全文获取类型
收费全文 | 5032篇 |
免费 | 700篇 |
国内免费 | 1302篇 |
专业分类
化学 | 5906篇 |
晶体学 | 66篇 |
力学 | 51篇 |
综合类 | 32篇 |
数学 | 13篇 |
物理学 | 966篇 |
出版年
2024年 | 11篇 |
2023年 | 65篇 |
2022年 | 156篇 |
2021年 | 172篇 |
2020年 | 248篇 |
2019年 | 177篇 |
2018年 | 170篇 |
2017年 | 191篇 |
2016年 | 281篇 |
2015年 | 273篇 |
2014年 | 309篇 |
2013年 | 461篇 |
2012年 | 367篇 |
2011年 | 362篇 |
2010年 | 315篇 |
2009年 | 347篇 |
2008年 | 322篇 |
2007年 | 361篇 |
2006年 | 340篇 |
2005年 | 291篇 |
2004年 | 323篇 |
2003年 | 241篇 |
2002年 | 202篇 |
2001年 | 169篇 |
2000年 | 130篇 |
1999年 | 111篇 |
1998年 | 129篇 |
1997年 | 99篇 |
1996年 | 82篇 |
1995年 | 79篇 |
1994年 | 54篇 |
1993年 | 43篇 |
1992年 | 31篇 |
1991年 | 25篇 |
1990年 | 13篇 |
1989年 | 17篇 |
1988年 | 20篇 |
1987年 | 12篇 |
1986年 | 4篇 |
1985年 | 13篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1972年 | 2篇 |
1967年 | 1篇 |
排序方式: 共有7034条查询结果,搜索用时 15 毫秒
71.
The effects of some organic solvents and acids on the atomic fluorescence of tin in air-hydrogen flames have been examined. Ketones and alcohols greatly reduced the florescence sensitivity in fuel rich air-hydrogen flame whereas organic acids generally enhanced the fluorescence signal. The depressive effect of organic solvents was found to be highly dependent on the fuel to oxidant ratio in the flame. An attempt has been made to explain these effects, on the basis of possible reactions occurring in the flame.On leave from Institute of Chemistry, University of the Punjab, Lahore 54590, PakistanOn leave from Department of Analytical Chemistry, University of Zaragoza, Zaragoza, Spain 相似文献
72.
Preparation and characterization of nitrogen-doped TiO2 photocatalyst in different acid environments
Ye Cong Ling Xiao Jinlong Zhang Feng Chen Masakazu Anpo 《Research on Chemical Intermediates》2006,32(8):717-724
Nitrogen-doped TiO2 powders were successfully prepared by a wet method, i.e., a micro-emulsion-hydrothermal method, in different acid environments.
Several characterization techniques, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and UV-visible diffuse
reflectance spectra, were combined to determine the crystal phase, concentration and chemical states of the nitrogen doped
in TiO2. The high photocatalytic activity of the nitrogen-doped TiO2 was evaluated through the decomposition of rhodanmine B under visible light irradiation. It was suggested that the doped
nitrogen formed oxynitride (NO) and produced impurity states at higher above the valence band of TiO2. Therefore, the nitrogen doping could enhance the response of photocatalyst to the visible light and improve the photocatalytic
activity because of the narrowing of band gap of TiO2. 相似文献
73.
TiO2光催化反应及其在环境保护中的应用 总被引:8,自引:0,他引:8
本文简要介绍了TiO2光催化剂的作用机理,讨论了影响TiO2光催化效率的因素及解决途径,综述了光催化在环境保护中的最新应用。 相似文献
74.
75.
76.
77.
We have obtained novel photosensitive materials containing a semiconductor photocatalyst and a dye sensitizer. We have studied the activity of the latter in the reaction of photoreduction of methylene blue, and we consider possible mechanisms for the photocatalytic effect. 相似文献
78.
Adel Attia Markéta Zukalová Jiří Rathouský Arnošt Zukal Ladislav Kavan 《Journal of Solid State Electrochemistry》2005,9(3):138-145
A mesoporous electrode material whose structure is composed of anatase nanocrystals stabilized by alumina is reported. Powder X-ray diffraction shows the anatase phase only, but micro-Raman spectroscopy shows that the materials have a core-shell morphology with grains of bulk anatase covered by a thin rutile layer on the surface. This structure is unique when compared to analogous materials stabilized by zirconia (PNNL-1). Nitrogen adsorption isotherms demonstrate a monotonous increase in surface area and mesopore volume with increasing Al content. Thin film electrodes from these materials were characterized by lithium insertion electrochemistry. Cyclic voltammograms exhibit significant differences in Li accommodation in Al-free and Al-stabilized materials. 相似文献
79.
Liu B. Thomas P. S. Ray A. S. Williams R. P. 《Journal of Thermal Analysis and Calorimetry》2004,76(1):115-122
The effect of sampling conditions on the decomposition of electrolytic manganese dioxide using thermal methods is reported.
Significant differences were observed in the mechanism of the decomposition by simply changing the reaction environment from
a closed pan to an open pan configuration. The purge gas atmosphere was also observed to influence the decomposition mechanism.
As a product of the decomposition is oxygen, the change in the mechanism observed between the experimental conditions may
be explained in terms of the ease of removal of oxygen from the reaction site.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
80.
Djaoued Y. Badilescu Simona Ashrit P.V. Bersani D. Lottici P.P. Brüning R. 《Journal of Sol-Gel Science and Technology》2002,24(3):247-254
TiO2 nanocrystalline thin films with varying degree of porosity have been prepared using a low temperature method. TiO2 films of the anatase form have been obtained by using a polyethylene glycol (PEG) modified sol-gel method. Densification and crystallization of the films was found to result from the thermal treatment of the dip coated films in boiling water. The films have been characterized by Raman, XRD, FTIR, AFM and optical methods. Highly transparent films with transmission in excess of 85% and porosity as high as 58% are formed predominantly of anatase crystallites of dimensions of the order of 5 nm. Initial results on lithium intercalation into these films resulting in an efficient optical modulation in the visible and near infrared regions demonstrate a good potential of these films for electrochromic applications. 相似文献