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   110826篇
  免费   7520篇
  国内免费   5819篇
化学   64996篇
晶体学   1383篇
力学   6298篇
综合类   387篇
数学   13541篇
物理学   37560篇
  2023年   967篇
  2022年   1505篇
  2021年   2354篇
  2020年   2870篇
  2019年   2989篇
  2018年   3308篇
  2017年   3171篇
  2016年   4077篇
  2015年   2993篇
  2014年   4102篇
  2013年   5866篇
  2012年   6139篇
  2011年   6492篇
  2010年   5011篇
  2009年   5031篇
  2008年   5369篇
  2007年   4960篇
  2006年   4506篇
  2005年   4038篇
  2004年   3512篇
  2003年   3100篇
  2002年   3211篇
  2001年   2849篇
  2000年   2267篇
  1999年   1888篇
  1998年   1720篇
  1997年   1464篇
  1996年   1430篇
  1995年   1231篇
  1994年   1278篇
  1993年   1201篇
  1992年   1142篇
  1991年   1192篇
  1990年   1193篇
  1989年   1089篇
  1988年   966篇
  1987年   956篇
  1986年   905篇
  1985年   949篇
  1984年   943篇
  1983年   831篇
  1982年   811篇
  1979年   805篇
  1978年   812篇
  1977年   809篇
  1976年   927篇
  1975年   822篇
  1974年   841篇
  1973年   845篇
  1972年   756篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Theoretical and Computational Fluid Dynamics - The present study aims to simulate a collision of two droplets containing immiscible liquids by employing a three- dimensional incompressible smoothed...  相似文献   
42.
43.
44.
Incorporation of a non-hexagonal ring into a nanographene framework can lead to new electronic properties. During the attempted synthesis of naphthalene-bridged double [6]helicene and heptagon-containing nanographene by the Scholl reaction, an unexpected azulene-embedded nanographene and its triflyloxylated product were obtained, as confirmed by X-ray crystallographic analysis and 2D NMR spectroscopy. A 5/7/7/5 ring-fused substructure containing two formal azulene units is formed, but only one of them shows an azulene-like electronic structure. The formation of this unique structure is explained by arenium ion mediated 1,2-phenyl migration and a naphthalene to azulene rearrangement reaction according to an in-silico study. This report represents the first experimental example of the thermodynamically unfavorable naphthalene to azulene rearrangement and may lead to new azulene-based molecular materials.  相似文献   
45.
Hierarchically porous metal–organic frameworks (HP-MOFs) are promising in various applications. Most reported HP-MOFs are prepared based on the generation of mesopores in microporous frameworks, and the formed mesopores are connected by microporous channels, limiting the accessibility of mesopores for bulky molecules. A hierarchical structure is formed by constructing microporous MOFs in uninterrupted mesoporous tunnels. Using the confined space in as-prepared mesoporous silica, highly dispersed metal precursors for MOFs are coated on the internal surface of mesoporous tunnels. Ligand vapor-induced crystallization is employed to enable quantitative formation of MOFs in situ, in which sublimated ligands diffuse into mesoporous tunnels and react with metal precursors. The obtained hierarchically porous composites exhibit record-high adsorption capacity for the bulky molecule trypsin. The thermal and storage stability of trypsin is improved upon immobilization on the composites.  相似文献   
46.
Russian Journal of General Chemistry - 8-Phenyltetrazolo[5,1-b][1,3,4]thiadiazepine was obtained as a result of intermolecular cyclization of 1-amino-1H-tetrazole-5-thiol and 3-phenyl-2-propynal....  相似文献   
47.
The results of investigation of optical image detectors designed for the largest problem, near-VUV, range of the spectrum are presented. The possibility of using a dual-stage image detection system to appreciably lower the sensitivity threshold and make computer data processing feasible is considered. The integration of a UV module into a wideband image detector is studied.  相似文献   
48.
49.
We present the fabrication of core-shell-satellite Au@SiO2-Pt nanostructures and demonstrate that LSPR excitation of the core Au nanoparticle can induce plasmon coupling effect to initiate photocatalytic hydrogen generation from decomposition of formic acid. Further studies suggest that the plasmon coupling effect induces a strong local electric field between the Au core and Pt nanoparticles on the SiO2 shell, which enables creation of hot electrons on the non-plasmonic-active Pt nanoparticles to participate hydrogen evolution reaction on the Pt surface. In addition, small SiO2 shell thickness is required in order to obtain a strong plamon coupling effect and achieve efficient photocatalytic activities for hydrogen generation.  相似文献   
50.
Russian Journal of Organic Chemistry - Binder-free iron- and nickel-containing micro-, meso-, and macroporous zeolites FeHY and NiHY were found to effectively catalyze Knoevenagel condensation of...  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