全文获取类型
收费全文 | 10772篇 |
免费 | 452篇 |
国内免费 | 131篇 |
专业分类
化学 | 7611篇 |
晶体学 | 98篇 |
力学 | 529篇 |
综合类 | 3篇 |
数学 | 1289篇 |
物理学 | 1825篇 |
出版年
2024年 | 24篇 |
2023年 | 97篇 |
2022年 | 494篇 |
2021年 | 446篇 |
2020年 | 371篇 |
2019年 | 457篇 |
2018年 | 456篇 |
2017年 | 377篇 |
2016年 | 616篇 |
2015年 | 431篇 |
2014年 | 584篇 |
2013年 | 1092篇 |
2012年 | 840篇 |
2011年 | 796篇 |
2010年 | 563篇 |
2009年 | 460篇 |
2008年 | 507篇 |
2007年 | 455篇 |
2006年 | 320篇 |
2005年 | 328篇 |
2004年 | 205篇 |
2003年 | 197篇 |
2002年 | 165篇 |
2001年 | 86篇 |
2000年 | 62篇 |
1999年 | 68篇 |
1998年 | 44篇 |
1997年 | 54篇 |
1996年 | 50篇 |
1995年 | 36篇 |
1994年 | 42篇 |
1993年 | 23篇 |
1992年 | 40篇 |
1991年 | 35篇 |
1990年 | 33篇 |
1989年 | 41篇 |
1988年 | 37篇 |
1987年 | 37篇 |
1986年 | 33篇 |
1985年 | 41篇 |
1984年 | 38篇 |
1983年 | 23篇 |
1982年 | 31篇 |
1981年 | 21篇 |
1980年 | 23篇 |
1979年 | 22篇 |
1978年 | 19篇 |
1977年 | 13篇 |
1976年 | 16篇 |
1974年 | 16篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
911.
Janjua Muhammad M. Khan Najeeb U. Khan Waqar A. Khan Waseem S. Ali Hafiz Muhammad 《Journal of Thermal Analysis and Calorimetry》2021,143(3):2039-2052
Journal of Thermal Analysis and Calorimetry - The thermal performance of an isothermal horizontal cylinder with different selected cross sections in cross-flow was investigated numerically. These... 相似文献
912.
Sajjad Uzair Hussain Imtiyaz Hamid Khalid Bhat Showkat Ahmad Ali Hafiz Muhammad Wang Chi-Chuan 《Journal of Thermal Analysis and Calorimetry》2021,145(4):1911-1923
Journal of Thermal Analysis and Calorimetry - Owing to the high nucleation site density and relatively robust behavior, sintered coated surfaces are of great interest for thermal management via... 相似文献
913.
Waqas Hassan Farooq Umar Khan Shan Ali Alshehri Hashim M. Goodarzi Marjan 《Journal of Thermal Analysis and Calorimetry》2021,145(4):2033-2044
Journal of Thermal Analysis and Calorimetry - The increasing need of the modern era of technology for better ways to increase the heat transfer performance of thermal systems has made nanoliquids... 相似文献
914.
