全文获取类型
收费全文 | 2281篇 |
免费 | 456篇 |
国内免费 | 471篇 |
专业分类
化学 | 697篇 |
晶体学 | 43篇 |
力学 | 144篇 |
综合类 | 464篇 |
数学 | 437篇 |
物理学 | 544篇 |
无线电 | 879篇 |
出版年
2023年 | 49篇 |
2022年 | 78篇 |
2021年 | 106篇 |
2020年 | 96篇 |
2019年 | 15篇 |
2018年 | 415篇 |
2017年 | 347篇 |
2016年 | 81篇 |
2015年 | 24篇 |
2013年 | 79篇 |
2012年 | 7篇 |
2011年 | 18篇 |
2010年 | 17篇 |
2009年 | 26篇 |
2008年 | 17篇 |
2007年 | 19篇 |
2006年 | 4篇 |
2005年 | 12篇 |
2004年 | 18篇 |
2003年 | 24篇 |
2002年 | 57篇 |
2001年 | 26篇 |
2000年 | 39篇 |
1999年 | 162篇 |
1998年 | 11篇 |
1997年 | 37篇 |
1996年 | 7篇 |
1995年 | 14篇 |
1994年 | 65篇 |
1993年 | 128篇 |
1992年 | 154篇 |
1991年 | 172篇 |
1990年 | 230篇 |
1989年 | 236篇 |
1988年 | 164篇 |
1987年 | 7篇 |
1986年 | 40篇 |
1975年 | 3篇 |
1974年 | 3篇 |
1972年 | 46篇 |
1971年 | 19篇 |
1970年 | 20篇 |
1969年 | 21篇 |
1968年 | 19篇 |
1967年 | 12篇 |
1966年 | 8篇 |
1965年 | 6篇 |
1963年 | 9篇 |
1961年 | 9篇 |
1959年 | 5篇 |
排序方式: 共有3208条查询结果,搜索用时 11 毫秒
151.
本文使用单带双谷理论研究了GaAs/AlGaAs量于阱中的Г-X混和现象.介绍了Г态、X态和能级高于势垒的谐振态的特点.给出了谐振态能级随势阱和势垒层宽变化的关系.阐述了超薄层量子阱和非限定态的一些有趣的特性.在此基础上提出了一个超晶格能带的形成模型并对最新的一些实验结果给出了恰当的解释. 相似文献
152.
Kiatnida?Treerattrakoon Warangkana?Chanthima Chayachon?Apiwat Tararaj?Dharakul Suwussa?BamrungsapEmail authorView authors OrcID profile 《Mikrochimica acta》2017,184(7):1941-1950
The authors report on the conjugation of monoclonal antibodies against the biomarker epithelial cell adhesion molecule (EpCAM) to silica nanoparticles doped with the dye Cy5 (Cy5-SiNPs). Conjugation was performed on the Cy5-SiNPs that were previously coated with a layer of protein G which serves as a linker controlling the orientation of the antibody. The conjugation method takes advantage of site specific interactions between the protein G and constant domains (Fc) of the antibody. The method warrants the antibody binding sites (Fab) to be faced outwards such that the conjugates maintain their affinity for binding the analyte (EpCAM). In vitro analysis by confocal fluorescence imaging and flow cytometry using analytical wavelengths comparable with the excitation and emission wavelength of Cy5-SiNPs at 643 and 662 nm, respectively. The result demonstrated the oriented conjugate to specifically bind to target cells (HT-29) with a sensitivity that is 12 times higher than that of conjugates prepared by conventional EDC coupling. In vivo fluorescence imaging of mice bearing the HT-29 tumor highlighted time-dependent accumulation of the oriented conjugates at the tumor site. As indicated by biodistribution studies hepatic excretion of the oriented probes occurs, however tumor fluorescence still remains for up to 14 days post injection. This research demonstrates that the oriented conjugates derived herein can improve target cell detection sensitivity and can be successfully applied in tumor imaging, which should drive further development of new classes of effective fluorescence contrast agents for cancer diagnostics. 相似文献
153.
154.
155.
156.
157.
Yushu?Shi Guoqing?Zhang Jiaojiao?Li Yong?ZhangEmail authorView authors OrcID profile Yanbao?Yu Qin?Wei 《Mikrochimica acta》2017,184(5):1379-1387
The authors describe a highly sensitive and selective photoelectrochemical (PEC) assay for mercury(II) ions. It is based on a dual signal amplification strategy. The first enhancement results from the surface plasmon resonance (SPR) of Au@Ag nanoparticles (NPs) absorbed on MoS2 nanosheets. Here, the injection of hot electrons of Au@Ag NPs into MoS2 nanosheets produces a strong photocurrent, while background signals are strongly reduced. The second enhancement results from the use of a thymine rich ct-DNA aptamer attached to the Au@Ag-MoS2 nanohybrid. The DNA specifically binds Hg(II) ions to form thymine-Hg(II)-thymine (T-Hg-T) complexes. This leads to the formation of a hairpin-shaped dsDNA structure. The use of a CdSe quantum dot label at the terminal end of the ct-DNA further facilitates electron–hole separation. The photocurrent of the detector is measured as a function of Hg(II) concentration at a bias voltage of 0.1 V and under irradiation of 430 nm light. Due to the two-fold amplification strategy presented here, the linear range extends from 10 pmol·L?1</sup> to 100 nmol·L?1</sup>, with a detection limit of 5 pmol·L?1</sup> (at S/N?=?3). 相似文献
158.
159.