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991.
The cosmic coincidence problem is a serious challenge to dark energy model. We suggest a quantitative criteria for judging the severity of the coincidence problem. Applying this criteria to three different interacting models, including the interacting quintessence, interacting phantom, and interacting Chaplygin gas models, we find that the interacting Chaplygin gas model has a better chance to solve the coincidence problem. Quantitatively, we find that the coincidence index C for the interacting Chaplygin gas model is smaller than that for the interacting quintessence and phantom models by six orders of magnitude. 相似文献
992.
The bright one- and two-soliton solutions of the coupled mixed derivative nonlinear Schrödinger equations in birefringent optical fibers are obtained by using the Hirota's bilinear method. The investigation on the collision dynamics of the bright vector solitons shows that there exists complete or partial energy switching in this coupled model. Such parametric energy exchanges can be effectively controlled and quantificationally measured by analyzing the collision dynamics of the bright vector solitons. The influence of two types of nonlinear coefficient parameters on the energy of each vector soliton, is also discussed. Based on the significant energy transfer between the two components of each vector soliton, it is feasible to exploit the future applications in the design of logical gates, fiber directional couplers and quantum information processors. 相似文献
993.
Based on the lumped parameter method, this study establishes an experimental scheme for YAG laser absorptance measurement. Laser absorptance is measured on artificial diamond and cubic boron nitride materials under different laser power levels at room temperature. This study presents an analysis of the influence of laser spot size, and number of repeated laser irradiation, heat-insulating material, etc. on absorptance. A theoretical parameter is provided for the process of laser truing and dressing of the corresponding abrasive wheel, and it is important for the analysis and modeling of laser-material interactions. Meanwhile, a reference for measuring the laser absorptance of material with the same physical performance is put forward. 相似文献
994.
A scheme of all-optical data format conversion from nonreturn-to-zero to return-to-zero is proposed using quantum-dot semiconductor optical amplifiers (QD SOAs) assisted Mach-Zehnder interferometer (MZI). The proposed scheme has the potential to operate at much larger bit rate ∼160 Gb/s, and the converted signal has a lower frequency chirp. 160 Gb/s all-optical format conversion is verified through numerical simulations, and the output contrast ratio and Q-factor are analyzed to evaluate the system performance. With properly selected parameters, the converted signal with a contrast ratio over 8 dB and a Q-factor over 8 can be achieved. 相似文献
995.
FWM mitigation based on serial correlation reduction by partial transmit sequence in coherent optical OFDM systems 总被引:1,自引:0,他引:1
Weilin Li 《Optics Communications》2009,282(18):3676-3679
Because of the narrow frequency interval among sub-carriers, FWM becomes one of the dominant nonlinearities in Coherent Optical OFDM systems. The dependence of the FWM noises on the serial correlation is investigated and the variance of FWM noises and SNR are derived theoretically in the case of independent distribution. The Partial Transmit Sequence (PTS) is introduced to reduce serial correlation approaching the independent distribution. The concept of average auto-correlation coefficient are employed to evaluate the reduction of the correlation. FWM noises are reduced efficiently without signal distortions and decreased spectral efficiency compared with the traditional algorithms. 相似文献
996.
A novel scheme of time-stacked optical code label based on optical code division multiple (OCDM) technique for optical packet switching network is proposed, in which two-dimensional wavelength-time OCDM code is used as the optical label. Packet loss rate and system characteristic based on the proposed scheme are studied. Results show that less packet loss rate of proposed scheme can be achieved as compared with that of one-dimension time-stacked optical code label system. 相似文献
997.
We present an ab initio study of the structural, elastic and electronic properties of the antiperovskite compounds AlCSc3 and AlNSc3. The calculated lattice parameters and equilibrium volumes are in good agreement with the available experimental data. Single-crystal elastic constants were calculated and the polycrystalline elastic moduli were estimated according to Voigt, Reuss and Hill’s approximations. The band structure shows a metallic character of both compounds; strong hybridization between Sc d–C p (or N p) and Sc d–Al p states was observed from the partial density of states. A significant charge transfer from Al to C (or N) atoms was observed. Moreover, these compounds are bonded by a mixture of ionic–covalent bonding. 相似文献
998.
Molecular dynamics simulations using a Coulomb–Buckingham potential have been used to investigate the process of wurtzite GaN films growth, including the appearance of films in early stage, regulation of growth, structure of the surface and the dynamic features. The simulations show that the N atoms and Ga atoms are absorbed on the lattice of substrate and take on a distinct sandwich structure. Time evolution of the mean square displacements and diffusion coefficient of the deposited atoms are observed, the results show that the clusters will become stable with the increase of time steps and the atoms reach the initial stable state after 25 ps; N atoms reach the equilibrium positions more quickly than Ga atoms. It is proved by radial distribution function and the ratio of vacancy of every deposited layer that the crystalline characters of the films will become better as the time steps increase and weaker from bottom to top. 相似文献
999.
阐述了光纤Bragg光栅化学传感的基本原理,推导并利用数值计算得出了腐蚀掉包层后的光纤Bragg光栅的纤芯有效折射率随外界折射率变化的关系.分析了温度对这种传感器造成的误差.研究表明,温度会造成光纤光栅变化和改变溶液折射率的大小,从而对传感器的测量造成影响.设计了一种温度补偿方案.实验分别研究了低浓度溶液和高浓度溶液中传感头两段不同光栅区的Bragg波长随温度的变化.结果表明:在清水中,传感头两段光栅区Bragg波长受到温度变化的影响基本相同,通过测量波长的差值可消除温度的影响;高浓度溶液中,传感头受温度影响造成的总波长漂移量约为未被腐蚀光栅区的波长漂移量的0.6,与理论的结果基本一致.传感头受温度影响造成的总波长漂移量可由未被腐蚀光栅区波长漂移量的大小得出,进而可消除温度对溶液传感的影响. 相似文献
1000.