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991.
992.
使用TDLAS技术进行动态压力测量已经成为压力测量领域的研究热点。波长调制法实验装置较为复杂,需要对多个参数进行设置,选择出最优的预设参数能够取得更好的实验效果,获得更高的测量精度。目前波长调制法的实验参数设置基本凭借个人经验,使用Matlab程序仿真结合波长调制法的TDLAS测量技术,能够对实验中需要进行预设的重要参数进行了分析。通过计算4990cm-1波段和6330cm-1波段附近的多条吸收峰,发现4990.09cm-1波段处的吸收峰更适合作为波长调制法的测量波段。以4990.09cm-1处的吸收峰为研究对象,进行了波长调制法压力测量仿真建模,计算了调制度、调谐频率和调制频率对二次谐波幅值和对称性的影响并深入地分析了影响因素,总结了其变化规律。在综合考虑抗噪性能和测量精度的情况下,选择了调制度为2.5,调谐频率30Hz,调制频率5kHz为最佳实验参数。基于Matlab的仿真模型能够快速计算大量参数点,更加直观地分析出对参数的影响趋势,为实验仪器和预设参数的选择提供依据。 相似文献
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Abstract The study of elastic distortions in piston-cylinder units of primary standards piston gauges is of importance for the improvement of pressure measurement accuracy. Preliminary work (GF. Molinar et al., 1989) on distortion calculations was carried out on a tungsten carbide (t.c.) piston-cylinder of 0.2 cm2 nominal effective area in the 100 MPa pressure range. The same calculations are now applied in the study of a similar piston-cylinder unit of hard steel (h.s.). The distortions on the outer surface of the cylinder are measured with strain gages and with a capacitance sensor. The calculated distortions, which can be also derived with other methods (G. Klingenberg 1989, R. Wisniewski et al. 1989), are compared with the experimental results obtained on the outer surface of the cylinder. The present two piston-cylinder units of h.s. and of t.c. were cross-floated up to 100 MPa and the ratio R = f(P) = Aeh.s./Aet.c. obtained experimentally is compared with the calculated. 相似文献
995.
Soft Mechanics: Contrast Agent Incorporation into Silicone Enables Real‐Time Flow‐Structure Analysis of Mammalian Vein‐Inspired Soft Pumps (Adv. Funct. Mater. 14/2015) 下载免费PDF全文
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Virtualization technology plays a key role in cloud computing. Thus, the security issues of virtualization tools (hypervisors, emulators, etc.) should be under precise consideration. However, threats of insider attacks are underestimated. The virtualization tools and hypervisors have been poorly protected from this type of attacks. Furthermore, hypervisor is one of the most critical elements in cloud computing infrastructure. Firstly, hypervisor vulnerabilities analysis is provided. Secondly, a formal model of insider attack on hypervisor is developed. Consequently, on the basis of the formal attack model, we propose a new methodology of hypervisor stability evaluation. In this paper, certain security countermeasures are considered that should be integrated in hypervisor software architecture. 相似文献
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As a special type of wireless sensor network, the chain‐type wireless sensor networks can be used to monitor narrow and long regions, such as roads, underground mine tunnels, rivers, and bridges. In this study, a perpendicular bisector division (PB) method was first presented, in which the location may be divided into more location sub‐areas by a perpendicular bisector of each of two location nodes. Compared with the triangulation division method in Approximate Point‐in‐Triangulation Test (APIT), the computable complexity of PB is lower, and the number of division areas is larger. Furthermore, in order to locate targets under rare location nodes, a virtual location node‐perpendicular bisector division (VPB) was presented by a virtual location node based on the geographic shape of the monitored area. Virtual location nodes increase the density of location nodes, which can improve the accuracy of the location in the location algorithm. Second, two range‐free location algorithms were proposed: the location algorithm based on PB (LAPB) and the location algorithm based on VPB (LAVPB). In the end, the location errors performance of APIT, LAPB, and LAVPB for locating miners in an underground mine tunnel was tested. The results show that LAPB and LAVPB have higher location accuracy and are more robust than APIT. LAVPB is more suitable for locating targets in harsh environments. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献