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排序方式: 共有620条查询结果,搜索用时 31 毫秒
191.
混浊大气介质调制传递函数的一般特征 总被引:3,自引:2,他引:1
基于混浊介质的调制传递函数(MTF)和在各向同性漫射光源照射下平行平面混浊介质出射光强度分布之间的等效原理,利用辐射传输算法DISORT数值计算了几种典型的均匀大气混浊介质的MTF,获得了整个空间频域内MTF的一般特征.结果显示,大气介质的MTF不但依赖于介质的光学厚度(散射和吸收),也依赖于介质的散射相函数.给出了大... 相似文献
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194.
Detailed term and level accounting (DTA and DLA) schemes have been developed to calculate the spectrally resolved and Rosseland
and Planck mean opacities of plasmas in local thermodynamic equilibrium. Various physical effects, such as configuration interaction
effect (including core-valence electron correlations effect and relativistic effect), detailed line width effect (including
the line saturation effect), etc., on the opacity of plasmas have been investigated in detail. Some of these physical effects
are less capable or even impossible to be taken into account by statistical models such as unresolved transition arrays, super-transition-array
or average atom models. Our detailed model can obtain accurate opacity of plasmas. Using this model, we have systematically
investigated the radiative opacities of low, medium and high-Z plasmas under different conditions of temperature and density. For example, for aluminum plasma, in the X-ray region, we
demonstrated the effects of autoionization resonance broadening on the opacity for the first time. Furthermore, the relativistic
effects play an important role on the opacity as well. Our results are in good agreement with other theoretical ones although
better agreement can be obtained after the effects of autoionization resonance broadening and relativity have been considered.
Our results also show that the modelling of the opacity is very complicated, since too many physical effects influence the
accuracy of opacity.
For medium and high-Z plasmas, however, there are systematic discrepancies unexplained so far between the theoretical and experimental opacities.
Here, the theoretical opacities are mainly obtained by statistical models. To clarify the discrepancies, efforts from both
sides are needed. From the view-point of theory, however, a DLA method, in which various physical effects can be taken into
account, should be useful in resolving the difference. Taking gold plasma as an example, we studied in detail the effects
of core-valence electron correlation and line width on the opacity. Our DLA results correctly explained, for the first time,
the relative intensity of the two strong absorption peaks located near the photon energy of 70 and 80 eV, which was experimentally
observed by Eidmann et al. [Europhys. Lett., 1998, 44: 459]. 相似文献
195.
A. Milandri F. AsllanajG. Jeandel J.R. Roche 《Journal of Quantitative Spectroscopy & Radiative Transfer》2002,74(5):585-603
Coupled radiative and conductive heat transfer in a fibrous medium formed by silica fibres is investigated in this paper by not taking account of the axial symmetry for the distribution of fibres or the boundary conditions. Radiative properties of the medium are calculated by using the Mie theory. The model obtained depends only on optical parameters (indices of silica) and on morphological parameters (diameter and orientation of the fibres, density of the medium). Simulations make it possible to study the strongly anisotropic behaviour of the scattering of the radiation by a fibre and to study the influence of various parameters on the radiative properties of the medium. The results of the Mie theory make possible the simulation of the heat transfer coupled by radiation and conduction. To do this, we introduce a new numerical scheme able to simulate heat transfer in the lack of axial symmetry. With this model, we can show the effects of distribution of fibres and temperature on the thermal behaviour of the medium as well as showing the importance of the phenomenon of scattering in fibrous media. 相似文献
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给出了一层有下垫反射面的非球形粒子散射的标量辐射传输方程一、二阶迭代解,推导了相函数各阶Legendre展开系数与随机小椭球粒子相函数的对应关系,提出了一层随机小椭球粒子介电常数和单位面积粒子数的迭代反演方法.通过两次各方位角上双站散射测量,反演随机小椭球粒子的介电常数和单位面积粒子数.本方法比现有文献的一些反演方法易于实现,可应用于颗粒性复合材料介电与结构特性以及地表背景参数的反演研究
关键词:
辐射传输方程
迭代解
反演
相函数
介电常数 相似文献
198.
Joan Boulanger 《Journal of Quantitative Spectroscopy & Radiative Transfer》2005,91(2):189-209
This two part study is devoted to the numerical treatment of short-pulsed laser near infra-red spectroscopy. The overall goal is to address the possibility of numerical inverse treatment based on a recently developed direct model to solve the transient radiative transfer equation. This model has been constructed in order to incorporate the last improvements in short-pulsed laser interaction with semi-transparent media and combine a discrete ordinates computing of the implicit source term appearing in the radiative transfer equation with an explicit treatment of the transport of the light intensity using advection schemes, a method encountered in reactive flow dynamics. The incident collimated beam is analytically solved through Bouger-Beer-Lambert extinction law.In this first part, the direct model is extended to fully non-homogeneous materials and tested with two different spatial schemes in order to be adapted to the inversion methods presented in the following second part. As a first point, fundamental methods and schemes used in the direct model are presented. Then, tests are conducted by comparison with numerical simulations given as references. In a third and last part, multi-dimensional extensions of the code are provided. This allows presentation of numerical results of short pulses propagation in 1, 2 and 3D homogeneous and non-homogeneous materials given some parametrical studies on medium properties and pulse shape. For comparison, an integral method adapted to non-homogeneous media irradiated by a pulsed laser beam is also developed for the 3D case. 相似文献
199.
用 NaD_2线激发钠蒸汽(T=523°K),探测3P→3S,5S→3P,4D→3P 的荧光强度,得到 Na(3P)+Na(3P)→Na(4D)+Na(3S)碰撞激发能量转移截面为2.4×10~(-15)(cm)~2.并将本文和国内外文献数值作了比较,结果相符. 相似文献
200.
运用时间分辨激光诱导荧光技术和激光诱导等离子体方法测量了铂原子的15条奇宇称高激发态能级的自然辐射寿命.测量结果处于6.1到116 ns之间,且误差低于10%.经比较,与前人结果在误差范围内符合很好.据文献调研所知,结果中有5条高度接近60000 cm~(-1)的高激发态能级的寿命值是未见报道的. 相似文献