首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   158篇
  免费   11篇
电工技术   1篇
化学工业   32篇
金属工艺   8篇
机械仪表   8篇
建筑科学   12篇
能源动力   4篇
轻工业   23篇
水利工程   2篇
石油天然气   12篇
无线电   2篇
一般工业技术   40篇
冶金工业   2篇
原子能技术   3篇
自动化技术   20篇
  2023年   2篇
  2022年   4篇
  2021年   6篇
  2020年   4篇
  2019年   6篇
  2018年   9篇
  2017年   6篇
  2016年   7篇
  2015年   7篇
  2014年   9篇
  2013年   25篇
  2012年   7篇
  2011年   10篇
  2010年   7篇
  2009年   7篇
  2008年   6篇
  2007年   3篇
  2006年   9篇
  2005年   8篇
  2004年   9篇
  2003年   2篇
  2002年   1篇
  2001年   1篇
  2000年   1篇
  1999年   1篇
  1998年   1篇
  1997年   2篇
  1996年   2篇
  1991年   2篇
  1990年   2篇
  1979年   2篇
  1978年   1篇
排序方式: 共有169条查询结果,搜索用时 15 毫秒
71.
Abundant field data collected within the past twelve years or so show that all published explanations for the origin of this 2.4MM sq. km region violates some of these data. Among them, one fact is of paramount importance. This is the discovery that none of the great east-west fracture zones is a boundary between different, but coeval, lithofacies. Instead, several major facies boundaries (in rocks of various ages) form a zigzag pattern across the various blocks of the region. This fact, in turn, means that most published tectonic interpretations, including those of plate tectonics, are incorrect.
In Part 2 of this paper, the Authors now point out that the recently-proposed surge-tectonics hypothesis explains all field data. If the surge-tectonics hypothesis is correct, most of the Tibetan Plateau, including its Cambrian-through-Tertiary section, is prospective. They conclude, therefore, that Tibet could eventually become a major petroleum-producing province of the world.  相似文献   
72.
Elemental boron is one of the most valuable high-tech boron products and it has highest energy density 14 kcal/g in the world for this type of product. With the rapid advancements in technology in recent years, a demand has grown for a light materials with functionality and excellent properties such as high hardness, high melting point, high strength, high chemical resistance and nuclear characteristics that can be used in the fields of aerospace, aviation, automotive and solar cells. In this study boron oxide was reduced using carbon monoxide via a batch system to produce elemental boron. To determine the most suitable conditions for the reduction reaction different temperatures and different CO/B2O3 mol ratio parameters were studied. As a result of thermodynamic calculations for the most efficient parameters for reaction temperature was 140–210 °C and the CO/B2O3 mol ratio being studied was 3/1 and 2/1 for the batch system. Boron oxide reduction was performed by carbon monoxide gas with the pressure set at 10 bar. Characterization of the product was carried out by using X-Ray Diffractometer (XRD), Fourier Transform Infrared Spectroscopy (FT-IR) and Scanning Electron Microscopy (SEM) at optimum temperature and mol ratio (140 °C and 3/1). Boron phase was seen in both XRD and FT-IR analysis. Also, SEM analysis was performed in order to observe morphological structure of elemental boron.  相似文献   
73.
The Kansai Electric Power Co. Inc. (KEPCO) and Mitsubishi Materials Corporation (MMC) have been developing intermediate temperature solid oxide fuel cells (IT-SOFCs) which are operable at a temperature range between 600 and 800 °C. There are some significant features in IT-SOFC of KEPCO–MMC: (1) highly conductive lanthanum gallate-based oxide is adopted as an electrolyte to realize high-performance disk-type electrolyte-supported cells; (2) the cell-stacks with seal-less structure using metallic separators allow residual fuel to burn around the stack and the combustion heat is utilized for thermally self-sustainable operation; (3) the separators have flexible arms by which separate compressive forces can be applied for manifold parts and interconnection parts. We are currently participating in the project by New Energy and Industrial Technology Development Organization (NEDO) to develop 10 kW-class combined heat and power (CHP) systems. In FY2006, a 10 kW-class module was developed, with which the electrical efficiency of 50%HHV was obtained based on DC 12.6 kW. In the first quarter of FY2007, the 10 kW-class CHP system using the module gave the electrical efficiency of 41%HHV on AC 10 kW and the overall efficiency of 82%HHV when exhaust heat was recovered as 60 °C hot water. Currently, the operation has been accumulated for about 2500 h to evaluate the long-term stability of the system.  相似文献   
74.
Computational studies on tetranitro derivatives of [2,2]paracyclophane are carried out at B3LYP/6-31G(d,p) level of theory. Optimized geometries, electronic structures and some thermodynamic properties have been obtained in their ground states. Also, detonation performances were evaluated by the Kamlet-Jacobs equations, based on the quantum-chemical calculated densities and heat of formation values. Aromaticities were investigated by performing NICS (nucleus independent chemical shift) calculations using the gauge invariant atomic orbital (GIAO) approach at the same theoretical level. The results show that these kinds of compounds possess some properties of energetic materials and if these stable tetra-nitro substituted [2,2]paracyclophanes can be synthesized, they may be potential candidates for powerful energetic materials.  相似文献   
75.
