全文获取类型
收费全文 | 30512篇 |
免费 | 4104篇 |
国内免费 | 3967篇 |
专业分类
化学 | 22300篇 |
晶体学 | 443篇 |
力学 | 1588篇 |
综合类 | 334篇 |
数学 | 3884篇 |
物理学 | 10034篇 |
出版年
2024年 | 49篇 |
2023年 | 463篇 |
2022年 | 631篇 |
2021年 | 848篇 |
2020年 | 967篇 |
2019年 | 983篇 |
2018年 | 847篇 |
2017年 | 847篇 |
2016年 | 1184篇 |
2015年 | 1252篇 |
2014年 | 1476篇 |
2013年 | 2044篇 |
2012年 | 2424篇 |
2011年 | 2672篇 |
2010年 | 1924篇 |
2009年 | 1942篇 |
2008年 | 2118篇 |
2007年 | 1934篇 |
2006年 | 1766篇 |
2005年 | 1556篇 |
2004年 | 1239篇 |
2003年 | 982篇 |
2002年 | 977篇 |
2001年 | 862篇 |
2000年 | 731篇 |
1999年 | 642篇 |
1998年 | 539篇 |
1997年 | 482篇 |
1996年 | 510篇 |
1995年 | 412篇 |
1994年 | 396篇 |
1993年 | 369篇 |
1992年 | 345篇 |
1991年 | 295篇 |
1990年 | 255篇 |
1989年 | 219篇 |
1988年 | 193篇 |
1987年 | 150篇 |
1986年 | 158篇 |
1985年 | 159篇 |
1984年 | 106篇 |
1983年 | 70篇 |
1982年 | 73篇 |
1981年 | 54篇 |
1980年 | 54篇 |
1979年 | 59篇 |
1978年 | 41篇 |
1976年 | 38篇 |
1974年 | 40篇 |
1973年 | 45篇 |
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
41.
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.
42.
43.
44.
45.
46.
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
47.
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
48.
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
49.
50.
Resistivity-temperature characteristics of sol gel YBa2Cu3Oy samples synthesized in flowing oxygen atmosphere 下载免费PDF全文
The relationship of resistivity versus synthesizing temperature of sol gel YBa_2Cu_3O_y samples was studied when prepared under flowing oxygen conditions. A set of high-temperature ρ-T curves was obtained for the whole process. After the sample finished the test measuring, its resistivity was ρ_{300}=9.83×10^{-3 }Ω·cm at room temperature. The ρ-T curve also showed that the orthorhombic-tetragonal phase transformation of sol-gel YBa_2Cu_3O_y sample occurred at 581℃ for the sample in the rising temperature process, but at 613℃ in the cooling process, lower than that of the samples made by using the conventional powder metallurgy methods. 相似文献