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   545324篇
  免费   5559篇
  国内免费   1372篇
化学   280985篇
晶体学   7749篇
力学   26362篇
综合类   17篇
数学   70778篇
物理学   166364篇
  2021年   5272篇
  2020年   5834篇
  2019年   6595篇
  2018年   8644篇
  2017年   8795篇
  2016年   12202篇
  2015年   6702篇
  2014年   11076篇
  2013年   24470篇
  2012年   19391篇
  2011年   22995篇
  2010年   17144篇
  2009年   16942篇
  2008年   21684篇
  2007年   21508篇
  2006年   19541篇
  2005年   17476篇
  2004年   16231篇
  2003年   14554篇
  2002年   14431篇
  2001年   14999篇
  2000年   11603篇
  1999年   9002篇
  1998年   7831篇
  1997年   7678篇
  1996年   7173篇
  1995年   6483篇
  1994年   6457篇
  1993年   6220篇
  1992年   6566篇
  1991年   7022篇
  1990年   6722篇
  1989年   6639篇
  1988年   6447篇
  1987年   6239篇
  1986年   5972篇
  1985年   7558篇
  1984年   7895篇
  1983年   6645篇
  1982年   6948篇
  1981年   6463篇
  1980年   6120篇
  1979年   6620篇
  1978年   6872篇
  1977年   6725篇
  1976年   6669篇
  1975年   6405篇
  1974年   6206篇
  1973年   6485篇
  1972年   4759篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
121.
122.
123.
124.
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   
125.
126.
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   
127.
128.
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   
129.
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   
130.
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