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51.
The paper generalizes paraxial complex geometrical optics (PCGO) for Gaussian beam (GB) propagation in nonlinear media of Kerr type. Ordinary differential equations for the beam amplitude and for complex curvature of the wave front are derived, which describe the evolution of axially symmetric GB in a Kerr type nonlinear medium. It is shown that PCGO readily provides the solutions of NLS equation obtained earlier from diffraction theory on the basis of the aberration-free approach. Besides reproducing classical results of self-focusing PCGO readily describes an influence of the initial curvature of the wave front on the beam evolution in a medium of Kerr type including a nonlinear graded-index fiber. The range of applicability of the PCGO theory is discussed as well which is helpful for avoiding nonphysical solutions. 相似文献
52.
53.
采用基于密度泛函理论(DFT)中的广义梯度近似 (GGA),在考虑自旋多重度的情况下,对NiMgn(n=1—12)团簇进行了构型优化,频率分析和电子性质计算.结果表明:n=1,2时,体系的基态为自旋三重态,n≥3时,为单重态;Ni原子掺杂使主团簇结构发生了明显变化. n≤8时,三角双锥,四角双锥结构主导着NiMgn基态团簇的生长行为; n在9—12之间时,主团簇Mgn+1(n=1—12)的基于三棱柱构型的基态演化行为发生了一定程度的改变;n≥6时,Ni原子陷入了主团簇内部;掺杂使体系的平均结合能增大,能隙减小;n=4,6,10是团簇的幻数;不同尺寸团簇的s, p, d轨道杂化中,Ni原子3d, 4p成分所起作用不同; NiMg6基态结构具有很高的对称性(Oh),很好的稳定性和化学活性,能隙仅为0.25eV.
关键词:
n团簇')" href="#">NiMgn团簇
几何结构
稳定性
化学活性 相似文献
54.
55.
Seyed Hossein Hendi Fereshteh Azari Ebrahim Rahimi Mina Elahi Zahra Owjifard Zahra Armanfard 《Annalen der Physik》2020,532(10):2000162
It is known that scalar-tensor gravity models can be studied in Einstein and Jordan frames. In this paper, a model of scalar-tensor gravity in Einstein's frame is considered to calculate the Lifshitz-like black hole solutions with different horizon topologies. Thermodynamic properties and first order van der Waals-like phase transition are studied, and it is found that the Lifshitz parameter affects the phase structure. In addition, thermal stability is investigated by using the behavior of heat capacity and various methods of geometrical thermodynamics. 相似文献
56.
Ping Xia Zhang Yong Fang Zhao Feng You Hao Xin Ying Li 《International journal of quantum chemistry》2008,108(5):937-944
Noble‐gas‐noble‐metal hydroxides NgAuOH (Ng = Kr, Xe) are investigated at the MP2 theoretical level. All species are found to be in Cs symmetry with an approximate linear Ng? Au? O moiety. The noble‐gas‐noble‐metal bond lengths are comparable with covalent limits, and the corresponding binding energies have been computed to be 59.6 and 83.4 kJ/mol for KrAuOH and XeAuOH, respectively. Except the charge‐induced dipole contribution to the binding energies, the remainder could be ascribed to the higher‐order charge‐induction energies, dispersion energies, the contributions of multipole moments on AuOH and covalent effects. The title species are sufficiently chemical bound and are expected to be stable species theoretically. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2008 相似文献
57.
研究激光光束海面反射光强的方向分布特性对海上光电对抗等领域的工程实践具有重要意义.本文采用分形方法模拟粗糙海面,并在海面基准坐标系中建立起描述粗糙海面几何特征的数学方程,然后基于蒙特卡罗方法模拟高斯光束,依据几何光学原理在基准坐标系下推导了高斯光束的海面反射模型,采用该模型可以编程计算激光光束海面反射光强的方向分布.将模拟计算结果与实验结果进行了对比分析,结果表明该模型可以较好地反映激光光束海面反射光强的分布趋势,验证了模型的有效性. 相似文献
58.
本文进一步将修正迭代法推广到薄圆板轴对称后屈曲分析中,由此获得该问题的一种新的近似解析解.作者期望将此方法应用于更为复杂结构的板的后屈曲分析中去. 相似文献
59.
Kouki Ikuta Tsutomu Kudo Noboru Yoshikane Nilesh J. Vasa Yuji Oki Mitsuo Maeda 《Optical Review》1999,6(5):464-470
Improvement of an infrared light detection and ranging (IR-lidar) system for a short range (0–1000 m) and with high resolution is studied to enhance a geometrical form factor. Theoretical modeling of Mie scattering echo signals agrees with the experimental results. Introduction of a lens in front of the detector is effective for increasing the geometrical form factor, and a significant improvement in the received signal intensity is achieved, especially for short-range measurements around 100 m. This is useful for the IR-lidar system with a detector diameter of less than 1 mm. In the theoretical model, a ray-tracing technique was applied and a transmitting laser beam with Gaussian profile was considered for better accuracy. 相似文献
60.
J.M. Hughes E.I. von Nagy-Felsobuki 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,6(2):185-192
The electronic structure and molecular properties of helides of the form (where , Al-Ar and ) were studied using the CCSD(T) method in conjunction with the series of correlation-consistent basis sets. The highest level
of theory employed, the CCSD(T)-FC/cc-pVQZ model, was used to elucidate trends in bond lengths, dissociation energies and harmonic frequencies. The more highly
charged species were found to have shorter bond lengths than the singly charged species. The ground states of the helide cations
were often those with longer bond lengths when compared with the excited state ions.
Received: 11 May 1998 / Received in final form: 2 September 1998 相似文献