首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:从到   被引次数:从到   他引次数:从到 提示：输入*表示无穷大
全文获取类型
  收费全文   140篇
  免费   10篇
专业分类
化学   32篇
物理学   118篇
出版年
  2024年   1篇
  2022年   4篇
  2021年   9篇
  2020年   6篇
  2019年   5篇
  2018年   3篇
  2017年   8篇
  2016年   8篇
  2015年   4篇
  2014年   7篇
  2013年   5篇
  2012年   9篇
  2011年   16篇
  2010年   11篇
  2009年   12篇
  2008年   4篇
  2007年   9篇
  2006年   3篇
  2005年   2篇
  2004年   1篇
  2001年   2篇
  1999年   3篇
  1998年   2篇
  1997年   1篇
  1995年   1篇
  1992年   10篇
  1991年   3篇
  1990年   1篇
排序方式： 共有150条查询结果，搜索用时 15 毫秒
41.
Summary The experimental results on four-wave Raman and hyper-Raman scattering in a laser-produced and electric-discharge plasma are presented. It has been shown that in spectra of four-wave mixing processes resonances appear due to the Raman and hyper-Raman scattering on atomic and ionic excited states. The temporal behaviour of the scattered-signal intensity has been found to be connected with the population relaxation of atomic and ionic excited states. We have observed for the first time the resonance in the spectrum of coherent hyper-Raman scattering in electric-discharge plasma associated with the electron transition between the excited and autoionizing state of a copper atom. Paper presented at the ?XI European CARS Workshop?, Florence, Italy, 23–25 March, 1992.  相似文献   
42.
Summary We have carried out parallel studies of the quenching process in Na(3p)+H2 collisions and the possible reactive process in Na(3p)+H2 (v ″=1,2,3) collisions. Rich CARS spectra which were obtained at H2 pressure of 100 mbar and oven temperature of 600 K indicate the presence of vibrationally excited H2 and photochemically produced NaH molecules. Temporal resolution of NaH CARS lines was employed in order to rule out competing collisional processes. We make use of resonantly enhanced CARS methods which enabled us to achieve very high sensitivity for NaH detection. Paper presented at the ?XI European CARS Workshop?, Florence, Italy, 23–25 March, 1992.  相似文献   
43.
    
Raman spectroscopy provides the unique opportunity to nondestructively analyze chemical concentrations in individual cells on the submicrometer length scale without the need for optical labels. This enables the rapid assessment of cellular biochemistry inside living cells, and it allows for their continued analysis. Here, we review recent developments in the analysis of single cells, subcellular compartments, and chemical imaging based on Raman spectroscopy. Spontaneous Raman spectroscopy provides for the full spectral assessment of cellular biochemistry, while coherent Raman techniques, such as coherent anti‐Stokes Raman scattering is primarily used as an imaging tool comparable to confocal fluorescence microscopy. These techniques are complemented by surface‐enhanced Raman spectroscopy, which provides higher sensitivity and local specificity, and also extends the techniques to chemical indicators, i.e. pH sensing. We review the strengths and weaknesses of each technique, demonstrate some of their applications and discuss their potential for future research in cell biology and biomedicine.  相似文献   
44.
    
Because each nonlinear optical (NLO) imaging modality is sensitive to specific molecules or structures, multimodal NLO imaging capitalizes the potential of NLO microscopy for studies of complex biological tissues. The coupling of multiphoton fluorescence, second‐harmonic generation, and coherent anti‐Stokes Raman scattering (CARS) has allowed investigation of a broad range of biological questions concerning lipid metabolism, cancer development, cardiovascular disease, and skin biology. Moreover, recent research shows the great potential of using a CARS microscope as a platform to develop more advanced NLO modalities such as electronic‐resonance‐enhanced four‐wave mixing, stimulated Raman scattering, and pump‐probe microscopy. This article reviews the various approaches developed for realization of multimodal NLO imaging as well as developments of new NLO modalities on a CARS microscope. Applications to various aspects of biological and biomedical research are discussed.  相似文献   
45.
    
A novel approach toward phase‐locking of two independently produced yet energetically degenerate coherent anti‐Stokes Raman scattering (CARS) processes is put forward. The proposed all‐optical implementation involves a modified Mach–Zehnder interferometer, which is utilized to transfer phase coherence from three totally uncorrelated laser beams into two degenerate CARS beams that are produced in two distinct Raman active samples. Such a CARS interferometer based on coherent phase transport allows explicit measurement and control of phase differences between the two phase‐locked degenerate CARS processes, and hence may find applications in pertinent research fields such as CARS spectroscopy (tomography) as well as quantum information processing and transfer. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   
46.
    
