全文获取类型
收费全文 | 30966篇 |
免费 | 3106篇 |
国内免费 | 2110篇 |
专业分类
化学 | 17075篇 |
晶体学 | 556篇 |
力学 | 1912篇 |
综合类 | 133篇 |
数学 | 3000篇 |
物理学 | 13506篇 |
出版年
2024年 | 52篇 |
2023年 | 401篇 |
2022年 | 768篇 |
2021年 | 758篇 |
2020年 | 818篇 |
2019年 | 851篇 |
2018年 | 818篇 |
2017年 | 762篇 |
2016年 | 1089篇 |
2015年 | 1049篇 |
2014年 | 1290篇 |
2013年 | 1887篇 |
2012年 | 2342篇 |
2011年 | 2571篇 |
2010年 | 1787篇 |
2009年 | 1854篇 |
2008年 | 2017篇 |
2007年 | 1827篇 |
2006年 | 1787篇 |
2005年 | 1458篇 |
2004年 | 1191篇 |
2003年 | 898篇 |
2002年 | 841篇 |
2001年 | 1200篇 |
2000年 | 849篇 |
1999年 | 751篇 |
1998年 | 516篇 |
1997年 | 529篇 |
1996年 | 417篇 |
1995年 | 368篇 |
1994年 | 323篇 |
1993年 | 282篇 |
1992年 | 274篇 |
1991年 | 239篇 |
1990年 | 206篇 |
1989年 | 162篇 |
1988年 | 140篇 |
1987年 | 120篇 |
1986年 | 100篇 |
1985年 | 107篇 |
1984年 | 73篇 |
1983年 | 57篇 |
1982年 | 34篇 |
1981年 | 37篇 |
1980年 | 23篇 |
1979年 | 24篇 |
1977年 | 22篇 |
1976年 | 28篇 |
1975年 | 32篇 |
1974年 | 24篇 |
排序方式: 共有10000条查询结果,搜索用时 296 毫秒
31.
X. Dong 《Discrete and Computational Geometry》2002,27(1):85-97
We prove that the homotopy types of two naturally defined simplicial complexes are related in the following way: one is homotopy
equivalent to a multiple suspension of the canonical Alexander dual of the other. These simplicial complexes arise in free
resolutions of semigroup rings and modules. The relation between their homotopy types was conjectured by Reiner, and was suggested
by a homological consequence of a result due independently to Danilov and Stanley on canonical modules of normal semigroup
rings. Our proof is purely topological, and gives an alternative proof of their result. We also prove a generalization of
a result of Hochster saying that these rings are Cohen—Macaulay, and indicate a new proof of Ehrhart's reciprocity law for
rational polytopes.
Received October 3, 2000, and in revised form April 2, 2001, and May 10, 2001. Online publication November 7, 2001. 相似文献
32.
33.
34.
35.
研究了不同比例的PVK与齐聚PPV衍生物DBVP掺杂体系的能量转移和发光特性.通过对PVK,DBVP及PVK:DBVP掺杂体系的UV-vis,PL和PLE光谱的研究,分析了PVK与DBVP之间的能量转移过程.利用PVK在体系中类似于溶剂的分散作用,制备了结构为ITO/PEDOT/PVK:DBVP/LiF/Al的电致发光器件,研究了掺杂体系的电致发光性能.结果表明,在掺杂体系的光致发光和电致发光中,PVK的发射被有效地抑制,PVK与DBVP之间发生了非常有效的能量转移,通过调节PVK与DBVP的比例,可以获得蓝色和绿色发光,同时可以改善器件的发光性能,当PVK与DBVP的重量比为1∶2时,器件的绿色发光效率达到1·06cd/A,此时发光亮度为52cd/m2. 相似文献
36.
主要介绍了一个引理,这个引理奠定了K4-同胚图K4(α,1,1,δ,ε,η)色性研究的基础。 相似文献
37.
The results of laser induced deposition of copper on polyimide substrate from copper electrolyte solution are reported. Unlike most work reported in the literatures where CW Ar+ lasers were used, a second harmonic (532 nm wavelength) Q-switch Nd:YAG laser was used for our experiments. The deposition process was conducted by laser-catalyzing of the polyimide surface and subsequent photothermal-accelerated reduction of copper-complex ions in an alkaline reducing environment. The characteristics of the deposited copper line were investigated in terms of laser beam scanning speed, and the number of scans. The surface morphology and chemical composition of the deposited copper were analyzed using field emission scanning electron microscope (FESEM) and energy dispersive spectrometer (EDX). The optimum processing conditions have been identified. The copper deposit was found to adhere well to the substrate. 相似文献
38.
The orientation-selective growth of LaNiO3 films on Si(100) by pulsed laser deposition using a MgO buffer 总被引:4,自引:0,他引:4
X.Y. Chen K.H. Wong C.L. Mak J.M. Liu X.B. Yin M. Wang Z.G. Liu 《Applied Physics A: Materials Science & Processing》2002,75(4):545-549
Highly (100)-oriented, (110)-oriented and polycrystalline LaNiO3 (LNO) films were successfully prepared on Si(100) using an oriented MgO film as a buffer. It was somewhat surprising to find
that that the orientation relation between the LNO film and the corresponding MgO buffer was: LNO(100)\MgO(110), LNO(110)\MgO(111)
and LNO(polycrystalline)\MgO(100). The crystalline quality of the LNO films was shown to be sensitive to the preparation conditions
of the MgO buffer. The film surface was very smooth, without micrometer-sized droplets being observed. All LNO films were
of metallic conductivity, with a room-temperature resistivities of approximately 250, 280 and 420 μΩ cm for the (110)-oriented,
(100)-oriented and polycrystalline LNO, respectively.
Received: 2 April 2001 / Accepted: 23 October 2001 / Published online: 3 June 2002 相似文献
39.
Based on the Collins formula and irradiance moments definition, the propagation of the kurtosis parameter of super-Gaussian beams through a spherically aberrated lens is studied. Detailed numerical results are given. It is shown that, as compared with aberration-free super-Gaussian beams, the profile of spherically aberrated super-Gaussian beams can be leptokurtic, mesokurtic or platykurtic, depending on the aberration and propagation distance. The results for the spherically aberrated Gaussian beams can be dealt with as a special case treated in this paper. Finally, the advantage of our method is pointed out. 相似文献
40.