全文获取类型
收费全文 | 15800篇 |
免费 | 2793篇 |
国内免费 | 1843篇 |
专业分类
化学 | 11271篇 |
晶体学 | 164篇 |
力学 | 1165篇 |
综合类 | 72篇 |
数学 | 1664篇 |
物理学 | 6100篇 |
出版年
2024年 | 36篇 |
2023年 | 339篇 |
2022年 | 435篇 |
2021年 | 538篇 |
2020年 | 635篇 |
2019年 | 588篇 |
2018年 | 533篇 |
2017年 | 485篇 |
2016年 | 843篇 |
2015年 | 736篇 |
2014年 | 927篇 |
2013年 | 1140篇 |
2012年 | 1466篇 |
2011年 | 1457篇 |
2010年 | 988篇 |
2009年 | 934篇 |
2008年 | 1085篇 |
2007年 | 952篇 |
2006年 | 864篇 |
2005年 | 765篇 |
2004年 | 537篇 |
2003年 | 438篇 |
2002年 | 431篇 |
2001年 | 354篇 |
2000年 | 308篇 |
1999年 | 333篇 |
1998年 | 275篇 |
1997年 | 247篇 |
1996年 | 273篇 |
1995年 | 271篇 |
1994年 | 194篇 |
1993年 | 150篇 |
1992年 | 155篇 |
1991年 | 145篇 |
1990年 | 128篇 |
1989年 | 102篇 |
1988年 | 86篇 |
1987年 | 67篇 |
1986年 | 50篇 |
1985年 | 41篇 |
1984年 | 30篇 |
1983年 | 25篇 |
1982年 | 14篇 |
1981年 | 16篇 |
1980年 | 9篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1972年 | 1篇 |
1957年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
61.
Controlling the gain shape of Er^3+—doped fluorozirconate fibre amplifier by a coherent field 下载免费PDF全文
We proposed a four-level system to explore the quantum interference effects on optical amplification.We found that the gain of the probe.including positions and values of gain peaks,can be adjusted by changing the coherent field and the incoherent pumping.At the same time,we can also modify the absorption profile of electromagnetically induced transparency by the incoherent pump.The results provide a method to flatten the gain of Erbium-doped fibre amplifiers. 相似文献
62.
Piaoping Yang Jianfeng Yu Zhenlü Wang Qingsheng Liu Tonghao Wu 《Reaction Kinetics and Catalysis Letters》2004,83(2):275-282
Mg-Al, Zn-Al and Ni-Al hydrotalcite-like compounds with high crystallinity were synthesized by using the decomposing property
of urea at high temperature. The crystallinity and the regularly of the samples were much preferable to those synthesized
by other methods.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
63.
64.
在氨性溶液中,光照射对ZnTPPS的形成影响很大。光-极谱试验表明:光电流(i_p)与浓度(c)间有以下的关系:对Zn(NH_3)_4~(2+),i_p∝C_((Zn)(NH_3)_4)~(2+)_~(1/2),对H_2TPPS,i_p∝C_(H_2TPPS),ZnTPPS络合物还原波的i_p不明显。本文对其差异性和光电流产生的原因做了初步探讨。 相似文献
65.
Reactions of the hydrated electron, H atoms, 2-propanol, and methanol radicals with the TiO2 nano-particles have been studied either directly or by competition kinetics. The radicals were produced by radiolysis of 2-propanol, t-butanol, or methanol aqueous solutions in acid pH's. The reactions involve electron injection to the conduction band. As expected, the t-butanol radical is inert towards TiO2 under our conditions, while the other reducing radicals react with TiO2. The reactivity decreases in the order: eaq−>H>CH3COHCH3>CH2OH. Two TiO2 nanocrystallite sizes, with average diameters of 1.0 and 4.7 nm were compared. For equal concentrations (in terms of TiO2 molecules), the rate of electron injection shows relatively little dependency on particle size. The rates of interfacial electron transfer and transfer coefficient are also reported. 相似文献
66.
大学物理实验教学改革的实践与思索 总被引:10,自引:0,他引:10
本主要介绍了我校近年来在大学物理实验课程体系和教学内容改革的实践及下一步改革的思路。 相似文献
67.
Single-crystalline layered lithium manganese oxide nanorods were prepared via a low-temperature molten salt synthesis method. The material was investigated by a variety of techniques, including X-ray powder diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectrum (XPS). 相似文献
68.
69.
70.
Thin films of polystyrene (PS), poly(methyl methacrylate) (PMMA) and polystyrene-polyacrylonitrile copolymer (PS-AN), containing various embedded transition-metal complexes, have been studied by FTIR microscopy. The spatial distributions of the transition-metal carbonyl complexes throughout the thin organic polymer films have been determined by a two-dimensional IR mapping procedure. The spectral variations observed in the distribution of the metal carbonyls throughout the different polymer films are discussed. The IR data show that the technique used to prepare the organometallic-embedded thin films (viz. freeze-drying of solutions followed by hot mechanical pressing of the residues) does in general lead to homogeneous films which may eventually find industrial application, e.g. as membrane sensors for small molecules. 相似文献