全文获取类型
收费全文 | 4362篇 |
免费 | 599篇 |
国内免费 | 1075篇 |
专业分类
化学 | 5337篇 |
晶体学 | 45篇 |
力学 | 31篇 |
综合类 | 16篇 |
物理学 | 607篇 |
出版年
2024年 | 11篇 |
2023年 | 36篇 |
2022年 | 48篇 |
2021年 | 127篇 |
2020年 | 177篇 |
2019年 | 161篇 |
2018年 | 152篇 |
2017年 | 173篇 |
2016年 | 193篇 |
2015年 | 268篇 |
2014年 | 266篇 |
2013年 | 497篇 |
2012年 | 360篇 |
2011年 | 344篇 |
2010年 | 292篇 |
2009年 | 300篇 |
2008年 | 291篇 |
2007年 | 286篇 |
2006年 | 265篇 |
2005年 | 264篇 |
2004年 | 210篇 |
2003年 | 201篇 |
2002年 | 130篇 |
2001年 | 105篇 |
2000年 | 113篇 |
1999年 | 84篇 |
1998年 | 80篇 |
1997年 | 79篇 |
1996年 | 46篇 |
1995年 | 44篇 |
1994年 | 45篇 |
1993年 | 27篇 |
1992年 | 23篇 |
1991年 | 12篇 |
1990年 | 20篇 |
1989年 | 17篇 |
1988年 | 17篇 |
1987年 | 33篇 |
1986年 | 38篇 |
1985年 | 60篇 |
1984年 | 25篇 |
1983年 | 24篇 |
1982年 | 36篇 |
1981年 | 30篇 |
1980年 | 18篇 |
1979年 | 6篇 |
1978年 | 2篇 |
排序方式: 共有6036条查询结果,搜索用时 19 毫秒
51.
A new, simple procedure to deactivate fused silica capillaries without hydrothermal treatment is proposed. Based on high temperature reactions of octamethylcyclotetrasiloxane (D4) in the presence of oxygen, this procedure results, upon coating with dimethylsilicone (SE-30), in columns which give almost symmetric peaks for as little as 150 pg of critical compounds, such as decylamine, thereby demonstrating very high inertness. A mechanism of the deactivation procedure, which, in contrast to previously developed procedures, is based on thermal reactions under aerobic conditions, is proposed. 相似文献
52.
Weihong Ji Tianlu Zhang Zhiguo Lu Jie Shen Jing Hu Yunwei Niu Zuobing Xiao Xin Zhang 《中国化学快报》2019,30(3):747-749
Mesoporous silica nanospheres loaded with sandela 803 (S803@MS-S) are prepared for application to wallpaper. The nano-fragrance has high encapsulation efficiency and property of photo-driven release. 相似文献
53.
54.
Xiaofeng Zhang Shen Lin Xinqing Chen Jiebo Chen Liuyi Yang Minghong Luo 《Frontiers of Chemistry in China》2007,2(4):419-421
Mesoporous aluminophosphate was prepared by using G4.0 poly(amido amine)dendrimer as a template and characterized by Fourier
transform infrared spectrometer (FTIR), X-ray diffraction (XRD), transmission electron microscopy (TEM) and N2 adsorption/desorption methods. Results show that the title compound exhibits a typical mesoporous structure with the average
pore size from 5 to 8 nm. The formation mechanism of the nanoporous structure using dendrimer as a template was also discussed.
__________
Translated from Journal of Fujian Normal University (Natural Science Edition), 2007, 23(2): 67–70 [译自: 福建师范大学学报 (自然科学版)] 相似文献
55.
56.
Summary The paper deals with the use of controlled-porosity glasses (CPGs) as adsorbents for HPLC. The physicochemical and chromatographic properties of small-pore CPGs are compared to the analogous properties of silica gels. The results show good correlation between them and suggest the possibility of application of CPGs as adsorbents for liquid chromatography. 相似文献
57.
手性液晶聚硅氧烷毛细管柱的制备及应用 总被引:3,自引:0,他引:3
合成了一种手性液晶侧链的聚硅氧烷固定液,并涂制成毛细管柱,此柱适合于分离各种取代基的酚类异构体。对柱效和选择性进行了评价。 相似文献
58.
Berquier Jean-Marc Nael Pascal Jupille Jacques Jacquiod Catherine 《Journal of Sol-Gel Science and Technology》2000,19(1-3):83-87
Fourier Transform Infrared transmission spectroscopy is used to characterize surfactant-templated silica films on glass. The calcination process is followed in situ and evidence for the removal of the surfactant along the Hoffman reaction is given. Once calcined, the surface of the pores of the mesoporous films is proven by deuteration experiment to be hydroxylated. Bands are attributed to isolated and hydrogen-bonded silanols. Silylation reaction with hexamethyldisilazane only occurs with isolated silanol groups. 相似文献
59.
以多聚甲醛为还原剂,采用液相还原法制备了Pt/CMK-3直接甲醇燃料电池(DMFC)阳极催化剂,并采用透射电镜和X射线衍射技术对其进行了表征. 结果表明,有序介孔碳CMK-3具有规整的二维有序孔道结构,为DMFC中电子和燃料的传输提供了方便的路径,同时它较大的比表面积使得Pt纳米粒子很好地分散在其表面; Pt/CMK-3催化剂中Pt粒子的平均粒径为2.8 nm, 小于E-TEK公司的商品化Pt/XC-72和以甲醇为还原剂制备的Pt/C-M催化剂,并且粒径分布范围窄,结晶度低. 察了Pt/CMK-3催化剂对甲醇的电催化氧化性能,发现Pt/CMK-3催化剂对甲醇氧化的电催化性能优于Pt/XC-72和Pt/C-M催化剂. 相似文献
60.
Summary The various techniques and methodologies of thermal conductivity measurement have been conventionally based on the determination of the rate of directional heat flow through a material having a unit temperature differential between its opposing faces. The constancy of this rate depends on the material density, its thermal resistance and the heat flow path itself. The last of these variables contributes most significantly to the true value of steady-state axial and radial heat dissipation depending on the magnitude of transient thermal diffusivity along these directions. The purpose of this paper is to exemplify the above features by defined parameters of heat flow measurement by existing methodologies. No new method is proposed here. Importantly, the relationship between the rate of heat transfer, total heat transferred and thermal conductivity at a given temperature under steady-state conditions for a fixed heat flow path will be illustrated. 相似文献