全文获取类型
收费全文 | 240967篇 |
免费 | 51789篇 |
国内免费 | 50646篇 |
专业分类
化学 | 105613篇 |
晶体学 | 4377篇 |
力学 | 11084篇 |
综合类 | 3548篇 |
数学 | 23171篇 |
物理学 | 92132篇 |
无线电 | 103477篇 |
出版年
2024年 | 1430篇 |
2023年 | 3777篇 |
2022年 | 6717篇 |
2021年 | 6946篇 |
2020年 | 6434篇 |
2019年 | 6859篇 |
2018年 | 6565篇 |
2017年 | 9011篇 |
2016年 | 8327篇 |
2015年 | 11382篇 |
2014年 | 12834篇 |
2013年 | 16010篇 |
2012年 | 18253篇 |
2011年 | 19592篇 |
2010年 | 22197篇 |
2009年 | 22930篇 |
2008年 | 17449篇 |
2007年 | 16323篇 |
2006年 | 15372篇 |
2005年 | 13564篇 |
2004年 | 12075篇 |
2003年 | 9090篇 |
2002年 | 8584篇 |
2001年 | 8532篇 |
2000年 | 7703篇 |
1999年 | 5280篇 |
1998年 | 3667篇 |
1997年 | 3117篇 |
1996年 | 3347篇 |
1995年 | 3610篇 |
1994年 | 3629篇 |
1993年 | 3794篇 |
1992年 | 3207篇 |
1991年 | 2752篇 |
1990年 | 2296篇 |
1989年 | 2416篇 |
1988年 | 2239篇 |
1987年 | 1439篇 |
1986年 | 1457篇 |
1985年 | 1024篇 |
1984年 | 1148篇 |
1983年 | 535篇 |
1982年 | 1021篇 |
1981年 | 856篇 |
1980年 | 867篇 |
1979年 | 622篇 |
1978年 | 567篇 |
1977年 | 649篇 |
1976年 | 1058篇 |
1972年 | 541篇 |
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
101.
102.
103.
The Mathematical Intelligencer encourages comments about the material in this issue. Letters to the editor should be sent
to either of the editors-in-chief, Chandler Davis or Marjorie Senechal. 相似文献
104.
Q. Gong R. N tzel P.J. van Veldhoven T.J. Eijkemans J.H. Wolter 《Journal of Crystal Growth》2005,280(3-4):413-418
We report on the shape transition from InAs quantum dashes to quantum dots (QDs) on lattice-matched GaInAsP on InP(3 1 1)A substrates. InAs quantum dashes develop during chemical-beam epitaxy of 3.2 monolayers InAs, which transform into round InAs QDs by introducing a growth interruption without arsenic flux after InAs deposition. The shape transition is solely attributed to surface properties, i.e., increase of the surface energy and symmetry under arsenic deficient conditions. The round QD shape is maintained during subsequent GaInAsP overgrowth because the reversed shape transition from dot to dash is kinetically hindered by the decreased ad-atom diffusion under arsenic flux. 相似文献
105.
106.
107.
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
108.
The equivalence of three (2 1)-dimensional soliton equations is proved, and the quite generalsolutionswitha some arbitrary functions of x, t and y respectively are obtained. By selecting the arbitrary functions, many specialtypes of the localized excitations like the solitoff solitons, multi-dromion solutions, lump, and multi-ring soliton solutionsare obtained. 相似文献
109.
Summary High-purity indium was analysed by spark source mass spectrometry, using electrical and photoplate detection. For the calibration of the differences in elemental sensitivity, a standard sample was prepared in which 10 impurities were determined by graphite furnace atomic absorption spectrometry. In this way accuracies of less than 40% were obtained for relatively homogeneous elements at ppm and sub-ppm level. About 40 elements could be determined with detection limits of 10 to 30 ppb. Two pattern recognition methods, principal component analysis and clustering analysis, were applied to obtain information on trace element distribution, which indicated that a number of elements were strongly spatially correlated in the analysed sample.
On leave from: Department of Chemistry, Nanjing Normal University, Nanjing, People's Republic of China 相似文献
Chemische Analyse und Verteilungsbestimmung von Spurenelementen in Indium-Matrix durch Funkenquellen-Massenspektrometrie
On leave from: Department of Chemistry, Nanjing Normal University, Nanjing, People's Republic of China 相似文献
110.
本文研究了FZ与CZ硅中铜与电子辐照缺陷的相互作用.实验表明,这种作用使扩铜并经电子辐照的n型FZ硅出现两个未经报道的新的深中心,E(0.043)和E(0.396).前者只存在于FZ硅而不存在于CZ硅.后者在扩铜并经电子辐照的n型FZ和CZ硅中都存在.电子辐照再加适当温度的热处理还可电激活硅中的铜,另外,铜的存在还使硅中双空位的退火温度显著地降低.种种实验表明,在硅中与铜有关的六个主要能级分别对应于六种不同结构的深中心,在这些深中心之中既包含铜又包含点缺陷.其中E(0.043)很可能是铜与间隙硅原子的络合物,而E(0.167)及H(0.411)则很可能是铜与空位的不同形态的络合物. 相似文献