全文获取类型
收费全文 | 1105篇 |
免费 | 166篇 |
国内免费 | 298篇 |
专业分类
化学 | 943篇 |
晶体学 | 38篇 |
力学 | 8篇 |
综合类 | 5篇 |
数学 | 3篇 |
物理学 | 572篇 |
出版年
2023年 | 16篇 |
2022年 | 27篇 |
2021年 | 41篇 |
2020年 | 48篇 |
2019年 | 60篇 |
2018年 | 45篇 |
2017年 | 74篇 |
2016年 | 70篇 |
2015年 | 64篇 |
2014年 | 80篇 |
2013年 | 121篇 |
2012年 | 117篇 |
2011年 | 96篇 |
2010年 | 74篇 |
2009年 | 101篇 |
2008年 | 85篇 |
2007年 | 68篇 |
2006年 | 67篇 |
2005年 | 66篇 |
2004年 | 42篇 |
2003年 | 32篇 |
2002年 | 49篇 |
2001年 | 18篇 |
2000年 | 22篇 |
1999年 | 19篇 |
1998年 | 16篇 |
1997年 | 7篇 |
1996年 | 9篇 |
1995年 | 3篇 |
1994年 | 8篇 |
1993年 | 3篇 |
1992年 | 4篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1987年 | 2篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有1569条查询结果,搜索用时 328 毫秒
61.
S. Cint Pinzaru Cs. Müller S. Tomi M. M. Venter B. I. Cozar B. Glamuzina 《Journal of Raman spectroscopy : JRS》2015,46(7):597-604
While recording SERS spectra of pure β‐carotene at sub‐micromole concentrations for reference purpose, we discovered an unusual spectral response never reported before. In pre‐resonance conditions with the 532‐nm line, SERS of β‐carotene with AgNPs exhibits among the strong υ(CC) mode at 1512 cm−1 unshifted from normal Raman spectrum, additional strong bands at 1649, 1575 and 1387 cm−1 as well as other medium bands not observed in the Raman spectrum of the crystalline powder. Such behavior is explained in terms of selection rules relaxation upon cyclohexene terminal rings of the β‐carotene interaction with the NP surface. AFM images of the SERS system suggested dimers and trimers clustering of the nanoparticles with adsorbed β‐carotene. In light of the new SERS feature the consequences in correct interpretation of the SERS imaging from complex biosystems containing carotenoids are discussed. Relative intensity ratio of the β‐carotene band at 1512 cm−1 and water against concentration allowed a reliable SERS calibration curve for 50 to 500 nmol l−1 concentration range and provided quantitative SERS assessment of the carotenoid content in the sea urchin (Paracentrotus lividus) gonads extracts. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
62.
Shwetha U. R Maha Abdallah Alnuwaiser Latha M. S Virupaxappa S. Betageri Shilpa V. A M. Ijaz Khan Kamel Guedri 《印度化学会志》2022,99(9):100606
The present research highlights physical significance of green combination of metal oxide nanomaterials utilizing medicinal plant which has widely analyzed in different medical applications i.e., medicinal science, therapeutics. In this paper, we discussed environmentally benign approach for synthesizing silver doped copper oxide nanoparticles (Ag–CuO NPs) utilizing (ACLE). Scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS) were utilized to confirm the size, crystalline structure and surface morphology of the obtained nanomaterials. The monoclinic crystalline structure of the Ag–CuO NPs as produced was revealed by XRD patterns. Morphological analysis disclosed the nano-based spherical configuration of Ag–CuO NPs, as well as their morphology and elemental composition. The anti-diabetic effect of Ag–CuO NPs was further investigated utilizing a yeast cell model and amylase inhibition. Here, a decrease in intracellular glucose and a delay in carbohydrate digestion indicate promising antidiabetic action. Furthermore, the prepared nanomaterial showed anticancer potential against the MCF-7 cancer cell line, with an IC 50 value of 11.21 g/ml. 相似文献
63.
《印度化学会志》2022,99(11):100770
Individual and mix metal nanoparticles of Ag and Au have been prepared by the reducing method where citrate was used as reducing/stabilizing agent. The prepared NPs were characterized with UV/Visible and transmission electron microscopic (TEM) tools. The characteristic peak in UV/Visible at 525, 444 and 531 nm for Au, Ag and Ag/Au mix NPs respectively, gave primary confirmation of prepared NPs. TEM analysis showed the size of nanoparticles as 44.04, 19.78 and 30.93 nm for Ag, Au and Ag/Au mix NPs respectively. Congo and alizarin red dye interactions studies have been performed with prepared NPs to see the removal of the pollutants from water. Congo dye has shown weaker interaction as compared to alizarin due to structural symmetry. Amongst all, the AgNPs have shown maximum 67% and 75% interactions with Congo red and alizarin respectively due to high negative charges on the surface. The Au, Ag and Au/Ag mix NPs have shown stronger interaction with bovine serum albumin (BSA) protein up to 51, 59, 55% respectively, estimated through UV/Vis and physicochemical analysis. The biological evaluations of the prepared NPs have shown their antibacterial activity against Gram + ve and –ve species showing up to 9 cm zone of inhibition. The BSA interaction and antibacterial activity of NPs reveal the importance of NPs in medicinal field. 相似文献
64.
