全文获取类型
收费全文 | 960篇 |
免费 | 59篇 |
国内免费 | 43篇 |
专业分类
化学 | 613篇 |
晶体学 | 15篇 |
力学 | 19篇 |
综合类 | 6篇 |
数学 | 198篇 |
物理学 | 211篇 |
出版年
2023年 | 15篇 |
2022年 | 20篇 |
2021年 | 35篇 |
2020年 | 27篇 |
2019年 | 33篇 |
2018年 | 29篇 |
2017年 | 19篇 |
2016年 | 43篇 |
2015年 | 39篇 |
2014年 | 43篇 |
2013年 | 51篇 |
2012年 | 42篇 |
2011年 | 60篇 |
2010年 | 41篇 |
2009年 | 34篇 |
2008年 | 53篇 |
2007年 | 53篇 |
2006年 | 40篇 |
2005年 | 36篇 |
2004年 | 35篇 |
2003年 | 25篇 |
2002年 | 43篇 |
2001年 | 24篇 |
2000年 | 16篇 |
1999年 | 12篇 |
1998年 | 4篇 |
1997年 | 12篇 |
1996年 | 14篇 |
1995年 | 4篇 |
1994年 | 8篇 |
1993年 | 10篇 |
1990年 | 4篇 |
1988年 | 4篇 |
1987年 | 4篇 |
1985年 | 9篇 |
1984年 | 8篇 |
1983年 | 11篇 |
1980年 | 3篇 |
1978年 | 4篇 |
1977年 | 5篇 |
1976年 | 7篇 |
1975年 | 6篇 |
1974年 | 3篇 |
1973年 | 5篇 |
1935年 | 3篇 |
1927年 | 3篇 |
1914年 | 3篇 |
1913年 | 4篇 |
1909年 | 4篇 |
1908年 | 4篇 |
排序方式: 共有1062条查询结果,搜索用时 0 毫秒
1.
采用固源Si分子束外延,在较高的生长温度于Si(100)衬底上制备出Si1-xGex/Si量子阱发光材料。发光样品的质量和特性通过卢瑟福背散射、X射线双晶衍射及光致发光评估。背散射实验中观察到应变超晶格的反常沟道效应;X射线分析表明材料的生长是共度的、无应力释放的,结晶完整性好。低温光致发光主要是外延合金量子阱中带边激子的无声发射和横光学声子参与的激子复合。并讨论了生长温度对量于阱发光的影响。 相似文献
2.
In this paper, we present some counterexamples which show that there is no theory on the spectrum of homogeneous compact operators which parallels the Riesz-Schauder theory on the spectrum of linear compact operators. These counterexamples also illustrate that it is impossible to study in a unified setting the Fucik spectrum of the Laplacian: -△w = au+ - bu- inΩand u = 0 on (?)Ω, as well as the spectrum of the p-Laplacian: -div(|(?)u| p-2(?)u) = λ|u|p-2u and u = 0 on (?)Ω. 相似文献
3.
Formation of p-type ZnO film on InP substrate by phosphor doping 总被引:3,自引:0,他引:3
Kyu-Hyun Bang Deuk-Kyu Hwang Min-Chul Park Young-Don Ko Ilgu Yun Jae-Min Myoung 《Applied Surface Science》2003,210(3-4):177-182
ZnO thin film was initially deposited on InP substrate by radio frequency (rf) magnetron sputtering and the diffusion process was performed using the closed ampoule technique where Zn3P2 was used as the dopant source. To verify the junction formation of ZnO thin films, the electrical properties were measured, and the effects of Zn3P2 diffusion on ZnO thin films were investigated. It is observed that the electrical property of the film is changed from n-type to p-type by dopant diffusion effect. Based on the results, it is confirmed that ZnO thin films can be a potential candidate for ultraviolet (UV) optical devices. 相似文献
4.
Chepoi showed that every breadth first search of a bridged graph produces a cop-win ordering of the graph. We note here that Chepoi's proof gives a simple proof of the theorem that G is bridged if and only if G is cop-win and has no induced cycle of length four or five, and that this characterization together with Chepoi's proof reduces the time complexity of bridged graph recognition. Specifically, we show that bridged graph recognition is equivalent to (C4,C5)-free graph recognition, and reduce the best known time complexity from O(n4) to O(n3.376). 相似文献
5.
6.
Urs P. Wild Hans J. Griesser Vo Dinh Tuan Jean F.M. Oth 《Chemical physics letters》1976,41(3):450-455
The emission spectra of the second excited singlet state of [18] annulene and of monofluoro [18] annulene (in a 3-methylpentane glass at 4 K) are reported. The large energy gap between the first and second excited singlet states inhibits fast internal conversion and favours the appearance of S2 → S0 emission. In addition, fluorescence from the S1 state can be observed in monofluoro [13] annulene by exciting into the S2 or directly into the S1 absorption. 相似文献
7.
U. Wannagat F. Vielberg H. Voß K. Hensen W. Sarholz 《Monatshefte für Chemie / Chemical Monthly》1969,100(4):1127-1132
The enthalpies of formation of the addition compounds F4Si(py)2, Cl4Si(py)2, Br4Si(py)2 and I4Si(py)4 have been measured calorimetrically by two different ways (see table 1). It was not possible to confirm enthalpy data published in7, 8. The sequence SiF44~SiBr4>SiI4(?) is proposed for the acceptor power of the silicon tetrahalides towards pyridine. 相似文献
8.
An application of a new standardization method for rapid activation mass analysis with registration of the strongly absorbed low-energy gamma radiation is described. This method makes it possible to avoid the use of the time-consuming and laborious method of Internal Standard. 相似文献
9.
Van Bang Le 《Periodica Mathematica Hungarica》1993,27(2):105-124
For a finite or infinite graphG, theGallai graph (G) ofG is defined as the graph whose vertex set is the edge setE(G) ofG; two distinct edges ofG are adjacent in (G) if they are incident but do not span a triangle inG. For any positive integert, thetth iterated Gallai graph
t
(G) ofG is defined by (
t–1(G)), where 0(G):=G. A graph is said to beGallai-mortal if some of its iterated Gallai graphs finally equals the empty graph. In this paper we characterize Gallai-mortal graphs in several ways. 相似文献
10.
Cyperene epoxide 2, on treatment with formic acid, gives about ten products of which the two major ones have been isolated and characterised. The allylic alcohol 3 is the product of an allylic rearrangement. The diol 5 is produced by a multistep rearrangement, the mechanism of which is remarkable in that the first elementary step cannot be concerted. The structure of the diol 5 has been confirmed by correlation with α-cedrene. 相似文献