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   404356篇
  免费   2072篇
  国内免费   443篇
化学   177906篇
晶体学   4951篇
力学   24543篇
综合类   3篇
数学   66514篇
物理学   132954篇
  2021年   3452篇
  2020年   3788篇
  2019年   4624篇
  2018年   12127篇
  2017年   12587篇
  2016年   11419篇
  2015年   4474篇
  2014年   7721篇
  2013年   14129篇
  2012年   14624篇
  2011年   21808篇
  2010年   15747篇
  2009年   16072篇
  2008年   20013篇
  2007年   22241篇
  2006年   11715篇
  2005年   13511篇
  2004年   11415篇
  2003年   11265篇
  2002年   10261篇
  2001年   9137篇
  2000年   7346篇
  1999年   5330篇
  1998年   5041篇
  1997年   4808篇
  1996年   4280篇
  1995年   3850篇
  1994年   3918篇
  1993年   3895篇
  1992年   3948篇
  1991年   4389篇
  1990年   4299篇
  1989年   4341篇
  1988年   4085篇
  1987年   4105篇
  1986年   3802篇
  1985年   4464篇
  1984年   4774篇
  1983年   4066篇
  1982年   4311篇
  1981年   3949篇
  1980年   3658篇
  1979年   4175篇
  1978年   4395篇
  1977年   4505篇
  1976年   4505篇
  1975年   4220篇
  1974年   4094篇
  1973年   4303篇
  1972年   3559篇
排序方式: 共有10000条查询结果,搜索用时 23 毫秒
101.
102.
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   
103.
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   
104.
Sybachin  A. V.  Stepanova  D. A. 《Colloid Journal》2021,83(4):531-531
Colloid Journal - An Erratum to this paper has been published: https://doi.org/10.1134/S1061933X21330024  相似文献   
105.
This mini-review highlights key structural features that should be taken into account when creating ambipolar redox-active closed-shell metal-free molecules. This type of compound is strongly required for the fabrication of all-organic ‘poleless’ batteries and semiconductors. The suggested strategies aimed at stabilization of both oxidized (cationic) and reduced (anionic) redox-states are based on the comprehensive analysis of the most successful structures taken from the recent publications.  相似文献   
106.
Transport in Porous Media - In the original publication of the article, Table 2 was published incorrectly.  相似文献   
107.
Transport in Porous Media - A macroscopic model that accounts for the effect of momentum dispersion on flows in porous media is proposed. The model is based on the pore scale prevalence hypothesis...  相似文献   
108.
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   
109.
110.
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