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Electrokinetic gating, functioning as a micro-valve, has been widely employed in microfluidic chips for sample injection and flow switch. Investigating its valving performance is fundamentally vital for microfluidics and microfluidics-based chemical analysis. In this paper, electrokinetic gating valve in microchannels was evaluated using optical imaging technique. Microflow profiles at channels junction were examined, revealing that molecular diffusion played a significant role in the valving disable; which could cause analyte leakage in sample injection. Due to diffusion, the analyte crossed the interface of the analyte flow and gating flow, and then formed a cometic tail-like diffusion area at channels junction. From theoretical calculation and some experimental evidences, the size of the area was related to the diffusion coefficient and the velocity of analytes. Additionally, molecular diffusion was also believed to be another reason of sampling bias in gated injection. 相似文献
84.
光脉冲在标准单模光纤中演化形成孤子的实验研究 总被引:3,自引:0,他引:3
利用二次谐波频率分辨光学门脉冲分析仪从实验上分析研究了具有啁啾的10 GHz光脉冲在不同输入功率下演化形成孤子的规律和特点。实验发现:输入脉冲在光纤中传输3.5个色散长度时,其时间宽度、频率啁啾和时间带宽积都随着输入功率的增加而减小。当输入功率大于一阶孤子功率的理论值时,光脉冲能够演化形成孤子;脉冲在随后传输过程中其宽度基本保持不变,波形、频率啁啾和时间带宽积仍随着传输距离的变化而变化;输入功率越高,形成的一阶孤子脉冲的宽度越窄。当输入功率小于一阶孤子功率的理论值时,输出脉冲的时间宽度随着传输距离的增加而增加,频率啁啾随着传输距离的增加而减小,光脉冲不能演化形成孤子。 相似文献
85.
Bixue Hou Guofu Chen Zhiqi Hao Shan Feng Shuyan Wang Yishan Wang Guozhi Wang 《中国科学A辑(英文版)》1999,42(8):852-858
The experimental results of imaging through flesh tissue using fs electronic holographic gating method is reported. In the
experiment, Ti: sapphire mode-locked laser is used as light source, of which the repetition rate is 100 MHz, central wavelength
800 nm, duration of pulse 20 fs, output power 80 mW. Tissue is a 7 mm thick chicken slice, and the imaged object is a metal
wire with diameter of 0.5 mm. A general CCD is used to record holograms and a clear image of metal wire is obtained. Several
relevant problems are discussed. 相似文献
86.
提出了菲涅耳波带板(FZP)无运动卷积偏振选通全息术,该技术的原理与菲涅耳波带板扫描全息术相同,但在成像系统结构上作了重大改进,改进内容主要有两个方面:第一,使用扩展光源,用多个菲涅耳波带板在物体上的投影叠加形成卷积运算来取代机械扫描,克服了扫描造成的系统不稳定性和限制实际应用的耗时问题;第二,用CCD取代光电倍增管,使物体上所有的点都同时成像在CCD靶面上,达到实时采集整个全息图的目的。对线偏振光和圆偏振光经过散射介质脂肪乳剂(Intralipid)溶液后偏振度的变化规律进行了实验研究,研究表明,在米氏散射区,圆偏振光比线偏振光更容易保持偏振态。应用菲涅耳波带板无运动卷积偏振选通成像系统,采用圆偏振光作为入射光,对嵌埋在浓度为1%、深度为2 cm的脂肪乳剂溶液中的金属丝(直径0.4 mm)进行了成像实验,结果表明,菲涅耳波带板无运动卷积偏振选通全息术原理是可行的。 相似文献
87.
针对于多目标在机载多普勒盲区测量数据丢失下的跟踪问题,提出了一种鲁棒无偏转换自适应门限的CPHD(Robust Unbiased Converted Measurements-Adaptive Gating-Cardinalized Probability Hypothesis Density,RUCM-AG-CPHD)算法。该算法首先对目标测量信息进行无偏转换,并将无偏转换得到的噪声协方差矩阵做解耦;然后设计增益调节矩阵提高滤波器在目标量测数据丢失下的鲁棒性;最后采用自适应门限去除不相关的量测信息,同时保证检测到新出现的目标,从而有效地降低了算法的计算复杂度。仿真结果表明该算法的有效性和可行性,可以更加准确的估计出目标在盲区内测量信息丢失下的目标个数和状态,且计算量相对于传统的CPHD算法减少了8.6%。 相似文献
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89.
June T. Ruszkowski Raymond Damadian Anthony Giambalvo Antoinette Gomes David Hertz Robert Lufkin S. David Smith Donald Wortham 《Magnetic resonance imaging》1986,4(6):497-502
Spin echo images of the carotid arteries in longitudinal view have been obtained by selection of oblique imaging planes. Blood flow within the lumen in the region of the carotid bifurcation has been visualized through the use of cardiac gating during end diastole. Using a surface coil placed about the mandible, high resolution images [(0.75 mm)2 per pixel) were obtained with scan times typically equal to 9 min and image data matrix equal to 256 × 256. Images obtained with this technique of MRI carotid angiography demonstrate blood flow phenomenon as well as vascular anatomy. 相似文献
90.
Guido Buonincontri Carmen Methner Thomas Krieg T. Adrian Carpenter Stephen J. Sawiak 《Magnetic resonance imaging》2014
Radial acquisitions can suffer from trajectory errors leading to reduced image quality. Here we present a new method of trajectory correction that uses all spokes of a radial acquisition and compare it to an existing method that uses a two-spoke pre-scan calibration. For both methods, estimates of the necessary shifts were made using magnitude or phase data and the performances were compared. The additional effect of B0 correction was considered in all cases. Mouse cardiac scans were used for the comparisons and we also compared the quality of navigator signals obtained from the radial data with each technique. 相似文献