全文获取类型
收费全文 | 23830篇 |
免费 | 3779篇 |
国内免费 | 3256篇 |
专业分类
化学 | 18130篇 |
晶体学 | 284篇 |
力学 | 1560篇 |
综合类 | 264篇 |
数学 | 2829篇 |
物理学 | 7798篇 |
出版年
2024年 | 48篇 |
2023年 | 420篇 |
2022年 | 496篇 |
2021年 | 679篇 |
2020年 | 895篇 |
2019年 | 895篇 |
2018年 | 777篇 |
2017年 | 737篇 |
2016年 | 1068篇 |
2015年 | 1075篇 |
2014年 | 1375篇 |
2013年 | 1653篇 |
2012年 | 2087篇 |
2011年 | 2150篇 |
2010年 | 1582篇 |
2009年 | 1427篇 |
2008年 | 1611篇 |
2007年 | 1408篇 |
2006年 | 1397篇 |
2005年 | 1176篇 |
2004年 | 982篇 |
2003年 | 837篇 |
2002年 | 914篇 |
2001年 | 761篇 |
2000年 | 595篇 |
1999年 | 531篇 |
1998年 | 392篇 |
1997年 | 335篇 |
1996年 | 371篇 |
1995年 | 300篇 |
1994年 | 236篇 |
1993年 | 196篇 |
1992年 | 199篇 |
1991年 | 202篇 |
1990年 | 153篇 |
1989年 | 135篇 |
1988年 | 96篇 |
1987年 | 82篇 |
1986年 | 87篇 |
1985年 | 64篇 |
1984年 | 56篇 |
1983年 | 45篇 |
1982年 | 34篇 |
1981年 | 33篇 |
1980年 | 30篇 |
1978年 | 24篇 |
1977年 | 25篇 |
1976年 | 23篇 |
1974年 | 20篇 |
1973年 | 26篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
101.
Jin Cheng Ching-Lung Lin Gen Nakamura 《Proceedings of the American Mathematical Society》2005,133(8):2359-2367
In this paper we prove the following kind of unique continuation property. That is, the zero on each geodesic of the solution in a real analytic hypersurface for second order anisotropic hyperbolic systems with real analytic coefficients can be continued along this curve.
102.
103.
杨青 《高等学校计算数学学报(英文版)》2003,12(2)
The mathematical model of semiconductor devices is described by the initial boundary value problem of a system of three nonlinear partial differential equations. One equation in elliptic form is for the electrostatic potential; two equations of convection-dominated diffusion type are for the electron and hole concentrations. Finite volume element procedure are put forward for the electrostatic potential, while upwind 相似文献
104.
Optical characterization of bromo-alkoxyl-substituted copper phthalocyanine derivative thin films 总被引:2,自引:0,他引:2
A series of thin films of copper phthalocyanine derivatives with bromine and alkoxyl substituents [CuPc(OC8H17)4Brm, m=0,1,2,4] were prepared on single-crystal silicon substrates by spin coating. The ellipsometric spectra of the films have been studied on a rotating analyzer–polarizer type of scanning ellipsometer. The optical, dielectric constants and absorption coefficients of the films in 500–800 nm wavelength region were obtained. The results show that the complex refractive index, dielectric constants and absorption coefficient of these thin films are influenced regularly by bromine substituent on conjugated macrocycle. It was found that there are approximately linear relationships between the resonance absorption wavelengths of the films and the average number of bromine atoms substituted on the phthalocyanine ring. 相似文献
105.
Hong‐Qing Wang Zhao‐Jie Liu Li‐Min Yang Ming‐Wu Ding 《Journal of heterocyclic chemistry》2004,41(3):393-397
A series of new 1H‐pyrazolo[3,4‐d]pyrimidin‐4(5H)‐one Derivatives 5 has been designed and regio‐selectively synthesized via a tandem aza‐Wittig reaction. The structures of all compounds prepared have been confirmed by 1H NMR, IR, EI‐MS spectroscopy and elemental analyses. The results of preliminary bioassay indicate that most compounds 5 possess an inhibition effect against Botrytis cinereapers and Pyricularia oryzae at the concentration of 50 mg/L. 相似文献
106.
The SmF_(2.01)was synthesized by reducing SmF_3 in H_2 stream.As it was doped inKM_gF_3 and KCaF_3.there was emission of Sm~(2+) in KMgF_3 but no emission of Sm~(2+) inKCaF_3 was observed. 相似文献
107.
108.
PURE STATE APPROACH TO C(x)_αZ_nLIBINGREN;LINQING(InstituteofMathematics,AcademiaSinica,Beijing100080,China.Projectsupportedbyth?.. 相似文献
109.
Qing Shi Dong Yang Yanlei Su Jian Li Zhongyi Jiang Yanjun Jiang Weikang Yuan 《Journal of nanoparticle research》2007,9(6):1205-1210
Lipase from Candida rugosa was covalently anchored onto acid-treated multi-walled carbon nanotubes (MWNTs) through a self-catalytic mechanism. A variety
of characterization techniques including FTIR, Raman spectroscopy, and XPS were employed to demonstrate the formation of the
ester linkage between lipase and MWNTs. The MWNTs-lipase biocomposites showed significantly increased solubility in some common-used
organic solvents, such as THF, DMF and chloroform. This study may offer a novel and facile route for covalent modification
of carbon nanotubes, and expand the potential utilization of both lipases and MWNTs in the fields of biocatalyst and biosensor. 相似文献
110.