全文获取类型
收费全文 | 2279篇 |
免费 | 93篇 |
国内免费 | 22篇 |
专业分类
化学 | 1637篇 |
晶体学 | 13篇 |
力学 | 87篇 |
综合类 | 1篇 |
数学 | 348篇 |
物理学 | 308篇 |
出版年
2024年 | 8篇 |
2023年 | 25篇 |
2022年 | 134篇 |
2021年 | 175篇 |
2020年 | 105篇 |
2019年 | 89篇 |
2018年 | 87篇 |
2017年 | 74篇 |
2016年 | 124篇 |
2015年 | 72篇 |
2014年 | 81篇 |
2013年 | 194篇 |
2012年 | 132篇 |
2011年 | 147篇 |
2010年 | 88篇 |
2009年 | 81篇 |
2008年 | 101篇 |
2007年 | 95篇 |
2006年 | 78篇 |
2005年 | 78篇 |
2004年 | 60篇 |
2003年 | 60篇 |
2002年 | 42篇 |
2001年 | 26篇 |
2000年 | 17篇 |
1999年 | 20篇 |
1998年 | 9篇 |
1997年 | 6篇 |
1996年 | 18篇 |
1995年 | 6篇 |
1994年 | 8篇 |
1993年 | 13篇 |
1992年 | 16篇 |
1991年 | 11篇 |
1990年 | 8篇 |
1989年 | 3篇 |
1988年 | 4篇 |
1987年 | 3篇 |
1986年 | 10篇 |
1985年 | 9篇 |
1984年 | 6篇 |
1983年 | 9篇 |
1982年 | 10篇 |
1980年 | 10篇 |
1979年 | 9篇 |
1978年 | 8篇 |
1976年 | 4篇 |
1975年 | 5篇 |
1974年 | 2篇 |
1971年 | 2篇 |
排序方式: 共有2394条查询结果,搜索用时 15 毫秒
71.
Souilah Mohammed Hachi Mohamed Fitri Asmae Benjelloun Adil Touimi El Khattabi Souad Benzakour Mohammed Mcharfi Mohammed Zgou Hsaine 《Research on Chemical Intermediates》2021,47(2):875-893
Research on Chemical Intermediates - A series of D–π–A architectures dyes with Coumarin-based derivatives as difluorenylaminocoumarin (DF) and diphenylaminocoumarin (DP) have been... 相似文献
72.
Increased environmental concerns and global warming have diverted focus from eco-friendly bio-composites. Naturals fibers are abundant and have low harvesting costs with adequate mechanical properties. Hazards of synthetic fibers, recycling issues, and toxic byproducts are the main driving factors in the research and development of bio-composites. Bio-composites are degradable, renewable, non-abrasive, and non-toxic, with comparable properties to those of synthetic fiber composites and used in many applications in various fields. A detailed analysis is carried out in this review paper to discuss developments in bio-composites. The review covers structure, morphology, and modifications of fiber, mechanical properties, degradable matrix materials, applications, and limitations of bio-composites. Some of the key sectors employing bio-composites are the construction, automobile, and packaging industries. Furthermore, bio-composites are used in the field of medicine and cosmetics. 相似文献
73.
74.
Basma H. Amin Mohamed I. Abou-Dobara Mostafa A. Diab Essam A. Gomaa Mohammed A. El-Mogazy Adel Z. El-Sonbati Mohamed S. EL-Ghareib Mostafa A. Hussien Hanaa M. Salama 《应用有机金属化学》2020,34(8):e5689
A novel series of mixed-ligand complexes of 5,5′-{(1E,1E′)-1,4-phenelynebis(diazene-2,1-diyl)}bis(quinolin-8-ol) (H2L1) as a primary ligand and 4-aminoantipyrine(L2) as a secondary ligand with Mn(II) ion were prepared using two general formulae: [Mn2(H2L1)2(L2)2X4].4Cl (X = OH2( 1 ), ONO2−( 2 ), Cl=nil; OAc( 3 ), Cl = nil) and [Mn2(H2L1)(L2)2(O2SO2)2]( 4 ). Free ligands and their complexes were characterized. Electronic absorption spectra of the mixed-ligand complexes indicate a distorted octahedral geometry around the central metal ion, and the anions X− are in the axial positions for all compounds. The ligands behave in a neutral bidentate manner, through nitrogen atoms and oxygen atoms of the carbonyl group (L2), whereas H2L1 coordinated through nitrogen and OH groups as a neutral bidentate ligand. All complexes do not contain coordinated water molecules, but complex ( 1 ) contains four water molecules. The water molecules are removed in a single step. The complexes exhibited magnetic susceptibility corresponding to five unpaired electrons. The antimicrobial activity of the Mn(II) mixed-ligand complexes ( 1–4 ) against two gram-positive bacteria, three local gram-negative bacteria, and three fungi species was tested. Mn(II) mixed-ligand complex ( 2 ) exhibited significant antibacterial activity against Bacillus cereus, Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, and Pseudomonas sp. Mixed-ligand complex ( 2 ) exhibited a high potential cytotoxicity against the growth of human lung cancer cells. 相似文献
75.
