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81.
82.
This paper reported an enhanced photoluminescence of CaSb2O6:Bi3+ by efficient charge compensation. Charge compensated CaSb2O6:Bi3+,M+ (M=Li, Na and K) phosphors were prepared using a co-precipitation technique followed by heat-treatment. The structure and morphology of the as-prepared CaSb2O6:Bi3+,M+ samples were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). The results revealed that the obtained CaSb2O6:Bi3+,M+ samples are hexagonal crystal structure and this structure was retained regardless of co-doping by Li+, Na+ or K+. All samples showed sphere-like shape with particle size of 40–80 nm. The optical properties of products were studied by UV–vis diffuse reflectivity, photoluminescence spectra and luminescence decay measurements. Under the excitation of 336 nm light, all of the samples exhibited a strong blue emission peaking around 437 nm, which is attributed to the 3P1–1S0 transition of the Bi3+ ion. It was found that the charge compensation has significant effect on the photoluminescence properties of CaSb2O6:Bi3+ and the best luminescence properties have been achieved for CaSb2O6:0.75Bi3+,0.75 Na+. The mechanism for the enhancement of the blue emission has also been studied in detail. Our results suggested that the optical properties of oxide nanostructures can be tailored through co-doping with aliovalent ions and the favorable luminescence properties of CaSb2O6:Bi3+,Na+ make it potential for lighting and display applications. 相似文献
83.
本项目主要针对TCS系统中的厚度自动调整功能进行了仔细研究,主要介绍了微张力控制功能、刚度补偿技术以及自动校准过程的实现等,具有良好的推广价值。 相似文献
84.
Combining the experimental research with the simulation calculation, the error evaluation for Zernike polynomials fitting (ZPF) based phase compensation of digital holographic microscopy (DHM) is performed. The obtained results show that the reconstructed phase with high precision can be obtained by ZPF phase compensation algorithm. Moreover, the phase error for ZPF based phase compensation algorithm increases with both the variation of object height and object transverse area, the larger variation of object height, the larger of phase error, and the larger of object transverse area, the faster increase of RMS phase error. To decrease the error of ZPF phase compensation algorithm, it is required to ensure one of the variations of object height and object transverse area to be a small value. Importantly, the proposed method supplies a useful tool for the error evaluation of phase compensation algorithm. 相似文献
85.
Detecting moving objects from video frame sequences has a lot of useful applications in computer vision. This proposed method of moving object detection first estimates the bi-directional optical flow fields between (i) the current frame and the previous frame and between (ii) the current frame and the next frame. The bi-directional optical flow field is then subjected to normalization and enhancement. Each normalized and enhanced optical flow field is then divided into non-overlapping blocks. The moving objects are finally detected in the form of binary blobs by examining the histogram based thresholded values of such optical flow field of each block as well as the optical flow field of the candidate flow value. Our technique has been conceptualized, implemented and tested on real video data sets with complex background environment. The experimental results and quantitative evaluation establish that our technique achieves effective and efficient results than other existing methods. 相似文献
86.
Several methods have been proposed for motion correction of high angular resolution diffusion imaging (HARDI) data. There have been few comparisons of these methods, partly due to a lack of quantitative metrics of performance. We compare two motion correction strategies using two figures of merit: displacement introduced by the motion correction and the 95% confidence interval of the cone of uncertainty of voxels with prolate tensors. What follows is a general approach for assessing motion correction of HARDI data that may have broad application for quality assurance and optimization of postprocessing protocols. Our analysis demonstrates two important issues related to motion correction of HARDI data: (1) although neither method we tested was dramatically superior in performance, both were dramatically better than performing no motion correction, and (2) iteration of motion correction can improve the final results. Based on the results demonstrated here, iterative motion correction is strongly recommended for HARDI acquisitions. 相似文献
87.
相位波带片型时间透镜研究 总被引:1,自引:0,他引:1
基于Opti-System软件,对相位波带片型时间透镜进行了深入研究。明确了中心波长对相位波带片型时间透镜焦距色散补偿量的影响机理,建立了中心波长、色散补偿量与输出光脉冲消光比及脉冲宽度间的关系。研究结果表明,相位波带片型时间透镜的焦距色散补偿量,在1 310~1 550 nm波长范围与光信号中心波长呈近似线性关系。通过线性拟合,得出焦距色散补偿量与中心波长的线性关系公式。对于不同波长的输入光波,可通过公式确定最佳焦距色散补偿量,实现最窄脉宽和最优消光比的光脉冲输出。研究结果可为优化相位波带片型时间透镜设计提供理论指导,进而拓宽相位波带片型时间透镜的应用范围。 相似文献
88.
89.
为了克服现有目标高度补偿算法存在的模型假设不合理、实际应用效果难以保证等问题,本文以目标恒海拔等速运动为前提,利用协同单元提供的目标指示信息,对两坐标雷达的空间目标跟踪问题重新进行了研究.首先根据不同坐标系间的转换关系,构建了目标高度的准确表达式.然后通过恒等变换和合理的近似,得到了目标高度的估计公式,并利用绝对值不等式和柯西-施瓦茨不等式,推导得到了高度估计公式的误差.最后联合目标高度估计公式和两坐标雷达的缺维量测方程,采用扩展卡尔曼滤波方法,实现了目标空间状态的估计.仿真结果表明:本文算法可有效地对目标高度进行补偿,获得稳定、可靠的目标空间状态估计,从而为两坐标雷达目标空间状态估计问题提供了相对有效完善的解决方法. 相似文献
90.
《Mechatronics》2015
While omnidirectional wheels enable a holonomic drive and a good maneuverability, the slippage of the wheels as an inherent characteristic of the omnidirectional wheels prevents using rotary shaft encoders as a reliable source of data for the robot’s odometry. When installed on a climbing robot, omnidirectional wheels may suffer from additional slippage on the surface. In a previous study, we described how the resulting vibration decreases the trajectory following accuracy of the robot, and why rotary encoders, as the most popular dead reckoning method cannot be used. In this paper, we address this problem by integration of low cost and light weight exteroceptive sensors, i.e. an accelerometer and an optical flow sensor. The Omniclimber climbing robot was used as the testing platform in this study. Omniclimbers are omnidirectional climbing robots that can climb and navigate over flat and curved structures. We attempt to compensate the errors due to the wheel slippage through closing the position control loop without significantly increasing the robot’s weight, cost and complexity of the robot. We also integrated an algorithm which corrects the robot kinematics on the curved structures based on the curvature diameter and the robot’s heading angle. Taking advantage of these sensors and algorithms we could make remarkable improvements on the path following accuracy of the Omniclimbers, which is presented in this article. 相似文献