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   722139篇
  免费   18523篇
  国内免费   8987篇
化学   380991篇
晶体学   10254篇
力学   36878篇
综合类   332篇
数学   93484篇
物理学   227710篇
  2021年   8396篇
  2020年   9317篇
  2019年   9954篇
  2018年   11988篇
  2017年   11897篇
  2016年   16906篇
  2015年   10803篇
  2014年   16312篇
  2013年   34267篇
  2012年   28967篇
  2011年   33463篇
  2010年   24134篇
  2009年   23730篇
  2008年   29748篇
  2007年   29230篇
  2006年   26748篇
  2005年   23714篇
  2004年   21673篇
  2003年   19257篇
  2002年   18840篇
  2001年   19790篇
  2000年   15637篇
  1999年   12619篇
  1998年   10774篇
  1997年   10618篇
  1996年   10012篇
  1995年   9003篇
  1994年   8753篇
  1993年   8316篇
  1992年   8799篇
  1991年   9122篇
  1990年   8705篇
  1989年   8374篇
  1988年   8238篇
  1987年   7982篇
  1986年   7576篇
  1985年   9563篇
  1984年   10094篇
  1983年   8412篇
  1982年   8787篇
  1981年   8373篇
  1980年   7932篇
  1979年   8369篇
  1978年   8726篇
  1977年   8592篇
  1976年   8606篇
  1975年   8170篇
  1974年   7994篇
  1973年   8395篇
  1972年   5971篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
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   
12.
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   
13.
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   
14.
15.
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   
16.
Refractory wounds have always been an important issue to healthcare systems, whose healing process is always delayed by multiple factors, including bacterial infections, chronic inflammation, and excessive exudates, etc. Employing multifunctional wound dressings is recognized as an effective strategy to deal with refractory wounds, which has yielded promising outcomes in recent years. Among these advanced wound dressings, fibrous dressings have gained growing attention due to their unique merits. Such wound dressings have demonstrated great potential in delivering theranostic agents, such as antibacterial agents, anti-inflammatory drugs, growth factors, and diagnostic probes, etc., for the purposes of accelerating wound healing. This paper reviews the development of multifunctional fibrous dressings and their applications in treating refractory wounds. The construction approaches of novel fibrous dressing with capabilities of antibacterial, anti-inflammation, exudate management and diagnosis were also introduced. Furthermore, the existing problems and challenges are also discussed briefly.  相似文献   
17.
18.
Journal of Structural Chemistry - The structures of Ni(II), Cu(II), and Zn(II) complexes with anions of 2,5-pyrrolyl-disubstituted nitronyl nitroxide (L1) and iminonitroxide (L2) diradicals (HL1 is...  相似文献   
19.
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   
20.
Theoretical and Mathematical Physics - We describe the procedure of dimensional reduction of massless fields in $$(d+1)$$ -dimensional Minkowski space to massive fields in $$d$$ dimensions in 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