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   1313626篇
  免费   28803篇
  国内免费   7421篇
化学   648210篇
晶体学   12829篇
力学   74867篇
综合类   94篇
数学   240960篇
物理学   372890篇
  2020年   15980篇
  2019年   16066篇
  2018年   13776篇
  2016年   27748篇
  2015年   20283篇
  2014年   29978篇
  2013年   73783篇
  2012年   37908篇
  2011年   35477篇
  2010年   37039篇
  2009年   39353篇
  2008年   34251篇
  2007年   29903篇
  2006年   35335篇
  2005年   28351篇
  2004年   29423篇
  2003年   27316篇
  2002年   25103篇
  2001年   27000篇
  2000年   22459篇
  1999年   20038篇
  1998年   18701篇
  1997年   19314篇
  1996年   19117篇
  1995年   18489篇
  1994年   18063篇
  1993年   17547篇
  1992年   17578篇
  1991年   17860篇
  1990年   17070篇
  1989年   17116篇
  1988年   16725篇
  1987年   16747篇
  1986年   15667篇
  1985年   22177篇
  1984年   23460篇
  1983年   19567篇
  1982年   21263篇
  1981年   20481篇
  1980年   19803篇
  1979年   20144篇
  1978年   21417篇
  1977年   21069篇
  1976年   20802篇
  1975年   19462篇
  1974年   19099篇
  1973年   19614篇
  1972年   14104篇
  1968年   12173篇
  1967年   12535篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Moscow University Chemistry Bulletin - A piezoactive nanofiber composite PVDF film with TiO2 nanoparticles included in it was synthesized by electrospinning. The composition, morphology and...  相似文献   
2.
Moscow University Chemistry Bulletin - Hydrodistillation (HD), steam distillation (SD) and microwave-assisted hydrodistillation (MAHD) extraction methods were assessed for their effects on yield,...  相似文献   
3.
Moscow University Chemistry Bulletin - This review is devoted to the development, properties, and application of biosensors based on graphene nanomaterials. It is shown that such biosensors are...  相似文献   
4.
Moscow University Chemistry Bulletin - NAD+-dependent formate dehydrogenase (FDH, EC 1.2.1.2) from bacterium Staphylococcus aureus (SauFDH) is the most active enzyme among FDHs of this group;...  相似文献   
5.
Theoretical and Experimental Chemistry - The electronic and spatial structure of 3,4-ethylenedioxythiophene oligomer containing 12 units (E12) in 0, +1, +2, +3, and +4 charge states has been...  相似文献   
6.
Heteroatom-containing polymers have strong potential as sustainable replacements for petrochemicals, show controllable monomer–polymer equilibria and properties spanning plastics, elastomers, fibres, resins, foams, coatings, adhesives, and self-assembled nanostructures. Their current and future applications span packaging, house-hold goods, clothing, automotive components, electronics, optical materials, sensors, and medical products. An interesting route to these polymers is the catalysed ring-opening copolymerisation (ROCOP) of heterocycles and heteroallenes. It is a living polymerization, occurs with high atom economy, and creates precise, new polymer structures inaccessible by traditional methods. In the last decade there has been a renaissance in research and increasing examples of commercial products made using ROCOP. It is better known in the production of polycarbonates and polyesters, but is also a powerful route to make N-, S-, and other heteroatom-containing polymers, including polyamides, polycarbamates, and polythioesters. This Review presents an overview of the different catalysts, monomer combinations, and polymer classes that can be accessed by heterocycle/heteroallene ROCOP.  相似文献   
7.
Tetrahedral main-group compounds are normally configurationally stable, but P-epimerization of the chiral phosphiranium cations syn- or anti-[Mes*P(Me)CH2CHPh][OTf] (Mes*=2,4,6-(t-Bu)3C6H2) occurred under mild conditions at 60 °C in CD2Cl2, resulting in isomerization to give a syn-enriched equilibrium mixture. Ion exchange with excess [NBu4][Δ-TRISPHAT] (Δ-TRISPHAT=Δ-P(o-C6Cl4O2)3) followed by chromatography on silica removed [NBu4][OTf] and gave mixtures of syn- and anti-[Mes*P(Me)CH2CHPh][Δ-TRISPHAT]?x[NBu4][Δ-TRISPHAT]. NMR spectroscopy showed that isomerization proceeded with epimerization at P and retention at C. DFT calculations are consistent with a mechanism involving P-C cleavage to yield a hyperconjugation-stabilized carbocation, pyramidal inversion promoted by σ-interaction of the P lone pair with the neighboring β-carbocation, and ring closure with inversion of configuration at P.  相似文献   
8.
Journal of Solution Chemistry - Liquid–liquid equilibrium (LLE) data and phase diagrams for new aqueous two-phase systems (ATPSs) containing 1-butyl-3-methylimidazolium chloride...  相似文献   
9.
Journal of Solution Chemistry - A polemic is given regarding the apparent molal volumes reported in the recent paper by Mohammadi and coworkers. The authors’ calculated apparent molal volumes...  相似文献   
10.
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