全文获取类型
收费全文 | 21546篇 |
免费 | 4570篇 |
国内免费 | 2571篇 |
专业分类
化学 | 8421篇 |
晶体学 | 528篇 |
力学 | 2115篇 |
综合类 | 287篇 |
数学 | 2253篇 |
物理学 | 15083篇 |
出版年
2024年 | 31篇 |
2023年 | 190篇 |
2022年 | 442篇 |
2021年 | 609篇 |
2020年 | 628篇 |
2019年 | 547篇 |
2018年 | 584篇 |
2017年 | 806篇 |
2016年 | 944篇 |
2015年 | 813篇 |
2014年 | 1166篇 |
2013年 | 1812篇 |
2012年 | 1486篇 |
2011年 | 1481篇 |
2010年 | 1362篇 |
2009年 | 1439篇 |
2008年 | 1391篇 |
2007年 | 1408篇 |
2006年 | 1343篇 |
2005年 | 1214篇 |
2004年 | 1206篇 |
2003年 | 1033篇 |
2002年 | 916篇 |
2001年 | 768篇 |
2000年 | 752篇 |
1999年 | 660篇 |
1998年 | 552篇 |
1997年 | 449篇 |
1996年 | 396篇 |
1995年 | 312篇 |
1994年 | 280篇 |
1993年 | 260篇 |
1992年 | 220篇 |
1991年 | 158篇 |
1990年 | 153篇 |
1989年 | 149篇 |
1988年 | 144篇 |
1987年 | 97篇 |
1986年 | 96篇 |
1985年 | 62篇 |
1984年 | 45篇 |
1983年 | 22篇 |
1982年 | 51篇 |
1981年 | 43篇 |
1980年 | 34篇 |
1979年 | 35篇 |
1978年 | 28篇 |
1977年 | 18篇 |
1976年 | 14篇 |
1973年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 156 毫秒
101.
102.
关于体上分块矩阵的群逆 总被引:1,自引:0,他引:1
本文利用分块矩阵方法.研究了体上两个矩阵乘积的群逆的存在性及表示形式,给出了体上两个矩阵乘积群逆存在的充分必要条件和表示形式.并且在一定条件下.给出了体上分块矩阵的群逆存在性及表示形式. 相似文献
103.
Based on the effective-field theory with self-spin correlations and the differential operator technique,physical properties of the spin-2 system with biaxial crystal field on the simple cubic, body-centered cubic, as well as faced-centered lattice have been studied. The influences of the external longitudinal magnetic field on the magnetization,internal energy, specific heat, and susceptibility have been discussed in detail. The phenomenon that the magnetization in the ground state shows quantum effects produced by the biaxial transverse crystal field has been found. 相似文献
104.
Ryohei Tsuda Sayaka Kaino Hisashi Kokubo Shin-Ichiro Imabayashi Masayoshi Watanabe 《Colloids and surfaces. B, Biointerfaces》2007,56(1-2):255-Optics
Redox properties of phenothiazine-labeled poly(ethyl glycidy ether)-block-poly(ethylene oxide) (PT-EGEn-b-EOm) are reversibly changed by core-shell micelle formation. In the temperature range higher than the critical micellization temperature (cmt), the anodic potential of PT group positively shifts and concomitantly its anodic current decrease, or levels off compared to those of the reference polymer PT-EOm without the thermo-responsive EGEn segment. The former alteration is caused by incorporation of hydrophobic PT groups into a core of the micelle and the latter by the decrease in the diffusion coefficient of PT groups due to formation of the core-shell micelles. The cmt value and the temperature-dependent alteration in the redox properties strongly depend on the polymer structure, especially the length of thermo-responsive EGEn segment. The electrochemically determined hydrodynamic radii of the polymer aggregates seem to be overestimated, compared to the values reported for the aggregates of other thermo-responsive polymers with similar molecular weights, implying the presence of electrochemically inactive PT groups in the copolymers having longer thermo-responsive segments. 相似文献
105.
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
106.
107.
I. A. Anoshko V. S. Ermachenko L. E. Sandrigailo 《Journal of Applied Spectroscopy》2007,74(1):102-106
We present the results of a spectroscopic study of a nonequilibrium plasma in a Hall accelerator, in particular for such an
important parameter as the electron temperature. For the studied conditions, we used the semicoronal equilibrium model, which
relates the intensity ratios for two successive ionization steps for the same element.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 1, pp. 93–96, January–February, 2007. 相似文献
108.
Tensile impact experiments of EC8.0−24×7 glass fiber bundles at different low temperaturesT(14°C, −40°C and −10°C) and strain rates ɛ were carried out, and complete stress-strain curves were obtained. Within the range
of the experiment temperatures and strain rates, it is found that the initial modulusE, the ultimate strength σmax and the unstable strain ɛ
b
of the glass fiber bundles all increase with ɛ at an identicalT. At an identical ɛ, with the decrease ofT, E and σmax increase; but ɛ
b
increases when 10°C>T>−40°C and decreases when −40°C>T>−100°C. The strain-rate- and temperature-dependent bimodal Weibull statistical constitutive theory was adopted for the statistical
analysis of the experimental results, and the Weibull parameters of single fiber were obtained. The results show that the
bimodal Weibull distribution function is suitable to represent the strength distribution of the glass fiber at low temperature
and different strain rates. The differences in the mechanical properties between EC8.0−24×7 and EC5.5−12 ×14 glass fiber bundles
were also discussed.
Project supported by the National Natural Science Foundation of China (No. 19772058). 相似文献
109.
基于阿贝尔黑格斯变量的杨-米尔斯理论的红外阿贝尔化 总被引:1,自引:0,他引:1
通过SU(2)规范场的法捷耶夫-Niemi分解给出了有效阿贝尔-黑格斯型作用量的
一个计算方法. 具体指出了该分解中所用的自然规范固定以及阿贝尔投射与杨-米尔斯理论的红外动力学之间的内在关系. 推导出了色电场的一个伦敦型方程. 相似文献
110.