全文获取类型
收费全文 | 128914篇 |
免费 | 26462篇 |
国内免费 | 11836篇 |
专业分类
化学 | 103736篇 |
晶体学 | 1307篇 |
力学 | 6732篇 |
综合类 | 677篇 |
数学 | 13249篇 |
物理学 | 41511篇 |
出版年
2024年 | 258篇 |
2023年 | 2182篇 |
2022年 | 3074篇 |
2021年 | 3649篇 |
2020年 | 5169篇 |
2019年 | 5954篇 |
2018年 | 4268篇 |
2017年 | 3634篇 |
2016年 | 7813篇 |
2015年 | 7665篇 |
2014年 | 8653篇 |
2013年 | 10797篇 |
2012年 | 11483篇 |
2011年 | 11103篇 |
2010年 | 8735篇 |
2009年 | 8489篇 |
2008年 | 8485篇 |
2007年 | 7193篇 |
2006年 | 6549篇 |
2005年 | 5700篇 |
2004年 | 4616篇 |
2003年 | 3937篇 |
2002年 | 4609篇 |
2001年 | 3651篇 |
2000年 | 3168篇 |
1999年 | 2471篇 |
1998年 | 1792篇 |
1997年 | 1753篇 |
1996年 | 1689篇 |
1995年 | 1433篇 |
1994年 | 1224篇 |
1993年 | 1060篇 |
1992年 | 936篇 |
1991年 | 861篇 |
1990年 | 711篇 |
1989年 | 537篇 |
1988年 | 402篇 |
1987年 | 327篇 |
1986年 | 345篇 |
1985年 | 283篇 |
1984年 | 169篇 |
1983年 | 125篇 |
1982年 | 103篇 |
1981年 | 60篇 |
1980年 | 43篇 |
1979年 | 12篇 |
1978年 | 2篇 |
1957年 | 31篇 |
1936年 | 3篇 |
1922年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
Conductive composite films of poly(styrene‐co‐n‐butylacrylate) copolymers filled with low‐density, Ni‐plated core‐shell polymeric particles were prepared and their behaviors of positive temperature coefficient of resistance (PTCR) were investigated. When the conductive fillers in the composite film were loaded beyond the critical volume, 10 up to 25 vol %, composite films exhibited a unique electrical resistant transition behavior, which the electrical resistance rapidly increased by several orders of magnitude at the critical temperature. The PTCR transition temperature, in general, occurred before the glass transition temperature of polymer matrix. Further increased the conductive filler loading to 30 vol %, the overpacked conduction paths were formed in the entire composite and the PTCR effects became blurred. While the composite film treated with thermal cycle several times from room temperature up to 120 °C, the electrical resistivity increased accompanied with the shift of the PTCR transition to lower temperature. The reason might have been caused by the formed interfacial cracks within the composite film. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 322–329, 2007 相似文献
993.
Wei‐Lie Xiao Jian‐Xin Pu Rui‐Rui Wang Liu‐Meng Yang Xiao‐Li Li Sheng‐Hong Li Rong‐Tao Li Sheng‐Xiong Huang Yong‐Tang Zheng Han‐Dong Sun 《Helvetica chimica acta》2007,90(8):1505-1513
Seven new highly oxygenated nortriterpenoids, rubriflorins D–J ( 1 – 7 ), were isolated from the leaves and stems of Schisandra rubriflora, and their structures were elucidated on the basis of extensive analysis of spectroscopic data. These new compounds feature the opening of ring A compared with related known nortriterpenoids isolated from the genus Schisandra and showed weak activity against HIV‐1. 相似文献
994.
995.
996.
997.
Hua Ning LIU Wen Peng ZHANG 《数学学报(英文版)》2007,23(5):915-924
The main purpose of this paper is to use the generalized Bernoulli numbers, Gauss sums and the mean value theorems of Dirichlet L-functions between a quadratic residue and its inverse modulo p value formula. to study the asymptotic property of the difference (a prime), and to give an interesting hybrid mean 相似文献
998.
999.
Yi‐Ming Xie Ji‐Huai Wu 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(5):m220-m221
The title compound, [HgCl2(C10H8N2)]n, features two‐dimensional [HgCl2(4,4′‐bipy)]n neutral networks (4,4′‐bipy is 4,4′‐bipyridine), based on an octahedral Hg atom coordinated by four μ2‐Cl atoms and two μ2‐4,4′‐bipy ligands in trans positions, yielding a HgCl4N2 octahedron. The structure has mmm symmetry about the Hg atoms, with most of the atoms on at least one mirror plane, but the unsubstituted C atoms of the 4,4′‐bipy rings are disordered across a mirror plane. Photoluminescent investigations reveal that the title compound displays a strong emission in the green region, which probably originates from a ligand‐to‐ligand charge‐transfer transition. 相似文献
1000.
Zhao‐Peng Deng Shan Gao Li‐Hua Huo Hui Zhao 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(5):m225-m227
In the title complex, [Mn(SO4)(C3H7NO)(H2O)2]n, each MnII ion has a distorted octahedral geometry formed by three O atoms of three different sulfate groups, one O atom of a dimethylformamide ligand and two water molecules. The sulfate groups act as tridentate bridging ligands connecting the MnII ions into a two‐dimensional layer structure which can be regraded as a 4.82 network. 相似文献