首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   2621篇
  免费   477篇
  国内免费   438篇
化学   1516篇
晶体学   48篇
力学   103篇
综合类   90篇
数学   442篇
物理学   1337篇
  2024年   3篇
  2023年   20篇
  2022年   61篇
  2021年   74篇
  2020年   101篇
  2019年   89篇
  2018年   81篇
  2017年   76篇
  2016年   77篇
  2015年   37篇
  2014年   356篇
  2013年   405篇
  2012年   220篇
  2011年   317篇
  2010年   248篇
  2009年   329篇
  2008年   204篇
  2007年   111篇
  2006年   107篇
  2005年   42篇
  2004年   110篇
  2003年   61篇
  2002年   72篇
  2001年   57篇
  2000年   47篇
  1999年   38篇
  1998年   33篇
  1997年   26篇
  1996年   26篇
  1995年   21篇
  1994年   20篇
  1993年   13篇
  1992年   18篇
  1991年   4篇
  1990年   4篇
  1989年   4篇
  1988年   1篇
  1987年   3篇
  1985年   5篇
  1984年   2篇
  1982年   1篇
  1981年   3篇
  1980年   1篇
  1979年   1篇
  1978年   1篇
  1977年   1篇
  1976年   2篇
  1974年   1篇
  1973年   1篇
  1959年   1篇
排序方式: 共有3536条查询结果,搜索用时 36 毫秒
1.
Magnetically retrieval CuFe2O4@MIL-101(Cr) metal–organic framework was successfully prepared from easily available starting materials and characterized using various spectroscopic and analytical techniques such as powder X-ray diffraction, scanning electron microscopy, energy dispersive X-ray, transmission electron microscopy, elemental mapping, Fourier transform infrared spectroscopy, thermogravimetric analysis, X-ray photoelectron spectroscopy, Brunauer–Emmett–Teller, vibrating sample magnetometer, and inductively coupled plasma optical emission spectroscopy. The catalyst was then used in the synthesis of benzodiazepines containing a triazole moiety in water. The advantages of this protocol include high yields, reusability of the catalyst, and gram-scale synthesis.  相似文献   
2.
Polyaniline (PANI)/MIL-88A(Fe) (Px@M88) composites were constructed through a simple one-pot hydrothermal method. The photocatalytic and photo-Fenton activities of Px@M88 composites toward reduction of Cr(VI) and degradation organic pollutants were explored by white light irradiation. PANI, as a conductive polymer, can improve MIL-88A(Fe)’s conductivity and the efficiency of photogenerated e–h+ pair separation. In the presence of H2O2, a photo-Fenton reaction occured to boost the degradation efficiency of organic pollutants like bisphenol A. In addition, P9@M88 showed excellent recycling and stability in cycling experiments. Finally, a possible reaction mechanism for photocatalytic degradation was proposed and verified by X-ray photoelectron spectroscopy and electron spin resonance determination and electrochemical characterizations.  相似文献   
3.
4.
Palladium nanoparticle‐incorporated metal–organic framework MIL‐101 (Pd/MIL‐101) was successfully synthesized and characterized using X‐ray diffraction, nitrogen physisorption, X‐ray photoelectron, UV–visible and infrared spectroscopies, and transmission electron microscopy. The characterization techniques confirmed high porosity and high surface area of MIL‐101 and high stability of nano‐size palladium particles. Pd/MIL‐101 nanocomposite was investigated for the Sonogashira cross‐coupling reaction of aryl and heteroaryl bromides with various alkynes under copper‐free conditions. The reusability of the catalyst was tested for up to four cycles without any significant loss in catalytic activity. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   
5.
6.
A novel metal-doped metal–organic framework (MOF) was developed by incorporating salen–Mg into NH2–MIL-101(Cr) structure under ambient conditions. The Schiff base complex was successfully prepared by condensing salicylaldehyde with a free amino group and then coordinating metal ions. Such a structure can endow the sample with higher CO2 adsorption performance. At 0°C and 1 bar, the salen–Mg-modified sample achieves the maximum adsorption capacity of 2.18 mmol g−1 for CO2, which was 5.8% higher than the pristine salen–MOF under the same conditions. Notably, the Freundlich model indicates that the CO2 adsorption process of all samples conforms to reversible adsorption. However, the correlation coefficients (R2) of the Mg-doped sample are lower than that of the pristine sample. Besides, the CO2/N2 adsorption selectivity and isosteric heat also show a similar trend. These results indicate that the salen–Mg can enhance the interaction between the material and CO2 molecules.  相似文献   
7.
8.
9.
10.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号