硫醇配体保护的高核银纳米团簇具有丰富的结构和性能, 在光致发光、 生物传感、 纳米材料等方面具有广阔的应用前景. 然而, 精确控制高核Ag/S纳米团簇的尺寸和结构面临着巨大的挑战, 构建高核Ag/S纳米团簇的可行策略也一直是人们关注的焦点. 近年来, 随着合成方法和表征技术的不断发展, 高核Ag/S纳米团簇的合成和性能研究方面均取得了显著的成就. 本文总结了含20个或以上Ag原子的Ag/S纳米团簇的合成方法(直接还原法、 阴离子模板法及配体交换法), 对部分高核Ag/S纳米团簇的结构进行了探讨, 并展望了未来研究的趋势. 相似文献
65.
Abdurrahman Turksoy Samir Bouayad-Gervais Prof. Franziska Schoenebeck 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(46):e202201435
While the N-trifluoromethylation of cyclic ureas is of interest for the potential to fundamentally change the properties of these biologically relevant moieties, the single synthetic procedure known to date describing their access only gives 4,4-disubstituted or fused aromatic cyclic N-CF3 urea derivatives. We herein report an alternative approach to unleash access to the 4-monosubstituted imidazolidinone motif. The strategy relies on straightforward cyclization of readily accessible acyclic ureas, enabled by Ag-catalysis or light-assisted proton coupled electron transfer. The cyclic core is shown to be highly robust and amenable to various derivatizations, such as tandem Ni-catalysis, C−B, C−N, C−C cross couplings or C−H functionalizations, tolerating basic, nucleophilic and/or oxidizing conditions. 相似文献
66.
Jun Zhou Prof. Sha Yang Yesen Tan Huaisheng Cheng Dr. Jinsong Chai Prof. Manzhou Zhu 《化学:亚洲杂志》2021,16(19):2973-2977
The change in the valence state of nanocluster can induce remarkable changes in the properties and structure. However, achieving the valence state changes in nanoclusters is still a challenge. In this work, we use Cu2+ as dopant to “oxidize” [Ag62S12(SBut)32]2+ (4 free electrons) to obtain the new nanocluster: [Ag62−xCuxS12(SBut)32]4+ with 2 free electrons. As revealed by its structure, the [Ag62−xCuxS12(SBut)32]4+ (x=10∼21) has a similar structure to that of [Ag62S12(SBut)32]2+ precursor and all the Cu atoms occupy the surface site of nanocluster. It′s worth noting that with the Cu atoms doping, the [Ag62−xCuxS12(SBut)32]4+ nanocluster is more stable than [Ag62S12(SBut)32]2+ at higher temperature and in electrochemical cycle. This result has laid a foundation for the subsequent application and exploration. Overall, this work reveals crystals structure of a new Ag−Cu nanocluster and offers a new insight into the electron reduction/oxidation of nanocluster. 相似文献
67.
Adesola A. Adeleke Sizwe J. Zamisa Md. Shahidul Islam Kolawole Olofinsan Veronica F. Salau Chunderika Mocktar Bernard Omondi 《Molecules (Basel, Switzerland)》2021,26(5)
A series of fifteen silver (I) quinoline complexes Q1–Q15 have been synthesized and studied for their biological activities. Q1–Q15 were synthesized from the reactions of quinolinyl Schiff base derivatives L1–L5 (obtained by condensing 2-quinolinecarboxaldehyde with various aniline derivatives) with AgNO3, AgClO4 and AgCF3SO3. Q1–Q15 were characterized by various spectroscopic techniques and the structures of [Ag(L1)2]NO3 Q1, [Ag(L1)2]ClO4 Q6, [Ag(L2)2]ClO4 Q7, [Ag(L2)2]CF3SO3 Q12 and [Ag(L4)2]CF3SO3 Q14 were unequivocally determined by single crystal X-ray diffraction analysis. In vitro antimicrobial tests against Gram-positive and Gram-negative bacteria revealed the influence of structure and anion on the complexes′ moderate to excellent antibacterial activity. In vitro antioxidant activities of the complexes showed their good radical scavenging activity in ferric reducing antioxidant power (FRAP). Complexes with the fluorine substituent or the thiophene or benzothiazole moieties are more potent with IC50 between 0.95 and 2.22 mg/mL than the standard used, ascorbic acid (2.68 mg/mL). The compounds showed a strong binding affinity with calf thymus-DNA via an intercalation mode and protein through a static quenching mechanism. Cytotoxicity activity was examined against three carcinoma cell lines (HELA, MDA-MB231, and SHSY5Y). [Ag(L2)2]ClO4 Q7 with a benzothiazole moiety and [Ag(L4)2]ClO4 Q9 with a methyl substituent had excellent cytotoxicity against HELA cells. 相似文献
68.
