全文获取类型
收费全文 | 101813篇 |
免费 | 17994篇 |
国内免费 | 12457篇 |
专业分类
化学 | 72043篇 |
晶体学 | 1177篇 |
力学 | 6716篇 |
综合类 | 700篇 |
数学 | 11968篇 |
物理学 | 39660篇 |
出版年
2024年 | 234篇 |
2023年 | 1984篇 |
2022年 | 3003篇 |
2021年 | 3596篇 |
2020年 | 4162篇 |
2019年 | 3996篇 |
2018年 | 3491篇 |
2017年 | 3358篇 |
2016年 | 4793篇 |
2015年 | 4856篇 |
2014年 | 5848篇 |
2013年 | 7583篇 |
2012年 | 9393篇 |
2011年 | 9681篇 |
2010年 | 6728篇 |
2009年 | 6581篇 |
2008年 | 7144篇 |
2007年 | 6226篇 |
2006年 | 5725篇 |
2005年 | 4739篇 |
2004年 | 3645篇 |
2003年 | 2948篇 |
2002年 | 2798篇 |
2001年 | 2330篇 |
2000年 | 2046篇 |
1999年 | 2097篇 |
1998年 | 1696篇 |
1997年 | 1643篇 |
1996年 | 1600篇 |
1995年 | 1308篇 |
1994年 | 1188篇 |
1993年 | 960篇 |
1992年 | 835篇 |
1991年 | 705篇 |
1990年 | 626篇 |
1989年 | 468篇 |
1988年 | 411篇 |
1987年 | 330篇 |
1986年 | 310篇 |
1985年 | 247篇 |
1984年 | 164篇 |
1983年 | 128篇 |
1982年 | 93篇 |
1981年 | 79篇 |
1980年 | 74篇 |
1979年 | 50篇 |
1978年 | 37篇 |
1977年 | 51篇 |
1976年 | 35篇 |
1973年 | 33篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
992.
Bamboo-shaped Ag-doped TiO2 nanowires with heterojunctions were synthesized by a simple solvothermal method. The diameter of the nanowires was about 50-100 nm, and they had a length of up to a few millimeters. The detailed structure of the heterojunction in the nanowire was also characterized. 相似文献
993.
In recent years, the synthesis of chiral tetrahedral clusters has been studied extensively and various types are accessible , which are a kind of organometallic compounds with greatly growing interest due to their potential application to asymmetric reaction catalysts. As an efficient 相似文献
994.
将钛酸四丁酯和硬脂酸在熔融状态下混合均匀后置于冷水浴中,使其凝固成凝胶,通过控制烧结过程中氧气的含量,成功地制备出粒度均匀、介电性能好的纳米晶TiO2.通过采用X射线光电子能谱和表面光电压谱对纳米晶TiO2表面状态的分析发现,材料表面存在大量的氧空位缺陷,暴露在粒子表面上的主要是一些金属Ti4+.纳米材料的这种表面状态对其极化性质具有重要的影响,使其在接近静态条件下的低频介电常数远大于常规材料的介电常数. 相似文献
995.
A portable chip-CE system with potential gradient detection (PGD) was developed and applied to the determinations of alkali metals and alkaloids. The separation efficiency appeared to be satisfactory and nonaqueous capillary electrophoresis (NACE) proved to be applicable to PGD or conductivity detection. The power supplies, separation and detection were built on a device of 3 kg in weight. A branch channel near the end of the separation channel was designed to perform PGD and make the application of relatively high field strength possible. The study is the first report on the application of PGD on the microchip platform. The design of the chip-CE system shows several advantages, such as simplicity, miniaturization and wide applicability. 相似文献
996.
Chen T Wang L Jiang G Wang J Dong X Wang X Zhou J Wang C Wang W 《The journal of physical chemistry. B》2005,109(10):4624-4630
The electrochemical behavior of poly(ferrocenyldimethylsilane-b-dimethylsiloxane) (PFDMS-b-PDMS) films deposited on a glassy carbon electrode was investigated by means of cyclic voltammetry (CV). The influences of the solvent, film thickness, temperature, and PDMS block length in PFDMS-b-PDMS on the electrode process were discussed. It was found that in 0.1 M aqueous LiClO(4) the electrochemical processes of the films on a glassy carbon electrode were complex and have a low rate of electron transport and mass diffusion. The kinetic parameters obtained indicated that the electrode process was controlled by both the electrode reaction and mass diffusion. 相似文献
997.
998.
Determination of ephedrine alkaloids by capillary electrophoresis 总被引:11,自引:0,他引:11
A simple and rapid method for the simultaneous determination of six ephedrine alkaloids (ephedrine, pseudoephedrine, norephedrine, norpseudoephedrine, methylephedrine and methylpseudoephedrine) in Ephedrae herba by capillary electrophoresis was developed. A buffer solution that contained 0.005 M barium hydroxide and 0.02 M isoleucine and adjusted to pH 10.0 with ammonia solution was found to be the most suitable electrolyte for this separation. The contents of the six alkaloids in the crude drug of Ephedrae herba could be easily determined. 相似文献
999.
The Raman scattering on a novel liquid crystal side chain polymer, poly-2,5-bis (p-meth-oxybenzoyloxy) styrene, has been performed. We observed that the characteristic Raman sp-ctra of the vinyl group in the monomer changed much deeply in the polymer, especially for the Raman line correponding to the C=C of the vinyl group which disappeared completly in the polymer. Contrast with that, the Raman spetra of the rest group did not present any substantial difference between the monomer and the polymer. These experimental facts show-ed that the vinyl group of the monomer was tranfered to the polymeric backbone while the chemical structure of the mesogenic unit in the monomer remained after the polymerization,and also conformed that it was successful in the synthesis of a liquid crystal side chain plymer without a flexible spacer between the mesomorphic unit and the molecular main chain. 相似文献
1000.
Jun Zhang Kaimin Liu Gengmei Xing Tongxiang Ren Shukuan Wang 《Journal of Radioanalytical and Nuclear Chemistry》2007,272(3):605-609
Gd@C82(OH)40 has been developed as a new generation of MRI contrast agent. But recently, it was found that Gd@C82(OH)
x
with a larger number of OH (x>36) would lead to cage break and hence, release of highly toxic Gd ions. We synthesized the more stable Gd@C82(OH)
x
with less OH-number, Gd@C82(OH)16, and studied its proton relaxivity and MRI images. The results indicate that Gd@C82(OH)16 also gives high proton relaxivity, even higher than that of (NMG)2-Gd-DTPA. The bio-distribution indicated that Gd@C82(OH)16 tends to be entrapped in the liver and kidney and remained in tissue for about 2 hours. The results suggest that the more
stable metallofullerene derivative Gd@C82(OH)16 can be the potential candidate of the new MRI contrast agent. 相似文献