全文获取类型
收费全文 | 88023篇 |
免费 | 15039篇 |
国内免费 | 8947篇 |
专业分类
化学 | 61075篇 |
晶体学 | 813篇 |
力学 | 5789篇 |
综合类 | 440篇 |
数学 | 10111篇 |
物理学 | 33781篇 |
出版年
2024年 | 319篇 |
2023年 | 1824篇 |
2022年 | 3117篇 |
2021年 | 3215篇 |
2020年 | 3578篇 |
2019年 | 3418篇 |
2018年 | 2978篇 |
2017年 | 2772篇 |
2016年 | 4167篇 |
2015年 | 4078篇 |
2014年 | 4895篇 |
2013年 | 6271篇 |
2012年 | 7969篇 |
2011年 | 8011篇 |
2010年 | 5386篇 |
2009年 | 5056篇 |
2008年 | 5525篇 |
2007年 | 4973篇 |
2006年 | 4616篇 |
2005年 | 3814篇 |
2004年 | 2947篇 |
2003年 | 2401篇 |
2002年 | 2237篇 |
2001年 | 1889篇 |
2000年 | 1659篇 |
1999年 | 1836篇 |
1998年 | 1555篇 |
1997年 | 1520篇 |
1996年 | 1557篇 |
1995年 | 1258篇 |
1994年 | 1106篇 |
1993年 | 913篇 |
1992年 | 830篇 |
1991年 | 742篇 |
1990年 | 617篇 |
1989年 | 494篇 |
1988年 | 403篇 |
1987年 | 336篇 |
1986年 | 322篇 |
1985年 | 262篇 |
1984年 | 196篇 |
1983年 | 140篇 |
1982年 | 111篇 |
1981年 | 98篇 |
1980年 | 94篇 |
1979年 | 52篇 |
1978年 | 54篇 |
1977年 | 65篇 |
1976年 | 53篇 |
1973年 | 54篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Dong Zheng Fu-Quan Wang Yuan-Guang Li Liang-Hong Guo Jing Cheng 《Analytica chimica acta》2004,508(2):225-231
Optimized combination of chemical agents was selected for sensitive electrochemical detection of dissolved ruthenium tris-(2,2′-bipyridine) (Ru-bipy). The detection was based on the chemical amplification mechanism, in which the anodic current of a redox-active analyte was amplified by a sacrificial electron donor in solution. On indium-doped tin oxide (ITO) electrodes, electrochemical reaction of the analyte was reversible, but that of the electron donor was greatly suppressed. Several transition metal complexes, such as ferrocene and tris-(2,2′-bipyridine) complexes of osmium, iron and ruthenium, were evaluated as model analyte. A correlation between the amplified current and the standard potential of the complex was observed, and Ru-bipy generated the largest current. A variety of organic bases, acids and zwitterions were assessed as potential electron donor. Sodium oxalate was found to produce the largest amplification factor. With Ru-bipy as the model analyte and oxalate as the electron donor, the analyte concentration curve was linear up to 50 μM, with a lower detection limit of approximately 50 nM. Preliminary work was presented in which a Ru-bipy derivative was attached to bovine serum albumin and detected electrochemically. Although the combination of Ru-bipy, oxalate and ITO electrode has been used before for electrochemiluminescent detection of Ru-bipy and oxalate, as well as electrochemical detection of oxalate, its utility in amplified voltammetric detection of Ru-bipy as a potential electrochemical label has not been reported previously. 相似文献
102.
103.
104.
Bijian Lan Chunming Liu Xiang Yin Hua Zhang Wei Xu Zhongyi Hua 《Frontiers of Chemistry in China》2006,1(3):296-299
Organic materials of D-π-A type MR-X (MR-1: p-dimethylaminophenylethenetrica-rbonitrile and MR-2: p-diphenylaminophenylethene tricarbonitrile) were designed and synthesized. The device with a sandwich structure shows good
rectificative phenomena. The highest rectification ratio 10000 was achieved in device Cu/MR-1/Ag, and about 100 in other device
M/MR-X/M (M: Cu, Ag). It has been found that rectificative phenomena exist only in the atmosphere-liquid interface region
by means of liquid adsorption, and electric field could help form the oriented molecular film.
__________
Translated from Journal of Fudan University (Natural Science), 2005, 44(4) (in Chinese) 相似文献
105.
It is proved that for any integerk≥ 54 000, there isN
k
>0 depending onk only such that every even integer ≥N
k
is a sum of two odd prime numbers andk powers of 2.
Project partially supported by RGC Research Grant (No.HKU 7122/97P) and Post-Doctoral Fellowship of the University of Hong
Kong. 相似文献
106.
107.
108.
109.
玻璃陶瓷材料中Tm3+离子红外到蓝色上转换发光 总被引:4,自引:0,他引:4
系统研究了PbF2+GeO2+WO3ⅩⅣTmF3玻璃陶瓷材料中,在近红外光(1.06μm)激发下,Tm3+离子的发光特性.实验中观测到Tm3+离子的两组峰值位置分别在20920cm-1和22173cm-1的蓝色上转换发光,并证实这两组上转换发光分别与吸收三个和四个光子有关,同时建立了上转换发光的模型.为了选择最佳掺杂浓度,详细地测量了Tm3+离子峰值为20920cm-1的蓝色上转换发光强度与TmF3浓度的关系. 相似文献
110.
A Generalization of Regular Left Acts 总被引:1,自引:0,他引:1
Liu Zhongkui 《东北数学》1997,(2)
AGeneralizationofRegularLeftActs*)LiuZhongkui(刘仲奎)(DepartmentofMathematics,NorthwestNormalUniversity,Lanzhou,730070)J.Ahsan(D... 相似文献