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排序方式: 共有1410条查询结果,搜索用时 31 毫秒
851.
给出了一种采用Γ型输入匹配网络的源简并共源低噪声放大器电路结构,分析了在低功耗情况下,高频寄生效应对低噪声放大器(LNA)输入阻抗及噪声特性的影响,并采用此结构设计了一款工作于L渡段的低功耗低噪声放大器.采用CMOS 0.18μm工艺,设计了完整的ESD保护电路,并进行了QFN封装.测试结果表明.在1.57 GHz工作频率下,该低噪声放大器的输入回波损耗小于-30 dB,输出回波损耗小于-14 dB,增益为15.5 dB,噪声系数(NF)为2.4 dB,输入三阶交调点(IIP3)约为-8 dBm.当工作电压为1.5 V时,功耗仅为0.9 mW. 相似文献
852.
853.
碎屑岩中长石蚀变形成次生孔隙的试验研究 总被引:1,自引:0,他引:1
次生孔隙发育带是深层寻找有利油气勘探目标区的基础,酸性地层水是含油气盆地内部物质迁移和能量交换的主要介质。利用含乙酸溶液,模拟地层水,对济阳坳陷的长石砂岩进行高温高压条件下溶蚀试验,使用扫描电镜、X-衍射分析设备对实验产物进行对比检测。实验证明:(1)高温高压条件下乙酸对长石矿物有很强的溶蚀作用。(2)斜长石比钾长石更容易遭到溶蚀。结合济阳坳陷深层勘探实际,认为深层长石溶蚀耗水作用导致岩石孔隙度变大,形成次生孔隙,从而改善深层储层物性。同时长石溶蚀耗水作用是油气运移成藏活动一种驱动力。 相似文献
854.
Mohammad Rezaee Yadollah YaminiMohammad Faraji 《Journal of chromatography. A》2010,1217(16):2342-2357
Dispersive liquid–liquid microextraction (DLLME) has become a very popular environmentally benign sample-preparation technique, because it is fast, inexpensive, easy to operate with a high enrichment factor and consumes low volume of organic solvent. DLLME is a modified solvent extraction method in which acceptor-to-donor phase ratio is greatly reduced compared with other methods. In this review, in order to encourage further development of DLLME, its combination with different analytical techniques such as gas chromatography (GC), high-performance liquid chromatography (HPLC), inductively coupled plasma-optical emission spectrometry (ICP-OES) and electrothermal atomic absorption spectrometry (ET AAS) will be discussed. Also, its applications in conjunction with different extraction techniques such as solid-phase extraction (SPE), solidification of floating organic drop (SFO) and supercritical fluid extraction (SFE) are summarized. This review focuses on the extra steps in sample preparation for application of DLLME in different matrixes such as food, biological fluids and solid samples. Further, the recent developments in DLLME are presented. DLLME does have some limitations, which will also be discussed in detail. Finally, an outlook on the future of the technique will be given. 相似文献
855.
856.
为了降低空调能耗,文中以水源制冷机房为模型,分析了影响制冷机房总能耗的主要运行参数,然后采用正交试验法对制冷机房在不同参数条件下的能耗进行了模拟,找到了各运行参数影响制冷机房总能耗和单位冷量能耗的主次顺序及基本规律。 相似文献
857.
Jianhui Zhang Jiming Chen Youxian Sun 《Wireless Communications and Mobile Computing》2009,9(6):805-818
Energy constraint is the most conspicuous characteristic in wireless sensor networks (WSN). Node deployment, dynamic topology control, and data transmission in WSN all consume a large amount of energy. Therefore, proper adjustment of transmission power (TP) contributes much energy saving. In this paper, a new TP adjustment method based on Fuzzy Control Theory, called FCTP, is proposed for the dynamic topology control. The simulation results show that this method is more robust to tolerate accidental interfere, more rapidly convergent, and more energy efficient than other TP adjustment approaches, which lead to longer network lifetime. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
858.
相对于传统的应用部署方式,云计算是基于互联网的一种并行处理技术,提供了一个高度可扩展和按需处理的服务。任务调度一直是云计算环境中的研究热点,在云计算环境中具有重要作用。能否合理分配任务到虚拟机资源上是重要问题之一。本文通过对任务请求的资源进行分析,对不同类型的任务进行聚类,将不同类型任务通过改进贪心调度算法合理分配到虚拟机资源上。通过Cloudsim平台模拟实验表明,该算法相对于Min-Min算法在节省能耗方面有较好的效果。 相似文献
859.
Application reconfiguration is essential to achieving flexibility and adaptability of wireless sensor networks (WSNs) used in environment monitoring. In this paper, we present an integrated reconfiguration scheme (IRS) for implementing environment adaptive application reconfiguration (EAAR) in WSNs. In our scheme, application reconfiguration is implemented with the push‐based paradigm for densely distributed nodes and the cluster‐based hybrid reconfiguration (CHR) paradigm for sparsely distributed nodes. We demonstrate the energy‐efficiency and scalability of our scheme by analyzing the energy consumption based on a randomly deployed sensor network. Moreover, we derive the density threshold of reconfiguration nodes (RNs) for determining if the nodes are densely or sparsely distributed, and choose the mode of operation for IRS. We use extensive simulation experiments to demonstrate the effectiveness of our scheme. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
860.
Minimizing the sensor-node energy consumption is an important consideration when designing wireless sensor networks. In this paper, we focus on the energy consumption issues related to communication of data from correlated sensor nodes. An optimization algorithm is proposed for minimizing the overall energy consumption of the hardware and the physical link. We perform a detailed trade-off analysis of the circuit energy consumption, the transmission energy consumption, the transmission time, the modulation symbol size, and the channel coding rate, over a wide range of transmission distances and correlation values. Thus, a new optimized communication schedule with much lower energy consumption than our benchmark scheme of optimized uncorrelated uncoded transmission is obtained. Compared to this scheme, the total energy consumption may be reduced by more than 83.5% for a correlation value of 0.6 and a transmission distance of 100 m when using the results from the proposed optimization. This is significant with respect to increasing the lifetime of a wireless sensor network. 相似文献