全文获取类型
收费全文 | 3955篇 |
免费 | 96篇 |
国内免费 | 27篇 |
专业分类
化学 | 2715篇 |
晶体学 | 28篇 |
力学 | 105篇 |
数学 | 468篇 |
物理学 | 762篇 |
出版年
2021年 | 31篇 |
2020年 | 45篇 |
2019年 | 32篇 |
2018年 | 33篇 |
2017年 | 30篇 |
2016年 | 61篇 |
2015年 | 67篇 |
2014年 | 81篇 |
2013年 | 183篇 |
2012年 | 210篇 |
2011年 | 279篇 |
2010年 | 124篇 |
2009年 | 94篇 |
2008年 | 170篇 |
2007年 | 235篇 |
2006年 | 226篇 |
2005年 | 212篇 |
2004年 | 177篇 |
2003年 | 134篇 |
2002年 | 163篇 |
2001年 | 65篇 |
2000年 | 77篇 |
1999年 | 49篇 |
1998年 | 47篇 |
1997年 | 51篇 |
1996年 | 71篇 |
1995年 | 55篇 |
1994年 | 56篇 |
1993年 | 59篇 |
1992年 | 44篇 |
1991年 | 51篇 |
1990年 | 42篇 |
1989年 | 35篇 |
1988年 | 29篇 |
1987年 | 34篇 |
1986年 | 21篇 |
1985年 | 41篇 |
1984年 | 42篇 |
1983年 | 27篇 |
1982年 | 40篇 |
1981年 | 43篇 |
1980年 | 51篇 |
1979年 | 53篇 |
1978年 | 32篇 |
1977年 | 34篇 |
1976年 | 34篇 |
1975年 | 28篇 |
1974年 | 41篇 |
1973年 | 41篇 |
1971年 | 22篇 |
排序方式: 共有4078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.
3.
4.
5.
Neil S. TrudingerXu-Jia Wang 《Journal of Functional Analysis》2002,193(1):1-23
In this paper, we continue previous investigations into the theory of Hessian measures. We extend our weak continuity result to the case of mixed k-Hessian measures associated with k-tuples of k-convex functions, on domains in Euclidean n-space, k=1,2,…,n. Applications are given to capacity, quasicontinuity, and the Dirichlet problem, with inhomogeneous terms, continuous with respect to capacity or combinations of Dirac measures. 相似文献
6.
The N-carboethoxy precursor to (±)-tecomanine has been prepared in 11 steps from 2-methyl-1-buten-3-yne. The key step, Pauson-Khand cyclization of a methylated 5-aza-6-nonen-1-yne succeeds, but only in low yield, a consequence of the dialkyl substitution about the azaenyne framework. Nevertheless, the overall sequence to that point is one of the more efficient to be described. 相似文献
7.
8.
9.
M. D. Roberts 《Czechoslovak Journal of Physics》1992,42(2):151-158
It is shown that: i) the Weyl tensor can be expressed in terms of the sum of a tensor and its double dual, where the tensor is constructed from the covariant derivatives of the Lanczos tensor, ii) a similar expression does not exist for the Riemann tensor in electromagnetic theory, iii) the electromagnetic field cannot be identified with the differential gauge freedom of the Lanczos tensor, iv) the symmetries of Einstein Maxwell theory and the Lanczos tensor do not prohibit the identification of the electromagnetic field with the algebraic gauge freedom of the Lanczos tensor, these symmetries require a differential equation relating the electromagnetic field tensor to the algebraic gauge vector and this is given. 相似文献
10.