全文获取类型
收费全文 | 19842篇 |
免费 | 3551篇 |
国内免费 | 2524篇 |
专业分类
化学 | 14096篇 |
晶体学 | 265篇 |
力学 | 1349篇 |
综合类 | 129篇 |
数学 | 2344篇 |
物理学 | 7734篇 |
出版年
2024年 | 50篇 |
2023年 | 408篇 |
2022年 | 569篇 |
2021年 | 684篇 |
2020年 | 823篇 |
2019年 | 756篇 |
2018年 | 702篇 |
2017年 | 657篇 |
2016年 | 1039篇 |
2015年 | 926篇 |
2014年 | 1130篇 |
2013年 | 1441篇 |
2012年 | 1869篇 |
2011年 | 1839篇 |
2010年 | 1298篇 |
2009年 | 1233篇 |
2008年 | 1399篇 |
2007年 | 1217篇 |
2006年 | 1100篇 |
2005年 | 964篇 |
2004年 | 667篇 |
2003年 | 576篇 |
2002年 | 603篇 |
2001年 | 497篇 |
2000年 | 405篇 |
1999年 | 406篇 |
1998年 | 317篇 |
1997年 | 276篇 |
1996年 | 313篇 |
1995年 | 296篇 |
1994年 | 224篇 |
1993年 | 176篇 |
1992年 | 177篇 |
1991年 | 172篇 |
1990年 | 151篇 |
1989年 | 110篇 |
1988年 | 97篇 |
1987年 | 75篇 |
1986年 | 63篇 |
1985年 | 49篇 |
1984年 | 40篇 |
1983年 | 34篇 |
1982年 | 23篇 |
1981年 | 17篇 |
1980年 | 11篇 |
1977年 | 5篇 |
1973年 | 5篇 |
1972年 | 5篇 |
1971年 | 4篇 |
1957年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
81.
在超高真空分子束外延(MBE)生长技术中,反射式高能电子衍射仪(RHEED)能实时显示半导体和金属外延生长过程,给出薄膜表面结构和平整度的信息,成为MBE必备的原位表面分 析仪.为了研究氧化物薄膜如高温超导(YBa2Cu3O7) 、铁电薄膜(Sr1-xBax TiO3)及它们的同质和异质外延结构的生长机理,获得高质量的符合各种应用 需要的氧化 物多层薄膜结构,在常规的制备氧化
关键词:
高温超导薄膜
RHEED 相似文献
82.
83.
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
84.
85.
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
86.
Hilbert空间上线性算子的Drazin可逆性 总被引:1,自引:0,他引:1
主要研究了Hilbert空间上两个Drazin可逆算子和的Drazin可逆性.同时,对上三角算子矩阵的Drazin可逆性也给出了详细的讨论. 相似文献
87.
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
88.
The detailed characterization of multifunctional hybrid organosilazane/organosilylamine telechelic oligomers by IR and 1H, 13C and 29Si NMR spectroscopy in one and two dimenions has been undertaken. The specific multifunctional oligomers, comprising NH/NH2 or SiCl functionalities depending on the monomer feed-ratio, were prepared from mono- and di-functionally reacted dichlorodimethylsilane (DDS) and mono-, di-, tri- and tetra-functionally reacted ethylenediamine (EDA). Varying the feed-ratio afforded control of the microstructures of the oligomers and the preparation of oligomers with, in some cases, conterminously located silicon–chlorine (SiCl) groups. The combination of the NMR methods with the IR technique has enabled the detailed microstructural characterization of the oligomers and the identification of the functionalities therein. This approach and the knowledge gained from the DDS/EDA system has been applied to the microstructural characterization of other hybrid organosilazane/silylamine preceramic telechelic oligomers. 相似文献
89.
90.
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