全文获取类型
收费全文 | 6156篇 |
免费 | 502篇 |
国内免费 | 619篇 |
专业分类
化学 | 760篇 |
晶体学 | 15篇 |
力学 | 740篇 |
综合类 | 101篇 |
数学 | 4338篇 |
物理学 | 1323篇 |
出版年
2024年 | 15篇 |
2023年 | 76篇 |
2022年 | 160篇 |
2021年 | 130篇 |
2020年 | 202篇 |
2019年 | 183篇 |
2018年 | 166篇 |
2017年 | 200篇 |
2016年 | 186篇 |
2015年 | 142篇 |
2014年 | 236篇 |
2013年 | 464篇 |
2012年 | 295篇 |
2011年 | 369篇 |
2010年 | 320篇 |
2009年 | 463篇 |
2008年 | 442篇 |
2007年 | 418篇 |
2006年 | 364篇 |
2005年 | 339篇 |
2004年 | 262篇 |
2003年 | 252篇 |
2002年 | 215篇 |
2001年 | 180篇 |
2000年 | 182篇 |
1999年 | 164篇 |
1998年 | 182篇 |
1997年 | 135篇 |
1996年 | 105篇 |
1995年 | 56篇 |
1994年 | 55篇 |
1993年 | 40篇 |
1992年 | 44篇 |
1991年 | 33篇 |
1990年 | 23篇 |
1989年 | 21篇 |
1988年 | 23篇 |
1987年 | 19篇 |
1986年 | 17篇 |
1985年 | 12篇 |
1984年 | 18篇 |
1983年 | 5篇 |
1982年 | 10篇 |
1981年 | 10篇 |
1980年 | 9篇 |
1979年 | 9篇 |
1978年 | 10篇 |
1975年 | 2篇 |
1974年 | 3篇 |
1972年 | 3篇 |
排序方式: 共有7277条查询结果,搜索用时 15 毫秒
11.
This paper presents an evaluation of the capability of turbulence models available in the commercial CFD code FLUENT 6.0 for their application to hydrofoil turbulent boundary layer separation flow at high Reynolds numbers. Four widely applied two‐equation RANS turbulence models were assessed through comparison with experimental data at Reynolds numbers of 8.284×106 and 1.657×107. They were the standard k–εmodel, the realizable k–εmodel, the standard k–ωmodel and the shear‐stress‐transport (SST) k–ωmodel. It has found that the realizable k–εturbulence model used with enhanced wall functions and near‐wall modelling techniques, consistently provides superior performance in predicting the flow characteristics around the hydrofoil. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
12.
A method for computing low Mach number flows using high‐resolution interpolation and difference formulas, within the framework of the Marker and Cell (MAC) scheme, is presented. This increases the range of wavenumbers that are properly resolved on a given grid so that a sufficiently accurate solution can be obtained without extensive grid refinement. Results using this scheme are presented for three problems. The first is the two‐dimensional Taylor–Green flow which has a closed form solution. The second is the evolution of perturbations to constant‐density, plane channel flow for which linear stability solutions are known. The third is the oscillatory instability of a variable density plane jet. In this case, unless the sharp density gradients are resolved, the calculations would breakdown. Under‐resolved calculations gave solutions containing vortices which grew in place rather than being convected out. With the present scheme, regular oscillations of this instability were obtained and vortices were convected out regularly. Stable computations were possible over a wider range of sensitive parameters such as density ratio and co‐flow velocity ratio. Copyright © 2004 John Wiley Sons, Ltd. 相似文献
13.
We measured the entire region of mesopic and photopic vision to determine the color zone covering the visual field with unique red, yellow, green, and blue hue components. Eight kinds of test stimuli in the natural color system (NCS) color notation system were used. These stimuli were presented at horizontal and vertical meridians, and at meridians inclined at 45° angles. The illuminance level was set at six levels: 0.01 lx-1000 lx. The evaluation method measured chromatic, white, and black components as well as the hue component of the stimuli. Results show that the color zone of the retina extended further into the periphery with increasing illuminance; the response of opponent colors y-b was shown to be greater than that of the opponent colors r-g. 相似文献
14.
Clemens Heuberger 《Periodica Mathematica Hungarica》2004,49(2):65-89
We study digit expansions with arbitrary integer digits in base q (q integer) and the Fibonacci base such that the sum of the absolute values of the digits is minimal. For the Fibonacci case, we describe a unique minimal expansion and give a greedy algorithm to compute it. Additionally, transducers to calculate minimal expansions from other expansions are given. For the case of even integer bases q, similar results are given which complement those given in [6]. 相似文献
15.
复数域上线性系统x=A(t)x,当A(t)=(aij(t))n×n具有(n,N,r) 差异性质且rn时,解的特征数j有估计λj-limt→∞1t∫tt0Reaj(τ)dτn-1r+1-nlimt→∞1t∫tt0A(τ)dτ,j=1,2,…,n,其中A(t)=max{|aij(t)|:i,j=1,2,…,n,i≠j.} 相似文献
16.
The equivalent geometrical configurations of linear ordered orthogonal arrays are determined when their strengths are 3 and 4. Existence of such geometrical configurations is investigated. They are also useful in the study of (T, M, S)-nets. 相似文献
17.
18.
YIN JIANXING 《高校应用数学学报(英文版)》1994,(4)
PACKINGPAIRSBYQUINTUPLES:THECASEOFZEROCONGRUENCEMOD4YINJIANXINGAbstract:LetD(v)denotethemaximumnumberofquintuplesofav-setofpo... 相似文献
19.
Let G be a graph with a nonempty edge set, and with rank rk(G), term rank Rk(G), and chromatic number χ(G). We characterize Rk(G) as being the maximum number of colors in certain proper colorings of G. In particular, we observe that χ(G)Rk(G), with equality holding if and only if (besides isolated vertices) G is either complete or a star. For a twin-free graph G, we observe the bound
and we show that this bound is sharp. 相似文献
20.
In this note, we study convergence rates in the law of large numbers for independent and identically distributed random variables under sublinear expectations. We obtain a strong L^p-convergence version and a strongly quasi sure convergence version of the law of large numbers. 相似文献