全文获取类型
收费全文 | 21629篇 |
免费 | 2212篇 |
国内免费 | 1805篇 |
专业分类
化学 | 12636篇 |
晶体学 | 388篇 |
力学 | 1446篇 |
综合类 | 128篇 |
数学 | 2631篇 |
物理学 | 8417篇 |
出版年
2024年 | 30篇 |
2023年 | 220篇 |
2022年 | 449篇 |
2021年 | 502篇 |
2020年 | 522篇 |
2019年 | 561篇 |
2018年 | 539篇 |
2017年 | 483篇 |
2016年 | 718篇 |
2015年 | 699篇 |
2014年 | 953篇 |
2013年 | 1293篇 |
2012年 | 1639篇 |
2011年 | 1886篇 |
2010年 | 1400篇 |
2009年 | 1403篇 |
2008年 | 1534篇 |
2007年 | 1342篇 |
2006年 | 1285篇 |
2005年 | 960篇 |
2004年 | 797篇 |
2003年 | 641篇 |
2002年 | 636篇 |
2001年 | 779篇 |
2000年 | 665篇 |
1999年 | 494篇 |
1998年 | 381篇 |
1997年 | 331篇 |
1996年 | 365篇 |
1995年 | 298篇 |
1994年 | 224篇 |
1993年 | 186篇 |
1992年 | 180篇 |
1991年 | 182篇 |
1990年 | 154篇 |
1989年 | 137篇 |
1988年 | 93篇 |
1987年 | 78篇 |
1986年 | 70篇 |
1985年 | 72篇 |
1984年 | 57篇 |
1983年 | 46篇 |
1982年 | 48篇 |
1981年 | 40篇 |
1980年 | 32篇 |
1979年 | 26篇 |
1978年 | 28篇 |
1977年 | 21篇 |
1975年 | 22篇 |
1974年 | 23篇 |
排序方式: 共有10000条查询结果,搜索用时 234 毫秒
91.
92.
P. Q. Khanh 《Journal of Optimization Theory and Applications》1995,87(2):359-378
We prove the Kuhn-Tucker sufficient optimality condition, the Wolfe duality, and a modified Mond-Weir duality for vector optimization problems involving various types of invex-convexlike functions. The class of such functins contains many known generalized convex functions. As applications, we demonstrate that, under invex-convexlikeness assumptions, the Pontryagin maximum principle is a sufficient optimality condition for cooperative differential games. The Wolfe duality is established for these games.The author is indebted to the referees and Professor W. Stadler for valuable remarks and comments, which have been used to revise considerably the paper. 相似文献
93.
Fang Yao 《Journal of multivariate analysis》2007,98(1):40-56
The estimation of a regression function by kernel method for longitudinal or functional data is considered. In the context of longitudinal data analysis, a random function typically represents a subject that is often observed at a small number of time points, while in the studies of functional data the random realization is usually measured on a dense grid. However, essentially the same methods can be applied to both sampling plans, as well as in a number of settings lying between them. In this paper general results are derived for the asymptotic distributions of real-valued functions with arguments which are functionals formed by weighted averages of longitudinal or functional data. Asymptotic distributions for the estimators of the mean and covariance functions obtained from noisy observations with the presence of within-subject correlation are studied. These asymptotic normality results are comparable to those standard rates obtained from independent data, which is illustrated in a simulation study. Besides, this paper discusses the conditions associated with sampling plans, which are required for the validity of local properties of kernel-based estimators for longitudinal or functional data. 相似文献
94.
Charge density fluctuation of low frequency in a dusty plasma 总被引:2,自引:0,他引:2
The charge density fluctuation of low frequency in a dusty plasma, which is derived from the longitudinal dielectric permittivity
of the dusty plasma, has been studied by kinetic theory. The results show that theP value, which describes the relative charge density on the dust in the plasma, and the charging frequency of a dust particle
Ω
c
, which describes the ratio of charge changing of the dust particles, determine the character of the charge density fluctuation
of low frequency. For a dusty plasma ofP≪1, when the charging frequency Ω
c
, is much smaller than the dusty plasma frequency ωd, there is a strong charge density fluctuation which is of character of dust acoustic eigenwave. For a dusty plasma ofP≫1, when the frequency Ω
c
, is much larger than ω
d
there are weaker fluctuations with a wide spectrum. The results have been applied to the ionosphere and the range of radius
and density of dust particles is found, where a strong charge density fluctuation of low frequency should exist. 相似文献
95.
96.
We obtain sufficient conditions for the oscillation of all solutions of the higher order neutral differential equation dn/dm[y(t) + P(t) y(t - μ)] + Q(t) y(t ?σ) = 0, t ≧ t0 where n ≧ 1, P ? C[t0, ∞), R ], Q ? C[t0, ∞), R ] and τ, μ ? R +. Our results extend and improve several known results in the literature. 相似文献
97.
98.
The Hawking radiation of Dirac particles in an arbitrarily rectilinearly accelerating Kinnersley black hole with electromagnetic charge and cosmological constant is investigated by using the generalized tortoise coordinate transformation. Both the location and the temperature of the event horizon depend on the time and the polar angle. The Hawking thermal radiation spectrum of Dirac particles is also derived. 相似文献
99.
100.