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1.
《Soils and Foundations》2022,62(1):101092
The dynamic response of gap-graded soils is complex; it requires massive experimental and theoretical investigation in order for a sound understanding to be developed. The complexity of the behaviour of such soils arises partially due to the presence of many influential parameters, such as the finer sand/silt content (Fs), size ratio (Rd), and void ratio (e). In this contribution, experiments are conducted on a series of gap-graded soil mixtures, where the coarser sand is mixed with four different finer sands or non-plastic silt with different sizes, namely various Rd, and one well-graded material is also tested. The S-wave velocity (Vs) and low-pass threshold frequency (flp) are measured in the isotropic stress state using a triaxial apparatus equipped with planar piezoelectric transducers. The experimental results reveal that, for a given e or relative density (Dr), both flp and Vs decrease at a low Fs, but increase at a high Fs. The slope of the linear regression between flp and Vs appears to capture this transitional behaviour, depending on Fs and Rd, which can then be used to correlate the physical state of the gap-graded soil fabric. The transitional behaviour is more noticeable at a larger Rd, which is in line with the existing literature. To understand the effect of the Rd on the shear wave propagation at a low Fs, the particle-scale dispersion relation for binary chains is newly introduced and correlated with accompanying experimental observations. 相似文献
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为提升机械臂设备的准确分拣能力,设计基于RBF-BP算法的机械臂多自由度分拣控制系统。利用RBF-BP前馈神经网络,规划机械臂设备的运动轨迹路线,实现基于RBF-BP算法的机械臂运动轨迹建模。确定工业相机在总功能框架中所处连接位置,根据机械臂选型情况,确定可编程逻辑控制器、变频控制器对于所选机械臂元件的调节能力,完成对系统功能模块的开发。借助传输信道,将Sorting分拣指令、ToolControl控制指令反馈回核心控制主机,建立完整的指令执行回路,再联合相关硬件设备结构,实现基于RBF-BP算法的机械臂多自由度分拣控制系统设计。实验结果表明,在抓取能力相同的情况下,应用RBF-BP算法控制系统机械臂成功分拣的工件数量为19件,机械臂抓取成功率为95%,说明所设计系统满足提升机械臂准确分拣能力的设计初衷。 相似文献
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One of the most challenging issues in radio received signal strength (RSS)-based localization systems is the generation and distribution of a radio map with a coordinate system linked with spatial information in a large indoor space. This study proposes a novel spatial-tagged radio-mapping system (SRS) that effectively combines the heterogeneous properties of LiDAR and mobile phones to simultaneously perform both spatial and radio mappings. The SRS consists of synchronization, localization, and map building processes, and enables real-time spatial and radio mapping. In the synchronization process, the distance range, motion data, and radio signals obtained through the LiDAR and mobile phone are collected in nodal units according to the sensing time. In the localization process, a feature variance filter is used to control the number of features generated from LiDAR and estimate the positions at which the nodes are generated in real time according to the motion data and radio signals. In map building, the estimated positions of the nodes are used to extract spatial and radio maps by using a unified location coordinate system. To ensure mobility, the SRS is manufactured in the form of a backpack supporting LiDAR and a mobile phone; the usefulness of the system is experimentally verified. The experiments are performed in a large indoor shopping mall with a complex structure. The experimental results demonstrated that a common coordinate system could be used to build spatial and radio maps with high accuracy and efficiency in real time. In addition, the field applicability of the SRS to location-based services is experimentally verified by applying the constructed radio map to well-known fingerprinting algorithms using the heterogeneous mobile phones. 相似文献
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《International Journal of Hydrogen Energy》2022,47(8):5240-5249
Coke deposition has been considered to be one of the most important reasons hindering the stability of the catalyst during CH4/CO2 reforming. In this study, after the addition of P123 (PEG-PPG-PEG triblock copolymer), Ni2+ can be well-dispersed on the mesoporous molecular sieve MCM-41. And then, the catalysts were prepared by using N2 radio frequency (RF) discharge plasma for different treatment times to reduce the size of Ni particles, improve the anti-coking performance, and thereby improve the stability of the catalyst. The results showed that the catalyst NM-P123-PN2h exhibits superior catalytic properties in the CH4/CO2 reforming. The initial conversions of CH4 and CO2 were 90.80% and 89.60% at 750 °C, respectively. The catalyst NM-P123-PN2h showed highly coke resistance with less carbon deposition (1.12%) at 750 °C after 10 h of continuous reaction, while the carbon deposition of the catalyst NM-C was 37.32%. Compared with the traditional calcination method, the catalyst prepared by plasma treatment has a smaller particle size and better dispersibility of nickel. In particular, the nickel particle size of the catalyst NM-C was 8.37 nm, however, that of the catalyst NM-P123-PN2h was only 1.70 nm, and the nickel particle size was reduced by 5 times. Therefore, it can be concluded that the catalyst prepared under the combined action of P123 and RF plasma-treated can effectively improve the coke resistance of the catalyst and the stability of the CH4/CO2 reforming. 相似文献
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针对现有适用于单天线接收机的干扰抑制技术难以为周期调频(PFM)干扰和卫星导航信号提供足够分离度,导致消除干扰成分时卫星导航信号损伤较大的问题,该文提出一种基于周期截断数据矩阵奇异值分解的干扰抑制方法。利用调频干扰信号的周期性把分散在较大带宽的能量集中到重排数据中几个甚至单个频点;进而采用奇异值分解(SVD)将干扰与期望信号映射进不同的投影子空间以消除干扰成分。仿真结果表明该方法可以降低在剔除干扰时卫星导航信号损失,提升卫星导航接收机对抗宽带周期调频干扰的能力。 相似文献
7.
陆上集群无线电(Terrestrial Trunked Radio,TETRA)数字集群通信系统因其开放性易受到内外部电磁干扰。干扰信号的类型多种多样,针对不同的干扰样式,采取的抗干扰措施也各不相同,因此干扰信号的识别具有重大意义。基于此,提出了一种干扰信号智能识别技术。该技术首先对受到不同干扰后的TETRA音频数据进行特征提取,并筛选出具有分类能力的特征,其次使用决策树、支持向量机和随机森林3种分类模型对特征提取后的待测试信号进行智能分类识别。实验结果表明,使用的这3种模型能够有效判断TETRA系统中的信号是否受到干扰,以及受到何种样式的干扰,可为后续TETRA系统中的信号干扰识别提供参考。 相似文献
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