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1.
Land use morphology has profound effects both on city functions and peri-urban areas. They can either lead to conflicts with negative side effects or generate positive synergies. This study focuses on land use spatial configurations and interprets the interactions among them. In order to evaluate spatial planning policies, the measurement of urban land use patterns is considered to play an important role in the urban development process and deserves further attention. A comparative analysis of the land use patterns of the medium-sized Hellenic cities is attempted, there are also used using pre-existing metrics, some new data from the European Environment Agency Urban Atlas 2006 geodataset and population and construction census data concerning the last decade from the national Hellenic Statistical Authority data set. The Larger Urban Zones of the medium-sized Hellenic cities are chosen as a suitable study level based both on population size and socio-spatial procedures. The results provide interesting information about the diversification among medium-sized cities, while some particularities concerning urban procedures appear to emerge for some of them. Many discussion points arise from this study concerning the data availability, the method, the functional city area delineation and the Larger Urban Zones definition.  相似文献   
2.
Experimental data usable for evaluating cross sections of main fission product elements (Rh, Cs, Nd, Sm, Eu and Gd) in the epithermal energy range were measured. A cadmium-covered vessel containing a pure water or an aqueous solution of a fission product element was inserted at the center of TCA (Tank-type Critical Assembly) core. Reactivity effects were obtained by the difference in the critical water levels between a pure water and an aqueous solution in the vessel. The measured reactivity was more than 1 φ and it was greater than the experimental uncertainties. Since the adjoint thermal flux below the cadmium-cutoff energy are largely depressed in the vessel, the reactivity effects in epithermal energy range could be measured. The analyses for the experiments were performed using the SRAC code system and neutron transport calculation code TWOTRAN. The exact Perturbation theory was applied to calculate the reactivity effects of fission product elements. The calculated reactivity effects using JENDL-3.2 and ENDF/B-IV cross-section libraries were compared against the measured values. The analyses using JENDL-3.2 gave reasonable results for these measurements.  相似文献   
3.
Critical and subcritical masses were calculated for a sphere of five curium isotopes from 243Cm to 247Cm in metal and in metal-water mixtures considering three reflector conditions: bare, with a water reflector or a stainless steel reflector. The calculation were made mainly with a combination of a continuous energy Monte Carlo neutron transport calculation code, MCNP, and the Japanese Evaluated Nuclear Data Library, JENDL-3.2. Other evaluated nuclear data files, ENDF/B-VI and JEF-2.2, were also applied to find differences in calculation results of the neutron multiplication factor originated from different nuclear data files. A large dependence on the evaluated nuclear data files was found in the calculation results: more than 10%Δk/k relative differences in the neutron multiplication factor for a homogeneous mixture of 243Cm metal and water when JENDL-3.2 was replaced with ENDF/B-VI and JEF-2.2, respectively; and a 44% reduction in the critical mass by changing from JENDL-3.2 to ENDF/B-VI for 246Cm metal. The present study supplied basic information to the ANSI/ANS-8.15 Working Group for revision of the standard for nuclear criticality control of special actinide elements. The new or revised values of the subcritical mass limits for curium isotopes accepted by the ANSI/ANS-8.15 Working Group were finally summarized.  相似文献   
4.
In the framework of the development of burnup calculation method for commercial fast reactors, a sensitivity analysis was carried out to clarify the dependence of fuel burnup characteristics on nuclear data libraries (NDLs). The following NDLs were compared: JEF-2.2, ENDF/B-VI Release 5, JENDL-3.2 and JENDL-3.3. The NDL-dependence of material balance for main heavy metal nuclides (235U, 238U, 239Pu, 240Pu and 241Pu) was small, since the number densities at the end of one-cycle burnup did not change over 1 or 2% among the above-mentioned libraries. Relatively large differences were found for minor actinide nuclides, especially for 236U, 237Np, 242mAm, 243Am and curium isotopes. The number densities for these nuclides after burning up showed remarkable NDL-dependence over 5% through 50%. A burnup sensitivity analysis system based on the generalized perturbation theory enabled us to find out quantitatively the causative nuclides and reactions, as well as their energy regions.  相似文献   
5.
殷万军  刘玉奎 《微电子学》2012,42(4):547-550
从半导体器件物理角度出发,分析了P+-N-N+功率二极管零输入态下正向恒定电流IF与反向电流峰值IRM的解析关系。根据误差函数与初等函数的近似关系,推出简约解析关系式:(IRM/IF)=a+b×ln(IF+1)。在检测电路中引入反向平衡电流源,利用仿真软件Silvaco-Atlas获得瞬态仿真实验数据。通过Matlab软件对实验数据进行拟合分析,并对简约式适用范围和相关结论进行了验证。研究结果对P+-N-N+功率二极管的应用和相应电路系统的可靠性具有指导意义。  相似文献   
6.
对低压条件下自然循环回路内的两相间歇泉流动不稳定性进行了实验研究。同时,对RELAP5/MOD3.2程序计算低压自然循环间歇泉流动不稳定的可行性进行了验证分析。实验结果表明,低压条件下,间歇泉流动不稳定产生的根本原因在于有效驱动压头的周期性变化,与加热段内气液两相流动的形成-消失周期密切相关。下降段内流体温度越高,波动周期越短。实验数据与RELAP5/MOD3.2程序模拟计算结果符合较好,说明RELAP5/MOD3.2程序对模拟计算低压条件下自然循环间歇泉流动不定稳性具有较好的适用性。  相似文献   
7.
8.
Benchmark models of the critical experiments which measured reactivity effects of main fission product elements (Rh, Cs, Nd, Sm, Eu, and Gd) and of an important burnable poison element, erbium, were presented. These elements were dissolved in a vessel which was inserted into the central region of a fuel rod array of TCA (Tank-Type Critical Assembly). The atomic number densities of aqueous solutions in the vessel were calculated. Using these number densities, criticality calculations with MCNP 4A, TWOTRAN code, and JENDL-3.2 cross section library were performed for these experiments.  相似文献   
9.
In this study, a radio-activation experiment was conducted using stainless steel outside the active fuel region (active core) in the Toshiba Nuclear Critical Assembly (NCA) in order to verify the homogenization method by simulating the NCA experimental reactor system and understand the effects of this method on the analysis accuracy. In order to validate homogenization method, we simulated the system using the continuous energy Monte Carlo code MCNP, which allows heterogeneously modeling, and examined application of the homogenization method used for modeling commercial boiling water reactors (BWRs) with the TORT code. The calculation results of activation rate obtained by using the MCNP code with either heterogeneous or homogeneous models do not affect the calculation result of activation rate outside the active core. As the homogenization method was validated, the calculation of activation rate using the TORT code was performed with the same homogeneous model as in the MCNP calculation. The results of the activation rate calculation using the TORT code gave values 20 to 30% larger than the calculation results obtained via MCNP for 55Mn. This is considered to be caused by thermal energy group structure which is treated as one group.  相似文献   
10.
Fatigue-free Bi3.2La0.8Ti3O12 ferroelectric thin films were successfully prepared on p-Si (100) substrates using metalorganic solution deposition process. The orientation and formation of 5-layers thin films were studied under different processing conditions using XRD. Experimental results indicate that increase in annealing time at 700 °C after preannealing for 10 min at 400 °C can remarkably increase (200)-orientation of the films derived from the precursor solutions with two contents of citric acid. Meanwhile, high content of citric acid increases the film thickness and is conducive to the a-orientation of the films with the preannealing, and low concentration of the solution is conducive to the c-orientation of the films without the preannealing.  相似文献   
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