首先采用溶剂热法将1D TiO_2纳米带均匀地穿插到片层结构组装而成的3D ZnIn_2S_4微球中,所形成的异质结构能有效抑制光生电子-空穴对。其次利用光沉积法将0D Ag纳米粒子负载在3D ZnIn_2S_4/1D TiO_2异质结构上。得益于0D Ag纳米粒子的等离子体效应及电子助催化剂作用,三元3D ZnIn_2S_4/1D TiO_2/0D Ag复合光催化剂在分解水制氢方面表现出优异的性能。在模拟太阳光照射下,ZnIn_2S_4/TiO_2/Ag复合光催化剂的产氢速率达到715μmol·g~(-1)·h~(-1),相对于ZnIn_2S_4/TiO_2、ZnIn_2S_4/P25、ZnIn_2S_4、TiO_2和P25分别提高了2.7倍、3.3倍、3.8倍、184倍和518倍。同时借助于X射线衍射、扫描电子和透射电子显微镜、X射线光电子能谱和紫外可见漫反射光谱等表征手段进一步论证了复合催化剂的优异性能。 相似文献
69.
A Combined Experimental and Theoretical Study on the Formation of Ag Filaments on β‐Ag2MoO4 Induced by Electron Irradiation
下载免费PDF全文
![点击此处可从《Particle & Particle Systems Characterization》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Juan Andrés Mateus M. Ferrer Lourdes Gracia Armando Beltran Valeria M. Longo Guilherme H. Cruvinel Ricardo L. Tranquilin Elson Longo 《Particle & Particle Systems Characterization》2015,32(6):646-651
A combined experimental and theoretical study is presented to understand the novel observed nucleation and early evolution of Ag filaments on β‐Ag2MoO4 crystals, driven by an accelerated electron beam from an electronic microscope under high vacuum. The growth process, chemical composition, and the element distribution in these filaments are analyzed in depth at the nanoscale level using field‐emission scanning electron microscopy (FE‐SEM) and transmission electron microscopy (TEM) with energy‐dispersive spectroscopy (EDS) characterization. To complement experimental results, chemical stability, structural and electronic aspects have been studied systematically using first‐principles electronic structure theory within a quantum theory of atoms in molecules (QTAIM) framework. The Ag nucleation and formation on β‐Ag2MoO4 are a result of structural and electronic changes of the AgO4 tetrahedral cluster as a constituent building block of β‐Ag2MoO4, consistent with Ag metallic formation. The formation of Ag filament transforms the β‐Ag2MoO4 semiconductor from n‐ to p‐type concomitant with the appearance of Ag defects. 相似文献
70.
《Current Applied Physics》2015,15(7):829-832
Inverted organic solar cells (OSCs) based on poly (3-hexylthiophene) (P3HT):[6,6]-phenyl-C61 butyric acid methyl ester (PCBM) bulk heterojunctions (BHJ) were fabricated with optimized ZnO/Ag/ZnO multilayer and conventional indium–tin oxide (ITO) cathode electrodes and their performance was compared. The ZnO/Ag/ZnO multilayer films showed sheet resistances in the range 3.6–3.9 Ω/sq, while ITO exhibited 14.2 Ω/sq. On the one hand, the carrier concentration gradually decreased from 1.74 × 1022 to 4.33 × 1021 cm−3 as the ZnO thickness increased from 8 to 80 nm, respectively. The transmittance of the ZnO(40 nm)/Ag(19 nm)/ZnO(40 nm) films was ∼95% at 550 nm, which is comparable to that of ITO (∼96%). The multilayer films were smooth with a root mean square (RMS) roughness of 0.81 nm. OSCs fabricated with the ZnO(40 nm)/Ag(19 nm)/ZnO(40 nm) film showed a power conversion efficiency (2.63%) comparable to that of OSCs with a conventional ITO cathode (2.71%). 相似文献