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   590702篇
  免费   6863篇
  国内免费   1732篇
化学   285828篇
晶体学   7013篇
力学   29694篇
综合类   18篇
数学   100864篇
物理学   175880篇
  2021年   3971篇
  2020年   4556篇
  2019年   4814篇
  2018年   20506篇
  2017年   20782篇
  2016年   17157篇
  2015年   7461篇
  2014年   9588篇
  2013年   22031篇
  2012年   22764篇
  2011年   37093篇
  2010年   23931篇
  2009年   23997篇
  2008年   31505篇
  2007年   35434篇
  2006年   17707篇
  2005年   21717篇
  2004年   18200篇
  2003年   16802篇
  2002年   14248篇
  2001年   14244篇
  2000年   11001篇
  1999年   8383篇
  1998年   7038篇
  1997年   6615篇
  1996年   6258篇
  1995年   5831篇
  1994年   5783篇
  1993年   5604篇
  1992年   6218篇
  1991年   6172篇
  1990年   5918篇
  1989年   5721篇
  1988年   5745篇
  1987年   5646篇
  1986年   5326篇
  1985年   6970篇
  1984年   7099篇
  1983年   5629篇
  1982年   5743篇
  1981年   5725篇
  1980年   5304篇
  1979年   5729篇
  1978年   5870篇
  1977年   5693篇
  1976年   5669篇
  1975年   5231篇
  1974年   5170篇
  1973年   5172篇
  1972年   3617篇
排序方式: 共有10000条查询结果,搜索用时 515 毫秒
101.
102.
We consider conformal gravity as a gauge natural theory. We study its conservation laws and superpotentials. We also consider the Mannheim and Kazanas spherically symmetric vacuum solution and discuss conserved quantities associated to conformal and diffeomorphism symmetries.  相似文献   
103.
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   
104.
Journal of Sol-Gel Science and Technology - Multifunctional magnetic mesoporous nanocomposites are promising materials to remove the various pollutants from water due to the remarkable properties...  相似文献   
105.
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   
106.
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   
107.
Journal of Computer-Aided Molecular Design - Accurate predictions of acid dissociation constants are essential to rational molecular design in the pharmaceutical industry and elsewhere. There has...  相似文献   
108.
Russian Journal of Organic Chemistry - Herein, we report the sulfonamide-functionalized covalent organic framework (COF-SO3H), prepared by condensation of melamine and terephthalaldehyde and...  相似文献   
109.
Transport in Porous Media - In the original publication of the article, Table 2 was published incorrectly.  相似文献   
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