Samira Benmouloud Rachid Echarghaoui Si. Mohammed Sbaï 《Journal of Mathematical Analysis and Applications》2012,396(1):375-385
In this paper, by using the Lusternik–Schnirelmann category, we obtain a multiplicity result for a quasilinear elliptic system with both concave and convex nonlinearities and critical growth terms in bounded domains. 相似文献
76.
Dr. Mohammed Tariq Dr. Daniel Salavera Prof. Alberto Coronas Prof. Luis P. N. Rebelo Prof. Jose N. Canongia Lopes 《Chemphyschem》2013,14(9):1956-1968
In this work the applicability of four of the most commonly used viscosity mixing rules to [ionic liquid (IL)+molecular solvent (MS)] systems is assessed. More than one hundred (IL+MS) binary mixtures were selected from the literature to test the viscosity mixing rules proposed by 1) Hind (Hi), 2) Grunberg and Nissan (G–N), 3) Herric (He) and 4) Katti and Chaudhri (K–C). The analyses were performed by estimating the average (absolute or relative) deviations, AADs and ARDs, between the available experimental data and the predicted ideal mixture viscosity values obtained by means of each rule. The interaction terms corresponding to the adjustable parameters inherent to each rule were also calculated and their trends discussed. 相似文献
77.
78.
Ajaj Rahaf Shubyar Nasser Alashban Yazeed El-Sayed Samar Salah Tamar Al Yafei Mohammed A. Salem 《Journal of Radioanalytical and Nuclear Chemistry》2021,330(3):923-928
Journal of Radioanalytical and Nuclear Chemistry - Groundwater is the most valuable resource in arid regions, such as UAE. Estimations of natural radionuclide concentrations are important to... 相似文献
79.
Abdel-Kader Maged Saad Alam Prawez Alqarni Mohammed Hamed Salkini Mohamad Ayman 《平面色谱法杂志一现代薄层色谱法》2017,30(3):211-215
JPC – Journal of Planar Chromatography – Modern TLC - A novel, simple, and sensitive high-performance thin-layer chromatography (HPTLC) method has been successfully developed and... 相似文献
80.
Mohamed Laabd Lahoucine Atourki Hafsa Chafai Mohammed Bazzaoui Maria Elamine 《Journal of Dispersion Science and Technology》2017,38(9):1227-1233
This study sheds light on the removal of humic acid by-products (trimellitic and pyromellitic acids; TMA and PMA, respectively) from aqueous solution using conducting polypyrrole (PPy) as an effective adsorbent. The effects of experimental factors including contact time, solution pH, initial concentration, adsorbent dose, and temperature were systematically investigated. The pseudo-second-order kinetic model provides the best correlation with adsorption experimental data. The equilibrium adsorption was well described by the Langmuir model with maximum mono-layer adsorption capacities of 47.62 and 71.43?mg?g?1 for TMA and PMA, respectively. The analysis of thermodynamic parameters indicated that the adsorption process was spontaneous and endothermic in nature. In addition, we investigated the adsorption mechanism using the density functional theory (DFT) calculations. The TMA and PMA were physisorbed on the PPy surface through the formation of hydrogen bonds between carboxylic groups of adsorbate molecules and the amino group of the adsorbent. The calculated theoretical data were in good agreement with experiments. 相似文献