全文获取类型
收费全文 | 342371篇 |
免费 | 3199篇 |
国内免费 | 986篇 |
专业分类
化学 | 186471篇 |
晶体学 | 4942篇 |
力学 | 14349篇 |
综合类 | 12篇 |
数学 | 37416篇 |
物理学 | 103366篇 |
出版年
2020年 | 2876篇 |
2019年 | 3223篇 |
2018年 | 4370篇 |
2017年 | 4278篇 |
2016年 | 6299篇 |
2015年 | 3674篇 |
2014年 | 5804篇 |
2013年 | 14649篇 |
2012年 | 11031篇 |
2011年 | 13628篇 |
2010年 | 9614篇 |
2009年 | 9524篇 |
2008年 | 12840篇 |
2007年 | 12981篇 |
2006年 | 12098篇 |
2005年 | 11010篇 |
2004年 | 9770篇 |
2003年 | 8799篇 |
2002年 | 8733篇 |
2001年 | 9459篇 |
2000年 | 7434篇 |
1999年 | 5598篇 |
1998年 | 4881篇 |
1997年 | 4874篇 |
1996年 | 4505篇 |
1995年 | 3942篇 |
1994年 | 4005篇 |
1993年 | 3919篇 |
1992年 | 4269篇 |
1991年 | 4470篇 |
1990年 | 4180篇 |
1989年 | 4166篇 |
1988年 | 4037篇 |
1987年 | 3925篇 |
1986年 | 3751篇 |
1985年 | 4960篇 |
1984年 | 5165篇 |
1983年 | 4180篇 |
1982年 | 4617篇 |
1981年 | 4359篇 |
1980年 | 4114篇 |
1979年 | 4462篇 |
1978年 | 4705篇 |
1977年 | 4620篇 |
1976年 | 4658篇 |
1975年 | 4413篇 |
1974年 | 4457篇 |
1973年 | 4573篇 |
1972年 | 3066篇 |
1967年 | 2774篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Inas A. Abdallah Sherin F. Hammad Alaa Bedair Mohamed A. Abdelaziz Neil D. Danielson Ahmed H. Elshafeey Fotouh R. Mansour 《Biomedical chromatography : BMC》2022,36(6):e5365
Favipiravir is a potential antiviral medication that has been recently licensed for Covid-19 treatment. In this work, a gadolinium-based magnetic ionic liquid was prepared and used as an extractant in dispersive liquid–liquid microextraction (DLLME) of favipiravir in human plasma. The high enriching ability of DLLME allowed the determination of favipiravir in real samples using HPLC/UV with sufficient sensitivity. The effects of several variables on extraction efficiency were investigated, including type of extractant, amount of extractant, type of disperser and disperser volume. The maximum enrichment was attained using 50 mg of the Gd-magnetic ionic liquid (MIL) and 150 μl of tetrahydrofuran. The Gd-based MIL could form a supramolecular assembly in the presence of tetrahydrofuran, which enhanced the extraction efficiency of favipiravir. The developed method was validated according to US Food and Drug Administration bioanalytical method validation guidelines. The coefficient of determination was 0.9999, for a linear concentration range of 25 to 1.0 × 105 ng/ml. The percentage recovery (accuracy) varied from 99.83 to 104.2%, with RSD values (precision) ranging from 4.07 to 11.84%. The total extraction time was about 12 min and the HPLC analysis time was 5 min. The method was simple, selective and sensitive for the determination of favipiravir in real human plasma. 相似文献
2.
Yang T. L. Kao C. L. Kuo C. E. Yeh H. C. Li W. J. Li H. T. Chen C. Y. 《Chemistry of Natural Compounds》2022,58(5):825-827
Chemistry of Natural Compounds - A novel bibenzyl derivative, hydrangchinenin (1), was isolated from the stems of Hydrangea chinensis Maxim. (Hydrangeaceae). Its structure was determined on the... 相似文献
3.
Sakhautdinova G. F. Sakhautdinov I. M. Mustafin A. G. Yunusov M. S. 《Chemistry of Natural Compounds》2022,58(1):185-186
Chemistry of Natural Compounds - 相似文献
4.
Romanenko G. V. Fokin S. V. Bogomyakov A. S. Zueva E. M. Ovcharenko V. I. 《Journal of Structural Chemistry》2022,63(3):441-450
Journal of Structural Chemistry - The structures of Ni(II), Cu(II), and Zn(II) complexes with anions of 2,5-pyrrolyl-disubstituted nitronyl nitroxide (L1) and iminonitroxide (L2) diradicals (HL1 is... 相似文献
5.
Hassan E. A. M. Elabid A. E. A. Bashier E. O. Elagib T. H. H. 《Mechanics of Composite Materials》2022,58(2):261-270
Mechanics of Composite Materials - Carbon fiber (CF)/ polyamide (PA6) composites are one of the most promising thermoplastic materials for automobile applications. However, the interfacial... 相似文献
6.
Petrov P. A. Filippova E. A. Kompankov N. B. Sukhikh T. S. Sokolov M. N. 《Journal of Structural Chemistry》2022,63(3):470-475
Journal of Structural Chemistry - A new polymorph of the [ReCl3(MeCN)(PPh3)2] complex is synthesized and characterized by single crystal X-ray diffraction (XRD). Its recrystallization from the... 相似文献
7.
Russian Chemical Bulletin - New representatives of (O-Si)-chelate compounds, N-(fluorosilyl)methyl derivatives of N-methylacetamide, N-methylbenzamide, N-phenylacetamide, and N-phenylbenzamide,... 相似文献
8.
Russian Journal of Applied Chemistry - Recent achievements in the field of the development of preparation methods and study of structure and properties of epoxy nanocomposites with metal-containing... 相似文献
9.
Tsyganova S. I. Fetisova O. Yu. Mazurova E. N. Taran O. P. Kuznetsov B. N. 《Russian Journal of Applied Chemistry》2022,95(3):408-416
Russian Journal of Applied Chemistry - A method for the disposal of hydrolysis lignin waste based on its modification with ZnCl2 and FeCl3 and subsequent carbonization at 800°C was proposed.... 相似文献
10.
Numerical Algorithms - In this work, we propose a fractional extension of the one-dimensional nonlinear vibration problem on an elastic string. The fractional problem is governed by a hyperbolic... 相似文献