全文获取类型
收费全文 | 875篇 |
免费 | 71篇 |
国内免费 | 116篇 |
专业分类
化学 | 567篇 |
晶体学 | 6篇 |
力学 | 22篇 |
综合类 | 1篇 |
数学 | 35篇 |
物理学 | 164篇 |
综合类 | 267篇 |
出版年
2023年 | 27篇 |
2022年 | 40篇 |
2021年 | 27篇 |
2020年 | 48篇 |
2019年 | 43篇 |
2018年 | 33篇 |
2017年 | 21篇 |
2016年 | 44篇 |
2015年 | 41篇 |
2014年 | 43篇 |
2013年 | 41篇 |
2012年 | 53篇 |
2011年 | 66篇 |
2010年 | 43篇 |
2009年 | 40篇 |
2008年 | 60篇 |
2007年 | 41篇 |
2006年 | 41篇 |
2005年 | 35篇 |
2004年 | 38篇 |
2003年 | 26篇 |
2002年 | 27篇 |
2001年 | 19篇 |
2000年 | 14篇 |
1999年 | 15篇 |
1998年 | 27篇 |
1997年 | 15篇 |
1996年 | 16篇 |
1995年 | 12篇 |
1994年 | 17篇 |
1993年 | 4篇 |
1992年 | 5篇 |
1991年 | 6篇 |
1990年 | 9篇 |
1989年 | 10篇 |
1988年 | 8篇 |
1987年 | 3篇 |
1985年 | 2篇 |
1983年 | 1篇 |
1980年 | 1篇 |
排序方式: 共有1062条查询结果,搜索用时 281 毫秒
1.
多年来人们对实验教学加以重视的同时却陷入了一个误区:只重视做好课堂演示实验和学生分组实验,而忽视了课外小实验的作用.其实,经常性地引导学生自己动手,就地取材,开展课外小实验、小制作,对加强物理实验教学,加深对物理知识的理解,提高学生的分析解决问题的能力,将会起到重要的作用. 相似文献
2.
3.
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
4.
树脂吸附法处理水杨酸甲酯生产废水的研究 总被引:7,自引:0,他引:7
采用吸附树脂NDA—99处理水杨酸甲酯生产废水,结果表明该树脂时废水中的5磺基水杨酸及水杨酸均具有良好的吸附—脱附性能.废水经预处理和吸附处理后,CODCr由57000-59000mg/L降至6300mg/L左右,去除率接近89%.用IBV8%NaOH 3BVH2O作脱附剂,在温度为60℃、流量为IBV/h的条件下,脱附率接近100%,树脂可重复使用.高浓度脱附液经酸化、浓缩、冷却结晶,可回收5—磺基水杨酸,回收率为95%左右。纯度为78%。 相似文献
5.
Xianfeng?You Feng?Chen Jinlong?ZhangEmail author 《Journal of Sol-Gel Science and Technology》2005,34(2):181-187
TiO2 powders were prepared by sol–gel template method and calcined under different conditions. XRD, BET and TEM were used to characterize the TiO2 powders obtained. The photocatalytic activity of TiO2 was investigated by the degradation of methyl orange. It was found that TiO2 powder has the highest photocatalytic activity at a calcination temperature of 673 K. The effects of physical properties such as surface area, crystallinity and crystal phase on the photocatalytic activity of TiO2 were discussed. 相似文献
6.
7.
Inorganic electrides are a novel kind of ionic compounds in which the anions are electrons confined in a complex array of cavities or channels and the cations are nanoscale arrays of alkali metal ions that provide charge balance. In electrides the donated electron behaves like a low-density correlated electron gas, whereby the dimensionality of the electron gas and its electronic and magnetic properties are determined by the topology of the cavities in the host matrix. Unlike traditional electrides, in which alkali cations are encapsulated within an organic cage, inorganic electrides are thermally stable. The current inorganic electrides based on alkali metal loaded zeolites can be designed as useful reduced-dimensionality materials. Inorganic electrides are powerful reducing agents, and they are able to reduce small aromatic molecules to the radical anions within the channels of the zeolite. 相似文献
8.
9.
The chemical adsorption of H atoms on an (8,0) zigzag boron nitride nanotube is studied using the density functional theory with the supercell method. One to four H atoms per 32 B and 32 N are considered. The results show that H atoms prefer to adsorb on the top sites of adjacent B and N atoms to form an armchair chain along the tube axis. An even-odd oscillation behavior of the adsorption energy of H atoms on the tube is found, and the average adsorption energy of even H atoms is obviously bigger than that of odd H atoms. The results can be understood with the frontier orbital theory. Based on this adsorption behavior, several high-symmetric structures of H adsorbed boron nitride nanotubes with 50% and 100% coverages are studied. The pairs of lines' pattern with 50% coverage has the biggest average adsorption energy per H(2) among the chosen configurations, corresponding to approximately 4 wt % hydrogen storage. 相似文献
10.