We demonstrate the feasibility of single laser shot coherent anti‐Stokes Raman scattering thermometry with simultaneous measurement of intensities of hydrogen Q‐branch lines and their linewidths in a pulsed CH4/O2 combustion chamber operating at 20 MPa pressure and 3000 K temperature—parameters that are typical for full‐scale rocket engines. The measurements were done by means of a spectrograph combined with an interferometer having orthogonal directions of dispersions. This approach allows correct temperature evaluation that takes into account the directly measured linewidths. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   
47.
    
Coherent anti‐Stokes Raman scattering (CARS) spectroscopy of gas‐phase CO2 is demonstrated using a single femtosecond (fs) laser beam. A shaped ultrashort laser pulse with a transform‐limited temporal width of ∼7 fs and spectral bandwidth of ∼225 nm (∼3500 cm−1) is employed for simultaneous excitation of the CO2 Fermi dyads at ∼1285 and ∼1388 cm−1. CARS signal intensities for the two Raman transitions and their ratio as a function of pressure are presented. The signal‐to‐noise ratio of the single beam–generated CO2 CARS signal is sufficient to perform concentration measurements at a rate of 1 kHz. The implications of these experiments for measuring CO2 concentrations and rapid pressure fluctuations in hypersonic and detonation‐based chemically reacting flows are also discussed. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   
48.
    
We present a detailed theoretical and experimental characterization of a new methodology for stimulated Raman spectroscopy using two duplicates of a chirped, broadband laser pulse. Because of the linear variation of laser frequency with time (‘chirp’), when the pulses are delayed relative to one another, there exists a narrow bandwidth, instantaneous frequency difference between them, which, when resonant with a Raman‐active vibration in the sample, generates stimulated Raman gain in one pulse and inverse Raman loss in the other. This method has previously been used for coherent Raman imaging and termed ‘spectral focusing’. Here, gain and loss signals are spectrally resolved, and the spectrally integrated signals are used to determine the spectral resolution of the measured Raman spectrum. Material dispersion is used to generate a range of pulse durations, and it is shown that there is only a small change in the magnitude of the signal and the spectral resolution as the pulse is stretched from 800 to 1800 fs in duration. A quantitative theory of the technique is developed, which reproduces both the magnitude and linewidth of the experimental signals when third‐order dispersion and phase‐matching efficiency are included. The theoretical calculations show that both spectral resolution and signal magnitude are severely hampered by the third‐order dispersion in the laser pulse, and hence, a minimal amount of chirp produces the most signal with only a slight loss of spectral resolution. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   
49.
    
Coherent anti-Stokes Raman Spectroscopy (CARS) is a laser-based measurement technique widely applied across many science and engineering disciplines to perform non-intrusive gas diagnostics. CARS is often used to study combustion, where the measured spectra can be used to simultaneously recover multiple flow parameters from the reacting gas such as temperature and relative species mole fractions. This is typically done by using numerical optimization to find the flow parameters for which a theoretical model of the CARS spectra best matches the actual measurements. The most commonly used theoretical model is the CARSFT spectrum calculator. Unfortunately, this CARSFT spectrum generator is computationally expensive, and using it to recover multiple flow parameters can be prohibitively time-consuming, especially when experiments have hundreds or thousands of measurements distributed over time or space. To overcome these issues, several methods have been developed to approximate CARSFT using a library of pre-computed theoretical spectra. In this work, we present a new approach that leverages ideas from the machine learning literature to build an adaptively smoothed kernel-based approximator. In application on a simulated dual-pump CARS experiment probing a H2/air flame, we show that the approach can use a small number library spectra to quickly and accurately recover temperature and four gas species' mole fractions. The method's flexibility allows fine-tuned navigation of the trade-off between speed and accuracy and makes the approach suitable for a wide range of problems and flow regimes.  相似文献   
50.
    
Rapid label-free spectroscopy of biological and chemical specimen via molecular vibration through means of broadband coherent anti-Stokes Raman scattering (B-CARS) could serve as a basis for a robust diagnostic platform for a wide range of applications. A limiting factor of CARS is the presence of a non-resonant background (NRB) signal, endemic to the technique. This background is multiplicative with the chemically resonant signal, meaning the perturbation it generates cannot be accounted for simply. Although several numerical approaches exist to account for and remove the NRB, they generally require some estimate of the NRB in the form of a separate measurement. In this paper, we propose a deep neural network architecture called V ery d E ep C onvolutional au TO encode R s (VECTOR), which retrieves the analytical Raman-like spectrum from CARS spectra through training of simulated noisy CARS spectra, without the need for an NRB reference measurement. VECTOR is composed of an encoder and a decoder. The encoder aims to compress the input to a lower dimensional latent representation without losing critical information. The decoder learns to reconstruct the input from the compressed representation. We also introduce skip connection that bypass from the encoder to the decoder, which benefits the reconstruction performance for deeper networks. We conduct abundant experiments to compare our proposed VECTOR to previous approaches in the literature, including the widely applied Kramers–Kronig method, as well as two another recently proposed methods that also use neural networks.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号