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   1531229篇
  免费   43672篇
  国内免费   19217篇
化学   773802篇
晶体学   22408篇
力学   86007篇
综合类   764篇
数学   275393篇
物理学   435744篇
  2021年   16460篇
  2020年   18997篇
  2019年   19377篇
  2018年   23307篇
  2017年   22170篇
  2016年   35297篇
  2015年   25392篇
  2014年   35447篇
  2013年   80951篇
  2012年   51409篇
  2011年   56505篇
  2010年   49568篇
  2009年   51487篇
  2008年   51250篇
  2007年   49182篇
  2006年   43493篇
  2005年   40420篇
  2004年   37793篇
  2003年   34725篇
  2002年   34010篇
  2001年   32059篇
  2000年   27689篇
  1999年   24872篇
  1998年   22840篇
  1997年   22572篇
  1996年   22690篇
  1995年   20524篇
  1994年   19825篇
  1993年   19143篇
  1992年   19208篇
  1991年   19361篇
  1990年   18443篇
  1989年   18315篇
  1988年   17807篇
  1987年   17652篇
  1986年   16658篇
  1985年   22982篇
  1984年   24097篇
  1983年   20211篇
  1982年   21883篇
  1981年   21050篇
  1980年   20359篇
  1979年   20563篇
  1978年   21855篇
  1977年   21406篇
  1976年   21179篇
  1975年   19916篇
  1974年   19600篇
  1973年   20087篇
  1972年   14523篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
11.
Zhang  Bing  Yang  Jie-qin  Liu  Ying  Hu  Bin  Yang  Yang  Zhao  Li  Lu  Qiang 《Cellulose (London, England)》2022,29(12):6565-6578
Cellulose - Heating is essential in various biomass pre-treatments and thermal conversion processes. It is of practical significance to study the characteristics of cellulose-lignin and...  相似文献   
12.
Automotive proton exchange membrane fuel cell stacks need to meet manufacturer specified rated beginning-of-life (BOL) performance before being assembled into vehicles and shipped off to customers. The process of “breaking-in” of a freshly assembled stack is often referred to as “conditioning.” It has become an intensely researched area especially in automotive companies, where imminent commercialization of fuel cell electric vehicles (FCEVs) demands a short, energy- and cost-efficient, and practical conditioning protocol. Significant advances in reducing the conditioning time from 1 to 2 days to as low as 4h or less, in some cases without the use of additional inert gases such as nitrogen, and with minimal use of hydrogen, and specialized test stations will be discussed.  相似文献   
13.
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   
14.
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   
15.
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   
16.
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   
17.
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   
18.
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   
19.
20.
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   
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