全文获取类型
收费全文 | 35515篇 |
免费 | 6313篇 |
国内免费 | 7535篇 |
专业分类
化学 | 25428篇 |
晶体学 | 858篇 |
力学 | 2437篇 |
综合类 | 953篇 |
数学 | 4601篇 |
物理学 | 15086篇 |
出版年
2024年 | 63篇 |
2023年 | 496篇 |
2022年 | 943篇 |
2021年 | 1132篇 |
2020年 | 1249篇 |
2019年 | 1260篇 |
2018年 | 1124篇 |
2017年 | 1331篇 |
2016年 | 1413篇 |
2015年 | 1700篇 |
2014年 | 1912篇 |
2013年 | 2612篇 |
2012年 | 2832篇 |
2011年 | 3092篇 |
2010年 | 2513篇 |
2009年 | 2571篇 |
2008年 | 2861篇 |
2007年 | 2598篇 |
2006年 | 2469篇 |
2005年 | 2165篇 |
2004年 | 1632篇 |
2003年 | 1257篇 |
2002年 | 1224篇 |
2001年 | 1056篇 |
2000年 | 1199篇 |
1999年 | 927篇 |
1998年 | 641篇 |
1997年 | 600篇 |
1996年 | 614篇 |
1995年 | 527篇 |
1994年 | 515篇 |
1993年 | 414篇 |
1992年 | 395篇 |
1991年 | 332篇 |
1990年 | 249篇 |
1989年 | 215篇 |
1988年 | 208篇 |
1987年 | 186篇 |
1986年 | 154篇 |
1985年 | 124篇 |
1984年 | 117篇 |
1983年 | 105篇 |
1982年 | 72篇 |
1981年 | 60篇 |
1980年 | 72篇 |
1979年 | 37篇 |
1978年 | 16篇 |
1977年 | 16篇 |
1975年 | 11篇 |
1974年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 546 毫秒
61.
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
62.
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
63.
Hydrodynamic Properties of Fe3O4 Kerosene-Based Ferrofluids with Narrow Particle Size Distribution 下载免费PDF全文
We investigate the hydrodynamic properties of Fe3O4 kerosene-based ferrofluids with narrow particle size distribution. The ferrofluids are synthesized by improving chemical coprecipitation technique. A narrow distribution of 8.6-10.8nm particle sizes is obtained from the magnetization curve with the free-form model based on the Bayesian inference theory. The fitting result is consistent with average particle size obtained from x-ray diffraction. With the increase of applied magnetic field and magnetic particle concentration, apparent viscosity of ferrofluids increases. At concentration 4.04%, the type of flow for the ferrofluid transforms from Newtonian to Bingham plastic fluid as the applied magnetic field increases. 相似文献
64.
65.
66.
YBa2Cu3O7-x (YBCO) bulk is one of the most important high temperature superconducting materials for magnetic levitation applications, because it has a high magnetic irreversibility field Hirr at liquid nitrogen temperature, and can grow into large grains. The levitation force of YBCO bulk is proportional to the critical current density (Jc) and grain radius (r)[1], so higher Jc and r are appreciated for YBCO bulks to achieve higher levitation force. Now single-domain YBCO bulks up to s… 相似文献
67.
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
68.
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
69.
周治修 《浙江大学学报(理学版)》2004,31(6):610-613
ZULLI L首先构造了一个用于计算纽结Kauffman尖括号多项式的模2矩阵,纽结的trip矩阵.为了构造链环的trip矩阵,引入了一个带标识的穿有m个孔的圆盘来取代纽结情形下的圆盘,其中m为链环的分支数.主要结果为:定理若状态S是从状态AA…A经过i1,i2,…,ip位置上的标记替换(A换成B)而得的状态.设Ts是将trip矩阵T的左上角的n×n子块中ai1i1,ai2i2,…,aipip之值进行替换(0→1或1→0)所得的矩阵,则#(L|S)=n+m-秩(Ts).因此计算链环Kauffman尖括号多项式就归结为计算一组模2矩阵的秩. 相似文献
70.