全文获取类型
收费全文 | 238378篇 |
免费 | 28693篇 |
国内免费 | 18953篇 |
专业分类
化学 | 136248篇 |
晶体学 | 2488篇 |
力学 | 16349篇 |
综合类 | 1123篇 |
数学 | 51680篇 |
物理学 | 78136篇 |
出版年
2024年 | 388篇 |
2023年 | 3256篇 |
2022年 | 4875篇 |
2021年 | 5716篇 |
2020年 | 6763篇 |
2019年 | 6245篇 |
2018年 | 14699篇 |
2017年 | 14122篇 |
2016年 | 13215篇 |
2015年 | 8373篇 |
2014年 | 9753篇 |
2013年 | 12736篇 |
2012年 | 18462篇 |
2011年 | 25105篇 |
2010年 | 15852篇 |
2009年 | 15781篇 |
2008年 | 17039篇 |
2007年 | 17957篇 |
2006年 | 9460篇 |
2005年 | 8879篇 |
2004年 | 7403篇 |
2003年 | 6629篇 |
2002年 | 5325篇 |
2001年 | 3966篇 |
2000年 | 3576篇 |
1999年 | 3719篇 |
1998年 | 3233篇 |
1997年 | 3020篇 |
1996年 | 3091篇 |
1995年 | 2582篇 |
1994年 | 2306篇 |
1993年 | 1970篇 |
1992年 | 1713篇 |
1991年 | 1531篇 |
1990年 | 1263篇 |
1989年 | 992篇 |
1988年 | 750篇 |
1987年 | 667篇 |
1986年 | 665篇 |
1985年 | 533篇 |
1984年 | 357篇 |
1983年 | 291篇 |
1982年 | 254篇 |
1981年 | 166篇 |
1980年 | 134篇 |
1979年 | 76篇 |
1978年 | 57篇 |
1973年 | 42篇 |
1957年 | 52篇 |
1914年 | 45篇 |
排序方式: 共有10000条查询结果,搜索用时 234 毫秒
231.
232.
The structure, chemical composition, and magnetic properties of electrochemically deposited nanocrystalline Co-Ni-Fe films
were investigated using a number of techniques. A high saturation magnetic induction up to B
s
= 21 kG was attained. An enhancement of the saturation magnetization compared to the ideal anticipated one was revealed,
which correlated with the nonlinear behavior of the structural phase composition and lattice parameters with the change of
the composition.
The text was submitted by the authors in English. 相似文献
233.
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
234.
The γcmc values of CTAB-SDS decrease from 63.67 mN/m at 10‡C to 36.38 mN/m at 90‡C, slightly lower than those of either CTAB or SDS.
Correspondingly, the CMC of CTAB-SDS decreases almost by half. The increase of surface activity of CTAB-SDS can be attributed
to the relatively weak electrostatic interaction at high temperature, which is supported by the increase of solubility of
CTAB-SDS with rise in temperature. Catalytic effect on oxidation of toluene derivatives with potassium permanganate follows
the order CTAB-SDS > SDS > CTAB. This is not caused by the dissociative effect of CTAB-SDS with low surface activity at low
temperature, as seen from the fact that almost all oxidative products can be retrieved for different toluene derivatives and
surfactants by mimicking the conditions of reaction. In the emulsifications of toluene derivatives at 90‡C, the time that
turbid water layers of surfactant solutions take to become clear is the same as that of the catalytic effect on oxidation
of toluene derivatives. Thus, it can be inferred that surfactants can improve the oxidation yields of toluene derivatives
by increasing the contact between two reacting phases. 相似文献
235.
Ji-Dong Lou Chun-Ling Gao Li Li Zhi-Gang Fang 《Monatshefte für Chemie / Chemical Monthly》2006,41(10):1071-1074
A new procedure for the selective oxidation of alcohols to the corresponding aldehydes and ketones with potassium permanganate
supported on aluminum silicate at room temperature under solvent-free conditions and shaking is reported. 相似文献
236.
The possibility of realizing SASE Free Election Laser in x-ray waveband with EM-wave wiggler is studied in this paper. SASE effect including saturation length, saturation power and nonlinear process is explored through a 3-D simulation code. A utilization of seed light from laser plasma x-ray is also analyzed, which demonstrates the feature of shortening the interaction length for saturation. The results show that sizeable output power of x-ray laser would be generated with a middle energy electron beam. 相似文献
237.
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
238.
239.
240.