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51.
Abstract The amount of atmospheric N deposition in Germany is actual rather uncertain. Estimates using standard methods indicate an N deposition of 30–35 kg N/ha × year. However, the results of long-term field experiments and newly by the ITNI (Integrated Total Nitrogen Input) system could prove a much higher N input of about 50–60 kg N/ha × year. The reason for this difference is that standard methods use wet-only or bulk collectors, which neglect gaseous and organic N deposition as well as direct N uptake by aerial plant parts. By contrast, the ITNI-system is able to measure the total atmospheric N input using the 15N isotope dilution method. The input of airborne N into a soil/plant system leads to a dilution of the abundance of a previously applied 15N tracer over a defined time period. The atmospheric N deposition can be calculated from this dilution. To estimate the actual N input in Central Germany, ITNI measurements were carried out from autumn 1998 to autumn 2000 at four locations in the German state of Saxony-Anhalt. Atmospheric N depositions between 45 and 75 kg N/ha × year were determined depending on the location. These results closely match to N balances of longterm field experiments. Furthermore, a relationship was found between N deposition and the plant species used as well as plant development. 相似文献
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机载控制视觉目标定位系统广泛应用于航空控制领域,对其进行设计和实现具有重要应用意义。针对机载控制视觉目标定位的特征,设计并实现了机载控制视觉目标定位系统,分析了系统的总体结构,包括视觉模块、飞控模块、导航模块以及无线传输模块,给出了系统主控箱、CAPA800主控制器、PCI04总线标准的主板、视觉传感器、PM1270T144C5N芯片的硬件结构,给出了系统的软件流程和视觉处理模块的流程,分析了基于CCS3.3代码开发调试平台的系统代码设计,最终实现机载控制视觉目标定位系统的设计与实现。实验结果说明,所设计系统获取的机载控制视觉目标清晰、有效,并且具有较高的目标定位效率和精度。 相似文献
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An automated atmospheric elemental mercury analyzer based on the dielectric barrier discharge (DBD) atomic emission technique was developed. The instrument is based on a gold-on tungsten coiled filament preconcentrator fashioned from commercial quartz-halogen lamps, a DBD excitation source and a radiation detector. An in-house program provided system control and data collection. Several types of radiation detectors, e.g., charge coupled device (CCD) array spectrometers, photomultiplier tubes (PMTs) and phototube (PT) are investigated. An argon plasma provided better performance than a nitrogen plasma. With ∼0.88 standard liters per min sampling rate and preconcentration for 2 min, the estimated (S/N = 3) detection limit was 0.12 ng/L (Hg0), the linear range extended at least to 6.6 ng Hg/L. Typical RSD values for determination at the single digit ng/L level ranged from 2.8 to 4.9%. In 19 separate calibrations conducted over 7 days, the calibration slope had a standard error of 1%. The system was applied to the determination of atmospheric mercury in two different locations. 相似文献
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The façade of a room is usually composed of different construction elements, one of which is the window. This fulfils both an aesthetic function and closes the wall opening. In order to improve thermal behaviour and control solar radiation, the window is fitted with different protection features, such as the shutter. In climate zones with many hours of sunlight, windows in residential buildings commonly incorporate a rolling shutter. Traffic noise and higher standards of energy saving, comfort, durability and sustainability in buildings means that windows now have to comply with stricter requirements, including their sound insulation from airborne noise. This work contains a summary of studies carried out on the sound insulation from airborne noise in several types of windows (double side-hung casement and double horizontal sliding sash) with built-on shutter and prefabricated box. For each type of window, an analysis was made of the effects of the interior finishings in the shutter box, the shutter position (whether fully retracted or extended) and the weighted sound reduction index of windows for traffic noise in accordance with EN ISO 717-1. 相似文献
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This paper concerns the development and experimental validation of prediction models using Statistical Energy Analysis (SEA) to calculate the airborne sound insulation of a timber–concrete composite floor. The complexity in modelling this floor is due to it having (1) a multilayer upper plate formed from concrete and Oriented Strand Board (OSB), (2) multiple types of rigid connector between the upper plate and the timber joists and (3) a resiliently suspended ceiling. A six-subsystem model treats the concrete–OSB plate as a single subsystem and three different five-subsystem models treat the combination of concrete, OSB and timber joists as a single orthotropic plate subsystem. For the orthotropic plate it is suggested that bending stiffnesses predicted using the theories of Huffington and Troitsky provide a more suitable and flexible approach than that of Kimura and Inoue. All SEA models are able to predict the weighted sound reduction index to within 2 dB of the measurement. The average difference (magnitude) between measurements and predictions in one-third octave bands is up to 4 dB. These results confirm that SEA can be used to model direct transmission across relatively complex floor constructions. However, this requires the inclusion of measured data in the SEA model, namely the dynamic stiffness of the resilient isolators and the cavity reverberation time. 相似文献
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飞行试验是对飞机的性能进行验证和确认的关键阶段,试飞测试是保障该阶段工作的重要内容;国内目前对于军机已拥有了成熟的测试技术、测试方法和可靠的测试设备,而对于民用飞机特别是大型民机的试飞测试目前还处在起步阶段;随着国家大飞机研制专项的不断推近,大型客机试飞测试需求逐步明确;从大型民机试飞测试需求和测试工作特点出发,对机载测试技术变革、遥测和数据处理技术等键技术在国外的最新发展和国内大型飞机的现状进行对比分析,可以看出我国民机试飞测试在网络化机载测试系统应用、遥测传输链路带宽、大数据快速处理等方面存在较大的挑战;在此基础上对应对挑战的发展策略和后续攻关的方向进行研究,可以为我国大型飞机特别是民机试飞测试技术的发展提供参考。 相似文献
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