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   2965篇
  免费   561篇
  国内免费   462篇
化学   2361篇
晶体学   45篇
力学   148篇
综合类   21篇
数学   350篇
物理学   1063篇
  2024年   6篇
  2023年   55篇
  2022年   95篇
  2021年   118篇
  2020年   145篇
  2019年   136篇
  2018年   112篇
  2017年   122篇
  2016年   175篇
  2015年   161篇
  2014年   187篇
  2013年   267篇
  2012年   260篇
  2011年   246篇
  2010年   226篇
  2009年   168篇
  2008年   203篇
  2007年   151篇
  2006年   155篇
  2005年   161篇
  2004年   131篇
  2003年   90篇
  2002年   103篇
  2001年   117篇
  2000年   70篇
  1999年   70篇
  1998年   36篇
  1997年   30篇
  1996年   25篇
  1995年   23篇
  1994年   22篇
  1993年   18篇
  1992年   16篇
  1991年   14篇
  1990年   20篇
  1989年   8篇
  1988年   5篇
  1987年   8篇
  1986年   12篇
  1985年   8篇
  1984年   4篇
  1983年   2篇
  1982年   3篇
  1981年   2篇
  1980年   1篇
  1979年   1篇
排序方式: 共有3988条查询结果,搜索用时 281 毫秒
101.
102.
The steam-assistant heteroatoms of sulfur and phosphorus dual-doped graphene film fabricated via an ice-template and thermal-activation approach demonstrates an excellent pseudocapacitive behavior in flexible electrochemical capacitors.  相似文献   
103.
104.
We propose a new general type of splitting methods for accretive operators in Banach spaces. We then give the sufficient conditions to guarantee the strong convergence. In the last section, we apply our results to the minimization optimization problem and the linear inverse problem including the numerical examples.  相似文献   
105.
106.
Catalytic allylic γ‐substitution with Morita‐Baylis‐Hillman (MBH) adducts for creating a new family of unsymmetrical dicarbonyl compounds was presented in this work, in which a variety of allylated amide products were achieved in good yields and high regioselectivity with excellent linear‐to‐branched ratios. Especially, it was found that the Pd/HZNU‐Phos complex exhibited remarkably high activity (with a TON up to 16800) in this transformation between dicarbonyl amides and MBH adducts. In addition, the possibly multisite interaction between multifunctional Pd/HZNU‐Phos catalyst system and substrates might responsible for its exceptionally high efficiency in this reaction.  相似文献   
107.
The mobility of free macromolecular chains is of importance to the growth of crystallites in a crystallizing sustainable polylactide (PLA), which was scarcely explored by rheology. In this study, the time‐resolved rheological properties for PLA during isothermal crystallization were investigated first, showing that the storage and loss modulus experience 2–3 decades of increase. The Avrami analysis reveals that the crystallization kinetics in rheological measurement protocol follows the homogeneous nucleation and three‐dimensional growth mechanism. The linear viscoelastic properties in the vicinity of physical gelation point were then studied at the inverse quenching temperature of 165 °C. The results show that physical gelation occurs when the critical absolute crystallinity reaches 13% as determined by the rheological method. Relaxation time spectra reveal that the interfacial relaxation is greatly retarded but the presence of growing spherulites possesses little constraint on the mobility of free chains in matrix especially before physical gelation point. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 1235–1244  相似文献   
108.
109.
110.
A red–near‐IR dual‐emissive nanocluster with the composition [Au10Ag2(2‐py?C≡C)3(dppy)6](BF4)5 ( 1 ; 2‐py?C≡C is 2‐pyridylethynyl, dppy=2‐pyridyldiphenylphosphine) has been synthesized. Single‐crystal X‐ray structural analysis reveals that 1 has a trigonal bipyramidal Au10Ag2 core that contains a planar Au4(2‐py?C≡C)3 unit sandwiched by two Au3Ag(dppy)3 motifs. Cluster 1 shows intense red–NIR dual emission in solution. The visible emission originates from metal‐to‐ligand charge transfer (MLCT) from silver atoms to phosphine ligands in the Au3Ag(dppy)3 motifs, and the intense NIR emission is associated with the participation of 2‐pyridylethynyl in the frontier orbitals of the cluster, which is confirmed by a time‐dependent density functional theory (TD‐DFT) calculation.  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