全文获取类型
收费全文 | 7895篇 |
免费 | 878篇 |
国内免费 | 751篇 |
专业分类
化学 | 861篇 |
晶体学 | 11篇 |
力学 | 553篇 |
综合类 | 255篇 |
数学 | 5303篇 |
物理学 | 2541篇 |
出版年
2024年 | 14篇 |
2023年 | 78篇 |
2022年 | 127篇 |
2021年 | 191篇 |
2020年 | 191篇 |
2019年 | 219篇 |
2018年 | 186篇 |
2017年 | 242篇 |
2016年 | 319篇 |
2015年 | 214篇 |
2014年 | 442篇 |
2013年 | 536篇 |
2012年 | 434篇 |
2011年 | 432篇 |
2010年 | 383篇 |
2009年 | 516篇 |
2008年 | 560篇 |
2007年 | 537篇 |
2006年 | 483篇 |
2005年 | 421篇 |
2004年 | 373篇 |
2003年 | 336篇 |
2002年 | 336篇 |
2001年 | 273篇 |
2000年 | 253篇 |
1999年 | 219篇 |
1998年 | 199篇 |
1997年 | 183篇 |
1996年 | 154篇 |
1995年 | 92篇 |
1994年 | 98篇 |
1993年 | 56篇 |
1992年 | 46篇 |
1991年 | 49篇 |
1990年 | 41篇 |
1989年 | 42篇 |
1988年 | 28篇 |
1987年 | 24篇 |
1986年 | 27篇 |
1985年 | 34篇 |
1984年 | 22篇 |
1983年 | 11篇 |
1982年 | 18篇 |
1981年 | 11篇 |
1980年 | 15篇 |
1979年 | 13篇 |
1978年 | 9篇 |
1977年 | 10篇 |
1976年 | 12篇 |
1957年 | 3篇 |
排序方式: 共有9524条查询结果,搜索用时 15 毫秒
41.
Hong-Nian Li Xiao-Xiong WangWang-Feng Ding 《Journal of Electron Spectroscopy and Related Phenomena》2006
Using X-ray photoemission measurements, we have determined the attenuation length of C 1s photoelectrons in C60 film to be 21.5 Å with the incident photon energy of Mg Kα radiation. The inelastic mean free path calculated with the TPP-2M algorithm coincides fairly well with the experimentally determined attenuation length, indicating the validity of the algorithm to fullerene and fullerides. The inelastic mean free paths for some fullerides, i.e. K3C60, K6C60, Ba4C60, Sm2.75C60 and Sm6C60 are calculated to help the quantitative analyses of the photoemission spectra for these compounds. 相似文献
42.
认为物质的质量(能量)存在形式可分为两部分,一部分是以纯物质形式存在的,另一部分是以纯重力场形式存在的.物质质量(能量)这两种形式各自对应着相应的能量 动量张量,物质总的能量-动量张量可表示为Tμν=T(Ⅰ)μν+T(Ⅱ)μν,这里,T(Ⅰ)μν,T(Ⅱ)μν分别代表物质纯物质部分和纯重力场部分的能量-动量张量.通过类比电磁理论,定义:ωμ≡-c2gμ0/g00,并引入一个反对称张量Dμν=ωμ/xν-ων/xμ,则物质纯重力场部分的能量-动量张量为T(Ⅱ)μν=(DμρDρν-gμνDαβDαβ/4
关键词:
能量-动量张量
纯重力场
重力场方程
标量重力势
矢量重力势 相似文献
43.
The possibilities of controlling the laser beam properties by a deformable mirror introduced into the laser optical cavity
were studied theoretically and experimentally. The experiments were performed under conditions of an industrial high power
transverse flow cw CO2 laser operating with a stable resonator of a folded configuration. A deformable bimorph mirror of a surface profile controlled
by the voltage applied to the mirror electrodes is implemented to the laser system as a back cavity mirror or as a one of
the inner folding mirrors. The near-and far-field characteristics of the laser beam versus the resonator configuration controlled
by the changes of the focal length of the deformable mirror are discussed in the paper. The analysis reveals that the resonator
with an inner deformable mirror is much more sensitive to the mirror curvature variations than the resonator in which the
deformable mirror is used as a back cavity mirror. The presented results show that dynamic and controllable changes in the
resonator properties result in the controlled modification and optimisation of the laser output power and spatial parameters
of the laser radiation. 相似文献
44.
WU Ke ZHAO Weizhong & GUO Hanying Department of Mathematics Capital Normal University Beijing China Institute of Theoretical Physics Chinese Academy of Sciences Beijing China 《中国科学A辑(英文版)》2006,(11)
In a way similar to the continuous case formally, we define in different but equivalent manners the difference discrete connection and curvature on discrete vector bundle over the regular lattice as base space. We deal with the difference operators as the discrete counterparts of the derivatives based upon the differential calculus on the lattice. One of the definitions can be extended to the case over the random lattice. We also discuss the relation between our approach and the lattice gauge theory and apply to the discrete integrable systems. 相似文献
45.
46.
The object of the present investigation is to introduce a new trigonometric method of summation which is both regular and
Fourier effective and determine its status with reference to other methods of summation (see §2-§4) and also give an application
of this method to determine the degree of approximation in a new Banach space of functions conceived as a generalized Holder
metric (see §5). 相似文献
47.
The theory of Ribaucour transformations for hypersurfaces in space forms is established. For any such hypersurface M, that admits orthonormal principal vector fields, it was shown the existence of a totally umbilic hypersurface locally associated to M by a Ribaucour transformation. A method of obtaining linear Weingarten surfaces in a three-dimensional space form is provided. By applying the theory, a new one-parameter family of complete constant mean curvature (cmc) surfaces in the unit sphere, locally associated to the flat torus, is obtained. The family contains a class of complete cmc cylinders in the sphere. In particular, one gets a family of complete minimal surfaces and minimal cylinders, locally associated to the Clifford torus.Mathematics Subject Classifications (2000): 53C20. 相似文献
48.
49.
通过PCR扩增出猪传染性胃肠炎病毒(TGEV)聚合酶部分片段,反向插入逆转录病毒表达载体pLXSN中,用脂质体法将重组质粒plxas-pol转染PA317细胞,经抗生素G418筛选出稳定的产毒细胞克隆,分别扩大培养后,取其上清液感染小鼠成纤维细胞NIH3T3,细胞克隆产生的重组病毒效价达9.0×105CFU/mL。用高效价假病毒感染IBRS2细胞,再经抗生素G418筛选,提取细胞克隆总RNA,经RT-PCR证明plxas-pol整合入IBRS2细胞。以TGEV感染IBRS2细胞和具有抗性的IBRS2细胞所产生的细胞病变为指标,证明该反义RNA对病毒有明显抑制作用,抑制率约为80%。用2×103和4×102TCID50/mL剂量的TGEV感染时,引起细胞死亡的时间分别为21 h和27 h,与对照组相比,抗性细胞系可明显延迟因病毒感染引起细胞死亡的时间。 相似文献
50.