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991.
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993.
对南瓜果肉多酚提取工艺及抗氧化性能进行了研究。通过单因素实验和响应曲面实验,研究超声功率、超声时间、乙醇浓度和料液比对南瓜果肉多酚提取效果的影响;通过还原力和DPPH自由基清除法对南瓜果肉多酚的抗氧化活性进行研究。实验结果表明,南瓜果肉多酚最佳提取工艺条件为:超声功率237.2W、超声时间11.65min、乙醇浓度96.80%、料液比为1∶21.4(g/mL),此条件下实际南瓜果肉多酚得率为5.629%;四个因素对南瓜多酚得率影响的主次顺序为:超声时间>乙醇浓度>料液比>超声功率;南瓜果肉多酚具有一定还原力和清除DPPH.的能力,且在一定范围内,多酚浓度与其抗氧化活性呈明显的线性关系。 相似文献
994.
为了解决传统神经网络算法在用于红外焦平面阵列(Infrared Focal Plane Array,IRFPA)非均匀性校正(Non-Uniformity Correction,NUC)时所面临的边缘模糊、收敛速度慢等问题,通过引入图像局部梯度特性对该算法进行了改进。通过用局部梯度相似度信息构造权值函数来对区域进行加权滤波,可以保留图像边缘信息。在迭代运算中,将梯度幅值加权的自适应参数规整因子加入了误差损失函数,并引入梯度幅值相关的自适应步长用以代替传统的固定步长,从而进一步提升了算法的校正效果和收敛速度。然后对算法的性能曲线和校正结果进行了分析。结果表明,与传统算法相比,改进的神经网络校正算法取得了更好的校正效果,其校正误差稳定低于前者,实现了有效抑制边缘模糊和提升收敛速度的目标。 相似文献
995.
Yang Tao Juan Francisco García Da-Wen Sun 《Critical reviews in food science and nutrition》2014,54(6):817-835
Wine aging is an important process to produce high-quality wines. Traditionally, wines are aged in oak barrel aging systems. However, due to the disadvantages of the traditional aging technology, such as lengthy time needed, high cost, etc., innovative aging technologies have been developed. These technologies involve aging wines using wood fragments, application of micro-oxygenation, aging on lees, or application of some physical methods. Moreover, wine bottling can be regarded as the second phase of wine aging and is essential for most wines. Each technology can benefit the aging process from different aspects. Traditional oak barrel aging technology is the oldest and widely accepted technology. The application of wood fragments and physical methods are promising in accelerating aging process artificially, while application of micro-oxygenation and lees is reliable to improve wine quality. This paper reviews recent developments of the wine aging technologies. The impacts of operational parameters of each technology on wine quality during aging are analyzed, and comparisons among these aging technologies are made. In addition, several strategies to produce high-quality wines in a short aging period are also proposed. 相似文献
996.
The pressurized liquid extraction and HPLC-DAD was developed for extraction and determination of bioactive lignans in Schisandra chinensis. The efficient PLE conditions employed methanol as extraction solvent, 125 °C of extraction temperature, 5 min of static extraction time and only one cycle. A rapid HPLC-DAD method was described for simultaneous determination of nine lignans, including schisandrol A, gomisin J, schisandrol B, tigloylgomisin H, angeloylgomisin H, schisandrin A, γ-schisandrin, gomisin N and schisandrin C. The extraction efficiency of PLE was observed to be comparable with reflux and sonication. In addition, the contents of nine lignans in S. chinensis from different regions were analysed by PLE and HPLC-DAD method. 相似文献
997.
T Hu YY Guo QF Zhou XK Zhong L Zhu JH Piao J Chen JG Jiang 《Journal of food science》2012,77(9):C975-C982
Eclipta prostrasta L. is a traditional Chinese medicine herb, which is rich in saponins and has strong antiviral and antitumor activities. An ultrasonic-assisted extraction (UAE) technique was developed for the fast extraction of saponins from E. prostrasta. The content of total saponins in E. prostrasta was determined using UV/vis spectrophotometric methods. Several influential parameters like ethanol concentration, extraction time, temperature, and liquid/solid ratio were investigated for the optimization of the extraction using single factor and Box-Behnken experimental designs. Extraction conditions were optimized for maximum yield of total saponins in E. prostrasta using response surface methodology (RSM) with 4 independent variables at 3 levels of each variable. Results showed that the optimization conditions for saponins extraction were: ethanol concentration 70%, extraction time 3 h, temperature 70 °C, and liquid/solid ratio 14:1. Corresponding saponins content was 2.096%. The mathematical model developed was found to fit well with the experimental data. Practical Application: Although there are wider applications of Eclipta prostrasta L. as a functional food or traditional medicine due to its various bioactivities, these properties are limited by its crude extracts. Total saponins are the main active ingredient of E. prostrasta. This research has optimized the extraction conditions of total saponins from E. prostrasta, which will provide useful reference information for further studies, and offer related industries with helpful guidance in practice. 相似文献
998.
在阵列式射频仿真系统中,采用射频天线阵列模拟目标信号角度运动,其控制原理是基于辐射信号的幅相合成。当工作频率发生捷变时,由于阵列控制器件的频响等因素,目标阵列角位置的模拟精度将发生变化。本文从目标阵列的角位置模拟原理出发,以二元组为例分析了频率捷变对射频仿真目标阵列精确位置控制系统的影响,为研究捷变频状态下目标阵列的精位控制技术提供了依据。 相似文献
999.
系统介绍了有源相控阵雷达的发展概况、组成与工作原理,对有源相控阵雷达在预警机上的应用进行了分析和研究,最后对有源相控阵雷达在预警机上的应用前景和研究趋势进行了展望。 相似文献
1000.