Soumaya Touzani Hamada Imtara Shankar Katekhaye Hamza Mechchate Hayat Ouassou Ali S. Alqahtani Omar M. Noman Fahd A. Nasr Hugo Fearnley James Fearnley Anant Paradkar Ilham ElArabi Badiaa Lyoussi 《Molecules (Basel, Switzerland)》2021,26(15)
The biological activities of propolis samples are the result of many bioactive compounds present in the propolis. The aim of the present study was to determine the various chemical compounds of some selected propolis samples collected from Palestine and Morocco by the High-Performance Liquid Chromatography–Photodiode Array Detection (HPLC-PDA) method, as well as the antioxidant and antibacterial activities of this bee product. The chemical analysis of propolis samples by HPLC-PDA shows the cinnamic acid content in the Palestinian sample is higher compared to that in Moroccan propolis. The results of antioxidant activity demonstrated an important free radical scavenging activity (2,2-Diphenyl-1-picrylhydrazyl (DPPH); 2,2′-azino-bis 3-ethylbenzothiazoline-6-sulphonic acid (ABTS) and reducing power assays) with EC50 values ranging between 0.02 ± 0.001 and 0.14 ± 0.01 mg/mL. Additionally, all tested propolis samples possessed a moderate antibacterial activity against bacterial strains. Notably, Minimum Inhibitory Concentrations (MICs) values ranged from 0.31 to 2.50 mg/mL for Gram-negative bacterial strains and from 0.09 to 0.125 mg/mL for Gram-positive bacterial strains. The S2 sample from Morocco and the S4 sample from Palestine had the highest content of polyphenol level. Thus, the strong antioxidant and antibacterial properties were apparently due to the high total phenolic and flavone/flavonol contents in the samples. As a conclusion, the activities of propolis samples collected from both countries are similar, while the cinnamic acid in the Palestinian samples was more than that of the Moroccan samples. 相似文献
915.
Elsayim Rasha AlOthman Monerah Alkhulaifi Manal Ali Rehab Doud Mohammed Elnagar Doaa 《Molecules (Basel, Switzerland)》2021,26(7)
Recently, concerns have been raised globally about antimicrobial resistance, the prevalence of which has increased significantly. Carbapenem-resistant Klebsiella pneumoniae (KPC) is considered one of the most common resistant bacteria, which has spread to ICUs in Saudi Arabia. This study was established to investigate the antibacterial activity of biosynthesized zinc oxide nanoparticles (ZnO-NPs) against KPC in vitro and in vivo. In this study, we used the aqueous extract of Acacia nilotica (L.) fruits to mediate the synthesis of ZnO-NPs. The nanoparticles produced were characterized by UV-vis spectroscopy, zetasizer and zeta potential analyses, X-ray diffraction (XRD) spectroscopy, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and transmission electron microscopy (TEM). The antimicrobial activity of ZnO-NPs against KPC was determined via the well diffusion method, and determining minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC), the results showed low MIC and MBC when compared with the MIC and MBC of Imipenem and Meropenem antibiotics. The results of in vitro analysis were supported by the results upon applying ZnO-NP ointment to promote wound closure of rats, which showed better wound healing than the results with imipenem ointment. The biosynthesized ZnO-NPs showed good potential for use against bacteria due to their small size, applicability, and low toxicity to human cells. 相似文献
916.
Lamya H. Al-Wahaibi Ahmed A. B. Mohamed Samar S. Tawfik Hanan M. Hassan Ali A. El-Emam 《Molecules (Basel, Switzerland)》2021,26(8)
The reaction of 5-(3,4-dimethoxyphenyl)-1,3,4-oxadiazole-2(3H)-thione 3 with formaldehyde solution and primary aromatic amines or 1-substituted piperazines, in ethanol at room temperature yielded the corresponding N-Mannich bases 3-arylaminomethyl-5-(3,4-dimethoxyphenyl)-1,3,4-oxadiazole-2(3H)-thiones 4a–l or 3-[(4-substituted piperazin-1-yl)methyl]-5-(3,4-dimethoxyphenyl)-1,3,4-oxadiazole-2(3H)-thiones 5a–d, respectively. The in vitro inhibitory activity of compounds 4a–l and 5a–d was assessed against pathogenic Gram-positive, Gram-negative bacteria, and the yeast-like pathogenic fungus Candida albicans. The piperazinomethyl derivatives 5c and 5d displayed broad-spectrum antibacterial activities the minimal inhibitory concentration (MIC) 0.5–8 μg/mL) and compounds 4j, 4l, 5a, and 5b showed potent activity against the tested Gram-positive bacteria. In addition, the anti-proliferative activity of the compounds was evaluated against prostate cancer (PC3), human colorectal cancer (HCT-116), human hepatocellular carcinoma (HePG-2), human epithelioid carcinoma (HeLa), and human breast cancer (MCF7) cell lines. The optimum anti-proliferative activity was attained by compounds 4l, 5a, 5c, and 5d. 相似文献
917.
