全文获取类型
收费全文 | 2953篇 |
免费 | 95篇 |
国内免费 | 3篇 |
专业分类
化学 | 2336篇 |
晶体学 | 15篇 |
力学 | 31篇 |
数学 | 304篇 |
物理学 | 365篇 |
出版年
2023年 | 17篇 |
2022年 | 58篇 |
2021年 | 100篇 |
2020年 | 74篇 |
2019年 | 54篇 |
2018年 | 55篇 |
2017年 | 49篇 |
2016年 | 121篇 |
2015年 | 113篇 |
2014年 | 112篇 |
2013年 | 193篇 |
2012年 | 210篇 |
2011年 | 290篇 |
2010年 | 184篇 |
2009年 | 137篇 |
2008年 | 200篇 |
2007年 | 151篇 |
2006年 | 152篇 |
2005年 | 148篇 |
2004年 | 80篇 |
2003年 | 80篇 |
2002年 | 81篇 |
2001年 | 33篇 |
2000年 | 19篇 |
1999年 | 39篇 |
1998年 | 32篇 |
1997年 | 23篇 |
1996年 | 23篇 |
1995年 | 15篇 |
1994年 | 10篇 |
1993年 | 10篇 |
1992年 | 17篇 |
1991年 | 7篇 |
1990年 | 9篇 |
1989年 | 11篇 |
1988年 | 9篇 |
1987年 | 8篇 |
1986年 | 10篇 |
1985年 | 8篇 |
1984年 | 16篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1981年 | 10篇 |
1980年 | 5篇 |
1979年 | 6篇 |
1978年 | 6篇 |
1977年 | 10篇 |
1976年 | 7篇 |
1974年 | 7篇 |
1973年 | 5篇 |
排序方式: 共有3051条查询结果,搜索用时 31 毫秒
81.
Giorgia Ferrari Giorgia Foca Matteo Manfredini Daniela Manzini Andrea Marchetti Lorenzo Tassi Alessandro Ulrici 《Journal of solution chemistry》2003,32(2):93-116
The density of the 2-chloroethanol (CE) + 2-methoxyethanol (ME) + 1,2-dimethoxye- thane (DME) ternary mixtures has been measured at different temperatures ranging from –10 to 80°C, and over the entire composition range. The experimental data have been used to check the validity of some relationships accounting for the dependence of the density on temperature and composition domains. Starting from the primary data, some derived quantities, such as excess molar volumes V
E, partial molar volumes
and partial excess molar volumes
, have been obtained. In these mixtures, V
E is always positive for the [CE(1) + ME(2)] binaries, while it is generally negative at all other experimental conditions, showing the greatest deviations along the binary axes corresponding to the binary subsystems in the sequence [CE(1) + DME(2)] < [CE(1) + ME(2)] < [ME(1) + DME(2)]. The results are compared and discussed to in terms of changes in molecular association and structural effects in these solvent systems. 相似文献
82.
M. Daňková E. Makrlík P. Vaňura 《Journal of Radioanalytical and Nuclear Chemistry》1997,221(1-2):251-253
From the extraction experiments and -activity measurements, the extraction constant corresponding to the Rb+(aq)+CsL+(nb)RbL+(nb)+Cs+(aq) equilibrium in the two-phase water-nitrobenzene system (L=valinomycin; aq=aqueous phase, nb=nitrobenzene phase) was evaluated in the form logK
ex (Rb+, CsL+)=0.9. Further, the stability constant of the valinomycin-rubidium complex in nitrobenzene saturated with water was calculated as log nb(RbL+)=11.7. 相似文献
83.
P. Vaňura E. Makrlík Z. Valentová 《Journal of Radioanalytical and Nuclear Chemistry》2002,253(3):527-529
Extraction of microamounts of cesium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H+B−) in the presence of dibenzo-24-crown-8 (DB24C8,L) has been investigated. The equilibrium data have been explained assuming that the complexes HL+ and CsL+ are extracted into the organic phase. The values of extraction and stability constants of the species in nitrobenzene saturated with water have been determined. 相似文献
84.
