全文获取类型
收费全文 | 6803篇 |
免费 | 1119篇 |
国内免费 | 603篇 |
专业分类
化学 | 3695篇 |
晶体学 | 115篇 |
力学 | 135篇 |
综合类 | 23篇 |
数学 | 130篇 |
物理学 | 4427篇 |
出版年
2024年 | 20篇 |
2023年 | 95篇 |
2022年 | 192篇 |
2021年 | 233篇 |
2020年 | 350篇 |
2019年 | 236篇 |
2018年 | 185篇 |
2017年 | 253篇 |
2016年 | 276篇 |
2015年 | 234篇 |
2014年 | 334篇 |
2013年 | 496篇 |
2012年 | 472篇 |
2011年 | 630篇 |
2010年 | 464篇 |
2009年 | 447篇 |
2008年 | 440篇 |
2007年 | 456篇 |
2006年 | 432篇 |
2005年 | 326篇 |
2004年 | 290篇 |
2003年 | 235篇 |
2002年 | 196篇 |
2001年 | 158篇 |
2000年 | 180篇 |
1999年 | 89篇 |
1998年 | 151篇 |
1997年 | 111篇 |
1996年 | 95篇 |
1995年 | 73篇 |
1994年 | 57篇 |
1993年 | 60篇 |
1992年 | 57篇 |
1991年 | 36篇 |
1990年 | 39篇 |
1989年 | 33篇 |
1988年 | 21篇 |
1987年 | 9篇 |
1986年 | 9篇 |
1985年 | 10篇 |
1984年 | 6篇 |
1983年 | 8篇 |
1982年 | 4篇 |
1981年 | 7篇 |
1980年 | 5篇 |
1978年 | 3篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1973年 | 2篇 |
排序方式: 共有8525条查询结果,搜索用时 15 毫秒
1.
Dr. Joaquim Torra Dr. Felipe Viela Dr. Diego Megías Dr. Begoña Sot Prof. Cristina Flors 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(19):e202200026
CRANAD-2 is a fluorogenic curcumin derivative used for near-infrared detection and imaging in vivo of amyloid aggregates, which are involved in neurodegenerative diseases. We explore the performance of CRANAD-2 in two super-resolution imaging techniques, namely stimulated emission depletion (STED) and single-molecule localization microscopy (SMLM), with markedly different fluorophore requirements. By conveniently adapting the concentration of CRANAD-2, which transiently binds to amyloid fibrils, we show that it performs well in both techniques, achieving a resolution in the range of 45–55 nm. Correlation of SMLM with atomic force microscopy (AFM) validates the resolution of fine features in the reconstructed super-resolved image. The good performance and versatility of CRANAD-2 provides a powerful tool for near-infrared nanoscopic imaging of amyloids in vitro and in vivo. 相似文献
2.
As a new type of quantum dots (QDs), hexagonal boron nitride quantum dots (BNQDs) exhibit promising potential in the applications of disease diagnosis, fluorescence imaging, biosensing, metal ion detection, and so on, because of their remarkable chemical stability, excellent biocompatibility, low cytotoxicity, and outstanding photoluminescence properties. However, the large-scale fabrication of homogeneous BNQDs still remains challenging. In this article, the properties and common fabrication methods of BNQDs are summarized based on the recent research progress. Then, the corresponding yields, morphologies, and fabrication mechanisms of these as-obtained BNQDs are discussed in detail. Moreover, the applications of these as-obtained BNQDs in different fields are also discussed. This article is expected to inspire new methods and improvements to achieve large-scale fabrication of homogeneous BNQDs, which will enable their practical applications in future. 相似文献
3.
Mohammad Azam Saud I. Al-Resayes Agata Trzesowska-Kruszynska Rafal Kruszynski S.F. Adil N.K. Lokanath 《Journal of Saudi Chemical Society》2019,23(5):636-641
A new derivative of dioxouranium(VI) salen complex, [UO2(L)(pyridine)], where [L = N,N′-Bis(2-hydroxybenzylidene)-2,2-dimethyl-1,3-propanediamine] is synthesized and characterized by elemental analysis (C, H, N), FT-IR, ESI-MS spectrometry, UV/Vis, fluorescence, 1H and 13C NMR spectroscopy and thermal gravimetric (TG) study. Furthermore, the single crystal X-ray diffraction measurements of the complex were carried out at 100 and 273 K. The crystal structure measurements revealed that the complex has distorted pentagonal bipyramidal geometry with uranium atom located at the centre and bonded to two phenoxy oxygen and two azomethine nitrogen in tetradenate fashion and one nitrogen from pyridine making it seven coordinated. In addition, the photoluminescence property of the complex was also recorded. 相似文献
4.
