全文获取类型
收费全文 | 3126篇 |
免费 | 131篇 |
国内免费 | 6篇 |
专业分类
化学 | 1839篇 |
晶体学 | 49篇 |
力学 | 88篇 |
数学 | 699篇 |
物理学 | 588篇 |
出版年
2023年 | 18篇 |
2022年 | 37篇 |
2021年 | 67篇 |
2020年 | 100篇 |
2019年 | 92篇 |
2018年 | 150篇 |
2017年 | 117篇 |
2016年 | 189篇 |
2015年 | 124篇 |
2014年 | 163篇 |
2013年 | 357篇 |
2012年 | 200篇 |
2011年 | 243篇 |
2010年 | 192篇 |
2009年 | 142篇 |
2008年 | 188篇 |
2007年 | 171篇 |
2006年 | 102篇 |
2005年 | 76篇 |
2004年 | 56篇 |
2003年 | 55篇 |
2002年 | 44篇 |
2001年 | 26篇 |
2000年 | 15篇 |
1999年 | 14篇 |
1998年 | 23篇 |
1997年 | 9篇 |
1996年 | 13篇 |
1993年 | 5篇 |
1992年 | 8篇 |
1988年 | 6篇 |
1985年 | 10篇 |
1984年 | 7篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1981年 | 5篇 |
1980年 | 5篇 |
1979年 | 6篇 |
1977年 | 8篇 |
1976年 | 5篇 |
1975年 | 6篇 |
1974年 | 5篇 |
1957年 | 7篇 |
1955年 | 5篇 |
1954年 | 7篇 |
1889年 | 10篇 |
1886年 | 8篇 |
1885年 | 18篇 |
1884年 | 6篇 |
1883年 | 6篇 |
排序方式: 共有3263条查询结果,搜索用时 15 毫秒
1.
2.
Ad. Hesekiel 《欧洲无机化学杂志》1885,18(2):3091-3100
3.
In order to investigate the relative effects of the differences between the structures and lipophilicities of 1, 10-dioxa-4, 7, 13, 16-tetra-azacyclo-octadecane (TA-18-crown-6) and the tetrabenzyl derivative of 1,10-dioxa-4, 7, 13, 16-tetra-azacyclo-octadecane (TBTA-18-crown-6) on their extraction-abilities and -selectivities for transition metal cations, constants of the overall extraction (logK
ex) of 1:1 (M:L) complexes, the distribution (K
D) for two diluents (CH2Cl2 and CHCl3) with different dielectric constants have been determined at 25 ± 0.1 °C. The magnitude of logK
ex is largely determined by that of K
D. The equilibrium constants of TA-18-crown-6 have been compared with those of TBTA-18-crown-6. It is found that:(i) logK
ex sequences of TA-18-crown-6 and TBTA-18-crown-6 for transition metals in CH2Cl2 lie in order: Fe3+ > Cu2+ > Mn2+ > Co2+ > Cd2+ > Ni2+ > Zn2+ and Fe3+ > Cu2+ > Co2+ > Mn2+ > Ni2+ > Cd2+ > Zn2+ respectively; (ii) the stability sequences of two types of tetra-aza-crown ethers with the transition metal cations in CHCl3 are the same as follows: Fe3+ > Ni2+ > Cu2+ > Co2+ > Zn2+ > Cd2+ > Mn2+, and (iii) unusual selectivities are observed for transition metal-tetra-aza-crowns, e.g. the high Fe3+/M
n+ selectivity factors (Sf) of TA-18-crown-6, except for the competitive-extractions for the special case in CHCl3 of TBTA-18-crown-6, it was found that the Mn2+/M
n+ values were relatively higher according to the other transition metal cations. A systematic sequence in these two types of solvents is not found for a given transition metal cation in terms of the variation of selectivity with the tetra-aza-crown ethers. The results provide alternatives for the rational design of other specific ligands on the transition metal cations. 相似文献
4.
A. Peláiz-Barranco O. García-Zaldívar F. Calderón-Piñar 《Solid State Communications》2005,133(8):515-519
The Ac behaviour of PLZT 6/80/20 ferroelectric ceramics was analyzed around and above the phase transition. Two relaxation processes are identified, showing that the so-called ‘universal relaxation law’ holds for the ceramics. A critical point in the values of the Ac conductivity, around the temperature corresponding to the maximum of the dielectric losses, is observed below the transition temperature due to the relaxor behaviour. The frequency dependence of the Ac conductivity at various temperatures and the hysteresis loops show classical relaxor behaviour with a diffuse phase transition. 相似文献
5.
The vibrational dynamics of protein folding is analyzed in the framework of Tsallis statistics. We employ exact expressions
for classical harmonic oscillators by considering the unnormalized constraints. As q→1, we show that these approximations agree with the result of Gaussian network model. 相似文献
6.
7.
8.
The luminous intensity unit of candela was realized based on filter-radiometer, which is traceable to detector-based primary standard electrical substitution cryogenic radiometer (ESCR). In that realization the traditional Osram Wi41/G-type incandescent lamp and filter-radiometer consisting of an aperture, a V(λ) filter and a silicon photodiode based trap detector were used as light source and detection element, respectively. Measurement techniques of effective aperture area, spectral transmittance of V(λ) filter and absolute responsivity of trap detector are also presented. 相似文献
9.
Mustafa Çelebier Ertan Şahin Nilgün Ancın Nurşen Altuntaş Öztaş Selma Gül Öztaş 《应用有机金属化学》2007,21(10):viii-viii
The article referenced above was first published online on 30 August 2007 with incorrect pagination; the pagination has now been corrected online and in print. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
10.
The interactive two-state model of cell membrane ion channels in an electric field is formulated on the Bethe lattice by means
of the exact recursion relations. The probability of channel opening or maximum fractions of open potassium and sodium channels
are obtained by solving a non-linear algebraic equation. Using known parameters for the conventional mean-field theory the
model gives a good agreement with the experiment both at low and high trans-membrane potential values. For intermediate voltages,
the numerical results imply that collective effects are introduced by trans-membrane voltage. 相似文献