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   6480篇
  免费   977篇
  国内免费   541篇
化学   4574篇
晶体学   31篇
力学   353篇
综合类   16篇
数学   786篇
物理学   2238篇
  2023年   146篇
  2022年   107篇
  2021年   225篇
  2020年   279篇
  2019年   233篇
  2018年   211篇
  2017年   172篇
  2016年   279篇
  2015年   264篇
  2014年   355篇
  2013年   438篇
  2012年   593篇
  2011年   618篇
  2010年   413篇
  2009年   349篇
  2008年   423篇
  2007年   373篇
  2006年   348篇
  2005年   265篇
  2004年   201篇
  2003年   157篇
  2002年   119篇
  2001年   125篇
  2000年   113篇
  1999年   125篇
  1998年   98篇
  1997年   87篇
  1996年   117篇
  1995年   101篇
  1994年   70篇
  1993年   62篇
  1992年   67篇
  1991年   56篇
  1990年   74篇
  1989年   53篇
  1988年   34篇
  1987年   29篇
  1986年   24篇
  1985年   18篇
  1984年   16篇
  1983年   16篇
  1982年   15篇
  1981年   10篇
  1980年   8篇
  1979年   20篇
  1978年   15篇
  1977年   14篇
  1976年   10篇
  1975年   13篇
  1973年   13篇
排序方式: 共有7998条查询结果,搜索用时 46 毫秒
21.
22.
23.
24.
Long-term stability test of Mo/HZSM-5-N catalysts(HZSM-5-N stands for nano-sized HZSM-5) in methane dehydroaromatization(MDA)reaction has been performed with periodic CH4-H2 switch at 1033-1073 K for more than 1000 h.During this test,methane conversion ranges from 13% to 16%,and mean yield to aromatics(i.e.benzene and naphthalene) exceeds 10%.N2-physisorption,XRD,NMR and TPO measurements were performed for the used Mo/HZSM-5 catalysts and coke deposition,and the results revealed that the periodic hydrogenation can effectively suppress coke deposition by removing the inert aromatic-type coke,thus ensuring Mo/HZSM-5 partly maintained its activity even in the presence of large amount of coke deposition.The effect of zeolite particle size on the catalytic activity was also explored,and the results showed that the nano-sized zeolite with low diffusion resistance performed better.It is recognized that the size effect was enhanced by reaction time,and it became more remarkable in a long-term MDA reaction even at a low space velocity.  相似文献   
25.
Elucidation of relationship among chemical structure, cellular uptake, localization, and biological activity of anticancer metal complexes is important for the understanding of their mechanisms of action. Organometallic rhenium(I) tricarbonyl compounds have emerged as potential multifunctional anticancer drug candidates that can integrate therapeutic and imaging capabilities in a single molecule. Herein, two mononuclear phosphorescent rhenium(I) complexes ( Re1 and Re2 ), along with their corresponding dinuclear complexes ( Re3 and Re4 ), were designed and synthesized as potent anticancer agents. The subcellular accumulation of Re1–Re4 was conveniently analyzed by confocal microscopy in situ in live cells by utilizing their intrinsic phosphorescence. We found that increased lipophilicity of the bidentate ligands could enhance their cellular uptake, leading to improved anticancer efficacy. The dinuclear complexes were more potent than the mononuclear counterparts. The molecular anticancer mechanisms of action evoked by Re3 and Re4 were explored in detail. Re3 with a lower lipophilicity localizes to lysosomes and induces caspase‐independent apoptosis, whereas Re4 with higher lipophilicity specially accumulates in mitochondria and induces caspase‐independent paraptosis in cancer cells. Our study demonstrates that subcellular localization is crucial for the anticancer mechanisms of these phosphorescent rhenium(I) complexes.  相似文献   
26.
27.
28.
Tan  Wei  Ren  Yuanlin  Guo  Yingbin  Liu  Yansong  Liu  Xiaohui  Qu  Hongqiang 《Cellulose (London, England)》2022,29(12):6941-6962
Cellulose - A novel DOPO derived multi-claw reactive flame retardant (DMCFR) was designed to improve the flame retardancy of lyocell fabric. The chemical structure of DMCFR was identified by proton...  相似文献   
29.
Tian  Xiu-Zhi  Yang  Rui  Ma  Jia-Jia  Ni  Yong-Hao  Deng  Hai-Bo  Dai  Lei  Tan  Jiao-Jun  Zhang  Mei-Yun  Jiang  Xue 《高分子科学》2022,40(7):789-798
Chinese Journal of Polymer Science - Antistatic and strength properties are of vital importance for polyurethane rubber used in moving parts of many industrial instruments. Herein, polyurethane was...  相似文献   
30.
Presented here is a class of novel axially chiral aryl‐p‐quinones as platform molecules for the preparation of non‐C2 symmetric biaryldiols. Two sets of aryl‐p‐quinone frameworks were synthesized with remarkable enantiocontrol by means of chiral phosphoric acid catalyzed enantioselective arylation of p‐quinones by central‐to‐axial chirality conversion. These aryl‐p‐quinones were then used to access a wide spectrum of highly functionalized non‐C2 symmetric biaryldiols with excellent retention of the enantiopurity.  相似文献   
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