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排序方式: 共有388条查询结果,搜索用时 15 毫秒
1.
This paper presents a study of velocity fluctuations occurring in the stably stratified atmospheric boundary layer over an Antarctic ice shelf. The approach is based on wavelet analysis which has advantages over conventional Fourier analysis. Two case studies are presented, comprising: pure turbulent flow and a large amplitude solitary wave. 相似文献
2.
We consider the onset of convection in an inclined anisotropic porous layer heated from below. To date the principle axes
of the permeability and diffusivity tensors have been assumed to be aligned with the coordinate directions. Therefore particular
emphasis is laid upon how the basic flow and criteria for the onset of convection are altered by the presence of oblique principle
axes. When these axes are not aligned with the coordinate directions and when the ratios of the principle permeabilities or
diffusivities are not too large or too small, we find that there is always a smooth transition in the orientation of the most
dangerous mode of instability as the inclination increases from the horizontal. In more extreme cases there may be sudden
changes in the orientation, Darcy–Rayleigh number and wavenumber. 相似文献
3.
A new nonlinear evolution equation is derived for surface solitary waves propagating on a liquid-air interface where the wave motion is induced by a harmonic forcing. Instead of the traditional approach involving a base state of the long wave limit, a base state of harmonic waves is assumed for the perturbation analysis. This approach is considered to be more appropriate for channels of length just a few multiples of the depth. The dispersion relation found approaches the classical long wave limit. The weakly nonlinear dispersive waves satisfy a KdV-like nonlinear evolution equation with steeper nonlinearity. 相似文献
4.
5.
Rational Design of Cyclometalated Iridium(III) Complexes for Three-Photon Phosphorescence Bioimaging
Dr. Chengzhi Jin Fengyin Liang Dr. Jinquan Wang Dr. Lili Wang Dr. Jiangping Liu Xinxing Liao Dr. Thomas W. Rees Bo Yuan Prof. Dr. Hui Wang Prof. Dr. Yong Shen Prof. Dr. Zhong Pei Prof. Dr. Liangnian Ji Prof. Dr. Hui Chao 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(37):16121-16125
Compared to 2PE (two-photon excitation) microscopy, 3PE microscopy has superior spatial resolution, deeper tissue penetration, and less defocused interference. The design of suitable agents with a large Stokes shift, good three-photon absorption (3PA), subcellular targeting, and fluorescence lifetime imaging (FLIM) properties, is challenging. Now, two IrIII complexes (3PAIr1 and 3PAIr2) were developed as efficient three-photon phosphorescence (3PP) agents. Calculations reveal that the introduction of a new group to the molecular scaffold confers a quadruple promotion in three-photon transition probability. Confocal and lifetime imaging of mitochondria using IrIII complexes as 3PP agents is shown. The complexes exhibit low working concentration (50 nm ), fast uptake (5 min), and low threshold for three-photon excitation power (0.5 mW at 980 nm). The impressive tissue penetration depth (ca. 450 μm) allowed the 3D imaging and reconstruction of brain vasculature from a living specimen. 相似文献
6.
7.
It is well known that the onset of convection in an inclined porous layer heated from below takes the form of longitudinal
vortices when Darcy’s law is valid. In this paper we consider briefly how the onset criterion alters when form drag, as modelled
by the Forchheimer terms, is significant. In general, the critical Rayleigh number increases substantially as form drag effects
strengthen, but the wavenumber rises by only a small amount. This numerical study is supplemented by a brief asymptotic analysis
of the case when the Forchheimer terms dominate and it is shown that the critical Rayleigh number increases in direct proportion
with the form drag parameter. 相似文献
8.
9.
H.C. Hemaka Bandalusena William B. Zimmerman Julia M. Rees 《ournal of non Newtonian Fluid Mechanics》2010,165(19-20):1302-1308
This paper analyzes flow of a power-law fluid in a microfluidic device for the purpose of discovering an algorithm for rheometry. Previous investigations have shown that measurement of the velocity field or the pressure field and the inlet flow rate in a microfluidic T-junction allow determination of rheological parameters uniquely. However, the range of shear induced within the flow domain was limited by the constant pressure drop applied across the micro-device. To avoid this control restriction and further develop our inverse technique, a constant flow rate system was investigated. With this configuration, the flow rate can be set appropriately to achieve a desired shear range and the rheological parameters can be inferred from the measurement of mean pressure at the inlet and at the junction. By assuming creeping flow conditions and the existence of a Hagen-Poiseuille-like law for the relationship between the pressure drop and the volumetric flow rate, the analysis produces an algorithm that is self-consistent (demonstrates the Hagen-Poiseuille law) and permits the inference of the power-law parameters from the ratio of any two field variables measured over a region (averaged), the pressure drop, and the volumetric flow rate. 相似文献
10.
Sherifull-Din Jamalud-Din D. Andrew S. Rees B. V. K. Reddy Arunn Narasimhan 《Heat and Mass Transfer》2010,46(3):333-343
Steady state natural convection of a fluid with Pr ≈ 1 within a square enclosure containing uniformly distributed, conducting square solid blocks is investigated. The side
walls are subjected to differential heating, while the top and bottom ones are kept adiabatic. The natural convection flow
is predicted employing the nondimensional volumetric flow rate (Qmax* Q_{\max }^{*} ) by using a network model and also using numerical simulations. For identical solid and fluid thermal conductivities (i.e.
k
s
= k
f
), a parametric study of the effect of number of blocks (N
2), gap size (δ) and enclosure Rayleigh number (Ra) on Qmax* Q_{\max }^{*} is performed using the two approaches. Network model predictions are observed to agree well with that from the simulations
until Raδ3 ~ 12. Considering the enclosure with blocks as a porous medium, for a fixed enclosure Ra number, increasing the number of blocks for a fixed volumetric porosity leads to a decrease in enclosure permeability, which
in turn reduces the flow rate. When the number of blocks is fixed, and for a given Ra number, the flow rate increases as the porosity increases by widening the gap between the blocks. 相似文献