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891.
892.
Patient motion during the acquisition of magnetic resonance imaging data causes loss of resolution and ghost repetitions of the moving structures in the reconstructed image. In this paper the motion is modeled as being translational, and it is shown that this causes either the magnitude or the phase of the data to be corrupted, depending upon whether the motion is within or perpendicular to the imaging plane. The problem of restoring the image using only the corrupted data and no knowledge about the motion is addressed. The restoration problem is nonlinear in general, but is linear in two special cases. An iterative algorithm is developed that uses projections onto convex sets for magnitude retrieval and generalized projections for phase retrieval. In both cases constraint sets containing all a priori knowledge are used, and this is shown to be necessary for rapid convergence. The two algorithms may be combined to restore images corrupted by three-dimensional motion. The algorithms were verified using simulated data. 相似文献
893.
用非平衡格林函数方法研究一种自旋场效应晶体管的电子输运特性。结果表明,不考虑自旋散射的作用,当漏极电压比较小时该器件能达到很高的磁阻比率。对该器件在考虑自旋散射和不考虑自旋散射下的输出电流进行对比,发现在铁磁平行(反平行)的条件下,考虑自旋散射时的输出电流要比不考虑自旋散射时的输出电流小(大)。研究结果揭示了该器件的物理机制,为该器件的优化设计提供了理论指导。 相似文献
894.
提出一种以高度集成的CMOS图像传感器模组作为光学图像接收器件,以高速DSP处理器作为核心处理器件的基于CMOS图像传感器和高速DSP处理器的图像采集系统。介绍了系统的硬软件设计和质心计算的算法。结果表明,基于高速DSP处理器的CMOS图像采集系统可作为独立单元存在,并具有体积小、处理速度快、成本低且功耗低等优点。 相似文献
895.
Economic Approaches for Cognitive Radio Networks: A Survey 总被引:1,自引:0,他引:1
Efficient resource allocation is one of the key concerns of implementing cognitive radio networks. Game theory has been extensively
used to study the strategic interactions between primary and secondary users for effective resource allocation. The concept
of spectrum trading has introduced a new direction for the coexistence of primary and secondary users through economic benefits
to primary users. The use of price theory and market theory from economics has played a vital role to facilitate economic
models for spectrum trading. So, it is important to understand the feasibility of using economic approaches as well as to
realize the technical challenges associated with them for implementation of cognitive radio networks. With this motivation,
we present an extensive summary of the related work that use economic approaches such as game theory and/or price theory/market
theory to model the behavior of primary and secondary users for spectrum sharing and discuss the associated issues. We also
propose some open directions for future research on economic aspects of spectrum sharing in cognitive radio networks. 相似文献
896.
Efficient Charge Injection in Organic Field‐Effect Transistors Enabled by Low‐Temperature Atomic Layer Deposition of Ultrathin VOx Interlayer 下载免费PDF全文
Yuanhong Gao Youdong Shao Lijia Yan Hao Li Yantao Su Hong Meng Xinwei Wang 《Advanced functional materials》2016,26(25):4456-4463
Charge injection at metal/organic interface is a critical issue for organic electronic devices in general as poor charge injection would cause high contact resistance and severely limit the performance of organic devices. In this work, a new approach is presented to enhance the charge injection by using atomic layer deposition (ALD) to prepare an ultrathin vanadium oxide (VOx) layer as an efficient hole injection interlayer for organic field‐effect transistors (OFETs). Since organic materials are generally delicate, a gentle low‐temperature ALD process is necessary for compatibility. Therefore, a new low‐temperature ALD process is developed for VOx at 50 °C using a highly volatile vanadium precursor of tetrakis(dimethylamino)vanadium and non‐oxidizing water as the oxygen source. The process is able to prepare highly smooth, uniform, and conformal VOx thin films with precise control of film thickness. With this ALD process, it is further demonstrated that the ALD VOx interlayer is able to remarkably reduce the interface contact resistance, and, therefore, significantly enhance the device performance of OFETs. Multiple combinations of the metal/VOx/organic interface (i.e., Cu/VOx/pentacene, Au/VOx/pentacene, and Au/VOx/BOPAnt) are examined, and the results uniformly show the effectiveness of reducing the contact resistance in all cases, which, therefore, highlights the broad promise of this ALD approach for organic devices applications in general. 相似文献
897.
898.
899.
New Strategy for Polysulfide Protection Based on Atomic Layer Deposition of TiO2 onto Ferroelectric‐Encapsulated Cathode: Toward Ultrastable Free‐Standing Room Temperature Sodium–Sulfur Batteries 下载免费PDF全文
Dingtao Ma Yongliang Li Jingbo Yang Hongwei Mi Shan Luo Libo Deng Chaoyi Yan Muhammad Rauf Peixin Zhang Xueliang Sun Xiangzhong Ren Jianqing Li Han Zhang 《Advanced functional materials》2018,28(11)
The room temperature (RT) sodium–sulfur batteries (Na–S) hold great promise for practical applications including energy storage and conversion due to high energy density, long lifespan, and low cost, as well based on the abundant reserves of both sodium metal and sulfur. Herein, freestanding (C/S/BaTiO3)@TiO2 (CSB@TiO2) electrode with only ≈3 wt% of BaTiO3 additive and ≈4 nm thickness of amorphous TiO2 atomic layer deposition protective layer is rational designed, and first used for RT Na–S batteries. Results show that such cathode material exhibits high rate capability and excellent durability compared with pure C/S and C/S/BaTiO3 electrodes. Notably, this CSB@TiO2 electrode performs a discharge capacity of 524.8 and 382 mA h g?1 after 1400 cycles at 1 A g?1 and 3000 cycles at 2 A g?1, respectively. Such superior electrochemical performance is mainly attributed from the “BaTiO3‐C‐TiO2” synergetic structure within the matrix, which enables effectively inhibiting the shuttle effect, restraining the volumetric variation and stabilizing the ionic transport interface. 相似文献
900.