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31.
基于能量守恒和三波耦合波方程,建立了超短脉冲在参变过程中二次谐波产生时的I类和II类相位匹配条件、基波与谐波之间的群速延迟时间、以及群速失配对晶体长度限制的理论基础。以负单轴非线性光学晶体CsLiB6O10为例,分析和数值计算了超短脉冲宽度为100fs时,谐波的群速匹配长度随基波波长变化的规律。研究结果表明在I类相位匹配条件下,基波波长为642nm时,群速延迟最小,相应的群速匹配晶体长度最长为19.1mm;在II类相位匹配条件下,基波波长为767nm,群速延迟最小,群速匹配长度最长为0.89mm。 相似文献
32.
采用双波长注入一包含伪随机码发生器与相位调制器的光电振荡器可以同时得到非归零(NRZ)码,归零(RZ)码以及光,电时钟信号输出。该方案使用了光域耦合的双环路结构,在不增加有源器件的条件下实现边模抑制。相位调制器用于反馈调制并同时实现占空比可调的非归零码到归零码的转换。双波长的注入排除了编码信号在振荡器中引入的非时钟频率成分。实验给出了10 Gb/s工作速率下的结果,得到了抖动为637 fs的光信号输出。转换得到的归零码信号占空比约为33%。输出电时钟信号的相位噪声在频偏10 kHz处为-109 dBc/Hz,边模抑制比为58 dB。 相似文献
33.
Tse-Wei Chen Palraj Kalimuthu Pitchaimani Veerakumar King-Chuen Lin Shen-Ming Chen Rasu Ramachandran Vinitha Mariyappan Selvam Chitra 《Molecules (Basel, Switzerland)》2022,27(3)
Carbon-based nanocomposites have developed as the most promising and emerging materials in nanoscience and technology during the last several years. They are microscopic materials that range in size from 1 to 100 nanometers. They may be distinguished from bulk materials by their size, shape, increased surface-to-volume ratio, and unique physical and chemical characteristics. Carbon nanocomposite matrixes are often created by combining more than two distinct solid phase types. The nanocomposites that were constructed exhibit unique properties, such as significantly enhanced toughness, mechanical strength, and thermal/electrochemical conductivity. As a result of these advantages, nanocomposites have been used in a variety of applications, including catalysts, electrochemical sensors, biosensors, and energy storage devices, among others. This study focuses on the usage of several forms of carbon nanomaterials, such as carbon aerogels, carbon nanofibers, graphene, carbon nanotubes, and fullerenes, in the development of hydrogen fuel cells. These fuel cells have been successfully employed in numerous commercial sectors in recent years, notably in the car industry, due to their cost-effectiveness, eco-friendliness, and long-cyclic durability. Further; we discuss the principles, reaction mechanisms, and cyclic stability of the fuel cells and also new strategies and future challenges related to the development of viable fuel cells. 相似文献
34.
In this paper, we propose and demonstrate a new and original model for theoretical calculation and experimental measurement of the noise power spectral density (NPSD) in phase-modulated optical links. The phase modulation is operated in the RF frequency range by an external phase modulator. The NPSD is derived for the first time in interferometric systems, by considering all effects such as the 1/f FM noise of the laser and white noise applied to light from a 1550 nm DFB laser, with phase modulation. The results show for the first time the influence of the phase modulation index, modulation frequency and interferometric delay in the phase-to-intensity noise conversion. The experimental and simulation results of conversion of FM-noise to intensity noise in an optical link by considering the external RF phase modulation are shown with good agreement. 相似文献
35.
36.
采用常规透镜设计了适用于非真空环境中交叉偏振波(XPW)产生的双透镜聚焦系统,在相对较短的距离实现了长焦透镜聚焦的效果,并测量了聚焦后的激光脉冲,发现其没有显著的非线性相位积累,保证了激光光束质量.在非真空中采用双BaF_2晶体得到了XPW系统转换效率22%,光谱1.78倍展宽的净化脉冲输出,双透镜组合聚焦形式使得双BaF_2晶体间距在13—22 cm内可保证20%以上的XPW转换效率,双晶体间距的调节冗余度提高了两个量级,极大地降低了双晶转换效率对晶体间距的依赖.这种正负透镜组合聚焦的光路设计在非真空中实现了高效稳定的XPW输出,为后续的放大应用提供了高对比度、宽光谱的高质量种子源. 相似文献
37.
38.
In nature, different environmental factors make organisms to be programmed into different forms. However, it is difficult and significant to realize the field‐programmable logic conversion of sole logic system for molecular logic gates. Here, the concept of pH‐programmable “logic conversion” on the single logic gate based on the peculiar enzyme‐mimicking activity is presented. Inspired by natural enzymes with high pH‐stability and metal ions‐stimulated activity, pH‐independent and metal ions‐controllable catalase mimics (Co3O4 nanozymes) are designed by protein‐directed method. Although pH cannot directly change the activity of nanozymes, pH can change the existence state of metal ions and then the electron transfer rate on nanozymes. So, versatile roles of metal ions for catalase‐like and electrocatalytic activities are discovered on the premise of pH‐independency. For the proof‐of‐concept, OR/INHIBIT‐ and INHIBIT/AND‐switchable logic gates are facilely constructed using pH as the environmental stimulus and metal ions as inputs. Hence, the transformation of logic gate functions is realized without the change of logic gate elements and input molecules. This contribution may not only broaden the species and application area of nanozymes, but also open novel avenues for the molecular logic conversion and the metal ions sensor. 相似文献
39.
SUN Qin-jun SHI Xiao-lei GAO Li-yan ZHOU Shao-long WU Jun HAO Yu-ying 《光谱学与光谱分析》2018,38(11):3368-3373
研究利用静电纺丝制备的不同直径ZnO纳米纤维作为倒置结构有机太阳能电池的电子传输层对器件转化效率的影响。首先通过静电纺丝技术成功制备了半径在43~110 nm之间的ZnO纳米纤维,然后将ZnO纳米纤维作为电子传输层加入到倒置结构有机太阳能电池(ITO/ZnO∶ZnO nanofiber/PTB7∶PC70BM/MoO3/Al)。与平面结构的ZnO电子传输层相比,ZnO纳米纤维具有比表面积大等优点,增加了电子传输和抽取能力,提高了器件的光电转化效率。实验发现ZnO纳米纤维的直径越小,电池效率越大。当ZnO纳米纤维直径为(46±5)nm,接收时间为30 s时,作为电子传输层的电池效率提高了8%。 相似文献
40.
Phase-matched third-harmonic UV generation using low-order modes in a glass micro-fiber 总被引:1,自引:0,他引:1
Victor Grubsky 《Optics Communications》2007,274(2):447-450
We observe phase-matched third-harmonic generation at 355 nm in a low-order mode of a sub-micron diameter glass fiber. The third-harmonic signal exhibits a sharp resonance for a fiber diameter d = 0.49 ± 0.02 μm, in excellent agreement with the value d = 0.506 μm predicted by theory. The third-harmonic conversion efficiency is 2 × 10−6, and is limited by the pump power (1 kW) and effective fiber length (100 μm). 相似文献