全文获取类型
收费全文 | 21669篇 |
免费 | 3495篇 |
国内免费 | 2456篇 |
专业分类
化学 | 15058篇 |
晶体学 | 224篇 |
力学 | 1563篇 |
综合类 | 207篇 |
数学 | 2380篇 |
物理学 | 8188篇 |
出版年
2024年 | 71篇 |
2023年 | 414篇 |
2022年 | 737篇 |
2021年 | 814篇 |
2020年 | 869篇 |
2019年 | 834篇 |
2018年 | 709篇 |
2017年 | 609篇 |
2016年 | 1014篇 |
2015年 | 1057篇 |
2014年 | 1202篇 |
2013年 | 1576篇 |
2012年 | 1856篇 |
2011年 | 2023篇 |
2010年 | 1289篇 |
2009年 | 1230篇 |
2008年 | 1260篇 |
2007年 | 1149篇 |
2006年 | 1156篇 |
2005年 | 957篇 |
2004年 | 859篇 |
2003年 | 625篇 |
2002年 | 586篇 |
2001年 | 510篇 |
2000年 | 466篇 |
1999年 | 440篇 |
1998年 | 390篇 |
1997年 | 339篇 |
1996年 | 348篇 |
1995年 | 331篇 |
1994年 | 303篇 |
1993年 | 235篇 |
1992年 | 250篇 |
1991年 | 216篇 |
1990年 | 182篇 |
1989年 | 155篇 |
1988年 | 93篇 |
1987年 | 91篇 |
1986年 | 79篇 |
1985年 | 78篇 |
1984年 | 44篇 |
1983年 | 45篇 |
1982年 | 37篇 |
1981年 | 22篇 |
1980年 | 15篇 |
1979年 | 8篇 |
1977年 | 5篇 |
1975年 | 6篇 |
1969年 | 4篇 |
1957年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Uchiyama H Baron AQ Tsutsui S Tanaka Y Hu WZ Yamamoto A Tajima S Endoh Y 《Physical review letters》2004,92(19):197005
Phonons in nearly optimally doped HgBa(2)CuO(4+delta) were studied by inelastic x-ray scattering. The dispersion of the low-energy modes is well described by a shell model, while the Cu-O bond stretching mode at high energy shows strong softening towards the zone boundary, which deviates strongly from the model. This seems to be common in the hole-doped high-T(c) superconducting cuprates, and, based on this work, not related to a lattice distortion specific to each material. 相似文献
992.
The adsorption of cetyltrimethylammonium bromide (CTAB) on disturbed n-alkanethiolate self-assembled monolayers (SAMs) was investigated by electrochemical methods with potassium ferricyanide [K3Fe(CN)6] as a probe. Compared with the completely restrained signal at ordinary compact n-alkanethiolate SAMs, the electrochemical response of K3Fe(CN)6 at the disturbed n-alkanethiolate SAMs was partly restored and became progressively reversible in the presence of increasing concentrations of CTAB, which was employed to characterize the adsorption of cationic surfactants on hydrophobic SAMs. The effect of CTAB concentration on electrochemical impedance spectroscopy (EIS) plots indicated that CTAB experienced two different types of adsorptive behavior at the disturbed n-alkanethiolate SAMs: monomer adsorption at low concentrations below 1×10–6 M and monolayer adsorption at CTAB concentrations above 1×10–5 M. The adsorption of a series of cationic surfactants with similar structures to CTAB on disturbed n-alkanethiolate SAMs was also explored. These surfactants had similar adsorptive behavior and showed nearly linear adsorption characteristics with the length of their hydrophobic tails. 相似文献
993.
994.
995.
996.
Using FT-Raman spectroscopy, column wicking technique and the equations of Washburn as well as van Oss et al., the surface properties of xylan, the main component in hemicelluloses, has been characterized and estimated. Raman spectrum showed that xylan has been structured by acetyl group and methyl-bonded glucurono group. Obtained results show that the surface free energy of xylan is higher in comparison with literature reported values for cellulose because the former has a larger Lifshitz–van der Waals component than the latter. However, xylan has been found to have very smaller polarity and orientation data than that of cellulose. 相似文献
997.
The present study reported the ionic liquid (IL) used as running electrolyte in capillary zone electrophoresis (CZE) with beta-cyclodextrin (beta-CD) as modifier for the separation of anthraquinones extract of Chinese herb Paedicalyx attopevensis Pierre ex Pitard. The optimum running electrolyte was 60 mM 1-butyl-3-methylimizolium tetrafluoroborate (1B-3MI-TFB) solution with 4.0 mM beta-CD. The pH was 10.00 and the applied voltage was 20 kV with detection at 254 nm. The present method was compared with others and the effect of Joule heating was discussed as well. More significantly, this method is the development of the ionic liquids application to the capillary electrophoresis. 相似文献
998.
A facile and efficient nucleophilic difluoromethylation of primary alkyl halides has been disclosed through a novel nucleophilic substitution-reductive desulfonylation strategy, using difluoromethyl phenyl sulfone as a difluoromethyl anion ("CF(2)H(-)") equivalent. 相似文献
999.
Let X
1, X
2,... be a sequence of i.i.d. non-negative random variables with heavy tails. W e study logarithmic asymptotics for the distributions of the partial sums S
n
= X
1 + ··· + X
n
. Our main interest is in the crude estimates P(S
n
> n
x
) n
–x + 1 for appropriate values of x where is a specific parameter. The related conjecture proposed by Gantert (Stat. Probab. Lett. 49, 113–118) is investigated. 相似文献
1000.
深沪股市收益率分布特征的统计分析 总被引:8,自引:0,他引:8
本文通过对深沪两地股票市场的股指收益率数据进行分析,发现两地股票收益率分布均呈现"尖峰厚尾"反正态特征,本文通过引入Laplace分布代替过去人们常用的正态分布去刻画收益率分布,结果显示Laplace分布比正态分布拟合效率有了明显的提高。 相似文献