全文获取类型
收费全文 | 586篇 |
免费 | 35篇 |
国内免费 | 1篇 |
专业分类
化学 | 395篇 |
晶体学 | 2篇 |
力学 | 17篇 |
数学 | 36篇 |
物理学 | 106篇 |
无线电 | 66篇 |
出版年
2023年 | 6篇 |
2022年 | 11篇 |
2021年 | 25篇 |
2020年 | 19篇 |
2019年 | 19篇 |
2018年 | 20篇 |
2017年 | 19篇 |
2016年 | 46篇 |
2015年 | 23篇 |
2014年 | 33篇 |
2013年 | 81篇 |
2012年 | 35篇 |
2011年 | 33篇 |
2010年 | 17篇 |
2009年 | 26篇 |
2008年 | 35篇 |
2007年 | 29篇 |
2006年 | 20篇 |
2005年 | 23篇 |
2004年 | 18篇 |
2003年 | 15篇 |
2002年 | 9篇 |
2001年 | 6篇 |
2000年 | 1篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1997年 | 3篇 |
1996年 | 4篇 |
1995年 | 3篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 4篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 3篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1974年 | 1篇 |
1973年 | 3篇 |
1968年 | 1篇 |
1963年 | 1篇 |
排序方式: 共有622条查询结果,搜索用时 15 毫秒
31.
Mohammad Nasser H. EL-Sherbiny Gamal M. Hammad Ali A. Askar Ahmed A. El- Nour Salwa A. Abou 《Cellulose (London, England)》2022,29(3):1791-1805
Cellulose - Antibacterial coatings based on bacterial cellulose (BC) have been widely used in many fields including food packaging and wound dressing. In this study, we aimed to synthesis of... 相似文献
32.
Safari Nasimeh Imanzadeh Gholamhassan Asgharzadeh Roghayyeh Hosseyni Seyyedeh Tahereh Shamkhali Amir Nasser Soltanzadeh Zahra 《Chemistry of Heterocyclic Compounds》2021,57(6):640-645
Chemistry of Heterocyclic Compounds - In this work, new pyrazole derivatives were prepared by one-pot three-component reaction emloying symmetric and asymmetric 1,2-disulfonyl-hydrazines,... 相似文献
33.
M. Kazemzadeh Otoufi Nasser Shahtahmasebi Ahmad Kompany E. Kafshdar Goharshadi Ali Roghani 《Journal of Cluster Science》2014,25(5):1307-1317
This paper describes the homogeneous growth of gold shells on the surfaces of spherical dielectric silica nanoparticle cores by two different approaches: common two-step method (the name) and deposition–precipitation process. The methods basically are different in forming the precursor gold seed particles on silica. The structural and optical properties and morphology of the nanoparticles were characterized by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), UV–Vis spectrophotometery, and photo luminescence spectroscopy (PL). The results showed that, although in both the methods the core–shell nanoparticles can be reliably prepared in a controlled fashion with a favorable uniformity, but deposition–precipitation method indicated a better mechanical stability while it was more cost and time effective too. A regular red shift, from 488 to 662 nm, and peak broadening was also risen for the striking plasmon absorption peak as gold nanoseeds created by each of the two methods grew in size on silica cores. 相似文献
34.
Nasser Iranpoor Elham Etemadi-Davan 《Phosphorus, sulfur, and silicon and the related elements》2014,189(7-8):1165-1173
35.
Hani Nasser Abdelhamid Hui-Fen Wu 《Journal of the American Society for Mass Spectrometry》2014,25(5):861-868
We report an extremely sensitive and specific detection of mercuric ions (Hg2+) based on graphene assisted laser desorption/ionization mass spectrometry (GALDI-MS). Combining the highly selective coordination interactions between thymine (T) and Hg2+, we present a simple, effective, and novel approach, based on π–π interactions of the T-Hg2+-T complex and G that can serve as a platform and matrix for GALDI-MS. The present sensor not only exhibits high selectivity and sensitivity (picomolar) to Hg2+ in aqueous solution, but also can elucidate the chemical structures of the metal complexes. The significant advantage in the current approach is that there is no need for a sophisticated instrument, and no sample pretreatment is required to detect the Hg2+ ions. Figure
? 相似文献
36.
Aslanpanjeh Maryam Poursattar Marjani Ahmad Khalafy Jabbar Etivand Nasser 《Research on Chemical Intermediates》2020,46(1):165-177
Research on Chemical Intermediates - One-pot, three-component reaction of various aryl glyoxal monohydrates, 5-methylisoxazol-3-amine and 4-hydroxyquinolin-2(1H)-one in the presence of a catalytic... 相似文献
37.
This paper experimentally investigates the influence of carbon nanotubes (CNTs) on phase composition, microstructure deterioration, thermal behavior, and residual mechanical strengths of cementitious composites exposed to elevated temperatures. Cement mortars with small dosages of CNTs, 0.05% and 0.2% by weight of cement, were prepared and then heated at 25 °C, 150 °C, 200 °C, 450 °C, and 600 °C for two hours before being tested. The results show positive impact of the CNTs on the hydration process of cement mortar at room temperature and at higher temperatures up to 200 °C. Decomposition of the hydration products is obvious at 450 °C, whereas sever deterioration in the microstructure occurs at 600 °C. The nano reinforcement and bridging effect of the CNTs are obvious up to 450 °C. Thermal behavior characterization shows that CNTs incorporation enhances the thermal conductivity of the unheated and heat-treated mortar specimens. The decomposition of the hydration products needs more heat in the presence of CNTs. Finally, presence of CNTs significantly enhances the residual compressive and flexural strengths of heated mortar specimens for all studied temperatures. 相似文献
38.
39.
Nasser Metwally 《Physics letters. A》2011,375(48):4268-4273
A theoretical scheme is introduced to generate entangled network via Dzyaloshinskii-Moriya (DM) interaction. The dynamics of entanglement between different nodes, which is generated by direct or indirect interaction, is investigated. It is shown that, the direction of (DM) interaction and the locations of the nodes have a sensational effect on the degree of entanglement. The minimum entanglement generated between all the nodes is quantified. The upper and lower bounds of the entanglement depend on the direction of DM interaction, and the repetition of the behavior depends on the strength of DM. The generated entangled nodes are used as quantum channel to perform quantum teleportation, where it is shown that the fidelity of teleporting unknown information between the network members depends on the locations of the members. 相似文献
40.
Amorphous gallium nitride (a-GaN) thin films were deposited on glass substrate by electron beam evaporation technique at room
temperature and high vacuum using N
2 as carrier gas. The structural properties of the films was studied by X-ray diffraction (XRD) and scanning electron microscope
(SEM). It was clear from XRD spectra and SEM study that the GaN thin films were amorphous. The absorbance, transmittance and
reflectance spectra of these films were measured in the wavelength range of 300–2200 nm. The absorption coefficient spectral
analysis in the sharp absorption region revealed a direct band gap of E
g = 3:1 eV. The data analysis allowed the determination of the dispersive optical parameters by calculating the refractive
index. The oscillator energy E
0 and the dispersion energy E
d, which is a measure of the average strength of inter-band optical transition or the oscillator strength, were determined.
Electrical conductivity of a-GaN was measured in a different range of temperatures. Then, activation energy of a-GaN thin
films was calculated which equalled E
a = 0:434 eV. 相似文献