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   625327篇
  免费   5445篇
  国内免费   1521篇
化学   304909篇
晶体学   9024篇
力学   33211篇
综合类   24篇
数学   88611篇
物理学   196514篇
  2021年   5334篇
  2020年   5782篇
  2019年   6514篇
  2018年   13262篇
  2017年   13590篇
  2016年   14446篇
  2015年   7035篇
  2014年   11239篇
  2013年   25395篇
  2012年   22428篇
  2011年   30906篇
  2010年   22024篇
  2009年   22070篇
  2008年   28382篇
  2007年   30255篇
  2006年   20498篇
  2005年   21497篇
  2004年   18541篇
  2003年   17267篇
  2002年   15948篇
  2001年   17040篇
  2000年   13231篇
  1999年   9987篇
  1998年   8441篇
  1997年   8312篇
  1996年   7745篇
  1995年   6968篇
  1994年   6864篇
  1993年   6582篇
  1992年   7201篇
  1991年   7664篇
  1990年   7300篇
  1989年   7136篇
  1988年   6980篇
  1987年   6832篇
  1986年   6465篇
  1985年   8201篇
  1984年   8504篇
  1983年   7071篇
  1982年   7331篇
  1981年   6819篇
  1980年   6489篇
  1979年   7101篇
  1978年   7352篇
  1977年   7193篇
  1976年   7093篇
  1975年   6747篇
  1974年   6591篇
  1973年   6878篇
  1972年   4940篇
排序方式: 共有10000条查询结果,搜索用时 468 毫秒
131.
132.
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   
133.
134.
Silver nanoparticles (NPs) ranging in size from 40 to 100 nm were prepared in high yield by using an improved seed‐mediated method. The homogeneous Ag NPs were used as building blocks for 2D assembled Ag NP arrays by using an oil/water interface. A close‐packed 2D array of Ag NPs was fabricated by using packing molecules (3‐mercaptopropyltrimethoxysilane) to control the interparticle spacing. The homogeneous 2D Ag NP array exhibited a strong quadrupolar cooperative plasmon mode resonance and a dipolar red‐shift relative to individual Ag NPs suspended in solution. A well‐arranged 2D Ag NP array was embedded in polydimethylsiloxane film and, with biaxial stretching to control the interparticle distance, concomitant variations of the quadrupolar and dipolar couplings were observed. As the interparticle distance increased, the intensity of the quadrupolar cooperative plasmon mode resonance decreased and dipolar coupling completely disappeared. The local electric field of the 2D Ag NP array was calculated by using finite difference time domain simulation and qualitatively showed agreement with the experimental measurements.  相似文献   
135.
136.
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   
137.
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   
138.
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   
139.
Russian Journal of General Chemistry - Some new fluoro-heterocyclic compounds containing thiazole and pyridine moities have been synthesized and studied for their antiproliferative activity....  相似文献   
140.
In this research article, we describe the synthesis and characterization of mononuclear and dinuclear Cu complexes bound by a family of tridentate redox-active ligands with tunable H-bonding donors. The mononuclear Cu-anion complexes were oxidized to the corresponding “high-valent” intermediates by oxidation of the redox-active ligand. These species were capable of oxidizing phenols with weak O−H bonds via H-atom abstraction. Thermodynamic analysis of the H-atom abstractions, which included reduction potential measurements, pKa determination and kinetic studies, revealed that modification of the anion coordinated to the Cu and changes in the H-bonding donor did not lead to major differences in the reactivity of the “high-valent” CuY complexes (Y: hydroxide, phenolate and acetate), which indicated that the tridentate ligand scaffold acts as the H+ and e acceptor.  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