全文获取类型
收费全文 | 471篇 |
免费 | 52篇 |
国内免费 | 80篇 |
专业分类
化学 | 344篇 |
晶体学 | 1篇 |
力学 | 54篇 |
综合类 | 18篇 |
数学 | 71篇 |
物理学 | 115篇 |
出版年
2024年 | 1篇 |
2023年 | 7篇 |
2022年 | 6篇 |
2021年 | 14篇 |
2020年 | 14篇 |
2019年 | 12篇 |
2018年 | 12篇 |
2017年 | 9篇 |
2016年 | 13篇 |
2015年 | 21篇 |
2014年 | 34篇 |
2013年 | 30篇 |
2012年 | 21篇 |
2011年 | 25篇 |
2010年 | 20篇 |
2009年 | 29篇 |
2008年 | 30篇 |
2007年 | 34篇 |
2006年 | 26篇 |
2005年 | 29篇 |
2004年 | 24篇 |
2003年 | 23篇 |
2002年 | 23篇 |
2001年 | 17篇 |
2000年 | 13篇 |
1999年 | 15篇 |
1998年 | 11篇 |
1997年 | 13篇 |
1996年 | 16篇 |
1995年 | 10篇 |
1994年 | 10篇 |
1993年 | 5篇 |
1992年 | 10篇 |
1991年 | 5篇 |
1990年 | 5篇 |
1989年 | 4篇 |
1988年 | 3篇 |
1987年 | 4篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1982年 | 2篇 |
排序方式: 共有603条查询结果,搜索用时 18 毫秒
21.
G. G. G. Oliveira H. G. Ferraz J. S. R. Matos 《Journal of Thermal Analysis and Calorimetry》2005,79(2):267-270
Summary Taking into account the problems of desertification and agricultural practices able to provide income to the population at the semi-arid region of North-East Brazil, this work presents the results of the chemical and thermal characterization by TG and DSC of the seed derivatives of Cnidoscolus quercifolius , hereinafter called faveleira, aiming at the application of these materials as an alternative of food source for animals and for the human population at this region. The faveleira seed derivatives present thermodynamic properties similar to the ones of other foods utilized for human use, as well as an acceptable calorific value. According to TG and DSC results, was verified that the faveleira derivatives presents good thermal and oxidative stabilities. 相似文献
22.
Isothermal
titration microcalorimetry has been applied to investigate the compatibility
testing of risperidone oral solution with soft-drinks and the interaction
with tea tannin such as (–)-epigallocatechin, (–)-epicatechin,
theaflavin and their gallates. In aqueous solution, risperidone was exothermically
bound to tea tannin with binding affinity (103–104
M–1), small enthalpy and entropy changes
reflecting van der Waal’s interaction to form an insoluble complex at
1:1 molar ratio. The heat effect of risperidone titrated into soft-drinks
containing tannin was exothermic and proportional to the quantity of the complex.
While, no significant heat effect was found for risperidone titrated into
a pet-bottled water and an infusion of parched barley without tea tannin.
These results were agreed with stability testing of risperidone in some soft-drinks
by HPLC method. 相似文献
23.
高密度燃料HDF-1与橡胶的相容性研究 总被引:3,自引:0,他引:3
报道了在室温和70 ℃下橡胶材料G402氟硅胶、丁腈胶5171、丁腈胶4170、贮囊橡胶用合成的高密度燃料HDF-1浸泡后性能如伸长率、邵尔硬度、重量、面积体积的变化,并与采用3号喷气燃料(RP-3)实验结果进行对照。用红外光谱测定了燃料浸泡前后橡胶组成的变化。实验结果表明,G402氟硅胶和贮囊对于HDF-1和RP-3有相近的相容性,丁腈胶5171对HDF-1的相容性比对RP-3的相容性稍差,丁腈胶4170对HDF-1的相容性比对RP-3的相容性更差的结果。因此,丁腈胶5171和丁腈胶4170不能用于HDF-1储存和输送,原使用RP-3系统的橡胶密封件不能直接使用HDF-1。 相似文献
24.
