全文获取类型
收费全文 | 24178篇 |
免费 | 4167篇 |
国内免费 | 3119篇 |
专业分类
化学 | 17617篇 |
晶体学 | 288篇 |
力学 | 1350篇 |
综合类 | 229篇 |
数学 | 2614篇 |
物理学 | 9366篇 |
出版年
2024年 | 63篇 |
2023年 | 516篇 |
2022年 | 861篇 |
2021年 | 904篇 |
2020年 | 1084篇 |
2019年 | 1105篇 |
2018年 | 910篇 |
2017年 | 892篇 |
2016年 | 1207篇 |
2015年 | 1241篇 |
2014年 | 1456篇 |
2013年 | 1812篇 |
2012年 | 2276篇 |
2011年 | 2213篇 |
2010年 | 1487篇 |
2009年 | 1522篇 |
2008年 | 1715篇 |
2007年 | 1503篇 |
2006年 | 1335篇 |
2005年 | 1145篇 |
2004年 | 829篇 |
2003年 | 639篇 |
2002年 | 594篇 |
2001年 | 523篇 |
2000年 | 466篇 |
1999年 | 437篇 |
1998年 | 364篇 |
1997年 | 338篇 |
1996年 | 317篇 |
1995年 | 297篇 |
1994年 | 222篇 |
1993年 | 218篇 |
1992年 | 177篇 |
1991年 | 145篇 |
1990年 | 127篇 |
1989年 | 81篇 |
1988年 | 79篇 |
1987年 | 66篇 |
1986年 | 56篇 |
1985年 | 65篇 |
1984年 | 31篇 |
1983年 | 33篇 |
1982年 | 21篇 |
1981年 | 15篇 |
1980年 | 13篇 |
1979年 | 14篇 |
1977年 | 8篇 |
1976年 | 7篇 |
1975年 | 5篇 |
1965年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
本文主要根据τ与μ的不同取值分三种情况刻划了Cn中单位球上Dirichlet 型空间上的点乘子空间M(Dτ,Dμ),并通过两个函数的构造表明:当τ≤n时,包含 关系M(Dτ)(?)Dτ和当τ>μ,τ>n-1时,包含关系M(Dτ)(?) M(Dμ)是严格的. 相似文献
82.
Bai-suo JIN~ 《中国科学A辑(英文版)》2007,50(9):1303-1315
In the factor analysis model with large cross-section and time-series dimensions,we pro- pose a new method to estimate the number of factors.Specially if the idiosyncratic terms satisfy a linear time series model,the estimators of the parameters can be obtained in the time series model. The theoretical properties of the estimators are also explored.A simulation study and an empirical analysis are conducted. 相似文献
83.
Stimulated Raman adiabatic passage (STIRAP) has been successfully extended to multilevel system. During the STIRAP process, the intermediate levels have notable population which is detrimental if these levels could decay to other levels through spontaneous emission. This paper proposes a novel method to reduce the intermediate level population during the STIRAP process. A complete population transfer can be achieved in this modified STIRAP even if the intermediate level decays to other levels. 相似文献
84.
85.
Peng Feng 《Journal of Mathematical Analysis and Applications》2007,329(1):347-356
In this paper we establish the exact blow-up rate of the large solutions of a porous media logistic equation. We consider the carrying capacity function with a general decay rate at the boundary instead of the usual cases when it can be approximated by a distant function. Obtaining the accurate blow-up rate allows us to establish the uniqueness result. Our result covers all previous results on the ball domain and can be further adapted in a more general domain. 相似文献
86.
一类拟线性大系统的稳定性 总被引:1,自引:0,他引:1
彭晓林 《新疆大学学报(理工版)》1991,8(1):41-45
本文应用大系统的分解方法和一个推广的不等式,研究了一类拟线性大系统的稳定性问题,所得结果简洁、易于验证,且推导过程不复杂,最后给出了应用实例。 相似文献
87.
不确定市场条件下的稳健最优投资组合 总被引:1,自引:0,他引:1
本文假设风险资产和无风险资产收益的相关参数属于某个已知的凸多面体,分别讨论了在市场不存在无风险资产和存在无风险资产的情况下稳健最优投资组合问题,给出了问题的解析解,从而推广了Markowitz均值-方差模型的结果. 相似文献
88.
Z.J. Liu H.H. Long W.C. Ye X.X. Zou Z.L. Qin E.P. Li J.S. Chen 《Journal of magnetism and magnetic materials》2006
In this paper, specific issues related to high-density perpendicular magnetic recording processes, such as transition noise properties and cross-track correlation lengths, were investigated with the help of micromagnetic analysis. The effects of media parameters were taken into consideration, including intergranular exchange coupling, and exchange distribution, irregular grain shapes, magnetization saturation distribution, and anisotropy distribution. The micromagnetic simulation results showed that the effect of anisotropy distribution on transition noise is more significant than magnetization saturation distribution, and it is crucial to reduce this effect to achieve a high signal-to-noise ratio. Additionally, a new method to further estimate the partial erasure threshold was proposed to approximate the partial erasure effects, and the relation between the microtrack jitter and total track jitter was investigated. 相似文献
89.
The general relation between the standard expansion coefficients and the beta function for the QCD coupling is exactly derived in a mathematically strict way. It is accordingly found that an infinite number of logarithmic terms are lost in the standard expansion with a finite order, and these lost terms can be given in a closed form. Numerical calculations, by a new matching-invariant coupling with the corresponding beta function to four-loop level, show that the new expansion converges much faster. 相似文献
90.