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   375749篇
  免费   2657篇
  国内免费   892篇
化学   174994篇
晶体学   4930篇
力学   19689篇
综合类   1篇
数学   55018篇
物理学   124666篇
  2021年   2268篇
  2020年   2591篇
  2019年   2941篇
  2018年   11424篇
  2017年   12081篇
  2016年   9053篇
  2015年   3907篇
  2014年   5425篇
  2013年   12862篇
  2012年   13589篇
  2011年   22763篇
  2010年   14850篇
  2009年   14930篇
  2008年   20168篇
  2007年   23223篇
  2006年   10594篇
  2005年   14973篇
  2004年   11499篇
  2003年   10764篇
  2002年   8975篇
  2001年   8958篇
  2000年   6928篇
  1999年   5223篇
  1998年   4460篇
  1997年   4217篇
  1996年   3906篇
  1995年   3673篇
  1994年   3599篇
  1993年   3631篇
  1992年   3788篇
  1991年   3993篇
  1990年   3730篇
  1989年   3717篇
  1988年   3681篇
  1987年   3564篇
  1986年   3346篇
  1985年   4490篇
  1984年   4759篇
  1983年   3833篇
  1982年   4085篇
  1981年   3958篇
  1980年   3800篇
  1979年   3990篇
  1978年   4200篇
  1977年   4059篇
  1976年   4116篇
  1975年   3764篇
  1974年   3795篇
  1973年   3850篇
  1972年   2701篇
排序方式: 共有10000条查询结果,搜索用时 46 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.
Crystallography Reports - The crystal structure and crystallochemical features of a Fe-deficient zirconium-rich analog of eudialyte from the Lovozero alkaline massif (Kola peninsula) have been...  相似文献   
3.
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   
4.
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   
5.
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   
6.
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   
7.
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   
8.
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   
9.
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   
10.
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   
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