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   376649篇
  免费   7275篇
  国内免费   5229篇
化学   189149篇
晶体学   4769篇
力学   19881篇
综合类   329篇
数学   56248篇
物理学   118777篇
  2021年   3388篇
  2020年   3974篇
  2019年   4406篇
  2018年   12475篇
  2017年   12901篇
  2016年   10454篇
  2015年   5081篇
  2014年   6882篇
  2013年   13521篇
  2012年   14899篇
  2011年   23416篇
  2010年   15504篇
  2009年   15580篇
  2008年   20819篇
  2007年   23624篇
  2006年   11041篇
  2005年   14990篇
  2004年   11359篇
  2003年   10835篇
  2002年   9143篇
  2001年   8219篇
  2000年   6684篇
  1999年   4939篇
  1998年   4398篇
  1997年   4184篇
  1996年   4112篇
  1995年   3381篇
  1994年   3524篇
  1993年   3492篇
  1992年   3544篇
  1991年   3627篇
  1990年   3525篇
  1989年   3429篇
  1988年   3277篇
  1987年   3228篇
  1986年   3120篇
  1985年   3832篇
  1984年   4039篇
  1983年   3282篇
  1982年   3530篇
  1981年   3320篇
  1980年   3100篇
  1979年   3431篇
  1978年   3597篇
  1977年   3537篇
  1976年   3614篇
  1975年   3394篇
  1974年   3384篇
  1973年   3572篇
  1972年   2517篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
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   
72.
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   
73.
74.
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   
75.
76.
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   
77.
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   
78.
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   
79.
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   
80.
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   
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