR setup using a Tecan Freedom EVO liquid handler mounted with the Te-MagS magnetic separation device (Tecan, M?nnedorf, Switzerland). The protocols were validated for accredited forensic genetic work according to ISO 17025 using the Qiagen MagAttract DNA Mini M48 kit (Qiagen GmbH, Hilden, Germany) from fresh whole blood and blood from deceased individuals. The workflow was simplified by returning the DNA extracts to the original tubes minimizing the risk of misplacing samples. The tubes that originally contained the samples were washed with MilliQ water before the return of the DNA extracts. The PCR was setup in 96-well microtiter plates. The methods were validated for the kits: AmpF?STR Identifiler, SGM Plus and Yfiler (Applied Biosystems, Foster City, CA), GenePrint FFFL and PowerPlex Y (Promega, Madison, WI). The automated protocols allowed for extraction and addition of PCR master mix of 96 samples within 3.5h. In conclusion, we demonstrated that (1) DNA extraction with magnetic beads and (2) PCR setup for accredited, forensic genetic short tandem repeat typing can be implemented on a simple automated liquid handler leading to the reduction of manual work, and increased quality and throughput. 相似文献
5.
Spacecraft formation reconfiguration with collision avoidance 总被引:1,自引:0,他引:1
In this paper we present a behavioral control solution for reconfiguration of a spacecraft formation using the Null-Space Based (NSB) concept. The solution is task based, and aims to reconfigure and maintain a rigid formation while avoiding collisions between spacecraft. A model of relative translation is derived, together with a passivity-based sliding surface controller which globally stabilizes the equilibrium point of the closed-loop system. The NSB control method is implemented by giving each task different priorities and then calculating desired velocity and a Jacobian matrix for each spacecraft and each task. The velocity vector for each task is then projected into the null-space for higher prioritized tasks to remove conflicting velocity components. Simulation results are presented, showing that each spacecraft moves into the predefined formation without breaking any rules for the higher priority tasks, and all collisions are avoided. 相似文献
6.
洗油组分的提取、应用及前景 总被引:2,自引:1,他引:1
介绍了目前提取洗油组分的主要工艺过程及洗油中各组分的应用情况,指出我国应加强洗油加工利用的研究和其产品的开发应用:首先必需建设大型洗油加工装置,采用多种加工工艺,提取煤焦油特有的组分;其次提高洗油加工产品的纯度,获得高附加值的产品。 相似文献
7.
Trace Elements in the Si Furnace-Part II: Analysis of Condensate in Carbothermal Reduction of Quartz
Elena Dal Martello Gabriella Tranell Oleg Ostrovski Guangqing Zhang Ola Raaness Rune Berg Larsen Kai Tang Pramod Koshy 《Metallurgical and Materials Transactions B》2013,44(2):244-251
Silicon feedstock for production of solar-grade silicon should be as pure as possible to decrease the cost of manufacturing of solar cells. Impurities in quartz, carbonaceous materials, electrodes, and refractories are mostly present in the form of oxides. These oxides can be reduced to volatile gaseous compounds in presence of SiO(g) and CO(g) atmosphere and potentially leave the furnace or stay in the condensed reaction products, metal, and slag. This work investigates the conditions under which volatile impurities report to the gas phase in laboratory experiments with lumpy and pelletized mixtures of SiO2, SiC, and Si at 1923 K and 2123 K (1650 °C and 1850 °C), respectively, were carried out. The volatile compounds were generated by the reduction of quartz and collected in the form of condensate. The effects of the reaction temperature, quartz type, charge composition, pellets, and lumps on the composition of the condensate were studied. The trace elements in the charge input, reacting charge, and condensate were analyzed using inductively coupled plasma (ICP)-mass spectroscopy (MS) and X-ray diffraction (XRD). CO(g) and SiO(g), which are the major components in reduction reactions, formed four types of condensate: white, brown, green, and orange. The condensate constituents were amorphous SiO2, 3C:SiC, Si, and α-quartz. Each impurity present in the quartz charge entered the gas phase during quartz reduction and was detected in the condensate. Al and Fe show limited volatility. The volatility of Mn, P, and B depends on the charge mix: a higher PCO enhances the concentration of these elements in the gas phase. Fluid inclusions, common in hydrothermal quartz, enhance the distribution of the contaminants to the gas phase. Industrial campaigns on Si and Fe-Si production confirm the experimental results. 相似文献
8.
