全文获取类型
收费全文 | 69508篇 |
免费 | 14858篇 |
国内免费 | 5916篇 |
专业分类
化学 | 64858篇 |
晶体学 | 824篇 |
力学 | 2499篇 |
综合类 | 424篇 |
数学 | 5903篇 |
物理学 | 15774篇 |
出版年
2024年 | 112篇 |
2023年 | 666篇 |
2022年 | 1261篇 |
2021年 | 1433篇 |
2020年 | 2508篇 |
2019年 | 3807篇 |
2018年 | 2113篇 |
2017年 | 1784篇 |
2016年 | 4842篇 |
2015年 | 5096篇 |
2014年 | 5282篇 |
2013年 | 6496篇 |
2012年 | 5916篇 |
2011年 | 5302篇 |
2010年 | 5035篇 |
2009年 | 4893篇 |
2008年 | 4684篇 |
2007年 | 4000篇 |
2006年 | 3451篇 |
2005年 | 3111篇 |
2004年 | 2690篇 |
2003年 | 2335篇 |
2002年 | 3019篇 |
2001年 | 2131篇 |
2000年 | 1933篇 |
1999年 | 1081篇 |
1998年 | 651篇 |
1997年 | 616篇 |
1996年 | 642篇 |
1995年 | 508篇 |
1994年 | 498篇 |
1993年 | 383篇 |
1992年 | 353篇 |
1991年 | 306篇 |
1990年 | 236篇 |
1989年 | 174篇 |
1988年 | 162篇 |
1987年 | 131篇 |
1986年 | 127篇 |
1985年 | 121篇 |
1984年 | 73篇 |
1983年 | 71篇 |
1982年 | 48篇 |
1981年 | 38篇 |
1980年 | 41篇 |
1979年 | 20篇 |
1978年 | 16篇 |
1977年 | 9篇 |
1974年 | 9篇 |
1973年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
111.
Soliton interaction under the influence of higher-order effects 总被引:6,自引:0,他引:6
In this paper, we present exact N-soliton solution by employing simple, straightforward Darboux transformation based on the Lax pair for Hirota equation, a higher-order nonlinear Schrödinger (HNLS) equation. As examples, one- and two-soliton solutions in explicit forms are given and their properties are also analyzed. A bound solution without interaction will be theoretically predicted if one can adjust frequency shift for each soliton appropriately. Further, we obtain the approximate eigenvalues by employing two-soliton solution and discuss analytically the interaction between neighboring solitons under the influence of the higher-order effects. It is shown that the combined effects of the higher-order effects can restrain the interaction between neighboring solitons to some extent. The results are proved by directly solving HNLS equation numerically. 相似文献
112.
By using two sections of erbium doped fiber and a fiber optical reflector, a novel, highly efficient L bandamplifier is demonstrated with significantly power-conversion-efficiency enhancement and the gain increasing of as much as 13 dB. 相似文献
113.
114.
115.
116.
A graph G is N2‐locally connected if for every vertex ν in G, the edges not incident with ν but having at least one end adjacent to ν in G induce a connected graph. In 1990, Ryjá?ek conjectured that every 3‐connected N2‐locally connected claw‐free graph is Hamiltonian. This conjecture is proved in this note. © 2004 Wiley Periodicals, Inc. J Graph Theory 48: 142–146, 2005 相似文献
117.
ZHU Yabin ZHOU Yueliang LIU Zhen WANG Shufang CHEN Zhenghao U Huibin YANG Guozhen XlAO Ling Ren Hongtao JIAO Yulei Zheng Minghui 《中国科学G辑(英文版)》2004,47(2):165-172
The irreversibility field (Hirr) of Y-based superconductor is much higher than that of Bi-based superconductor. Y-based superconductor is capable of maintaining stable electrical currents in high magnetic field and electric field, so it is a better suited mate-rial for electric-current applications. Commonly, the Y-based tapes comprise a YBCO thick film deposited on a flexible substrate, typically with an intermediate buffer layer, and an overcoat of noble metal. In this process, the interm… 相似文献
118.
Mo2Ni3Si/NiSi metal silicide composite coatings with a fine microstructure consisting of Mo2Ni3Si primary dendrites and the interdendritic Mo2Ni3Si/NiSi eutectics were fabricated on austenitic stainless steel AISI 321 by laser cladding process. Small amplitude reciprocating sliding wear resistance of the coatings is evaluated as functions of normal load and slip amplitude and the wear mechanisms were discussed based on worn surface morphology observations. Results showed that the Mo2Ni3Si/NiSi coatings have excellent small amplitude reciprocating sliding wear resistance. 相似文献
119.
Ching‐Yuan Cheng Kuan‐Jiuh Lin 《Acta Crystallographica. Section C, Structural Chemistry》2006,62(8):m363-m365
In the title compound, catena‐poly[lithium‐μ3‐ethylenediphosphonato], [Li(C2H7O6P2)]n, the supramolecular monoclinic (C2/c) structure consists of one‐dimensional lithium chains [Li⋯Li = 2.7036 (8) Å] that are embedded within ethylenediphosphonate anions linked by strong symmetric hydrogen bonds [O⋯O = 2.473 (3) Å]. The Li atoms and the H atom in the symmetric hydrogen bond reside on twofold rotation axes and there is an inversion center at the mid‐point of the C—C bond of the ethylenediphosphonate ligand. 相似文献
120.
The inhomogeneous Dirichlet problems concerning divergence form elliptic equations are studied. Optimal regularity requirements on the coefficients and domains for the W1,p theory, 1 < p < ∞, are obtained. The principal coefficients are supposed to be in the John‐Nirenberg space with small BMO seminorms. The domain is a Reifenberg domain. These conditions for the W1,p theory not only weaken the requirements on the coefficients but also lead to a more general geometric condition on the domains. In fact, these domains might have fractal dimensions. © 2004 Wiley Periodicals, Inc. 相似文献