全文获取类型
收费全文 | 161803篇 |
免费 | 2398篇 |
国内免费 | 1210篇 |
专业分类
化学 | 89014篇 |
晶体学 | 2133篇 |
力学 | 6930篇 |
综合类 | 73篇 |
数学 | 16916篇 |
物理学 | 50345篇 |
出版年
2021年 | 1269篇 |
2020年 | 1425篇 |
2019年 | 1456篇 |
2018年 | 1721篇 |
2017年 | 1686篇 |
2016年 | 2916篇 |
2015年 | 1961篇 |
2014年 | 2898篇 |
2013年 | 6990篇 |
2012年 | 5772篇 |
2011年 | 7172篇 |
2010年 | 4936篇 |
2009年 | 4852篇 |
2008年 | 6400篇 |
2007年 | 6456篇 |
2006年 | 6010篇 |
2005年 | 5490篇 |
2004年 | 4860篇 |
2003年 | 4129篇 |
2002年 | 4118篇 |
2001年 | 4460篇 |
2000年 | 3420篇 |
1999年 | 2683篇 |
1998年 | 2305篇 |
1997年 | 2251篇 |
1996年 | 2041篇 |
1995年 | 1947篇 |
1994年 | 1927篇 |
1993年 | 1766篇 |
1992年 | 2028篇 |
1991年 | 2147篇 |
1990年 | 1951篇 |
1989年 | 1936篇 |
1988年 | 1874篇 |
1987年 | 1779篇 |
1986年 | 1706篇 |
1985年 | 2215篇 |
1984年 | 2344篇 |
1983年 | 1908篇 |
1982年 | 2084篇 |
1981年 | 1971篇 |
1980年 | 1900篇 |
1979年 | 2039篇 |
1978年 | 2203篇 |
1977年 | 2072篇 |
1976年 | 2116篇 |
1975年 | 2025篇 |
1974年 | 2077篇 |
1973年 | 2063篇 |
1972年 | 1355篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
41.
42.
I. F. Golovnev E. I. Golovneva L. A. Merzhievsky V. M. Fomin V. E. Panin 《Physical Mesomechanics》2015,18(3):179-186
Molecular dynamics simulation was performed to study the formation of cluster structure, interfaces, and surfaces with different curvature radii in a perfect nanocrystal passed through by a nonlinear wave. It is shown that this process is a type of nanostructure self-organization in response to an external energy flux with subsequent development of a strong rotational field. 相似文献
43.
Echabaane M. Hfaiedh S. Smiri B. Saidi F. Dridi C. 《Journal of Solid State Electrochemistry》2021,25(6):1797-1806
Journal of Solid State Electrochemistry - The fast and sensitive detection of copper ions would be essential for water monitoring. Herein, we report a novel development of an impedimetric sensor... 相似文献
44.
Hui Li Jian Liu Juan Zhao Huiting He Dr. Dabo Jiang Prof. Steven Robert Kirk Prof. Qiong Xu Dr. Xianxiang Liu Prof. Dulin Yin 《ChemistryOpen》2021,10(4):477-485
A series of tetraimidazolium salts with different anions was prepared and applied in the isomerization of β-pinene oxide. After examining the activity of different catalysts, a remarkable enhancement of the selectivity of perillyl alcohol (47 %) was obtained over [PEimi][HNO3]4 under mild reaction conditions and using DMSO as the solvent. Furthermore, noncovalent interactions between solvent molecules and the catalyst were found by FT-IR spectroscopy and confirmed by computational chemistry. The homogeneous catalyst showed excellent stability and was reused up to six times without significant loss. 相似文献
45.
Journal of Thermal Analysis and Calorimetry - Novel porous carbon sheets were developed as green, renewable, cost-effective, and efficient flame retardant material for thermoplastic polymers.... 相似文献
46.
Avramenko Andriy A. Shevchuk Igor V. Dmitrenko Nataliia P. Skitsko Ivan F. 《Journal of Thermal Analysis and Calorimetry》2022,147(22):12709-12719
Journal of Thermal Analysis and Calorimetry - The paper focuses on the analytical analysis of the propagation of a normal shock wave in an adiabatic gas flow with nanoparticles. A modified... 相似文献
47.
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
48.
Adly M. E. Gedawy E. M. El-Malah A. A. El-Telbany F. A. 《Russian Journal of Organic Chemistry》2019,55(8):1189-1196
Russian Journal of Organic Chemistry - Selenopheno[2,3-d]pyrimidine- and selenopheno[2,3-d][1,2,3]triazine-containing compounds were synthesized starting from... 相似文献
49.
Karen Beatriz Méndez-Rodríguez Nicté Figueroa-Vega César Arturo Ilizaliturri-Hernandez Mónica Cardona-Alvarado Jaime Antonio Borjas-García Carlos Kornhauser Juan Manuel Malacara Rogelio Flores-Ramírez Francisco Javier Pérez-Vázquez 《Biomedical chromatography : BMC》2020,34(12):e4956
Metabolomics is a potential tool for the discovery of new biomarkers in the early diagnosis of diseases. An ultra-fast gas chromatography system equipped to an electronic nose detector (FGC eNose) was used to identify the metabolomic profile of Volatile Organic Compounds (VOCs) in type 2 diabetes (T2D) urine from Mexican population. A cross-sectional, comparative, and clinical study with translational approach was performed. We recruited twenty T2D patients and twenty-one healthy subjects. Urine samples were taken and analyzed by FGC eNose. Eighty-eight compounds were identified through Kovats's indexes. A natural variation of 30% between the metabolites, expressed by study groups, was observed in Principal Component 1 and 2 with a significant difference (p < 0.001). The model, performed through a Canonical Analysis of Principal coordinated (CAP), allowed a correct classification of 84.6% between healthy and T2D patients, with a 15.4% error. The metabolites 2-propenal, 2-propanol, butane- 2,3-dione and 2-methylpropanal, were increased in patients with T2D, and they were strongly correlated with discrimination between clinically healthy people and T2D patients. This study identified metabolites in urine through FGC eNose that can be used as biomarkers in the identification of T2D patients. However, more studies are needed for its implementation in clinical practice. 相似文献
50.