Jonathan M. Polfus Wen Xing Marit Riktor Martin F. Sunding Paul Inge Dahl Sidsel M. Hanetho Tommy Mokkelbost Yngve Larring Marie‐Laure Fontaine Rune Bredesen 《Journal of the American Ceramic Society》2016,99(3):1071-1078
Dense symmetric membranes of CaTi0.85?xFe0.15MnxO3?δ (x = 0.1, 0.15, 0.25, 0.4) are investigated in order to determine the optimal Mn dopant content with respect to highest O2 flux. O2 permeation measurements are performed as function of temperature between 700°C–1000°C and as function of the feed side ranging between 0.01 and 1 bar. X‐ray photoelectron spectroscopy is utilized to elucidate the charge state of Mn, and synchrotron radiation X‐ray powder diffraction (SR‐XPD) is employed to investigate the structure symmetry and cell volume of the perovskite phase at temperatures up to 800°C. The highest O2 permeability is found for x = 0.25 over the whole temperature and ranges, followed by x = 0.4 above 850°C. The O2 permeability for x = 0.25 reaches 0.01 mL(STP) min?1 cm?1 at 925°C with 0.21 bar feed side and Ar sweep gas. X‐ray photoelectron spectroscopy indicates that the charge state of Mn changes from approx. +3 to +4 when x > 0.1, which implies that Mn mainly improves electronic conductivity for x > 0.1. The cell volume is found to decrease linearly with Mn content, which coincides with an increase in the activation energy of O2 permeability. These results are consistent with the interpretation of the temperature and dependency of O2 permeation. The sintering behavior and thermal expansion properties are investigated by dilatometry, which show improved sinterability with increasing Mn content and that the thermal expansion coefficient decreases from 12.4 to 11.9 × 10?6 K?1 for x = 0 and x = 0.25, respectively. 相似文献
9.
Hideto Kurokawa Hisataka Yakabe Isamu Yasuda Thijs Peters Rune Bredesen 《International Journal of Hydrogen Energy》2014
The surface adsorption effect of CO on the hydrogen permeability of a 12.5 micron-thick Pd77Ag23 membrane has been evaluated quantitatively under experimental conditions close to the operating conditions of the highly-efficient membrane reformer (MRF) system developed by Tokyo Gas. The permeability of the membrane was measured in the conditions of CO concentration between 1 and 5 vol.% at a temperature and pressure of up to 500 °C and 0.6 MPa, respectively. High feed flow rates and a microchannel module configuration were applied in the flux measurements to ensure that the results are obtained with limited influence of concentration polarization adjacent to the membrane surface and hydrogen depletion along the microchannel length. While the CO inhibition effect was close to negligible at 500 °C, it was significant at lower temperatures. At a feed pressure of 0.2 MPa, the CO inhibition effect was only 0.2% at a CO concentration of 1 vol.% and the effect was 3.6% at a CO concentration of 5 vol.% at 500 °C. The CO inhibition effect were 3.4% for 1 vol.% CO and 14.1% for 5 vol.% CO at 400 °C. Measurements were also carried out at a high feed pressure of 0.6 MPa to evaluate the pressure dependence of the CO inhibition effect. The CO inhibition effect decreased to 0.7% at a CO feed concentration of 5 vol.% at 500 °C. Lower CO inhibition effect were also observed at 450 and 400 °C compared to the data obtained with the feed pressure of 0.2 MPa, while the inhibition levels were almost the same at 350 °C. Though the CO inhibition effect is larger at a lower feed pressure of 0.2 MPa, the effect was only 0.2% at 1 vol.% CO at 500 °C, which is close to the operating conditions of the MRF system. This study quantitatively revealed that the CO inhibition effect on hydrogen flux is extremely small when the membrane is operated at temperatures equal to or higher than 500 °C, even for state-of-the-art thin membranes. The performance of the Tokyo Gas MRF seems thus mainly limited by concentration polarization effects. 相似文献
10.
Smithwick M Mabury SA Solomon KR Sonne C Martin JW Born EW Dietz R Derocher AE Letcher RJ Evans TJ Gabrielsen GW Nagy J Stirling I Taylor MK Muir DC 《Environmental science & technology》2005,39(15):5517-5523
Perfluoroalkyl substances were determined in liver tissues and blood of polar bears (Ursus maritimus) from five locations in the North American Arctic and two locations in the European Arctic. Concentrations of perfluorooctane sulfonate (PFOS), perfluorohexane sulfonate, heptadecafluorooctane sulfonamide, and perfluoroalkyl carboxylates with C(8)-C(15) perfluorinated carbon chains were determined using liquid chromatography tandem mass spectrometry. PFOS concentrations were significantly correlated with age at four of seven sampling locations, while gender was not correlated to concentration for any compound measured. Populations in South Hudson Bay (2000-2730 ng/g wet wt), East Greenland (911-2140 ng/g wet wt), and Svalbard (756-1290 ng/g wet wt) had significantly (P < 0.05) higher PFOS concentrations than western populations such as the Chukchi Sea (435-729 ng/g wet wt). Concentrations of perfluorocarboxylic acids (PFCAs) with adjacent chain lengths (i.e., C9:C10 and C10:C11) were significantly correlated (P < 0.05), suggesting PFCAs have a common source within a location, but there were differences in proportions of PFCAs between eastern and western location sources. Concentrations of PFOS in liver tissue at five locations were correlated with concentrations of four polychlorinated biphenyl congeners (180, 153, 138, and 99) in adipose tissue of bears in the same populations, suggesting similar transport pathways and source regions of PFOS or precursors. 相似文献