全文获取类型
收费全文 | 90048篇 |
免费 | 16983篇 |
国内免费 | 9274篇 |
专业分类
化学 | 61657篇 |
晶体学 | 915篇 |
力学 | 5746篇 |
综合类 | 512篇 |
数学 | 10106篇 |
物理学 | 37369篇 |
出版年
2024年 | 345篇 |
2023年 | 2048篇 |
2022年 | 3303篇 |
2021年 | 3396篇 |
2020年 | 3934篇 |
2019年 | 3513篇 |
2018年 | 3221篇 |
2017年 | 2881篇 |
2016年 | 4591篇 |
2015年 | 4376篇 |
2014年 | 5337篇 |
2013年 | 6790篇 |
2012年 | 8235篇 |
2011年 | 8434篇 |
2010年 | 5572篇 |
2009年 | 5413篇 |
2008年 | 5806篇 |
2007年 | 5086篇 |
2006年 | 4778篇 |
2005年 | 3830篇 |
2004年 | 2945篇 |
2003年 | 2303篇 |
2002年 | 2110篇 |
2001年 | 1819篇 |
2000年 | 1606篇 |
1999年 | 1846篇 |
1998年 | 1594篇 |
1997年 | 1576篇 |
1996年 | 1566篇 |
1995年 | 1326篇 |
1994年 | 1153篇 |
1993年 | 999篇 |
1992年 | 862篇 |
1991年 | 784篇 |
1990年 | 644篇 |
1989年 | 501篇 |
1988年 | 371篇 |
1987年 | 308篇 |
1986年 | 323篇 |
1985年 | 262篇 |
1984年 | 151篇 |
1983年 | 117篇 |
1982年 | 100篇 |
1981年 | 57篇 |
1980年 | 42篇 |
1979年 | 16篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1957年 | 31篇 |
1922年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
981.
Yongsong Luo Xiaohong Xia Yonggang Zhang Jialin Li Zhijie Jia 《Journal of solid state chemistry》2007,180(6):1928-1933
Luminescence of the short multiwalled carbon nanotubes (MWNTs) conjugated with carboxylic acid groups has been studied. The results show that the carboxyl-functionalized short MWNTs could emit luminescence and the emission peak appears at 500 nm with a corresponding optimal excitation wavelength centering at 310 nm. When the short MWNTs are filtered through 0.15 μm polytetrafluoroethylene (PTFE) membrane, the ultrashort MWNTs are obtained from the filtrate. An interesting feature for the ultrashort MWNTs is that the emission intensity is strengthened and the peak is slightly blue shifted to 460 nm. This result indicates that the luminescence properties of MWNTs are strongly affected by the tube length. After chemical oxidization cutting, defects and carboxylic acid groups at the tube end and/or sidewall can be produced; the more shorten of MWNTs, the better dispersion and carboxylic passivation of the nanotubes, and the more intense luminescence emissions. The broad emissions are logically attributed to the trapping of excitation energy by defect sites in the carboxyl-functionalized nanotube structure. 相似文献
982.
983.
Hai-Bin Tian Duan-Zhi Yin Lan Zhang Li-Hua Wang Chun-Fu Zhang Jun-Ling Li Wei Zhou Chun-Ying Wu Yong-Xian Wang 《Journal of Radioanalytical and Nuclear Chemistry》2004,262(2):383-389
The compound 3-{[4-(4-[18F]fluorophenyl)methyl]piperazin-1-yl}-methyl-1H-pyrrolo[2,3-b]pyridine ([18F]3), which is an analogue of L-745,870 binding D4
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
984.
The adsorption equilibrium isotherms of three aromatic sulfonic acid compounds, 2-naphthalenesulfonic acid, p-toluenesulfonic acid and p-chlorobenzenesulfonic acid, from aqueous solutions by macroporous weak base anion exchanger within the temperature range of 293 K-313 K were obtained. Several isotherm equations were correlated with the equilibrium data, and the experimental data was found to fit the three-parameter Redlich-Peterson equation best within the entire range of concentrations. The study showed that the hydrophobicity of solute has distinct influence on adsorption capacity of the anion exchanger for the aromatic sulfonic acid. Moreover, estimations of the isosteric enthalpy, free energy,and entropy change of adsorption were also reported. The positive isosteric enthalpy and entropy change for adsorption indicate an endothermic and entropy driven process in the present study. 相似文献
985.
986.
987.
2,6-O-diethyl-β-cyclodextrins were prepared and immobilized onto silica gel to develop a fluorosensor for dipyridamole. The analytical performance characteristics of the proposed sensor for analysis of dipyridamole were as follows: the detection limit was 0.8 nmol/L with a relative standard deviation of 1.4% for 10 determinations of 50 nmol/L of dipyridamole. The modification of β-CD improved the sensitivity and selectivity for measuring dipyridamole. The recommended method has been successfully tested for the determination of dipyridamole in clinical samples (urine and pharmaceutical preparations). 相似文献
988.
心脑血管病患者头发微量元素铜、锌含量调查 总被引:1,自引:0,他引:1
调查了心脑血管病患者头发微量元素铜、锌含量,发现患者发现Cu、Zn含量普通遇低于正常值。 相似文献
989.
990.
Using ClO2 as chemiluminescence (CL) oxidant, a novel homogeneous CL system in neutral and near neutral aqueous solution is proposed in this paper. ClO2 could oxidize sulfite in pH 5.0–8.5 acetate buffer to produce CL emission, and pipemidic acid could sensitize the CL system. The ClO2–SO32−–pipemidic acid reaction was used as a model CL system and explored the possibility of highly active and eco-friendly ClO2 being used as CL oxidant in neutral and near neutral aqueous solution. Combined with flow-injection analysis, the proposed CL system was applied to the automated dissolution testing of pipemidic acid tablet. Compared with the common strong acidic or strong basic CL system, this proposed CL owns its advantages. 相似文献