全文获取类型
收费全文 | 2671篇 |
免费 | 157篇 |
国内免费 | 524篇 |
专业分类
化学 | 3101篇 |
晶体学 | 8篇 |
力学 | 11篇 |
综合类 | 11篇 |
数学 | 3篇 |
物理学 | 218篇 |
出版年
2024年 | 2篇 |
2023年 | 18篇 |
2022年 | 38篇 |
2021年 | 43篇 |
2020年 | 69篇 |
2019年 | 60篇 |
2018年 | 55篇 |
2017年 | 89篇 |
2016年 | 95篇 |
2015年 | 75篇 |
2014年 | 101篇 |
2013年 | 272篇 |
2012年 | 111篇 |
2011年 | 144篇 |
2010年 | 128篇 |
2009年 | 148篇 |
2008年 | 165篇 |
2007年 | 180篇 |
2006年 | 184篇 |
2005年 | 177篇 |
2004年 | 169篇 |
2003年 | 141篇 |
2002年 | 123篇 |
2001年 | 89篇 |
2000年 | 102篇 |
1999年 | 83篇 |
1998年 | 59篇 |
1997年 | 52篇 |
1996年 | 68篇 |
1995年 | 66篇 |
1994年 | 58篇 |
1993年 | 50篇 |
1992年 | 48篇 |
1991年 | 20篇 |
1990年 | 16篇 |
1989年 | 9篇 |
1988年 | 4篇 |
1987年 | 9篇 |
1986年 | 2篇 |
1985年 | 5篇 |
1984年 | 7篇 |
1983年 | 4篇 |
1982年 | 2篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 5篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
排序方式: 共有3352条查询结果,搜索用时 31 毫秒
31.
32.
取向聚对苯二甲酸乙二酯纤维的非等温结晶动力学张志英,赵家森(天津纺织工学院材料科学系天津300160)关键词取向高聚物,聚对苯二甲酸乙二酯,非等温结晶,结晶动力学研究高聚物结晶动力学常用的等温方法有光透射法、密度法、显微镜法、X-射线衍射法、差示扫描... 相似文献
33.
溶剂热还原合成Cr2O3纳米管(英) 总被引:2,自引:0,他引:2
Cr2O3 nanotubes with diameters of 80 nm and lengths of 550 nm were synthesized in a solvothermal reduction system at 180 ℃. The acetyl acetone (AcAc) and ethylene glycol (EG) were used as the chelate agent and the reductant respectively in the system. An intermediate compound-Cr(Ⅲ)(C5H7O2)3 was formed to force Cr2O3to crystallize along one direction. 相似文献
34.
制取了4-二氰基亚甲基-2-甲基-6-对二甲胺基苯乙烯基-4H-吡喃(DCM)和1,2-双(5-甲基苯并恶唑)基乙烯(DT)两种荧光分子的LB膜以及两者的混合膜,以吸收光谱和荧光光谱探讨了膜中分子的构型,微环境,发光性能等特征,发现在LB膜的缀密排布环境中DCM顺式构型的含量较之在溶液中大为增加。 相似文献
35.
Marta Fernandez-Tarrio Carmen Alvarez-Lorenzo A. Concheiro 《Journal of Thermal Analysis and Calorimetry》2007,87(1):171-178
Tetronic®comprises X-shaped copolymers formed by four poly(propylene oxide) (PPO) andpoly(ethylene oxide) (PEO) block chains bonded to an ethylene diamine centralgroup. Micellization behaviour of three representative Tetronics (T304, T904and T1307) was characterized to gain an insight into the interactions betweenthe copolymer unimers and the state of water in their solutions. The enthalpyof demicellization, recorded at 37°C in an isoperibol microcalorimeter,indicated that the process was in all cases exothermic and the enthalpy rankedin the order T1307≥T904>>T304. Micellization is entropy-driven owing tohydrophobic interactions between the PPO chains.DSC analysisshowed that the crystallization and melting peaks of the free water remainingin T304 and T904 solutions were progressively shifted toward lower temperaturesas the surfactant proportion increased, owing to a colligative effect. Boundwater corresponded to 3 water molecules per EO repeating unit. In the caseof T1307, which has longer PEO chains, a splitting of the melting peak wasobserved, one peak appearing around 0°C due to free water and anotherat –15°C due to interfacial water. As T1307 proportion raised, theenthalpy of the former decreased, whilst the enthalpy of the latter increased.In 40% T1307 solutions, interfacial water overcame the proportion of freewater; there being 1 interfacial and 3 bound water molecules per EO repeatingunit. Gaussian deconvolution of FTIR spectra also enabled to characterizethe evolution of free water as a function of Tetronic proportion. The dependenceof micellization and water interaction behaviour on Tetronics structure shouldbe taken into account to use these copolymers as drug solubilizers and micellarcarriers. 相似文献
36.
A.M. Mota M.L.Simes Gonalves J.P. Farinha J. Buffle 《Colloids and surfaces. A, Physicochemical and engineering aspects》1994,90(2-3):271-278
In order to study the influence of the adsorption of fulvic compounds on voltammetric signals and to understand better the adsorption of these compounds on hydrophobic natural water interfaces, adsorption studies of macromolecules such as poly(ethylene glycol) (HO(CH2CH2O)n) with molecular weight of 8000 were done on the mercury/water interface by a.c. voltammetry at the potential of zero charge. The maximum surface concentration, adsorption equilibrium constant and adsorption rate constant have been determined from the global adsorption mechanism, controlled by two determining steps: diffusion and kinetics of adsorption at the interface. 相似文献
37.
38.
39.
meso-四(4-磺酸苯基)卟啉与Co(Ⅱ)的显色反应的研究 总被引:3,自引:0,他引:3
本文研究了弱酸性介质中钴(Ⅱ)与TPPS4的显色反应条件。实验发现胺类化合物质子化后,不参与成络反应,而均能使TPPS4试剂的吸光度大大降低,从而提高了测定的灵敏度,Co(Ⅱ)-TPPS4络合比为1:1,ε_(426)=3.54×10 ̄5,钴含量在0~5.0μg/25mL范围内呈线性,并用于烟草、茶叶中痕量钴的测定,得到了满意的结果。 相似文献
40.
The effects of the annealing on the properties of PET/PC block copolymers, obtained by reactive blending in the presence of different catalysts and for different mixing times, have been studied. The annealing, performed in conditions that promote the crystallization, has been used to better understand the role of block length in determining the phase behaviour. The copolymers characterized by blocks with molecular weight larger than 8000 are able to reorganize towards more ordered domains. This rearrangement maintains the phase separation, as two crystalline phases are present before and after annealing, due to the immiscibility of long blocks. In copolymers characterized by blocks with molecular weight equal to about 2500, that is the higher limit for the miscibility in the amorphous state in PET/PC block copolymers studied in this work, the rearrangement of the chains during annealing causes a phase separation leading to two crystalline phases. Only in the copolymers with molecular weight of blocks lower than 1500, the very short block length hinders the crystallization: therefore, only in this case a phase separation does not take place after annealing. 相似文献