The catalytic performance of ruthenium alkylidene complexes bearing tricyclohexylphosphine or 3-bromopyridine ligand in the ring opening metathesis polymerization (ROMP) of fluorine containing monomers, exo-N-4-fluorophenyl-7-oxanorbornene-5,6-dicarboximide (FPhONDI) and exo-N-4-fluorophenyl-norbornene-5,6-dicarboximide (FPhNDI) was investigated. Pure monomers were subjected to ROMP with RuCl2(PCy3)2(CHPh) (I), RuCl2(PCy3)(H2IMes)(CHPh) (II), RuCl2(3-Br-py)2(PCy3)(CHPh) (III) and RuCl2(3-Br-py)2(H2IMes)(CHPh) (IV). The polymers were fully characterized using NMR, DSC, SEM and GPC. Catalysts IIV displayed significant ROMP activity, allowing for the synthesis of the corresponding polymers with polydispersity indices (PDIs) in the range of 1.4–4.0. High molecular weight polymers (Mw up to 4.95 x105) were prepared in yields up to 90 %, depending on the initiator and monomer used.  相似文献   
76.
Development of high-capacity hydrogen-storage systems utilizing physisorption at high pressure and low temperature is hindered by poor understanding of the pore size/shape requirements for achieving the maximum hydrogen uptake. Tuning the carbon structure and pore size of carbide-derived carbons (CDCs) with high accuracy by using different starting carbides, chlorination temperatures and activation temperatures allows rational design of carbon materials with increased hydrogen-storage capacity. Systematic experimental investigation of a large number of CDCs with controlled pore size distributions and specific surface area (SSA) shows that pores larger than ∼1.5 nm contribute little to hydrogen storage. It has been experimentally demonstrated that, just as at ambient pressure, pores of 0.6–0.7 nm in diameter provide the largest H2 uptake per unit SSA at elevated pressures and liquid nitrogen temperatures. The effect of pore size was stronger than the effect of surface chemistry on the hydrogen uptake.  相似文献   
77.
The workpiece dynamics affect stability in machining of flexible parts. However, it is not a straightforward task to include it in the analysis since the workpiece dynamics continuously change due to mass removal and variation of the cutter contact. In this paper, a methodology for prediction of in-process workpiece dynamics is presented, which is based on a structural dynamic modification using the FE model of the workpiece. The cutter location (CL) file is used to determine the removed elements at each tool location along a cycle. The proposed approach is demonstrated on example cases, and simulations are verified through experiments.  相似文献   
78.
Myocardial infarction, caused by a major blockage of a coronary artery, creates a border zone (BZ) between perfused and nonperfused tissue, which is believed to be the origin of fatal cardiac arrhythmias. We used a combination of optical clearing and polarization-sensitive optical coherence tomography to visualize a three-dimensional organization of the BZ in isolated rabbit hearts (n=5) at the microscopic level with a high spatial resolution. We found that the BZ has a complex three-dimensional structure with nonperfused areas penetrating into perfused tissue with finger-like projections. These "fingers" may play an important role in the initiation and maintenance of ventricular arrhythmias.  相似文献   
79.
The inhibition characteristics of non-ionic surfactants of the TRITON-X series, namely TRITON-X-100 (TX-100), TRITON-X-165 (TX-165) and TRITON-X-305 (TX-305), on the corrosion of iron was studied in 1.0 M HCl solutions as a function of inhibitor concentration (0.005–0.075 g L−1) and solution temperature (278–338 K). Measurements were conducted based on Tafel extrapolation method. Electrochemical frequency modulation (EFM), a non-destructive corrosion measurement technique that can directly give values of corrosion current without prior knowledge of Tafel constants, is also presented. Experimental corrosion rates determined by the Tafel extrapolation method were compared with corrosion rates obtained by the EFM technique and an independent method of chemical analysis. The chemical method of confirmation of the corrosion rates involved determination of the dissolved cation, using ICP-AES (inductively coupled plasma atomic emission spectrometry). The aim was to confirm validation of corrosion rates measured by the Tafel extrapolation method. Results obtained showed that, in all cases, the inhibition efficiency increased with increase in temperature, suggesting that chemical adsorption occurs. The adsorptive behaviour of the three surfactants followed Temkin-type isotherm. The standard free energies of adsorption decreased with temperature, reflecting better inhibition performance. These findings confirm chemisorption of the tested inhibitors. Thermodynamic activation functions of the dissolution process were also calculated as a function of each inhibitor concentration. All the results obtained from the methods employed are in reasonable agreement.  相似文献   
80.
Taner Kavas   《Building and Environment》2006,41(12):1779-1783
The study was directed towards determining the usability of clay and fine wastes (CW and FW) of boron from the concentrator plant in Kirka (Turkey) as a fluxing agent in production of red mud (RM) brick. Both laboratory studies on the characterization of materials and industrial-scale tests for production of bricks were carried out. CW and FW, which have similar chemical composition but include different types and amounts of oxides, were added in amounts of 5, 10 and 15 wt% to RM, which consists of high amounts of Fe2O3, Al2O3, SiO2 and alkalies. Six different sets of samples have been produced and fired at 700, 800 and 900 °C. Dry shrinkage of green body, bending and compressive strength, firing shrinkage, water absorption, frost resistance and harmful magnesia and lime tests on heat-treated bodies have been performed. The mineralogical and mechanical tests showed that usability of boron wastes as a fluxing agent in the production of RM bricks was possible. In addition, the samples obtained by adding 15 wt% CW and FW to RM showed the best mechanical characteristic.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号