Rigid-rod aromatic polyimdies having polydimethylsiloxane side chains were prepared for the purpose of dispersing rigid-rod molecules in silicone matrices for molecular reinforcement. The polyimides were obtained by imidizing the polyamide-acids bearing the side chains either thermally or chemically, which were synthesized by reacting 4,4′-diaminobiphenyl-terminated polysiloxane macromonomers with pyromellitic dianhydride in THF. The polyamide-acid films obtained by removing the solvent were soluble in THF, but the polyimides were insoluble in any common solvent. The polyimides showed no melting transition below 350°C on DSC analysis, at which temperature the side chain started decomposing. Although all the polyimides were anisotropic as observed by a polarizing microscope, x-ray diffraction analysis suggested the presence of only limited chain organization. Blends with linear polydimethylsiloxanes were prepared by casting the THF solution containing the polyamide-acid and the polydimethylsiloxane, followed by solvent evaporation and thermal imidization. With relatively longer side chains, the polyimides were proved to be compatibilized with polydimethylsiloxanes. © 1994 John Wiley & Sons, Inc. 相似文献
25.
Excipient compatibility of a new chemical entity was assessed using an isothermal microcalorimeter. Mixtures of an active
pharmaceutical ingredient with a primary amine group and excipients were prepared in a 1:1 ratio and compatibility monitored
by exposing to 50, 60 and 70°C in presence of 200 mL of water. The new chemical entity, a primary amine, reacted with reducing
sugars such as lactose and resulted in a brown discoloration. This reaction is the Maillard type condensation reaction between
amines and reducing sugars. The rate of reaction was dependent on the temperature with rapid degradation at higher temperatures.
No other incompatibility was apparent between the primary amine and other excipients
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
26.
A new phosphorylcholine, (6-hydroxy) hexyl-2-(trimethylammonio) ethyl phosphate (HTEP), was synthesized andcharasterized. Segmented polyurethane (SPU) containing phosphorylcholine structure was synthesized based ondiphenylmethane diisocyanate (MDI), soft segment polytetramethylene glycol (PTMG) and HTEP, with 1,4-butanediol (BD)as a chain extender. The existence of phosphorylcholine structure on the surface of SPU was revealed by attenuated totalreflectance Fourier transform infrard spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS) and water contactangle measurements. The blood compatibilities of the polymers were evaluated by hemolytic testing and a platelet-richplasma (PRP) adhesion experiment, which was viewed by scanning electron microscopy (SEM) with polyurethane as areference. The novel segmented polyurethane containing phosphorylcholine structure showed improved blood compatibility. 相似文献
27.
O. Slisenko E. Lebedev P. Pissis A. Spanoudaki E. Kontou O. Grigoryeva 《Journal of Thermal Analysis and Calorimetry》2006,84(1):15-19
The structure-property relationships of thermoplastic
polymer blends based on poly(ether-urethane) ionomer (PEUI) and ion-containing
styrene-acrylic acid copolymer (S-co-AA(K))
have been investigated by using DMTA, DSC and TGA, as well as tensile tests.
Convergence of the glass transition temperature (Tg)
values of the PEUI and the S-co-AA(K) components
in the blends studied, as compared to the individual polymers, was found and
explained by improving compatibility of the components due to increasing effective
density of physical networks formed by ion-dipole and ion-ion interactions
of ionic groups of the components. Character of E'=f(T) and E'=f(T) dependencies confirms the increase of the effective
density of physical networks in the compositions studied compared to individual
PEUI and S-co-AA(K). Improvement of end-use
properties, i.e. thermal stability and tensile properties has been found for
the PEUI/S-co-AA(K) compositions with lower
content of S-co-AA(K) (i.e. <10 mass%)
and explained by formation of additional network of intermolecular ionic bonds
between the functional groups of PEUI and S-co-AA(K). 相似文献
28.
K. Terada T. Masuda Y. Yoshihashi E. Yonemochi 《Journal of Thermal Analysis and Calorimetry》2006,85(3):675-680
Isothermal
microcalorimetry was used to evaluate excipient compatibility of solid dosage
form. Oxybutynin hydrochloride and cefaclor were used as model drugs for compatibility
test with excipients. The calorimetric data for compatibility test were compared
with those of HPLC data. Evaluation of compatibility between drug and excipient
of solid dosage form might be possible to use isothermal microcalorimetry
instead of conventional method. By using microcalorimetric method, the evaluation
of the compatibility between drug and excipient could be successfully performed
with a simple operation in a short time. The application of the isothermal
microcalorimetry would be useful for the screening test of the drug compatibility
with excipients. 相似文献
29.
林乃煊 《广东微量元素科学》1995,2(10):60-63
通过对人体五行微量元素与食物吸收微量元素影响因素分析,采用“健脾开胃”均衡食疗配方,对百草元营养包的研制作了全面的介绍和论述。经临床患者食疗结果表明:总有效率为98%.该产品达到了预期设计目标与均衡食疗要求. 相似文献
30.