全文获取类型
收费全文 | 3247篇 |
免费 | 111篇 |
国内免费 | 32篇 |
专业分类
化学 | 2226篇 |
晶体学 | 14篇 |
力学 | 92篇 |
综合类 | 1篇 |
数学 | 632篇 |
物理学 | 425篇 |
出版年
2023年 | 19篇 |
2022年 | 80篇 |
2021年 | 88篇 |
2020年 | 79篇 |
2019年 | 69篇 |
2018年 | 72篇 |
2017年 | 50篇 |
2016年 | 125篇 |
2015年 | 108篇 |
2014年 | 126篇 |
2013年 | 192篇 |
2012年 | 245篇 |
2011年 | 273篇 |
2010年 | 173篇 |
2009年 | 167篇 |
2008年 | 243篇 |
2007年 | 214篇 |
2006年 | 204篇 |
2005年 | 153篇 |
2004年 | 127篇 |
2003年 | 115篇 |
2002年 | 104篇 |
2001年 | 36篇 |
2000年 | 30篇 |
1999年 | 29篇 |
1998年 | 19篇 |
1997年 | 16篇 |
1996年 | 26篇 |
1995年 | 19篇 |
1994年 | 16篇 |
1993年 | 23篇 |
1992年 | 18篇 |
1991年 | 8篇 |
1990年 | 14篇 |
1989年 | 4篇 |
1988年 | 11篇 |
1986年 | 8篇 |
1985年 | 7篇 |
1984年 | 6篇 |
1982年 | 6篇 |
1981年 | 7篇 |
1979年 | 7篇 |
1978年 | 6篇 |
1977年 | 3篇 |
1976年 | 4篇 |
1975年 | 4篇 |
1974年 | 8篇 |
1973年 | 3篇 |
1971年 | 3篇 |
1970年 | 4篇 |
排序方式: 共有3390条查询结果,搜索用时 0 毫秒
21.
A convenient procedure of synthesis of N-carbamoyl-protected propargylic amines substituted with a cyclopropyl group from α-amido sulfones and cyclopropylacetylene is described. The reaction is catalyzed by a chiral BINOL-type zinc complex and provides the corresponding products in good yields and enantioselectivities. 相似文献
22.
Jacques-Aurlien Sergent Hilarion Mathouet Christian Hulen Pedro Lameiras Marc Feuilloley Abdelhakim Elomri Nour-Eddine Lomri 《Molecules (Basel, Switzerland)》2022,27(9)
To develop new therapeutic molecules, it is essential to understand the biological effects and targets of clinically relevant compounds. In this article, we describe the extraction and characterization of two alkaloids from the roots of Isolona hexaloba—curine and guattegaumerine. The effect of these alkaloids on the multidrug efflux pump ABCB1 (MDR1/P-Glycoprotein) and their antiproliferative properties were studied. Compared to verapamil, a widely used inhibitor of P-gp, curine and guattegaumerine were found to be weak inhibitors of MDR1/P-Glycoprotein. The highest inhibition of efflux produced by verapamil disappeared in the presence of curine or guattegaumerine as competitors, and the most pronounced effect was achieved with curine. Altogether, this work has provided new insights into the biological effects of these alkaloids on the rat Mdr1b P-gp efflux mechanism and would be beneficial in the design of potent P-gp inhibitors. 相似文献
23.
We present a simplified correlation for calculating the dissolved gas moles in a pendant drop during the diffusion time, for several drop shapes. After this correlation is determined, the Yang and Gu (Ind Eng Chem Res 44:4474–4483, 2005) dynamic pendant drop volume analysis (DPDVA) method for calculation of mass diffusivity from the pendant drop volume variation against time can be used. We solved the differential equation in cylindrical coordinates for the mass transfer model of the gas diffusion into the liquid inside the pendant drop, using a different characteristic length (LC), instead of the outer radius of the syringe needle (rn) used in Yang and Gu (Ind Eng Chem Res 44:4474–4483, 2005) for defining the dimensionless variables. LC is the relationship between the pendant drop volume and its mass transfer surface area at the initial conditions. The generalized correlation saves time, simplifies the method application and the deviations in the diffusion coefficient calculation respect to the complete Yang and Gu model are below 6%. 相似文献
24.
25.
26.
27.
28.
Lie symmetries and solitons in nonlinear systems with spatially inhomogeneous nonlinearities 总被引:1,自引:0,他引:1
Belmonte-Beitia J Pérez-García VM Vekslerchik V Torres PJ 《Physical review letters》2007,98(6):064102
Using Lie group theory and canonical transformations, we construct explicit solutions of nonlinear Schr?dinger equations with spatially inhomogeneous nonlinearities. We present the general theory, use it to show that localized nonlinearities can support bound states with an arbitrary number solitons, and discuss other applications of interest to the field of nonlinear matter waves. 相似文献
29.
We study special regularity and decay properties of solutions to the IVP associated to the k-generalized KdV equations. In particular, for datum u 0 ∈ H 3/4+ (?) whose restriction belongs to H l ((b, ∞)) for some l ∈ ?+ and b ∈ ? we prove that the restriction of the corresponding solution u(·, t) belongs to H l ((β, ∞)) for any β ∈ ? and any t ∈ (0, T). Thus, this type of regularity propagates with infinite speed to its left as time evolves. 相似文献
30.