C. Maurel 《Surface science》2006,600(2):442-447
Light emitted in the tunneling junction of a scanning tunneling microscope has been used to establish the electrical characteristics of nanojunctions made of Au islands deposited on flat MoS2 surfaces. It is shown that these characteristics are those of rectifying contacts when the gold islands are isolated and that they evolve toward those of ohmic contacts when the island density increases. It is observed that the rectifying behavior also evolves over time as on infinite metal/semiconductor contacts. Using the STM tip, single gold islands can be manipulated on the MoS2 surface so that their electrical behavior can be changed depending on their position with regard to the other islands. 相似文献
5.
Spectral and temporal characteristics of metallic nanoparticles produced by femtosecond laser pulses
We study the time of flight optical emission from titanium and tungsten nanosized particles, generated through femtosecond laser-matter interaction in vacuum, in the wavelength spectral range from 300 to 900 nm. Typical spectra consist of broadband structureless signals similar to black body emission from a macroscopic object. Nanoparticles temperature, deduced from their emission spectra, decreases drastically as a function of their time of arrival at a given distance from the target. This behaviour is seen to be independent of individual particle velocities. 相似文献
6.
7.
碳纳米管(Carbon Nanotubes,CNTs)场发射平面显示器(Field Emission Display,FED)与其他显示器比较显示了其独特优点,被认为是未来理想的平面显示器之一。碳纳米管阴极作为器件的核心部分,其性能的好坏直接影响显示器的性能。针对30~60英寸(76.2~152.4cm)大屏幕显示器所用的厚膜工艺,即采用丝网印刷法制备了碳纳米管阴极阵列,研究了化学气相沉积法在不同温度下生长的CNTs的场发射电流-电压特性,找到了适合FED用碳纳米管的最佳生长温度。结果表明生长温度越高(750℃),CNTs场发射性能越好。并用荧光粉阳极测试这些CNTs的场发射发光显示效果,验证了上述结论。 相似文献
8.
I.A. Khotina L.S. Lepnev N.S. Burenkova P.M. Valetsky A.G. Vitukhnovsky 《Journal of luminescence》2004,110(4):232-238
New materials based on low-generation polyphenylene dendrimers with the light emission in the blue spectrum range were synthesized and examined for an efficient organic light emitting diodes (OLED) application. It has been shown that the ratio of p-phenylene groups with high fluorescence parameters to 1,3,5-triphenylbenzene groups with low fluorescent parameters may be the possible reason for the experimental variations of relative quantum yield of photoluminescence in the compounds explored. The quantum yield value is increased with a number of dendrimer generations up to 50–70%. The role of bromine atoms as the luminescence quenchers have been demonstrated, which is important for synthesis route choice. 相似文献
9.
R. Pizzoferrato L. Lagonigro T. Ziller A. Di Carlo R. Paolesse F. Mandoj A. Ricci C. Lo Sterzo 《Chemical physics》2004,300(1-3):217-225
We study the infrared emission at 1.54 μm of an organolanthanide complex, Er(III)-tetraphenylporphyrin [Er(TPP)acac], both as a result of direct optical excitation and via energy transfer from host π-conjugate polymers of type poly(arylene–ethynylene) [PAE]. In the first case, the emission of the neat complex is characterized in inert transparent materials and a value of the quantum yield at 1.54 μm φIR=4×10−4 is measured. Then, fluorescence resonance transfer is investigated in blends of Er(TPP)acac with PAEs by monitoring the quenching of the polymer fluorescence along with the enhancement of both the visible emission of the ligand and the near-infrared band of Er3+. These different procedures allow a detailed analysis of the transfer efficiency within a specific implementation of the Förster model for polymeric donors. The experimental values of the critical radius R0, ranging from 1.3 to 2.5 nm for the different blends, are in good agreement with theory for a wide interval of the physical and spectroscopic parameters. This suggests that other mechanisms for excitation transfer do not play a significant role in these materials. 相似文献
10.
Zhang Xinliang Huang Dexiu Sun Junqiang Liu Deming 《Optical and Quantum Electronics》2004,36(7):627-634
A simple scheme for single to multi-channel wavelength conversion based on cross-gain modulation of amplified spontaneous emission (ASE) spectrum in semiconductor optical amplifier (SOA) is described. Single to 16-channel wavelength conversion at 10 Gb/s is first demonstrated without any additional probe lights, the modulation information carried by input signal could be converted into arbitrary many channels if only the demultiplexer with enough channels is exploited. Output performance and pattern effects are investigated experimentally. 相似文献