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71.
Yoshiki Kaneoke Masahiro Furuse Suguru Inao Katsuyoshi Saso Kazuo Yoshida Yoshimasa Motegi Motomu Mizuno Akira Izawa 《Magnetic resonance imaging》1987,5(6):415-420
Measurements were made of T1 of bound water (T1b) and bound water fraction () for gelatin solutions and human tissues (sera, brain tumor, cerebral white matter). Bound water fraction in each sample was measured by means of thermal analysis (differential scanning calorimetry: DSC). T1 values were measured by FONAR QED 80-. T1b values were calculated by an equation derived from the fast-exchange two-state model. In the study of gelatin solutions, the relationship between T1 and water content differed depending on the sort of solutions. This was considered to be due to differences in T1b values. In each biological tissue the values of T1b and had different distributions. These results indicate that values of T1b and for biological tissues may be altered in correspondence to the changes in pathophysiological states in those tissues. 相似文献
72.
73.
《Particuology》2014
Fluidized beds with multiple jets have widespread industrial applications. The objective of this paper is to investigate the jet interactions and hydrodynamics of a fluidized bed with multiple jets. Discrete element modeling coupled with in-house CFD code GenIDLEST has been used to simulate a bed with nine jets. The results are compared with published experiments. Mono dispersed particles of size 550 μm are used with 1.4 times the minimum fluidization velocity of the particles. Both two and three dimensional computations have been performed. To the best of our knowledge, the results presented in this paper are the first full 3D simulations of a fluidized bed performed with multiple jets. Discrepancies between the experiment and simulations are discussed in the context of the dimensionality of the simulations. The 2D solid fraction profile compares well with the experiment close to the distributor plate. At higher heights, the 2D simulation over-predicts the solid fraction profiles near the walls. The 3D simulation on the other hand is better able to capture the solid fraction profile higher up in the bed compared to that near the distributor plate. Similarly, the normalized particle velocities and the particle fluxes compare well with the experiment closer to the distributor plate for the 2D simulation and the freeboard for the 3D simulation, respectively. A lower expanded bed height is predicted in the 2D simulation compared to the 3D simulation and the experiment. The results obtained from DEM computations show that a 2D simulation can be used to capture essential jetting trends near the distributor plate regions, whereas a full scale 3D simulation is needed to capture the bubbles near the freeboard regions. These serve as validations for the experiment and help us understand the complex jet interaction and solid circulation patterns in a multiple jet fluidized bed system. 相似文献
74.
The relationship between particle size distribution and viscosity of concentrated dispersions is of great industrial importance,
since it is the key to get high solids dispersions or suspensions. The problem is treated here experimentally as well as theoretically
for the special case of strongly interacting colloidal particles. An empirical model based on a generalized Quemada equation
is used to describe η as a function of volume fraction for mono- as well as multimodal dispersions. The pre-factor η˜ accounts for the shear rate dependence of η and does not affect the shape of the η vs φ curves. It is shown here for the
first time that colloidal interactions do not show up in the maximum packing parameter and φmax can be calculated from the particle size distribution without further knowledge of the interactions among the suspended particles.
On the other hand, the exponent ɛ is controlled by the interactions among the particles. Starting from a limiting value of
2 for non-interacting either colloidal or non-colloidal particles, ɛ generally increases strongly with decreasing particle
size. For a given particle system it then can be expressed as a function of the number average particle diameter. As a consequence,
the viscosity of bimodal dispersions varies not only with the size ratio of large to small particles, but also depends on
the absolute particle size going through a minimum as the size ratio increases. Furthermore, the well-known viscosity minimum
for bimodal dispersions with volumetric mixing ratios of around 30/70 of small to large particles is shown to vanish if colloidal
interactions contribute significantly.
Received: 7 June 2000/Accepted: 12 February 2001 相似文献
75.
本文证明了某些以anx(an为正代数数)为元素的连分式在代数点和超越点上值的代数无关性.特别地,某些关于简单连分数的代数无关性结果被扩充到更广泛的情形。 相似文献
76.
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78.
《Expositiones Mathematicae》2021,39(3):480-499
In this paper we recast the Serret theorem about a characterization of palindromic continued fractions in the context of polynomial continued fractions. Then, using the relation between symmetric tridiagonal matrices and polynomial continued fractions we give a quick exposition of the mathematical aspect of the perfect quantum state transfer problem. 相似文献
79.
A conventional block cyclic reduction algorithm operates by halving the size of the linear system at each reduction step, that is, the algorithm is a radix‐2 method. An algorithm analogous to the block cyclic reduction known as the radix‐q partial solution variant of the cyclic reduction (PSCR) method allows the use of higher radix numbers and is thus more suitable for parallel architectures as it requires fever reduction steps. This paper presents an alternative and more intuitive way of deriving a radix‐4 block cyclic reduction method for systems with a coefficient matrix of the form tridiag{ ? I,D, ? I}. This is performed by modifying an existing radix‐2 block cyclic reduction method. The resulting algorithm is then parallelized by using the partial fraction technique. The parallel variant is demonstrated to be less computationally expensive when compared to the radix‐2 block cyclic reduction method in the sense that the total number of emerging subproblems is reduced. The method is also shown to be numerically stable and equivalent to the radix‐4 PSCR method. The numerical results archived correspond to the theoretical expectations. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
80.
This paper addresses two different but related questions regarding an unbounded symmetric tridiagonal operator: its self-adjointness and the approximation of its spectrum by the eigenvalues of its finite truncations. The sufficient conditions given in both cases improve and generalize previously known results. It turns out that, not only self-adjointness helps to study limit points of eigenvalues of truncated operators, but the analysis of such limit points is a key help to prove self-adjointness. Several examples show the advantages of these new results compared with previous ones. Besides, an application to the theory of continued fractions is pointed out. 相似文献