The effects of ion implantation into thin films of the GbBaCuO on Si substrates without any buffer layer at 300 and 77 K have been studied. Using H+ ions, the superconducting transition temperature, the change of electrical properties from conducting to insulating, and the crystalline to amorphous structural transition in the films were studied as a function of ion dose. The implantation energy was 150 keV. 相似文献
85.
Extraction distribution of microamounts of strontium in the water-CsCl-15-crown-5 (15C5,L)-nitrobenzene-cesium dicarbollylcobaltate system has been investigated. The equilibrium data have been explained assuming that the CsL+, CsL2
+ and SrL2
2+ complexes are extracted into the organic phase. The values of extraction and stability constants of the species in nitrobenzene saturated with water have been determined. 相似文献
86.
Stańczak P Valensin D Juszczyk P Grzonka Z Valensin G Bernardi F Molteni E Gaggelli E Kozłowski H 《Chemical communications (Cambridge, England)》2005,(26):3298-3300
The interaction between the single hexarepeat unit of chicken prion protein [ChPrP(54-59)] and Cu(II) was investigated by NMR, finding different coordination modes for the trans/trans and cis/trans isomers. 相似文献
87.
From several cesium distribution experiments with 134 Cs tracer, the exchange extraction constant corresponding to the equilibrium Ag+ (aq)+CsL+ (nb)AgL+ (nb)+Cs+ (aq) in the two-phase water-nitrobenzene system (L = 18-crown-6; aq = aqueous phase, nb = nitrobenzene phase) was determined as log K
ex (Ag+ ,CsL+ ) = -0.6±0.1. Furthermore, the stability constant of the silver — 18-crown-6 complex in nitrobenzene saturated with water was evaluated for a temperature of 25 °C: log nb (AgL+ ) = 8.2±0.1. Finally, the individual extraction constant of the species AgL+ in the water-nitrobenzene system corresponding to the equilibrium AgL+ (aq)AgL+ (nb) was calculated: K
AgL+
= O1.2±0.1. 相似文献
88.
Valensin D Luczkowski M Mancini FM Legowska A Gaggelli E Valensin G Rolka K Kozlowski H 《Dalton transactions (Cambridge, England : 2003)》2004,(9):1284-1293
Potentiometric and spectroscopic data have shown that octarepeat dimer and tetramer are much more effective ligands for Cu(II) ions than simple octapeptide. Thus, the whole N-terminal segment of prion protein due to cooperative effects, could be more effective in binding of Cu(II) than simple peptides containing a His residue. The gain of the Cu(II) binding by longer octarepeat peptides derives from the involvement of up to four imidazoles in the coordination of the first Cu(II) ion. This type of binding increases the order of the peptide structure, which allows successive metal ions for easier coordination. 相似文献
89.
Christian Roussel Alexandru T. Balaban Ulf Berg Michel Chanon Roger Gallo Gerd Klatte Joseph A. Memiaghe Jacques Metzger Daniela Oniciu Johanna Pierrot-Sanders 《Tetrahedron》1983,39(24):4209-4219
The effect of the shape of a methyl group on reactivity, which cannot be accounted for by considering a methyl group as a spherical substituent with the appropriate van der Waals radius, was considered in kinetics of alkylalion of substituted pyridines and barriers to rotation and ground state conformations of an isopropyl group attached to a planar framework. The perturbation of a methyl group by an o-methyl group is accounted for by a unique conformational explanation which involves the polyhedral shape of the methyl group. 相似文献
90.
From extraction experiments with 133Ba as a tracer, the extraction constant corresponding to the equilibrium Ba2+(aq) + 2A-(aq) + 2L(nb) BaL2
2+(nb) + 2A-(nb) in the two-phase water-nitrobenzene system (A- = picrate, L = benzo-15-crown-5; aq = aqueous phase, nb = nitrobenzene phase) was evaluated as log K
ex (BaL2
2+, 2A-) = 5.7. Furthermore, the stability constant of the benzo-15-crown-5 - barium complex in nitrobenzene saturated with water was calculated: log bnb (BaL2
2+) = 14.6. 相似文献