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   89149篇
  免费   970篇
  国内免费   200篇
化学   49802篇
晶体学   1159篇
力学   3619篇
综合类   1篇
数学   9336篇
物理学   26402篇
  2021年   1038篇
  2020年   1151篇
  2019年   1341篇
  2018年   1749篇
  2017年   1807篇
  2016年   2467篇
  2015年   1285篇
  2014年   2026篇
  2013年   3895篇
  2012年   3679篇
  2011年   4184篇
  2010年   3101篇
  2009年   3055篇
  2008年   3771篇
  2007年   3711篇
  2006年   3558篇
  2005年   3176篇
  2004年   2940篇
  2003年   2637篇
  2002年   2625篇
  2001年   2396篇
  2000年   1766篇
  1999年   1388篇
  1998年   1257篇
  1997年   1149篇
  1996年   1046篇
  1995年   940篇
  1994年   888篇
  1993年   867篇
  1992年   916篇
  1991年   996篇
  1990年   931篇
  1989年   943篇
  1988年   847篇
  1987年   805篇
  1986年   770篇
  1985年   925篇
  1984年   1033篇
  1983年   870篇
  1982年   903篇
  1981年   808篇
  1980年   765篇
  1979年   820篇
  1978年   951篇
  1977年   977篇
  1976年   858篇
  1975年   811篇
  1974年   817篇
  1973年   784篇
  1972年   561篇
排序方式: 共有10000条查询结果,搜索用时 156 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.
4D printing is an exciting branch of additive manufacturing. It relies on established 3D printing techniques to fabricate objects in much the same way. However, structures which fall into the 4D printed category have the ability to change with time, hence the “extra dimension.” The common perception of 4D printed objects is that of macroscopic single-material structures limited to point-to-point shape change only, in response to either heat or water. However, in the area of polymer 4D printing, recent advancements challenge this understanding. A host of new polymeric materials have been designed which display a variety of wonderful effects brought about by unconventional stimuli, and advanced additive manufacturing techniques have been developed to accommodate them. As a result, the horizons of polymer 4D printing have been broadened beyond what was initially thought possible. In this review, we showcase the many studies which evolve the very definition of polymer 4D printing, and reveal emerging areas of research integral to its advancement.  相似文献   
3.
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   
4.
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   
5.
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   
6.
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   
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.
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.
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   
10.
Crystallography Reports - Membrane proteins, including ion channels, became the focus of structural proteomics midway through the 20th century. Methods for studying ion channels are diverse and...  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