全文获取类型
收费全文 | 347733篇 |
免费 | 4387篇 |
国内免费 | 1684篇 |
专业分类
化学 | 190918篇 |
晶体学 | 4879篇 |
力学 | 14715篇 |
综合类 | 66篇 |
数学 | 38566篇 |
物理学 | 104660篇 |
出版年
2020年 | 2693篇 |
2019年 | 2894篇 |
2018年 | 3687篇 |
2017年 | 3737篇 |
2016年 | 5706篇 |
2015年 | 3733篇 |
2014年 | 5566篇 |
2013年 | 14274篇 |
2012年 | 11709篇 |
2011年 | 14428篇 |
2010年 | 10025篇 |
2009年 | 9938篇 |
2008年 | 13398篇 |
2007年 | 13524篇 |
2006年 | 12824篇 |
2005年 | 11768篇 |
2004年 | 10416篇 |
2003年 | 9214篇 |
2002年 | 9139篇 |
2001年 | 10098篇 |
2000年 | 7750篇 |
1999年 | 5807篇 |
1998年 | 4918篇 |
1997年 | 4893篇 |
1996年 | 4714篇 |
1995年 | 4272篇 |
1994年 | 4313篇 |
1993年 | 4110篇 |
1992年 | 4505篇 |
1991年 | 4654篇 |
1990年 | 4323篇 |
1989年 | 4213篇 |
1988年 | 4113篇 |
1987年 | 4001篇 |
1986年 | 3941篇 |
1985年 | 5151篇 |
1984年 | 5323篇 |
1983年 | 4434篇 |
1982年 | 4790篇 |
1981年 | 4481篇 |
1980年 | 4228篇 |
1979年 | 4525篇 |
1978年 | 4854篇 |
1977年 | 4774篇 |
1976年 | 4865篇 |
1975年 | 4520篇 |
1974年 | 4657篇 |
1973年 | 4701篇 |
1972年 | 3489篇 |
1971年 | 2870篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
Kinetics and Catalysis - The catalytic properties of a nickel phosphide catalyst supported on silica gel in the reductive amination of carbonyl compounds were studied in a flow reactor using... 相似文献
2.
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
3.
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
4.
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
5.
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
6.
Filatova S. M. Guseva M. K. Bodrova T. G. Parshina D. V. Budanova U. A. Sebyakin Yu. L. 《Russian Journal of General Chemistry》2022,91(1):S13-S23
Russian Journal of General Chemistry - The review article traces the main trends of the synthetic approach to the solution of the problem of overcoming the resistance of pathogenic bacterial... 相似文献
7.
Set-Valued and Variational Analysis - In a Hilbert framework ℌ, we study the convergence properties of a Newton-like inertial dynamical system governed by a general maximally monotone... 相似文献
8.
Numerical Algorithms - In this paper, the block generalized product-type bi-conjugate gradient (GPBi-CG) method for solving large, sparse nonsymmetric linear systems of equations with multiple... 相似文献
9.
Kuz’mina L. G. Navasardyan M. A. Kalle P. Bezzubov S. I. 《Crystallography Reports》2021,66(3):420-423
Crystallography Reports - The crystal and molecular structures of Cl–C6H4–O–C16H33 (I) have been studied, and its differential scanning calorimetry (DSC) study is performed.... 相似文献