全文获取类型
收费全文 | 43673篇 |
免费 | 4706篇 |
国内免费 | 4205篇 |
专业分类
化学 | 21994篇 |
晶体学 | 374篇 |
力学 | 1462篇 |
综合类 | 264篇 |
数学 | 3653篇 |
物理学 | 9575篇 |
综合类 | 15262篇 |
出版年
2024年 | 135篇 |
2023年 | 585篇 |
2022年 | 1026篇 |
2021年 | 1134篇 |
2020年 | 1144篇 |
2019年 | 1105篇 |
2018年 | 982篇 |
2017年 | 983篇 |
2016年 | 1414篇 |
2015年 | 1539篇 |
2014年 | 1972篇 |
2013年 | 2559篇 |
2012年 | 2978篇 |
2011年 | 3281篇 |
2010年 | 2463篇 |
2009年 | 2498篇 |
2008年 | 2752篇 |
2007年 | 2613篇 |
2006年 | 2295篇 |
2005年 | 2016篇 |
2004年 | 1631篇 |
2003年 | 1343篇 |
2002年 | 1504篇 |
2001年 | 1326篇 |
2000年 | 1090篇 |
1999年 | 1140篇 |
1998年 | 987篇 |
1997年 | 936篇 |
1996年 | 928篇 |
1995年 | 858篇 |
1994年 | 771篇 |
1993年 | 674篇 |
1992年 | 605篇 |
1991年 | 561篇 |
1990年 | 487篇 |
1989年 | 414篇 |
1988年 | 370篇 |
1987年 | 271篇 |
1986年 | 216篇 |
1985年 | 207篇 |
1984年 | 116篇 |
1983年 | 82篇 |
1982年 | 79篇 |
1981年 | 56篇 |
1980年 | 54篇 |
1979年 | 60篇 |
1978年 | 43篇 |
1976年 | 39篇 |
1974年 | 41篇 |
1973年 | 48篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
The structural evolution in amorphous silicon and germanium thin films has been investigated by high-resolution transmission electron microscopy (HRTEM) in conjunction with autocorrelation function (ACF) analysis. The results established that the structure of as-deposited semiconductor films is of a high density of nanocrystallites embedded in the amorphous matrix. In addition, from ACF analysis, the structure of a-Ge is more ordered than that of a-Si. The density of embedded nanocrystallites in amorphous films was found to diminish with annealing temperature first, then to increase. The conclusions also corroborate well with the results of diminished medium-range order in annealed amorphous films determined previously by a variable coherence microscopy method. 相似文献
52.
Hui-Wen Lin 《Transactions of the American Mathematical Society》2002,354(5):1861-1868
In this article, we find some diagonal hypersurfaces that admit crepant resolutions. We also give a criterion for unique factorization domains.
53.
曾子炳 《上饶师范学院学报》2002,22(5):52-55
辛弃疾的诗词创作呈现出很大的差异性,他的词沉郁、以抒发情志为主,取代了传统的诗的功能,而他的诗则学理学诗,平易、以吟咏性理为务。这是其个性的体现,也关乎词体的成熟、时代的风气和文化发展的内在逻辑。 相似文献
54.
55.
56.
用经验赝势方法计算了体ZnSe以及ZnSe/GaAs单异质结系统中ZnSe外延层г、X、L等特殊对称点导带底能量随压力的变化。结果表明,同Si、Ge、GaAs等半导体材料不同,ZnSe的X点导带底具有正的压力系数,但比г点的压力系数小,这是ZnSe材料以及ZnSe基异质结构材料发生直接禁带向间接禁带的转变时所需转变压力较大的根本原因。研究了ZnSe/GaAs异质结构中晶格失配造成的应变对外延层г、X、L对称点压力系数的影响,表明这种晶格失配造成的应变可以极大地减小ZnSe外延层材料由直接禁带向间接禁带的转变压力。 相似文献
57.
58.
The crystal structure, magnetic and magnetotransport properties of the variation of B′-site transition metal in Sr2FeMO6 (M=Mo, W) with double perovskites structure have been investigated systematically. Measurements of magnetization vs. temperature at H=5 T show that Sr2FeMoO6 is a ferromagnet and Sr2FeWO6 is an antiferromagnet with TN∼35 K. Additionally, the large magnetoresistance ratio (MR) of ∼22% (H=3 T) at room temperature (RT) was observed in the Sr2FeWO6 compound. However, the Sr2FeMoO6 compound did not show any significant MR even at high fields and RT (MR∼1%; H=3 T and 300 K). The implications of these findings are supported by band structure calculations to explain the interaction between the 4d(Mo) and 5d(W) orbitals of transition metal ions and oxygen ions. 相似文献
59.
Yang Mujie Zhao Jian Li Aibing Shen Zhiquan Zhang Mingjian Lin Senhao 《Journal of polymer science. Part A, Polymer chemistry》1989,27(11):3829-3835
This paper reports that 60Co γ-ray irradiation can convert cis-polyphenylacetylene (cis-PPA) films prepared with rare-earth coordination catalysts to highly photosensitive materials. The dependence of the photosensitivity on irradiation dose, preparation methods, and microstructure of the PPA films has been investigated by means of a potential discharge technique. The photosensitivity was enhanced with increasing irradiation dose. The critical dose to produce a light response was 5 × 103 Gy. The maximum surface potential discharge rate was 618 V/s, and the dark decay was approximately 2 V/s for cis-PPA films irradiated with 60Co γ-ray (dose: 2 × 105 Gy). The cis-transoidal-PPA and an electrophotographic photoreceptor device incorporating cis-PPA showed a higher irradiation effect. The structure and properties of 60Co γ-ray irradiated rare-earth PPA films are similar to the unirradiated films. 相似文献
60.
Ching‐Yuan Cheng Kuan‐Jiuh Lin 《Acta Crystallographica. Section C, Structural Chemistry》2006,62(8):m363-m365
In the title compound, catena‐poly[lithium‐μ3‐ethylenediphosphonato], [Li(C2H7O6P2)]n, the supramolecular monoclinic (C2/c) structure consists of one‐dimensional lithium chains [Li⋯Li = 2.7036 (8) Å] that are embedded within ethylenediphosphonate anions linked by strong symmetric hydrogen bonds [O⋯O = 2.473 (3) Å]. The Li atoms and the H atom in the symmetric hydrogen bond reside on twofold rotation axes and there is an inversion center at the mid‐point of the C—C bond of the ethylenediphosphonate ligand. 相似文献