全文获取类型
收费全文 | 734篇 |
免费 | 77篇 |
国内免费 | 194篇 |
专业分类
化学 | 862篇 |
晶体学 | 15篇 |
力学 | 6篇 |
综合类 | 4篇 |
数学 | 1篇 |
物理学 | 117篇 |
出版年
2023年 | 10篇 |
2022年 | 12篇 |
2021年 | 21篇 |
2020年 | 36篇 |
2019年 | 33篇 |
2018年 | 31篇 |
2017年 | 41篇 |
2016年 | 52篇 |
2015年 | 40篇 |
2014年 | 45篇 |
2013年 | 85篇 |
2012年 | 59篇 |
2011年 | 72篇 |
2010年 | 66篇 |
2009年 | 65篇 |
2008年 | 52篇 |
2007年 | 58篇 |
2006年 | 38篇 |
2005年 | 45篇 |
2004年 | 36篇 |
2003年 | 21篇 |
2002年 | 14篇 |
2001年 | 7篇 |
2000年 | 14篇 |
1999年 | 7篇 |
1998年 | 4篇 |
1997年 | 7篇 |
1996年 | 9篇 |
1995年 | 7篇 |
1994年 | 4篇 |
1993年 | 3篇 |
1992年 | 5篇 |
1989年 | 2篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1982年 | 1篇 |
排序方式: 共有1005条查询结果,搜索用时 15 毫秒
151.
采用乳液、离子缔合法制备得到明胶(Gel)/β-纳米磷酸三钙(β-TCP)复合多孔微球,其尺寸可通过控制反应的搅拌速度进行调节. SEM和光学显微镜观察表明,明胶/β-TCP复合微球尺寸在20~40 μm之间,被包敷的磷酸三钙为200 nm左右,微球内部呈多孔结构. 当m(磷酸三钙)∶m(明胶)>0.4∶1时,有大量花瓣状晶体附着于复合微球的表面,是磷酸三钙溶解和明胶分子诱导重结晶所致. XRD与IR图谱表明,磷酸三钙纳米粒子与明胶之间存在化学键合,明胶/β-纳米磷酸三钙复合微球的微观结构与自然骨相似. DSC-TGA结果显示,90%的TCP在乳化过程中与明胶复合. 本文所制备的复合微球,为添加各种药物和促骨生长因子并实现缓释提供了优良的载体. 相似文献
152.
Cobalt oxide hollow microspheres with micro- and nano-scale composite structure: Fabrication and electrochemical performance 总被引:2,自引:0,他引:2
Co3O4 hollow microspheres with micro- and nano-scale composite structure self-assembled by nanosheets were successfully fabricated by the template-free wet-chemical approach. This method is simple, facile and effective. The Co3O4 hollow microspheres with good purity and homogeneous size were well characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform IR (FTIR), thermogravimetric analysis (TGA) and inductively coupled plasma atomic emission spectrometer (ICP). The formation mechanism was deeply studied. The micro- and nano-scale composite structure constructed by the porous nanosheets promotes to improve the electrochemical properties of Co3O4 hollow microspheres. The high discharge capacity of 1048 mAh g−1 indicates it to be the potential application in electrode materials of Li-ion battery. 相似文献
153.
Protein phosphorylation is one of the most important post-translational modifications. Due to the dynamic nature and low stoichiometry of the protein phosphorylation, enrichment of phosphopeptides from proteolytic mixtures is often necessary prior to their characterization by mass spectrometry. Many metal oxides such as titanium dioxide and zirconium dioxide have been successfully applied to isolation and enrichment of phosphopeptides. Recently, niobium pentoxide was proved to have the ability for selective enrichment of phosphopeptides. Considering the proximity of tantalum to niobium, we supposed that Ta2O5 can be used as affinity probes for phosphopeptide enrichment. In the work, we synthesized Fe3O4@Ta2O5 magnetic microspheres with core–shell structure for selective enrichment of phosphopeptides. To demonstrate its ability for selective enrichment of phosphopeptides, we applied Fe3O4@Ta2O5 magnetic microspheres to isolation and enrichment of the phosphopeptides from tryptic digestion of standard proteins and real samples, and then the enriched peptides were analyzed by matrix-assisted laser desorption mass spectrometry analysis (MALDI-MS) or liquid chromatography coupled to electrospray ionization mass spectrometry (LC–ESI-MS). Experiment results demonstrate that Ta2O5 coated-magnetic microspheres show the excellent potential for selective enrichment of phosphopeptides. 相似文献
154.
