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   529742篇
  免费   4166篇
  国内免费   1282篇
化学   269643篇
晶体学   7661篇
力学   26029篇
综合类   17篇
数学   67899篇
物理学   163941篇
  2021年   5042篇
  2020年   5498篇
  2019年   6235篇
  2018年   8419篇
  2017年   8566篇
  2016年   11649篇
  2015年   6198篇
  2014年   10469篇
  2013年   23535篇
  2012年   18393篇
  2011年   21829篇
  2010年   16453篇
  2009年   16306篇
  2008年   20698篇
  2007年   20540篇
  2006年   18636篇
  2005年   16646篇
  2004年   15498篇
  2003年   13979篇
  2002年   13870篇
  2001年   14764篇
  2000年   11372篇
  1999年   8767篇
  1998年   7614篇
  1997年   7488篇
  1996年   6946篇
  1995年   6269篇
  1994年   6278篇
  1993年   6037篇
  1992年   6388篇
  1991年   6882篇
  1990年   6585篇
  1989年   6511篇
  1988年   6341篇
  1987年   6149篇
  1986年   5885篇
  1985年   7427篇
  1984年   7786篇
  1983年   6544篇
  1982年   6835篇
  1981年   6341篇
  1980年   6013篇
  1979年   6520篇
  1978年   6759篇
  1977年   6651篇
  1976年   6600篇
  1975年   6309篇
  1974年   6145篇
  1973年   6435篇
  1972年   4716篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
23.
24.
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   
25.
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   
26.
27.
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   
28.
29.
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   
30.
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