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   1388371篇
  免费   30202篇
  国内免费   8110篇
化学   702810篇
晶体学   14938篇
力学   76089篇
综合类   141篇
数学   245898篇
物理学   386807篇
  2021年   13522篇
  2020年   16080篇
  2019年   16229篇
  2018年   14609篇
  2017年   12899篇
  2016年   28919篇
  2015年   21116篇
  2014年   30714篇
  2013年   74813篇
  2012年   41775篇
  2011年   41777篇
  2010年   39430篇
  2009年   41160篇
  2008年   39803篇
  2007年   36192篇
  2006年   40166篇
  2005年   33491篇
  2004年   33722篇
  2003年   31047篇
  2002年   31672篇
  2001年   31991篇
  2000年   26967篇
  1999年   23552篇
  1998年   21450篇
  1997年   20864篇
  1996年   19416篇
  1995年   18742篇
  1994年   18256篇
  1993年   17790篇
  1992年   18155篇
  1991年   18365篇
  1990年   17583篇
  1989年   17579篇
  1988年   17247篇
  1987年   17161篇
  1986年   16083篇
  1985年   22537篇
  1984年   23676篇
  1983年   19702篇
  1982年   21351篇
  1981年   20571篇
  1980年   19877篇
  1979年   20354篇
  1978年   21543篇
  1977年   21216篇
  1976年   20986篇
  1975年   19703篇
  1974年   19346篇
  1973年   19814篇
  1972年   14340篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Nikolaev  N. N. 《JETP Letters》2022,115(11):639-643
JETP Letters - A new approach to search for axions in the storage ring experiments, applicable at a short coherence time of the in-plane polarization as is the case for protons is discussed. The...  相似文献   
12.
Mathematical Programming - We provide a control-theoretic perspective on optimal tensor algorithms for minimizing a convex function in a finite-dimensional Euclidean space. Given a function...  相似文献   
13.
The artificially accurate design of nonmetal electrocatalysts’ active site has been a huge challenge because no pure active species with the specific structure could be strictly controlled by traditional synthetic methods. Species with a multiconfiguration in the catalyst hinder identification of the active site and the subsequent comprehension of the reaction mechanism. We have developed a novel electro-assisted molecular assembly strategy to obtain a pure pentagon ring on perfect graphene avoiding other reconstructed structures. More importantly, the active atom was confirmed by the subtle passivation process as the topmost carbon atom. Recognition of the carbon-defect electrocatalysis reaction mechanism was first downsized to the single-atom scale from the experimental perspective. It is expected that this innovative electro-assisted molecular assembly strategy could be extensively applied in the active structure-controlled synthesis of nonmetal electrocatalysts and verification of the exact active atom.  相似文献   
14.
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   
15.
The coordination chemistry of f-block elements (lanthanide and actinide) in molten salts has become a resounding topic in view of its great importance to the research and development (R&D) of molten salt reactors and pyroprocessing. In this Review article, a general overview of the coordination chemistry of f-block elements in molten salts is provided including past achievements and recent advances. Particular emphases are placed on the oxidation state, speciation, and solution structure of f-block metal ions in molten salts, as well as their relationships with the salt composition. Furthermore, this review briefly discusses the spectroscopic and theoretical methods that complement each other in revealing the coordination properties.  相似文献   
16.
From the implementation point of view, the printable magnetic Janus colloidal photonic crystals (CPCs) microspheres are highly desirable. Herein, we developed a dispensing-printing strategy for magnetic Janus CPCs display via a microfluidics-automatic printing system. Monodisperse core/shell colloidal particles and magnetic Fe3O4 nanoparticles precursor serve as inks. Based on the equilibrium of three-phase interfacial tensions, Janus structure is successfully formed, followed by UV irradiation and self-assembly of colloid particle to generate magnetic Janus CPCs microspheres. Notably, this method shows distinct superiority with highly uniform Janus CPCs structure, where the TMPTA/Fe3O4 hemisphere is in the bottom side while CPCs hemisphere is in the top side. Thus, by using Janus CPCs microspheres with two different structural colors as pixel points, a pattern with red flower and green leaf is achieved. Moreover, 1D linear Janus CPCs pattern encapsulated by hydrogel is also fabricated. Both the color and the shape can be changed under the traction of magnets, showing great potentials in flexible smart displays. We believe this work not only offers a new feasible pathway to construct magnetic Janus CPCs patterns by a dispensing-printable fashion, but also provides new opportunities for flexible and smart displays.  相似文献   
17.
18.
Chemistry of Natural Compounds - O- and N-propylamino-derivatives of betulin and betulonic acid oxime and methyl ester were synthesized. Their antitumor activity against a panel of 60 human cancer...  相似文献   
19.
Thin films with a nanometer-scale thickness are of great interest to both scientific and industrial communities due to their numerous applications and unique behaviors different from the bulk. However, the understanding of thin-film mechanics is still greatly hampered due to their intrinsic fragility and the lack of commercially available experimental instruments. In this review, we first discuss the progression of thin-film mechanical testing methods based on the supporting substrate: film-on-solid substrate method, film-on-water tensile tests, and water-assisted free-standing tensile tests. By comparing past studies on a model polymer, polystyrene, the effect of different substrates and confinement effect on the thin-film mechanics is evaluated. These techniques have generated fruitful scientific knowledge in the field of organic semiconductors for the understanding of structure–mechanical property relationships. We end this review by providing our perspective for their bright prospects in much broader applications and materials of interest.  相似文献   
20.
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