全文获取类型
收费全文 | 179462篇 |
免费 | 2322篇 |
国内免费 | 609篇 |
专业分类
化学 | 100136篇 |
晶体学 | 2147篇 |
力学 | 7295篇 |
综合类 | 8篇 |
数学 | 20587篇 |
物理学 | 52220篇 |
出版年
2020年 | 1426篇 |
2019年 | 1476篇 |
2018年 | 1745篇 |
2017年 | 1732篇 |
2016年 | 3043篇 |
2015年 | 2147篇 |
2014年 | 3062篇 |
2013年 | 7662篇 |
2012年 | 6267篇 |
2011年 | 7862篇 |
2010年 | 5186篇 |
2009年 | 5078篇 |
2008年 | 7089篇 |
2007年 | 7155篇 |
2006年 | 6856篇 |
2005年 | 6291篇 |
2004年 | 5658篇 |
2003年 | 4900篇 |
2002年 | 4868篇 |
2001年 | 4766篇 |
2000年 | 3707篇 |
1999年 | 2955篇 |
1998年 | 2610篇 |
1997年 | 2596篇 |
1996年 | 2365篇 |
1995年 | 2248篇 |
1994年 | 2263篇 |
1993年 | 2061篇 |
1992年 | 2308篇 |
1991年 | 2424篇 |
1990年 | 2191篇 |
1989年 | 2188篇 |
1988年 | 2103篇 |
1987年 | 1960篇 |
1986年 | 1932篇 |
1985年 | 2533篇 |
1984年 | 2681篇 |
1983年 | 2197篇 |
1982年 | 2407篇 |
1981年 | 2259篇 |
1980年 | 2208篇 |
1979年 | 2287篇 |
1978年 | 2481篇 |
1977年 | 2337篇 |
1976年 | 2325篇 |
1975年 | 2204篇 |
1974年 | 2251篇 |
1973年 | 2221篇 |
1972年 | 1462篇 |
1971年 | 1302篇 |
排序方式: 共有10000条查询结果,搜索用时 0 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.
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
3.
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
4.
Prof. Dr. Peter Hess 《Chemphyschem》2022,23(6):e202100880
In the periodic table the position of each atom follows the ‘aufbau’ principle of the individual electron shells. The resulting intrinsic periodicity of atomic properties determines the overall behavior of atoms in two-dimensional (2D) bonding and structure formation. Insight into the type and strength of bonding is the key in the discovery of innovative 2D materials. The primary features of 2D bonding and the ensuing monolayer structures of the main-group II–VI elements result from the number of valence electrons and the change of atom size, which determine the type of hybridization. The results reveal the tight connection between strength of bonding and bond length in 2D networks. The predictive power of the periodic table reveals general rules of bonding, the bonding-structure relationship, and allows an assessment of published data of 2D materials. 相似文献
5.
Foundations of Computational Mathematics - We develop some aspects of the homological algebra of persistence modules, in both the one-parameter and multi-parameter settings, considered as either... 相似文献
6.
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
7.
Semigroup Forum - It is well known that the set of isomorphism classes of extensions of groups with abelian kernel is characterized by the second cohomology group. In this paper we generalise this... 相似文献
8.
9.
Vasile M. Loots H. Vercammen L. Bruggeman M. Verrezen F. 《Journal of Radioanalytical and Nuclear Chemistry》2022,331(8):3349-3357
Journal of Radioanalytical and Nuclear Chemistry - In this paper a study for the selection of an NPE (nonylphenol ethoxylates)—free cocktail is discussed in order to be used for our routine... 相似文献
10.
Russian Chemical Bulletin - The N-methylation of primary carboxamides is based on two consecutive reactions. The silylation of the corresponding carboxamides with chloro(chloromethyl)dimethylsilane... 相似文献