全文获取类型
收费全文 | 6888篇 |
免费 | 297篇 |
国内免费 | 287篇 |
专业分类
化学 | 1098篇 |
晶体学 | 54篇 |
力学 | 566篇 |
综合类 | 33篇 |
数学 | 2362篇 |
物理学 | 3359篇 |
出版年
2024年 | 4篇 |
2023年 | 43篇 |
2022年 | 108篇 |
2021年 | 122篇 |
2020年 | 124篇 |
2019年 | 101篇 |
2018年 | 103篇 |
2017年 | 129篇 |
2016年 | 154篇 |
2015年 | 135篇 |
2014年 | 230篇 |
2013年 | 462篇 |
2012年 | 221篇 |
2011年 | 310篇 |
2010年 | 280篇 |
2009年 | 445篇 |
2008年 | 425篇 |
2007年 | 455篇 |
2006年 | 426篇 |
2005年 | 325篇 |
2004年 | 256篇 |
2003年 | 312篇 |
2002年 | 299篇 |
2001年 | 253篇 |
2000年 | 312篇 |
1999年 | 212篇 |
1998年 | 272篇 |
1997年 | 115篇 |
1996年 | 99篇 |
1995年 | 96篇 |
1994年 | 55篇 |
1993年 | 64篇 |
1992年 | 70篇 |
1991年 | 41篇 |
1990年 | 30篇 |
1989年 | 31篇 |
1988年 | 46篇 |
1987年 | 44篇 |
1986年 | 36篇 |
1985年 | 57篇 |
1984年 | 45篇 |
1983年 | 20篇 |
1982年 | 25篇 |
1981年 | 16篇 |
1980年 | 9篇 |
1979年 | 16篇 |
1978年 | 7篇 |
1977年 | 10篇 |
1976年 | 9篇 |
1973年 | 6篇 |
排序方式: 共有7472条查询结果,搜索用时 0 毫秒
41.
Fabio Schoen 《Journal of Global Optimization》1994,4(1):17-35
In this paper a new algorithm is proposed for global optimization problems. The main idea is that of modifying a standard clustering approach by sequentially sampling the objective function while adaptively deciding an appropriate sample size. Theoretical as well as computational results are presented. 相似文献
42.
本文讨论了在带有截断情况的线性回归模型中 ,响应变量均值的估计问题 .将经验似然的方法应用到带有截断情况的回归模型中 ,在估计响应变量的均值时构造了调整的经验似然统计量 ,证明了在一定的条件下 ,该统计量渐近服从 χ2 分布 ,给出了均值的置信区间 ,并与正态下得到的结果进行了比较 ,模拟的结果说明了经验似然的优良性 . 相似文献
43.
Testing goodness of fit for the distribution of errors in multivariate linear models 总被引:2,自引:0,他引:2
M.D. Jimnez Gamero J. Muoz García R. Pino Mejías 《Journal of multivariate analysis》2005,95(2):301-322
In this paper, to test goodness of fit to any fixed distribution of errors in multivariate linear models, we consider a weighted integral of the squared modulus of the difference between the empirical characteristic function of the residuals and the characteristic function under the null hypothesis. We study the limiting behaviour of this test statistic under the null hypothesis and under alternatives. In the asymptotics, the rank of the design matrix is allowed to grow with the sample size. 相似文献
44.
O. Maksimov P. Fisher M. Skowronski P.A. Salvador M. Snyder J. Xu X. Weng 《Journal of Crystal Growth》2008,310(11):2760-2766
MgO films were grown on (0 0 1) yttria-stabilized zirconia (YSZ) substrates by molecular beam epitaxy (MBE). The crystalline structures of these films were investigated using X-ray diffraction and transmission electron microscopy. Growth temperature was varied from 350 to 550 °C, with crystalline quality being improved at higher temperatures. The MgO films had a domain structure: (1 1 1)[1 1 2¯]MgO(0 0 1)[1 0 0]YSZ with four twin variants related by a 90° in-plane rotation about the [1 1 1]MgO axis. The observed epitaxial orientation was compared to previous reports of films grown by pulsed laser deposition and sputtering and explained as resulting in the lowest interface energy. 相似文献
45.
This paper attempts to reproduce numerically previous experimental findings with opposed flows and extends their range to quantify the effects of upstream pipes and nozzles with inviscid, laminar and turbulent flows. The choice of conservation equations, boundary conditions, algorithms for their solution, the degree of grid dependence, numerical diffusion and the validity of numerical approximations are justified with supporting calculations where necessary. The results of all calculations on the stagnation plane show maximum strain rates close to the annular exit from the nozzles and pipes for lower separations and it can be expected that corresponding reacting flows will tend to extinguish in this region with the extinction moving towards the axis. With laminar flows, the maximum strain rate increased with Reynolds number and the maximum values were generally greater than with inviscid flows and smaller than with turbulent flows. With large separations, the strain rates varied less and this explains some results with reacting flows where the extinction appeared to begin on the axis. The turbulent‐flow calculations allowed comparison of three common variants of a two‐equation first‐moment closure. They provided reasonable and useful indications of strain rates but none correctly represented the rms of velocity fluctuations on the axis and close to the stagnation plane. As expected, those designed to deal with this problem produced results in better agreement with experiment but were still imperfect. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
46.
47.
48.
A specific quantum Lax operator, forming a quantum U
q
(sl
n) chain, is suggested. The intertwining R
L
L relation is proved. The invariant local 2+1-dimensional reformulation of the auxiliary linear problem for the L-operator is discussed. 相似文献
49.
The K+−nucleus cross sections have been calculated in relativistic non-linear models taking into account the in-medium modifications of nucleons and mesons properties. More precisely, we have taken into account both the dressing of the nucleon effective mass by the scalar nuclear field in the target and the coupling of the mesons exchanged between the K+ and the nucleons to the polarization of the medium. First, using the most recent relativistic non-linear models, the in-medium σ, ω and ρ meson masses have been obtained in the nuclear matter rest frame. The influence of the non-linear contributions on the K+−nucleus cross sections has then been studied. Finally, we have compared our results with the experimental data. 相似文献
50.
This paper investigates regression quantiles (RQ) for unstable autoregressive models. The uniform Bahadur representation of the RQ process is obtained. The joint asymptotic distribution of the RQ process is derived in a unified manner for all types of characteristic roots on or outside the unit circle. It involves stochastic integrals in terms of a sequence of independent and identically distributed multivariate Brownian motions with correlated components. The related L-estimator is also discussed. The asymptotic distributions of the RQ and the L-estimator corresponding to the nonstationary componentwise arguments can be transformed into a function of a normal random variable and a sequence of i.i.d. univariate Brownian motions. This is different from the analysis based on the LSE in the literature. As an auxiliary theorem, a weak convergence of a randomly weighted residual empirical process to the stochastic integral of a Kiefer process is established. The results obtained in this paper provide an asymptotic theory for nonstationary time series processes, which can be used to construct robust unit root tests. 相似文献