全文获取类型
收费全文 | 3939篇 |
免费 | 141篇 |
国内免费 | 538篇 |
专业分类
化学 | 3629篇 |
晶体学 | 23篇 |
力学 | 14篇 |
综合类 | 16篇 |
数学 | 5篇 |
物理学 | 225篇 |
综合类 | 706篇 |
出版年
2024年 | 2篇 |
2023年 | 22篇 |
2022年 | 53篇 |
2021年 | 44篇 |
2020年 | 80篇 |
2019年 | 76篇 |
2018年 | 89篇 |
2017年 | 102篇 |
2016年 | 94篇 |
2015年 | 76篇 |
2014年 | 132篇 |
2013年 | 349篇 |
2012年 | 194篇 |
2011年 | 157篇 |
2010年 | 160篇 |
2009年 | 205篇 |
2008年 | 238篇 |
2007年 | 255篇 |
2006年 | 250篇 |
2005年 | 251篇 |
2004年 | 222篇 |
2003年 | 201篇 |
2002年 | 182篇 |
2001年 | 141篇 |
2000年 | 131篇 |
1999年 | 112篇 |
1998年 | 104篇 |
1997年 | 93篇 |
1996年 | 102篇 |
1995年 | 85篇 |
1994年 | 99篇 |
1993年 | 71篇 |
1992年 | 64篇 |
1991年 | 42篇 |
1990年 | 38篇 |
1989年 | 28篇 |
1988年 | 18篇 |
1987年 | 13篇 |
1986年 | 9篇 |
1985年 | 4篇 |
1984年 | 7篇 |
1983年 | 2篇 |
1982年 | 5篇 |
1981年 | 7篇 |
1980年 | 1篇 |
1979年 | 6篇 |
1978年 | 1篇 |
1977年 | 1篇 |
排序方式: 共有4618条查询结果,搜索用时 15 毫秒
51.
Takeshi Ishijima Yoshiki Mizumori Kenji Kikuchi Atsushi Suzuki Takuji Okaya 《Colloid and polymer science》2005,283(7):799-804
Polymerization of vinyl acetate (VAc) in various fatty acids (carbon numbers 4–18) was carried out. Chain transfer constants to the acids were determined to be 20–35×10–4, from which the constant to a methylene group was obtained to be 0.73×10–4. Viscometry in aqueous solution of derived poly (vinyl alcohol) (PVA) showed the usual behavior in terms of Huggins constant obtained by the Schulz–Blaschkes equation for PVAs derived from fatty acid systems lower than hexadecanoic acid. PVA derived from octadecanoic acid system showed abnormality, indicating association of alkyl groups. Contact angles on surfaces of PVAs cast from aqueous solutions were measured. While those of PVA derived from lower acid systems were 62°, those of PVAs derived from higher aids were higher and increased to 92° with increase in carbon number to octadecanoic acid. Alkyl groups in the PVAs were estimated to appear on the surfaces. Surface tension of aqueous solution of the PVA derived from octadecanoic acid showed high surface activity, and depended on pH of the solution, indicating the presence and cleavage of lactone ring at the combined portion between PVA and the acid. 相似文献
52.
53.
54.
设计合成了2-(N'-乙基咔唑-3'-烯基)-8-羟基喹啉. 以UV-Vis, 1H NMR, FT-IR, 元素分析和MS进行了结构表征, 并测定了产物的光致发光(PL)性质. 运用Gaussian98量子化学程序包, 采用B3LYP密度泛函(DFT)的方法, 在6-31G(d,p)水平上对分子的几何构型进行结构优化; 预测目标产物的振动光谱, 结果表明与实验值相符. 相似文献
55.
S. V. Rykov E. D. Skakovskii V. L. Murashko L. Yu. Tychinskaya M. P. Filatova 《Russian Chemical Bulletin》1995,44(1):176-177
The influence of low acoustic fields on the photolysis of benzyl acetate in solution was investigated. A change in the contributions of alternative photolysis mechanisms is caused by destruction of solvate shells.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 180–181, January, 1995.This study was financially supported by the Russian Foundation for Basic Research (Project No. 93-02-18102). 相似文献
56.
J. Howard Rytting Danny R. McHan Takeru Higuchi David J. W. Grant 《Journal of solution chemistry》1986,15(8):693-703
Henry's law constants have been determined for -butyrolactone (BL), ethyl acetate (EA), and 2-methyl-3-pentanol (MEP) in mixtures of iso-octane (ISO) and toluene (TOL), for BL, EA, TOL, and ISO in cinnamaldehyde (CIN) and for TOL and ISO in each other and in BL. From these data and published vapor pressures, the activity coefficients at infinite dilution and the standard molar Gibbs free energy of transfer, G
2
0
of the solutes from dilute solution in ISO to dilute solution in each solvent medium have been calculated. The different behavior patterns of BL and EA are attributed to differences in their abilities to exist in different conformations possessing different dipole moments. For polar solutes, G
2
0
decreases with increasing polarizability of the solvent and with increasing dipole moment of the solute, suggesting increased contributions from dipole-induced dipole (Debye) interactions. The sigmoidal plot of G
2
0
against the change in pair potential energy calculated from the classical expressions suggests that G
2
0
seriously underestimates the strength of the Debye interactions in comparison with the London interactions. 相似文献
57.
58.
(1)测定了醋酸十二烷基铵(DAA)在CAB-O-SIL上的吸附,其等温线属双平台或LS型[1-3,5];(2)NaCl的存在使DAA的吸附增加.但不影响其低浓度下第一平台的吸附量;HCl的存在则在全浓度范围内抑制了DAA的吸附,(3)测定了CAB-O-SIL颗粒在上述各溶液中的悬浮液的稳定性;(4)根据表面形成小胶团的吸附理论(即二步模型产)[2,3,5,],并借助电导跟踪溶液中发生的变化,满意地解释了吸附和聚沉的实验结果. 相似文献
59.
The thermal decomposition of cadmium acetate dihydrate in helium and in air atmosphere has been investigated by means of a
coupled TG-DTA-MS method combined with X-ray diffraction analysis. Dehydration of Cd(CH3COO)2·2H2O is a two-stage process with Cd(CH3COO)2·H2O as intermediate. The way of Cd(CH3COO)2 decomposition strongly depends on the surrounding gas atmosphere and the rate of heating. CdO, acetone and CO2 are the primary products of decomposition in air. In helium decomposition goes by two parallel and consecutive reactions
in which intermediates, Cd and CdCO3, are formed. Metallic cadmium oxidizes and cadmium carbonate decomposes giving CdO. Some of the metallic cadmium, depending
on the heating rate and the concentration of oxygen, evaporates. Acetone is partially oxidized in secondary reactions with
oxygen.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
60.