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   378614篇
  免费   2666篇
  国内免费   895篇
化学   176235篇
晶体学   5351篇
力学   19762篇
综合类   1篇
数学   55269篇
物理学   125557篇
  2021年   2306篇
  2020年   2629篇
  2019年   2987篇
  2018年   11437篇
  2017年   12095篇
  2016年   9100篇
  2015年   3925篇
  2014年   5480篇
  2013年   12940篇
  2012年   13643篇
  2011年   22803篇
  2010年   14912篇
  2009年   14982篇
  2008年   20227篇
  2007年   23258篇
  2006年   10675篇
  2005年   15004篇
  2004年   11541篇
  2003年   10810篇
  2002年   9019篇
  2001年   9030篇
  2000年   6987篇
  1999年   5257篇
  1998年   4491篇
  1997年   4316篇
  1996年   4222篇
  1995年   3792篇
  1994年   3708篇
  1993年   3751篇
  1992年   3913篇
  1991年   4139篇
  1990年   3866篇
  1989年   3849篇
  1988年   3701篇
  1987年   3586篇
  1986年   3356篇
  1985年   4509篇
  1984年   4776篇
  1983年   3849篇
  1982年   4106篇
  1981年   3978篇
  1980年   3807篇
  1979年   4012篇
  1978年   4226篇
  1977年   4087篇
  1976年   4138篇
  1975年   3783篇
  1974年   3809篇
  1973年   3875篇
  1972年   2712篇
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
1.
Journal of Experimental and Theoretical Physics - Dzyaloshinskii–Moriya interaction, DMI in short, represents an antisymmetric type of magnetic interactions that favor orthogonal orientation...  相似文献   
2.
Russian Journal of General Chemistry - Aminophosphabetaines, i.e., isobutyl {[alkyl(dimethyl)ammonio]methyl}phosphonates with higher alkyl substituents at the nitrogen atom, were obtained by a...  相似文献   
3.
Kinetics and Catalysis - The results of studies in the field of synthesis and characterization of layered double hydroxides (LDHs) obtained using solid-phase reactions are summarized. The effect of...  相似文献   
4.
Mechanics of Composite Materials - Carbon fiber (CF)/ polyamide (PA6) composites are one of the most promising thermoplastic materials for automobile applications. However, the interfacial...  相似文献   
5.
Journal of Structural Chemistry - A new polymorph of the [ReCl3(MeCN)(PPh3)2] complex is synthesized and characterized by single crystal X-ray diffraction (XRD). Its recrystallization from the...  相似文献   
6.
Nitrene transfer reactions have emerged as one of the most powerful and versatile ways to insert an amine function to various kinds of hydrocarbon substrates. However, the mechanisms of nitrene generation have not been studied in depth albeit their formation is taken for granted in most cases without definitive evidence of their occurrence. In the present work, we compare the generation of tosylimido iron species and NTs transfer from FeII and FeIII precursors where the metal is embedded in a tetracarbene macrocycle. Catalytic nitrene transfer to reference substrates (thioanisole, styrene, ethylbenzene and cyclohexane) revealed that the same active species was at play, irrespective of the ferrous versus ferric nature of the precursor. Through combination of spectroscopic (UV-visible, Mössbauer), ESI-MS and DFT studies, an FeIV tosylimido species was identified as the catalytically active species and was characterized spectroscopically and computationally. Whereas its formation from the FeII precursor was expected by a two-electron oxidative addition, its formation from an FeIII precursor was unprecedented. Thanks to a combination of spectroscopic (UV-visible, EPR, Hyscore and Mössbauer), ESI-MS and DFT studies, we found that, when starting from the FeIII precursor, an FeIII tosyliodinane adduct was formed and decomposed into an FeV tosylimido species which generated the catalytically active FeIV tosylimide through a comproportionation process with the FeIII precursor.  相似文献   
7.
Journal of Experimental and Theoretical Physics - The surface current density of charge carriers in two-dimensional doubly periodic n-type semiconductor superlattices in an external magnetic field...  相似文献   
8.
Russian Journal of Applied Chemistry - A method for the disposal of hydrolysis lignin waste based on its modification with ZnCl2 and FeCl3 and subsequent carbonization at 800°C was proposed....  相似文献   
9.
Journal of Applied Spectroscopy - Three simple, sensitive, precise, and rapid spectrophotometric methods are developed and optimized for the assay of vardenafil in pharmaceutical formulations. The...  相似文献   
10.
Mathematical Notes - Subspaces of the space of analytic functions on a convex domain in the complex plane that are invariant with respect to the differentiation operator are studied. The problem 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