全文获取类型
收费全文 | 157959篇 |
免费 | 1696篇 |
国内免费 | 397篇 |
专业分类
化学 | 85573篇 |
晶体学 | 2098篇 |
力学 | 6872篇 |
综合类 | 7篇 |
数学 | 15781篇 |
物理学 | 49721篇 |
出版年
2020年 | 1153篇 |
2019年 | 1215篇 |
2018年 | 1523篇 |
2017年 | 1479篇 |
2016年 | 2559篇 |
2015年 | 1638篇 |
2014年 | 2497篇 |
2013年 | 6598篇 |
2012年 | 5148篇 |
2011年 | 6520篇 |
2010年 | 4425篇 |
2009年 | 4412篇 |
2008年 | 5909篇 |
2007年 | 5994篇 |
2006年 | 5654篇 |
2005年 | 5206篇 |
2004年 | 4589篇 |
2003年 | 4030篇 |
2002年 | 4049篇 |
2001年 | 4450篇 |
2000年 | 3435篇 |
1999年 | 2649篇 |
1998年 | 2319篇 |
1997年 | 2308篇 |
1996年 | 2097篇 |
1995年 | 1991篇 |
1994年 | 1993篇 |
1993年 | 1852篇 |
1992年 | 2109篇 |
1991年 | 2185篇 |
1990年 | 1980篇 |
1989年 | 2007篇 |
1988年 | 1930篇 |
1987年 | 1827篇 |
1986年 | 1765篇 |
1985年 | 2281篇 |
1984年 | 2423篇 |
1983年 | 1978篇 |
1982年 | 2150篇 |
1981年 | 2038篇 |
1980年 | 1953篇 |
1979年 | 2099篇 |
1978年 | 2258篇 |
1977年 | 2133篇 |
1976年 | 2166篇 |
1975年 | 2087篇 |
1974年 | 2138篇 |
1973年 | 2114篇 |
1972年 | 1381篇 |
1971年 | 1234篇 |
排序方式: 共有10000条查询结果,搜索用时 62 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.
Low-flow chromatography has a rich history of innovation but has yet to reach widespread implementation in bioanalytical applications. Improvements in pump technology, microfluidic connections, and nano-electrospray sources for MS have laid the groundwork for broader application, and innovation in this space has accelerated in recent years. This article reviews the instrumentation used for nano-flow LC, the types of columns employed, and strategies for multidimensionality of separations, which are key to the future state of the technique to the high-throughput needs of modern bioanalysis. An update of the current applications where nano-LC is widely used, such as proteomics and metabolomics, is discussed. But the trend toward biopharmaceutical development of increasingly complex, targeted, and potent therapeutics for the safe treatment of disease drives the need for ultimate selectivity and sensitivity of our analytical platforms for targeted quantitation in a regulated space. The selectivity needs are best addressed by mass spectrometric detection, especially at high resolutions, and exquisite sensitivity is provided by nano-electrospray ionization as the technology continues to evolve into an accessible, robust, and easy-to-use platform. 相似文献
5.
Alawainati F. A. Manaa H. Henari F. Z. Biyiklioglu Z. Arslan T. Jaafar A. 《Journal of Applied Spectroscopy》2021,88(5):951-957
Journal of Applied Spectroscopy - Detailed measurements of nonlinear optical properties and optical limiting for four phthalocyanine (Pc) derivatives (PcCo, PcCu, PcMn, and PcSi) are reported. The... 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.
Kopytov G. F. Malyshko V. V. Goryachko A. I. Sharafan M. V. Churkina A. V. Moiseev A. V. Shashkov D. I. Lyasota O. M. 《Russian Physics Journal》2021,64(2):255-260
Russian Physics Journal - The specific features of the sorption activity of silver nanoparticles (AgNPs) on biodegradable polymers of natural (collagen) and artificial (polyamide 6.6) origin have... 相似文献
8.
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
9.
10.