Preparation of magnetic chitosan microspheres and its applications in wastewater treatment 总被引:1,自引:0,他引:1
The methods of preparation of magnetic chitosan microspheres have been introduced. In addition, their applications in the
wastewater treatment, based on different kinds of wastewater, have been reviewed, and their mechanisms have been discussed.
Supported by the Key Natural Science Foundation of China (Grant No. 50633030) 相似文献
155.
Polystyrene microspheres with an average diameter of 55 μm were prepared by suspension polymerization via oxidation of the monomer by ammonium persulfate. Poly-3-aminophenylboronic acid was grafted onto the surfaces of the polystyrene
microspheres to form polystyrene/poly-3-aminophenylboronic acid core- shell micospheres. The samples were characterized by
scanning electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy and nitrogen adsorption/desorption method.
The results show that poly-3-aminophenylboronic acid was successfully grafted to the surfaces of the polystyrene microspheres
by aromatic ring electronpairing interaction. The surfaces of the core-shell microspheres possessed a porous structure, with
the average pore diameter of 30.2 nm and the BET surface area of 193.26 m2/g.
__________
Translated from Chinese Journal of Applied Chemistry, 2008, 25(4) (in Chinese) 相似文献
156.
157.
158.
利用相分离工艺制备玉米醇溶蛋白(zein)纳米微球,微球粒径可控制在40 nm左右;经旋转蒸发制得zein溶胶体系,zein溶胶具有明显的丁达尔现象,静置数月不聚沉,Zeta电位法测得zein微球在pH值为4.0时分散性能最佳。 以纳米zein微球为固相稳定剂制备O/W型Pickering乳液,考察了zein胶体加入量、油水体积比等因素对乳液稳定性的影响。 实验结果表明,zein胶体加入量的质量分数控制为0.4%,高油水体积比将有利于Pickering乳液的长时间稳定。 基于zein分子的两亲结构和界面组装特点,提出了zein微球稳定Pickering乳液的作用机制。 相似文献
159.
Jing Yuan a b Zhenguo An a Bing Li a Jingjie Zhang a a Technical Institute of Physics Chemistry Chinese Academy of Sciences Beijing China b Graduate 《中国颗粒学报》2012,(4):475-479
Anatase TiO2 shells assembled on hollow glass microspheres(HGM)with tunable morphologies were successfully prepared through a controllable chemical precipitation method with urea as the precipitator. Thus,glass/TiO2 core/shell composite hollow spheres with low particle density(0.40 g/cm3)were fabricated.The phase structures,morphologies,particle sizes,shell thicknesses,and chemical compositions of the composite microspheres were characterized by X-ray diffraction(XRD),scanning electron microscopy (SEM),and energy dispersive X-ray spectroscopy(EDS).The morphology of the TiO2 shell can be tailored by properly monitoring the reaction system component and parameters.The probable growth mechanism and fabrication process of the core/shell products involving the nucleation and oriented growth of TiO2 nanocrystals on hollow glass microspheres was proposed.A low infrared radiation study revealed that the radiation properties of the products are greatly influenced by the unique product shell structures. A thermal conductivity study showed that the TiO2/HGM possess low thermal conductivity that is similar to that of the pristine HGMs.This work provides an additional strategy to prepare low-density thermal insulating particles with tailored morphologies and properties. 相似文献
160.
为了优化锂微粉等离子体球化的工艺,对感应耦合等离子体炬进行二维建模,将电磁场计算域扩展到等离子体放电区域之外的空气区域,利用COMSOL 软件进行多物理场模拟。得到了等离子体的电磁场、温度和速度分布,并对分布形成的物理机制进行分析。模拟发现等离子体区域线圈段存在上下两组对称的回流涡,线圈段中部靠近约束管处等离子体速度分布杂乱,有激烈的径向打壁现象,乱流预计会对约束管壁相应位置造成一条环状的破裂效果。基于模拟结果,提出在采用感应耦合等离子体球化锂微粉的工艺工程中,可以将注粉口下移,绕开上回流涡。 相似文献