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1.
针对甘薯秧蔓机械化回收过程中离散元仿真研究缺乏准确参数值的问题,采用直接测量和虚拟标定相结合的方法对碎甘薯茎秆和叶片离散元仿真参数进行研究。采用物理试验法获得碎甘薯秧的本征参数、碰撞恢复系数等参数值及碎甘薯秧颗粒的静摩擦系数参数范围,并为离散元法仿真设计了不同的参数组合。通过堆积角优化仿真试验确定甘薯叶片本征参数及其他不易直接测量的离散元仿真参数。Plackett-Burman试验表明,甘薯茎秆—甘薯茎秆和甘薯茎秆—45钢的静摩擦系数、甘薯茎秆—甘薯茎秆和甘薯茎秆—甘薯叶的滚动摩擦系数均显著影响堆积角。运用最陡爬坡试验和Box-Behnken优化试验标定了对碎甘薯秧堆积角有显著影响的参数值,以得到的参数进行颗粒堆积仿真试验,测得堆积角平均值为40.51°,与实测值相对误差为0.972%,说明物理试验加优化仿真试验来标定离散元参数是可行的,标定所得的参数可作为甘薯秧茎叶离散元仿真参数。 相似文献
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A field calibration experiment was carried out on salt‐affected clayey soil in Syria, to compare the sensitivity to soil electrical conductivity (ECe), and bulk density (ρb) of two instruments for estimating soil moisture: the neutron probe (NP) and the Diviner 2000 capacitance probe (CP). The results showed that the values of the correlation coefficient of the calibration were decreased when the ECe and ρb values increased; this decrease was more pronounced for the Diviner 2000, indicating that it was more sensitive to ρb and ECe than the NP. When only scaled frequency was used in the fitted equation, the Diviner 2000 in wet soil underestimated soil water content significantly at all depths, but especially in the top layer, by up to 0.09 cm3/cm3 compared with gravimetric determinations. However, in dry soil, the Diviner 2000 overestimated the volumetric water content by up to 0.05 cm3/cm3 in the top 15 cm, and by 0.03 cm3/cm3 at 30‐45 cm depth. The performance of the neutron probe was better overall; using a factory calibration curve no significant differences were observed between NP estimates and the gravimetric values. Including both ρb and ECe in the calibration equations improved the fits, although the regression coefficient (R2) for the Diviner 2000 remained low. 相似文献
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The two methods of estimating parameter in computable general equilibrium(CGE) model are introduced and compared:the calibration procedure and econometric estimation. The conclusions are:the estimation of parameter in CGE model must use the calibration procedure coupled with the econometric estimation method;the elasticity of output with respect to labor input,the marginal expenditure share for households and price elasticity of export demand are estimated by econometric estimation method;and other parameters of the CGE model can be get by calibration procedure. 相似文献
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In the past, the criterion for calibration has almost invariably been the stellar oriented ballistic camera,the method is a point to point comparison on the identical coordinate system. Deficiencies is follows: The request of weather is severe(cloudless night); The period is often long; the measure equipment of high precision can't be calibrated. While EMBET methods is used in calibration, it does not need criterion and it demands only that the measure elements is larger than 3,and the trajectory and many system errors of the measure elements can be simultaneously calculated with the measure data sequences. The error models of related equipments' measure elements and the EMBET of typical equipment group are given. The EMBET method is successfully used in Accuracy-analysis of Satellite Launch. 相似文献
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基于机器视觉的无损检测是植物生长建模的关键技术之一,对图像采集系统进行标定是实现无损检测的基本步骤.目前,摄像机标定的方法有传统标定方法、主动视觉标定法、自标定方法等.为此,对现有标定方法分别进行了讨论与比较,结果表明,传统线性标定法可以满足农作物无损检测的要求. 相似文献
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Sensitivity analyses using a one-at-a-time approach were carried out for leaching models which have been widely used for pesticide registration in Europe (PELMO, PRZM, PESTLA and MACRO). Four scenarios were considered for simulation of the leaching of two theoretical pesticides in a sandy loam and a clay loam soil, each with a broad distribution across Europe. Input parameters were varied within bounds reflecting their uncertainty and the influence of these variations on model predictions was investigated for accumulated percolation at 1-m depth and pesticide loading in leachate. Predictions for the base-case scenarios differed between chromatographic models and the preferential flow model MACRO for which large but transient pesticide losses were predicted in the clay loam. Volumes of percolated water predicted by the four models were affected by a small number of input parameters and to a small extent only, suggesting that meteorological variables will be the main drivers of water balance predictions. In contrast to percolation, predictions for pesticide loss were found to be sensitive to a large number of input parameters and to a much greater extent. Parameters which had the largest influence on the prediction of pesticide loss were generally those related to chemical sorption (Freundlich exponent nf and distribution coefficient Kf) and degradation (either degradation rates or DT50, QTEN value). Nevertheless, a significant influence of soil properties (field capacity, bulk density or parameters defining the boundary between flow domains in MACRO) was also noted in at least one scenario for all models. Large sensitivities were reported for all models, especially PELMO and PRZM, and sensitivity was greater where only limited leaching was simulated. Uncertainty should be addressed in risk assessment procedures for crop-protection products. 相似文献
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《Communications in Soil Science and Plant Analysis》2012,43(9-10):1532-1545
Abstract To increase the accuracy of remotely sensed data for agricultural forecasting, pixel values must be corrected for atmospheric effects and converted to spectral reflectance. The objective of this research was to compare two atmospheric correction methods of Landsat imagery under a range of atmospheric conditions. Ground‐based dark‐object subtraction (GDOS) is an image‐based calibration method that used in situ ground data that the dark‐object subtraction (DOS) method did not use, whereas atmospheric calibration (AC) is a model‐based calibration method that required a standard atmospheric profile refined with the use of in situ atmospheric data. GDOS and AC methods improved the reflectance values and had relationships with measured bands, which were approximately 1 to 1 in all bands. However, the GDOS generally had lower root‐mean‐square errors (RMSE) than AC. Data from this study suggest that at the present time the GDOS method may be more accurate than the AC method. 相似文献
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体积管是检定流量计的标准器。YTG型双向体积管,其外型尺寸、主体结构、检定速度、日常管理等方面,均比单向体积管有明显的优点,并具有独特的容积补偿性,给体积管的管理、使用带来极大方便。介绍了YTG型双向体积管的结构、技术指标及其优越性,并建议在条件允许的情况下,尽可能使用双向体积管。 相似文献