全文获取类型
收费全文 | 1648篇 |
免费 | 197篇 |
国内免费 | 155篇 |
专业分类
化学 | 1240篇 |
晶体学 | 35篇 |
力学 | 67篇 |
综合类 | 15篇 |
数学 | 167篇 |
物理学 | 476篇 |
出版年
2024年 | 8篇 |
2023年 | 24篇 |
2022年 | 44篇 |
2021年 | 52篇 |
2020年 | 46篇 |
2019年 | 49篇 |
2018年 | 46篇 |
2017年 | 33篇 |
2016年 | 54篇 |
2015年 | 73篇 |
2014年 | 80篇 |
2013年 | 120篇 |
2012年 | 126篇 |
2011年 | 143篇 |
2010年 | 76篇 |
2009年 | 72篇 |
2008年 | 110篇 |
2007年 | 93篇 |
2006年 | 78篇 |
2005年 | 81篇 |
2004年 | 80篇 |
2003年 | 52篇 |
2002年 | 53篇 |
2001年 | 49篇 |
2000年 | 56篇 |
1999年 | 35篇 |
1998年 | 21篇 |
1997年 | 24篇 |
1996年 | 31篇 |
1995年 | 21篇 |
1994年 | 20篇 |
1993年 | 25篇 |
1992年 | 27篇 |
1991年 | 22篇 |
1990年 | 21篇 |
1989年 | 7篇 |
1988年 | 6篇 |
1987年 | 8篇 |
1986年 | 5篇 |
1985年 | 5篇 |
1984年 | 9篇 |
1983年 | 3篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1973年 | 1篇 |
1970年 | 2篇 |
排序方式: 共有2000条查询结果,搜索用时 15 毫秒
101.
Li Xiaojing Zhang Xiaolin Zhao Xiaodong Yu Binbin Weng Liping Li Yongtao 《Applied biochemistry and biotechnology》2019,189(2):384-395
Applied Biochemistry and Biotechnology - The microbial fuel cell (MFC) provides an inexhaustible electron acceptor to generate current and enhance the degradation of organic compounds. In MFCs with... 相似文献
102.
103.
104.
105.
We prepared hyper-oxidized graphene (HOG) as a form of graphene derivative by additional oxidation of graphene oxide (GO) sheets. HOG, which formed more functional groups and isolated conjugated clusters on the sheets, accordingly showed high solubility in water and alcohols, high transmittance and film transparence, longer fluorescence decay constant time, and enhanced fluorescence in states of solution and solid. By contrast, GO has much weaker fluorescence in solution and its fluorescence is totally quenched in solid. The influences of concentration, metallic ions, and pH on HOG fluorescence in aqueous solution were also investigated in detail. Due to HOG’s strong fluorescence, direct visualization was realized on substrates and in solution. In addition, direct 3D fluorescence visualizations of HOG phase in polymer composites were achieved. These results show the great potential of HOG in a broad range of applications, from biological labeling, probes, and drug carriers to high-performance composites and nanomanipulation. 相似文献
106.
107.
Dr. Nuo‐Wei Zhang Prof. Chuan‐Jing Huang Xiao‐Quan Zhu Jing‐Dong Xu Prof. Wei‐Zheng Weng Prof. Hui‐Lin Wan 《化学:亚洲杂志》2012,7(8):1895-1901
The effects of calcination temperature and feedstock pretreatment on the catalytic performance of Co/γ‐Al2O3 catalysts were studied for partial oxidation of methane (POM) to synthesis gas, with emphasis on the role of feedstock pretreatment. The physicochemical properties of the catalysts were characterized by N2 adsorption, X‐ray diffraction (XRD), transmission electron microscopy (TEM), H2 temperature‐programmed reduction (H2‐TPR), and Raman spectroscopy. The results showed that the pretreatment of the catalyst by reaction gas significantly improved the catalytic activity and stability for the POM reaction. On the other hand, the effect of calcination temperature was less significant. Although the initial activity was increased by an increased calcination temperature, the catalyst without the feedstock pretreatment suffered a rapid deactivation. The reaction‐atmosphere pretreatment was revealed as a process that mainly modified the surface structure of the catalyst. In that process, the formation of a CoAl2O4‐like compound led to high Co metal dispersion after reduction, and the transformation of the carrier into α‐Al2O3 occurred over the catalyst surface. Both the high dispersion of cobalt and the presence of α‐Al2O3 surface phase were assumed as the important factors resulting in an excellent catalytic performance in terms of high activity and high stability. 相似文献
108.
Two new dicyanamide coordination polymers, {Mn(dmpz)[N(CN)2]2}2 (1) and {Cu(dmpz)[N(CN)2]2}2 (2)(dmpz=3,5-dimethylpyrazole), were synthesized and characterized by single crystal X-ray diffraction analysis and IR spectroscopy. In 1 and 2 the metal ions have two different coordination modes, where one is coordinated to four dicyanamide anions and two monodentate dmpz molecules to form a slightly distorted octahedral geometry, while the other adopts octahedral geometry, surrounded by four nitrile N atoms and two amide N atoms of the dicyanamide anions. Both complexes contain two alternating chains that are parallel to each other. 相似文献
109.
为了寻找生物活性良好的噻唑基丙烯腈类化合物, 利用2-[4-(2,6-二氟苯基)噻唑-2-基]乙腈(3)分别与取代氯甲酸酯4和取代苯基异氰酸酯6在碱存在下反应, 合成了8个2-[4-(2,6-二氟苯基)噻唑-2-基]-3-羟基-3-烃氧基丙烯腈化合物5和7个2-[4-(2,6-二氟苯基)噻唑-2-基]-3-羟基-3-取代苯胺基丙烯腈化合物7, 均为首次报道的丙烯腈类化合物. 化合物结构经1H NMR, IR, MS和元素分析表征. 初步生物活性测定结果表明, 在试验浓度下, 目标化合物均具有一定的杀虫和抑菌活性, 其中化合物5f和5h在100 mg/L浓度下对炭疽病菌的抑制率达95%; 化合物5g和7d在250 mg/L浓度下对棉红蜘蛛的致死率达85%. 相似文献
110.