Mohammad Shahidul Islam M. Ali Abdullah Mohammed Al-Majid Abdullah Saleh Alamary Saeed Alshahrani Sammer Yousuf Muhammad Iqbal Choudhary Assem Barakat 《Molecules (Basel, Switzerland)》2021,26(8)
The Friedel–Crafts reaction between substituted indoles as nucleophiles with chalcones-based benzofuran and benzothiophene scaffolds was carried out by employing a highly efficient bimetallic iron–palladium catalyst system. This catalytic approach produced the desired bis-heteroaryl products with low catalyst loading, a simple procedure, and with acceptable yield. All synthesized indole scaffolds 3a–3s were initially evaluated for their cytotoxic effect against human fibroblast BJ cell lines and appeared to be non-cytotoxic. All non-cytotoxic compounds 3a–3s were then evaluated for their anticancer activities against cervical cancer HeLa, prostate cancer PC3, and breast cancer MCF-7 cell lines, in comparison to standard drug doxorubicin, with IC50 values 1.9 ± 0.4 µM, 0.9 ± 0.14 µM and 0.79 ± 0.05 µM, respectively, and appeared to be moderate to weak anticancer agents. Fluoro-substituted chalcone moiety-containing compounds, 3b appeared to be the most active member of the series against cervical HeLa (IC50 = 8.2 ± 0.2 µM) and breast MCF-7 cancer cell line (IC50 = 12.3 ± 0.04 µM), whereas 6-fluroindol-4-bromophenyl chalcone-containing compound 3e (IC50 = 7.8 ± 0.4 µM) appeared to be more active against PC3 prostate cancer cell line. 相似文献
918.
Mohammad Baghery Mahmoudian Ali Reza Nejad Ahmad Iran 《Russian Journal of Electrochemistry》2021,57(6):567-579
Russian Journal of Electrochemistry - Zinc selenide has applications in the fabrication of low-cost solar cells and optoelectronic devices. Due to its optical properties and large direct bandgap,... 相似文献
919.
Doaa A. Osman Mario A. Macías Lamya H. Al-Wahaibi Nora H. Al-Shaalan Luke S. Zondagh Jacques Joubert Santiago Garcia-Granda Ali A. El-Emam 《Molecules (Basel, Switzerland)》2021,26(17)
The solid-state structural analysis and docking studies of three adamantane-linked 1,2,4-triazole derivatives are presented. Crystal structure analyses revealed that compound 2 crystallizes in the triclinic P-1 space group, while compounds 1 and 3 crystallize in the same monoclinic P21/c space group. Since the only difference between them is the para substitution on the aryl group, the electronic nature of these NO2 and halogen groups seems to have no influence over the formation of the solid. However, a probable correlation with the size of the groups is not discarded due to the similar intermolecular disposition between the NO2/Cl substituted molecules. Despite the similarities, CE-B3LYP energy model calculations show that pairwise interaction energies vary between them, and therefore the total packing energy is affected. HOMO-LUMO calculated energies show that the NO2 group influences the reactivity properties characterizing the molecule as soft and with the best disposition to accept electrons. Further, in silico studies predicted that the compounds might be able to inhibit the 11β-HSD1 enzyme, which is implicated in obesity and diabetes. Self- and cross-docking experiments revealed that a number of non-native 11β-HSD1 inhibitors were able to accurately dock within the 11β-HSD1 X-ray structure 4C7J. The molecular docking of the adamantane-linked 1,2,4-triazoles have similar predicted binding affinity scores compared to the 4C7J native ligand 4YQ. However, they were unable to form interactions with key active site residues. Based on these docking results, a series of potentially improved compounds were designed using computer aided drug design tools. The docking results of the new compounds showed similar predicted 11β-HSD1 binding affinity scores as well as interactions to a known potent 11β-HSD1 inhibitor. 相似文献