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   258295篇
  免费   6217篇
  国内免费   4731篇
化学   121295篇
晶体学   3661篇
力学   15437篇
综合类   323篇
数学   42678篇
物理学   85849篇
  2022年   2248篇
  2021年   2741篇
  2020年   3139篇
  2019年   3446篇
  2018年   11995篇
  2017年   12515篇
  2016年   8928篇
  2015年   3982篇
  2014年   5081篇
  2013年   8032篇
  2012年   11616篇
  2011年   19673篇
  2010年   12972篇
  2009年   13138篇
  2008年   16927篇
  2007年   19915篇
  2006年   6542篇
  2005年   11344篇
  2004年   7993篇
  2003年   7787篇
  2002年   6103篇
  2001年   4777篇
  2000年   3828篇
  1999年   2800篇
  1998年   2623篇
  1997年   2304篇
  1996年   2307篇
  1995年   1935篇
  1994年   1986篇
  1993年   1933篇
  1992年   1938篇
  1991年   2058篇
  1990年   1989篇
  1989年   1938篇
  1988年   1767篇
  1987年   1711篇
  1986年   1656篇
  1985年   1820篇
  1984年   1934篇
  1983年   1683篇
  1982年   1693篇
  1981年   1507篇
  1980年   1416篇
  1979年   1628篇
  1978年   1784篇
  1977年   1715篇
  1976年   1765篇
  1975年   1600篇
  1974年   1642篇
  1973年   1668篇
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
61.
62.
Russian Chemical Bulletin - Quantum chemical calculations and a comparative analysis of Raman spectra of 3,4,5-triphenyl-1-propyl-1,2-diphosphole (1),...  相似文献   
63.
64.
Two new compounds of fluorine: (C2H5)4N[I2F] and (C2H5)4N[Br2F], have been easily synthesized in a nearly quantitative by a direct reaction of (C2H5)4NF, I2 and Br2. The products were isolated and characterized by elemental analysis and spectroscopic methods such as: Fourier transform infrared spectroscopy (FTIR) and ultraviolet-visible spectroscopy (UV-Vis). These compounds have been studied computationally with the Scalar ZORA relativistic level of theory using the ADF program package. The molecular parameters, and vibrational spectra were calculated. The excitation energies were found by timedependent perturbation density functional theory (TD-DFT). Molecule optimization, frequencies and excitation energies were calculated with standard Slatertype-orbital (STO) basis sets with triple-zeta quality double plus polarization functions (TZ2P) for all atoms. The FTIR, UV-Vis spectra and assignment of principal transitions and total density of state (TDOS) were extracted using the GaussSum 2.2 program. The comparison between experimental and calculated values showes that the experimental results correlate well with the predicted data.  相似文献   
65.
Development of biocompatible porous supports is a promising strategy in the field of tissue engineering for the repair and regeneration of bone tissues with severe damage. Graphene oxide aerogels (GOAs) are excellent candidates for the manufacture of these systems due to their porosity, ability to imitate bone structure, and mechanical resistance, and according to their surface chemical reactivity, they can facilitate osseointegration, osteogenesis, osteoinduction and osteoconduction. In this review, synthesis of GOAs from the most primary source is described, and recent studies on the use of these functionalized carbonaceous foams as scaffolding for bone tissue regeneration are presented.  相似文献   
66.
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   
67.
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   
68.
Research on Chemical Intermediates - Combination of three aromatic carboxylic acids (5-nitroisophthalic acid (H2nip), 2,6-naphthalenedicarboxylic acid (H2ndc), tetrabromoterephthalic acid (H2tbta))...  相似文献   
69.
Journal of Thermal Analysis and Calorimetry - Coal O2/CO2 combustion is a promising carbon capture and storage technology for coal-fired power plant. Char consumption rate prediction is essential...  相似文献   
70.
Journal of Experimental and Theoretical Physics - We suggest that the principle of holographic duality be extended beyond conformal invariance and AdS isometry. Such an extension is based on a...  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