全文获取类型
收费全文 | 2066篇 |
免费 | 210篇 |
国内免费 | 257篇 |
专业分类
化学 | 499篇 |
晶体学 | 15篇 |
力学 | 229篇 |
综合类 | 37篇 |
数学 | 657篇 |
物理学 | 1096篇 |
出版年
2024年 | 4篇 |
2023年 | 10篇 |
2022年 | 28篇 |
2021年 | 27篇 |
2020年 | 41篇 |
2019年 | 52篇 |
2018年 | 50篇 |
2017年 | 55篇 |
2016年 | 48篇 |
2015年 | 52篇 |
2014年 | 86篇 |
2013年 | 164篇 |
2012年 | 108篇 |
2011年 | 148篇 |
2010年 | 140篇 |
2009年 | 115篇 |
2008年 | 129篇 |
2007年 | 134篇 |
2006年 | 148篇 |
2005年 | 138篇 |
2004年 | 115篇 |
2003年 | 85篇 |
2002年 | 85篇 |
2001年 | 77篇 |
2000年 | 76篇 |
1999年 | 63篇 |
1998年 | 59篇 |
1997年 | 32篇 |
1996年 | 39篇 |
1995年 | 39篇 |
1994年 | 22篇 |
1993年 | 13篇 |
1992年 | 15篇 |
1991年 | 21篇 |
1990年 | 12篇 |
1989年 | 18篇 |
1988年 | 8篇 |
1987年 | 12篇 |
1986年 | 7篇 |
1985年 | 12篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1982年 | 7篇 |
1981年 | 9篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1977年 | 4篇 |
1974年 | 3篇 |
1973年 | 7篇 |
1957年 | 1篇 |
排序方式: 共有2533条查询结果,搜索用时 406 毫秒
1.
Gas-phase 21Ne nuclear magnetic resonance spectra were measured at the natural abundance of 21Ne isotope for samples consisting of pressurized neon up to 60 bar at room temperature and applying the magnetic field of the strength B0 = 11.7574 T. It showed that the nuclear magnetic resonance frequency is linearly dependent on the density of gaseous neon. The resonance frequency was extrapolated to the zero-density point, and it permitted the determination of the 21Ne nuclear magnetic moment, μ(21Ne) = 0.6617774(10) μN. The present value of μ(21Ne) is not influenced by the bulk magnetic susceptibility of neon and interactions between neon atoms; therefore, it is more precise and reliable than the previous result obtained for μ(21Ne). 相似文献
2.
气垫导轨在刚体转动惯量测定实验中的应用 总被引:1,自引:0,他引:1
本文介绍了一种测量刚体转动惯量的新方法。即把气垫导轨和刚体转动仪结合起来来测量刚体的转动惯量,使传统的气垫导轨实验和刚体转动惯量测定实验得以更新,提高了实验测量的精度,拓展了实验内容。 相似文献
3.
利用解析和数值方法研究了在具有横向折射率周期性调制的克尔型非线性介质中光学格子孤子的传输,得到了孤子参数的演化方程以及格子孤子的形成和稳定传输的条件.结果表明:当光束的入射角小于某临界角度时,光束可被类似波导形式的路径俘获而稳定传输,该临界角随折射率调制周期、调制深度的增加而增大,且光束越窄临界值越大.此外,线性空间啁啾虽然对光束传输的中心位置没有任何影响,但会导致光束发散从而破坏格子孤子的形成和稳定传输,对此提出了采用特定功率取值来补偿啁啾作用从而形成格子孤子的方案.
关键词:
光孤子
光学格子
光传输
矩方法 相似文献
4.
We obtain exponential upper bounds for tails of distributions of generalized L-statistics based on a sample from an exponential distribution. We prove the asymptotic normality of generalized L-statistics based on a sample from the uniform distribution on [0,1] and of L-statistics with decomposed kernels (without any restrictions on the sample distribution type). 相似文献
5.
6.
Asymptotic chi-squared test statistics for testing the equality of moment vectors are developed. The test statistics proposed are generalized Wald test statistics that specialize for different settings by inserting an appropriate asymptotic variance matrix of sample moments. Scaled test statistics are also considered for dealing with nonstandard conditions. The specialization will be carried out for testing the equality of multinomial populations, and the equality of variance and correlation matrices for both normal and nonnormal data. When testing the equality of correlation matrices, a scaled version of the normal theory chi-squared statistic is proven to be an asymptotically exact chi-squared statistic in the case of elliptical data. 相似文献
7.
One influential parameter which mediates interactions between many types of molecules and biological membranes stems from
the lumped contributions of the transmembrane potential, dipole potential and the difference in the surface potentials on
both sides of a membrane. With relevance to cell physiology, such electrical features of a biomembrane are prone to undergoing
changes as a result of interactions with the aqueous surrounding. Among the most useful tools devoted to exploring changes
of electrical parameters of a lipid membrane induced by certain extracellular ions, lipid composition, and embedded membrane
peptides and proteins, are spectroscopic imaging and the inner field compensation (IFC) method. In this work we layout the
principles of a fully computerized version of the IFC method, which makes it more readily available to users. As a direct
application, we deployed this improved version of the IFC method to time-resolve changes induced by alamethicin monomers upon
membrane dipole potential, following their aggregation within an artificial lipid membrane. Intriguingly, even prior crossing
the membrane core, the membrane-bound alamethicin monomers are shown to significantly increase the dipole potential of the
monolayer they reside in. Such data further emphasize the yet less-explored interplay between membrane-based protein and peptides,
and the membrane dipole potential. 相似文献
8.
The decay process J/ψ→p X X→p P,where p,p and P are the proton,antiproton and pseudoscalar states,respectively,has been studied in terms of the angular distribution and the generalized moment analysis methods.The result shows that we can identify the spin,but cannot determine the parity of the baryon resonance state X produced in the process J/ψ→p X X→p P. 相似文献
9.
10.