全文获取类型
收费全文 | 7194篇 |
免费 | 827篇 |
国内免费 | 404篇 |
专业分类
化学 | 2000篇 |
晶体学 | 138篇 |
力学 | 1257篇 |
综合类 | 63篇 |
数学 | 1091篇 |
物理学 | 3876篇 |
出版年
2024年 | 10篇 |
2023年 | 60篇 |
2022年 | 159篇 |
2021年 | 181篇 |
2020年 | 195篇 |
2019年 | 149篇 |
2018年 | 171篇 |
2017年 | 208篇 |
2016年 | 165篇 |
2015年 | 194篇 |
2014年 | 247篇 |
2013年 | 616篇 |
2012年 | 363篇 |
2011年 | 448篇 |
2010年 | 348篇 |
2009年 | 418篇 |
2008年 | 410篇 |
2007年 | 429篇 |
2006年 | 417篇 |
2005年 | 355篇 |
2004年 | 343篇 |
2003年 | 313篇 |
2002年 | 295篇 |
2001年 | 224篇 |
2000年 | 234篇 |
1999年 | 157篇 |
1998年 | 204篇 |
1997年 | 178篇 |
1996年 | 144篇 |
1995年 | 108篇 |
1994年 | 98篇 |
1993年 | 75篇 |
1992年 | 96篇 |
1991年 | 40篇 |
1990年 | 55篇 |
1989年 | 36篇 |
1988年 | 37篇 |
1987年 | 24篇 |
1986年 | 31篇 |
1985年 | 37篇 |
1984年 | 28篇 |
1983年 | 10篇 |
1982年 | 28篇 |
1981年 | 12篇 |
1980年 | 11篇 |
1979年 | 10篇 |
1978年 | 13篇 |
1977年 | 6篇 |
1976年 | 9篇 |
1973年 | 10篇 |
排序方式: 共有8425条查询结果,搜索用时 0 毫秒
1.
Volker Elling. 《Mathematics of Computation》2006,75(256):1721-1733
A particular case of initial data for the two-dimensional Euler equations is studied numerically. The results show that the Godunov method does not always converge to the physical solution, at least not on feasible grids. Moreover, they suggest that entropy solutions (in the weak entropy inequality sense) are not well posed.
2.
B. Dubrulle F. Hersant 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,26(3):379-386
We generalize an analogy between rotating and stratified shear flows. This analogy is summarized in Table 1. We use this analogy
in the unstable case (centrifugally unstable flow vs. convection) to compute the torque in Taylor-Couette configuration, as a function of the Reynolds number. At low Reynolds
numbers, when most of the dissipation comes from the mean flow, we predict that the non-dimensional torque G = T/ν2
L, where L is the cylinder length, scales with Reynolds number R and gap width η, G = 1.46η3/2(1 - η)-7/4
R
3/2. At larger Reynolds number, velocity fluctuations become non-negligible in the dissipation. In these regimes, there is no
exact power law dependence the torque versus Reynolds. Instead, we obtain logarithmic corrections to the classical ultra-hard (exponent 2) regimes: G = 0.50
. These predictions are found to be in excellent agreement with avail-able experimental data. Predictions for scaling of velocity
fluctuations are also provided.
Received 7 June 2001 and Received in final form 7 December 2001 相似文献
3.
Geng Sheng WANG 《数学学报(英文版)》2005,21(5):1005-1014
This work is concerned with Pontryagin's maximum principle of optimal control problems governed by some non-well-posed semilinear heat equations. A type of approach to the non-well-posed optimal control problem is given. 相似文献
4.
Semra Harmandar 《Journal of Quantitative Spectroscopy & Radiative Transfer》2004,84(4):395-407
A radiation code based on method of lines solution of discrete ordinates method for radiative heat transfer in axisymmetric cylindrical enclosures containing absorbing-emitting medium was developed and tested for predictive accuracy by applying it to (i) test problems with black and grey walls (ii) a gas turbine combustor simulator enclosing a non-homogeneous absorbing-emitting medium and benchmarking its steady-state predictions against exact solutions and measurements. Comparisons show that it provides accurate solutions for radiative heat fluxes and can be used with confidence in conjunction with CFD codes based on the same approach. 相似文献
5.
Large eddy simulations of two basic configurations (decay of isotropic turbulence, and the academic plane channel flow) with heat transfer have been performed comparing several convection numerical schemes, in order to discuss their ability to evaluate temperature fluctuations properly. Results are compared with the available incompressible heat transfer direct numerical simulation data. It is shown that the use of regularizing schemes (such as high order upwind type schemes) for the temperature transport equation in combination with centered schemes for momentum transport equation gives better results than the use of centred schemes for both equations. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
6.
将爆磁压缩等效为电流源的方法,对爆磁压缩发生器通过脉冲变压器对脉冲形成线充电进行了理论分析,得出爆磁压缩发生器在负载上产生电流波形(简称负载电流)为直线情况和任意电流波形情况下充电电流和充电电压的表达式。分析表明变压器耦合互感与负载电流随时间变化增长率是脉冲形成线充电的两个重要参数,脉冲形成线第一个充电电压峰值与变压器的耦合互感和负载电流波形斜率成正比,负载电流波形斜率的变化可以改变充电电压峰值的时间,斜率不断增加可以延长第一个充电电压峰值时间,从而可能增加充电电压的幅值,提高爆磁压缩发生器能量的利用效率。 相似文献
7.
B. Sadashive Gowda G.S.V.L. Narasimham M.V. Krishna Murthy 《International Journal of Heat and Fluid Flow》1997,18(6):613-624
In this paper, a mathematical model for forced-air precooling of spherical food products in bulk is developed. The foods are arranged in horizontal layers stacked one above the other to form a rectangular parallelepiped with a vertical gap in between the product layers. The foods are cooled by chilled air blown along the height of the package. The governing equations for the conduction heat transfer in the foods, simultaneous heat and mass transfer at the food-air interface and in the air stream are solved numerically using finite-difference methods. A comprehensive numerical study is performed by varying the process parameters over a wide range. Typical results showing the variation of moist air properties along the height of the package and the effect of each parameter on the process time are presented. The ranges of parameters for advantageous operation of the precooling system are identified. Correlations are obtained for the process time based on the product center and mass-averaged temperatures in terms of process parameters. 相似文献
8.
9.
L. E. Payne G. A. Philippin V. Proytcheva 《Mathematical Methods in the Applied Sciences》2007,30(15):1885-1898
In this paper, we investigate the continuous dependence on the geometry and the initial time for solutions u( x , t) of a class of nonlinear parabolic initial‐boundary value problems. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
10.
We consider the Maxwell-Cattaneo system of equations for generalized heat conduction where the temperature and heat flux satisfy a nonstandard auxiliary condition which prescribes a combination of their values initially and at a later time. We obtain L2 bounds for the temperature and heat flux by means of Lagrange identities. These bounds extend the range of validity for the parameter in the nonstandard condition under a constraint on the coefficients in the differential equations. 相似文献