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101.
Behavioural transition during the estuarine migration of wild Atlantic salmon (Salmo salar L.) smolt
F. Martin R. D. Hedger J. J. Dodson L. Fernandes D. Hatin F. Caron F. G. Whoriskey 《Ecology of Freshwater Fish》2009,18(3):406-417
Abstract – Ultrasonic telemetry and hydrodynamic modelling were used to study the migratory behaviour of 54 wild Atlantic salmon ( Salmo salar ) smolt captured in freshwater during their downstream migration and tracked in 2 years through a shallow estuary system. A high-density, fixed array of receivers provided detailed spatial and temporal resolution of behaviour in the second year of study. Smolt migration in the river occurred mostly at night and downstream migration was slower during the day. In the estuary, smolt moved seaward on ebbing tides and landward on flooding tides. The effect of current velocity was greater during the night than during the day. We documented for the first time that current velocity and diurnal period only accounted for approximately one-third of the variation in smolt ground speeds in the estuary, indicating that smolt movements were far less passive than previously reported. Smolt energetic status had no effect on smolt swimming behaviour or migratory performance. With an increase in salinity, smolt seaward movements during flooding tides were more frequent, and overall seaward ground velocity increased. The increase in salinity experienced by the smolt during their migration through the leading edge of saltwater intrusion thus induced a behavioural transition from a more passive, fluvial migration to a more active- and seaward-oriented migration. 相似文献
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针对摄像机静止的情况,提出了一种可运用于实时监控中的运动目标检测与跟踪的方法.采用更新函数实现背景实时更新,通过差分算法检测运动目标.在跟踪模块中,提出建立帧间目标“关系矩阵”实现多个运动目标匹配,并采用卡尔曼滤波器预测目标参数,在运动目标相互遮挡的情况下,根据预测参数跟踪目标,获得目标轨迹.通过多个图像序列测试,算法具有良好的实时性和适应环境变化的能力. 相似文献
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An approach is described on the automated tracking of interference circle fringe to get the flatness accurately based on the Equal Inclination Interference Theory (EIIT). The system,based on the theory of EIIT, can be applied to grasp the changing fringe information, which is white alternating with black through the CCD camera. Following the basic principle of fringes image centro-symmetric, we create some windows, process only the interference fringes information in the windows. According to the position of the processed interference fringe and the position of the last adjacent interference fringe in the windows, the interference fringe variation value N from the starting measured point is received, it implies the changed altitude value from the starting measurement point. This method allows us not only get the fringe information of the half-wavelength integer multiple but also denote those of the half-wavelength decimal multiple. The system is proved to be effective experimentally. It is useful in metrology department for the high-precision flatness standard unit. 相似文献
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This paper analyzes the principle of THS(Traditional Holo-Spectrum) technique,and in allusion to the deficiency of THS that only can be used in stationary signal,a new holo-spectrum technique based on order tracking is proposed.By order tracking sampling technology,non-stationary signal in the time domain is transformed into stationary signal in the angle domain,then the THS technique can be applied.Through this way,the influence of non-stationary to THS is reduced and the application of THS is extended.The paper researches the principle of order tracking holo-spectrum and verified by a simulation experiment.The simulation result and error analysis demonstrate that this method can be valid used to analyze the non-stationary signal.The spectrum is distinct and the effect is apparent. 相似文献
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针对池塘养殖中投喂作业需要全塘均匀覆盖的应用场景,存在人工投饲强度大、饲料利用率低的问题,设计一种能够适应不同多边形池塘的养殖船自动导航控制系统。控制系统采用低成本北斗定位模块和高精度电子罗盘进行组合导航,获取池塘养殖船的位置和航向信息作为导航控制器的输入,通过构建基于PD算法的导航控制器,实现航行过程中的路径跟踪。设计一种多边形回纹线导航路径规划算法,能够快速实现多边形池塘的导航路径规划。开展池塘导航试验,试验结果表明:采用所设计的自动导航系统,养殖船能够按照规划的路径航行,在水面行驶速度为0.4~0.5 m/s时,稳定跟踪后最大误差小于2.62 m,平均跟踪误差小于1.30 m,导航精度满足池塘养殖自动投饲要求。 相似文献
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针对复杂红外背景下单一跟踪算法难以准确定位运动目标的问题,提出了基于尺度无迹卡尔曼滤波(SUKF,scale unscented Kalman filter)与尺度不变特征变换(SIFT,scale invariant featuretransform)相结合的红外运动目标跟踪方法。首先,通过SUKF算法对状态空间进行滤波估计,确定运动目标的初步位置,并以此建立局部SIFT特征检测域。其次,SIFT算法在该局部检测域内对运动目标进行特征提取与匹配,最终实现对目标的准确定位;同时,利用定位结果更新并校正SUKF的状态模型。实验结果表明,本文提出的基于SUKF-SIFT的跟踪策略与相关算法相比,体现出较好的跟踪效果与实时性能。 相似文献