全文获取类型
收费全文 | 19536篇 |
免费 | 3689篇 |
国内免费 | 2915篇 |
专业分类
化学 | 14476篇 |
晶体学 | 323篇 |
力学 | 1109篇 |
综合类 | 233篇 |
数学 | 1920篇 |
物理学 | 8079篇 |
出版年
2024年 | 64篇 |
2023年 | 384篇 |
2022年 | 712篇 |
2021年 | 784篇 |
2020年 | 859篇 |
2019年 | 892篇 |
2018年 | 769篇 |
2017年 | 751篇 |
2016年 | 1052篇 |
2015年 | 1078篇 |
2014年 | 1268篇 |
2013年 | 1578篇 |
2012年 | 1963篇 |
2011年 | 1957篇 |
2010年 | 1416篇 |
2009年 | 1324篇 |
2008年 | 1385篇 |
2007年 | 1277篇 |
2006年 | 1141篇 |
2005年 | 951篇 |
2004年 | 685篇 |
2003年 | 529篇 |
2002年 | 587篇 |
2001年 | 519篇 |
2000年 | 362篇 |
1999年 | 360篇 |
1998年 | 279篇 |
1997年 | 200篇 |
1996年 | 163篇 |
1995年 | 132篇 |
1994年 | 121篇 |
1993年 | 116篇 |
1992年 | 104篇 |
1991年 | 96篇 |
1990年 | 73篇 |
1989年 | 49篇 |
1988年 | 35篇 |
1987年 | 23篇 |
1986年 | 20篇 |
1985年 | 20篇 |
1984年 | 17篇 |
1983年 | 12篇 |
1982年 | 7篇 |
1981年 | 6篇 |
1980年 | 5篇 |
1979年 | 5篇 |
1971年 | 2篇 |
1959年 | 4篇 |
1957年 | 2篇 |
1936年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
具P-Laplacian算子型周期边值问题解的存在性 总被引:8,自引:0,他引:8
本文利用拓扑度理论和一些分析技巧讨论了具p—Laplacian算子型周期边值问题(φp(χ’))’+d/dt gradF(χ)+gradG(χ)=e(t),χ(0)=χ(T),χ’(0)=χ’(T)解的存在性,在对阻尼项d/dtgradF(χ)没有任何限制的前提下,给出了解存在的充分条件. 相似文献
72.
73.
Convergence rates of cascade algorithms 总被引:2,自引:0,他引:2
Rong-Qing Jia 《Proceedings of the American Mathematical Society》2003,131(6):1739-1749
We consider solutions of a refinement equation of the form
where is a finitely supported sequence called the refinement mask. Associated with the mask is a linear operator defined on by . This paper is concerned with the convergence of the cascade algorithm associated with , i.e., the convergence of the sequence in the -norm.
where and is a constant. In particular, we confirm a conjecture of A. Ron on convergence of cascade algorithms.
where is a finitely supported sequence called the refinement mask. Associated with the mask is a linear operator defined on by . This paper is concerned with the convergence of the cascade algorithm associated with , i.e., the convergence of the sequence in the -norm.
Our main result gives estimates for the convergence rate of the cascade algorithm. Let be the normalized solution of the above refinement equation with the dilation matrix being isotropic. Suppose lies in the Lipschitz space , where 0$"> and . Under appropriate conditions on , the following estimate will be established:
where and is a constant. In particular, we confirm a conjecture of A. Ron on convergence of cascade algorithms.
74.
A novel long-lasting afterglow phosphor ZrO2:Ti is prepared by the conventional solid-stated method and their luminescent properties are investigated. A bluish white strong and broad emissive band, which is attributed to originate from the recombination of electrons trapped by F+ centers and the holes created in Valence band, is observed under 254 nm UV irradiation. The identical color long afterglow, which lasts about 1 h, is found in the ZrO2:Ti phosphor after removing the 254 nm UV light. The mechanism of the long lasting phosphorescence (LLP) has been discussed based on the thermoluminescence (TL) results. The replacement of Zr by Ti produces more anion vacancies, resulting in the enhanced photoluminescence (PL) and LLP of ZrO2:Ti sample. These results indicate that ZrO2:Ti phosphor has potential promising applications. 相似文献
75.
The relativistic problem of neutral fermions subject to PT-symmetric trigonometric potential (∼iαtanαx) in 1+1 dimensions is investigated. By using the basic concepts of the supersymmetric quantum mechanics formalism and the functional analysis method, we solve exactly the position-dependent effective mass Dirac equation with the vector coupling scheme and obtain the bound state solutions in closed form. The behavior of the energy spectra is discussed in detail. 相似文献
76.
CHEN Bin ZHANG Jun-Feng 《理论物理通讯》2005,44(9)
We construct the two-flux colliding plane wave solutions in higher-dimensional gravity theory with dilaton,and two complementary fluxes. Two kinds of solutions have been obtained: Bell-Szekeres (BS) type and homogeneous type. After imposing the junction condition, we find that only the BS type solution is physically well-defined. Furthermore, we show that the future curvature singularity is always developed for our solutions. 相似文献
77.
机器人在完成其规划动作时,常可能要通过其运动链的奇点,这时求解其运动学逆问题的通用算法遇到本质的困难,本文给出了一种算法,它可以成功地克服这个困难。文中还给出了计算实例。 相似文献
78.
79.
80.
The time-dependent multilevel approach(TDMA) and B-spline expansion technique are used to study the coherent population transfer between the quantum states of a potassium atom by a single frequency-chirped microwave pulse.The Rydberg potassium atom energy levels of n=6-15,l=0-5 states in zero field are calculated and the results are in good agreement with other theoretical values.The time evolutions of the population transfer of the six states from n=70 to n=75 in different microwave fields are obtained.The results show that the coherent control of the population transfer from the lower states to the higher ones can be accomplished by optimizing the microwave pulse parameters. 相似文献