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   1212篇
  免费   44篇
  国内免费   7篇
化学   783篇
晶体学   5篇
力学   42篇
数学   260篇
物理学   173篇
  2023年   3篇
  2022年   26篇
  2021年   22篇
  2020年   20篇
  2019年   18篇
  2018年   25篇
  2017年   18篇
  2016年   49篇
  2015年   37篇
  2014年   45篇
  2013年   87篇
  2012年   68篇
  2011年   93篇
  2010年   53篇
  2009年   66篇
  2008年   82篇
  2007年   79篇
  2006年   76篇
  2005年   59篇
  2004年   54篇
  2003年   52篇
  2002年   53篇
  2001年   13篇
  2000年   13篇
  1999年   11篇
  1998年   9篇
  1997年   8篇
  1996年   8篇
  1995年   7篇
  1994年   10篇
  1993年   14篇
  1992年   9篇
  1991年   4篇
  1990年   4篇
  1989年   5篇
  1988年   5篇
  1987年   6篇
  1986年   5篇
  1985年   2篇
  1984年   16篇
  1983年   10篇
  1982年   3篇
  1981年   3篇
  1980年   3篇
  1977年   2篇
  1976年   2篇
  1975年   1篇
  1974年   1篇
  1963年   1篇
  1935年   1篇
排序方式: 共有1263条查询结果,搜索用时 15 毫秒
81.
82.
The aim of this study is to identify and characterize the parts of an extensive form game that are ??relevant?? to determining whether the outcome of a certain strategy profile is an equilibrium outcome. We formally define what we mean by ??relevant?? and refer to the associated collection of information sets as essential. We apply this idea to a number of classic equilibrium concepts and discuss some implications of our approach.  相似文献   
83.
Radical anions from several 3,4‐aryl‐disubstituted derivatives of 1,2,5‐thiadiazole 1,1‐dioxide were accumulated through chemical reduction of the substrates in aprotic solvents. The radical anions were characterized by electron spin resonance and cyclic voltammetry. DFT theoretical calculations were also performed for the 3,4‐diphenyl derivative. The course of the reductions was followed using cyclic voltammetry. Uncommon reductants, such as amides, were found to be effective under certain conditions. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   
84.
85.
Formation of an o-quinone methide via C-C fragmentation of a zwitterion formed by intramolecular excited state proton transfer from an o-allylphenol derivative is reported for the first time.  相似文献   
86.
87.
The principal values of the 13C chemical shift tensors in potassium carbonate (K2CO3), trithiocarbonate (K2CS3), bicarbonate (KHCO3), methylcarbonate (KO2COCH3), S-methyl-monothiocarbonate (KO2CSCH3), O-methyl-monothiocarbonate (KOSCOCH3), S-methyl-dithiocarbonate (KOSCSCH3), and O-methyl-dithiocarbonate (KS2COCH3), were measured in solid-state nuclear magnetic resonance experiments. Chemical shift tensor calculations on the corresponding isolated anions were used to assign the chemical shift tensor orientations in the molecular frames of all anions. The correlation between experimental and calculated principal values improves significantly when the calculations are performed on isolated anions with proton-optimized X-ray geometries rather than on isolated anions with fully optimized geometries. Further considerable improvement in the correlation is achieved by utilizing the embedded ion method, which was recently developed to include electrostatic crystal potentials in chemical shift tensor calculations on ionic compounds. Similarities and differences in the chemical shift tensor orientations and principal values of the trigonal sp2 carbon atoms in the carbonate and thiocarbonate anions are compared with those known for condensed polyaromatic hydrocarbons.  相似文献   
88.
89.
Self-assembling porphyrin-modified peptides   总被引:1,自引:0,他引:1  
[structure: see text] We report the synthesis and characterization of a novel supramolecular assembly that features long-range electronic coupling between porphyrins covalently attached to a designed peptide scaffold. The resulting construct self-assembles to form extended organized aggregates in which the porphyrins engage in exciton coupling.  相似文献   
90.
The magnetization reversal in exchange-biased ferromagnetic-antiferromagnetic (FM-AFM) bilayers is investigated. Different reversal pathways on each branch of the hysteresis loop, i.e., asymmetry, are obtained both experimentally and theoretically when the magnetic field is applied at certain angles from the anisotropy direction. The range of angles and the magnitude of this asymmetry are determined by the ratio between the FM anisotropy and the interfacial FM-AFM exchange anisotropy. The occurrence of asymmetry is linked with the appearance of irreversibility, i.e., finite coercivity, as well as with the maximum of exchange bias, increasing for larger anisotropy ratios. Our results indicate that asymmetric hysteresis loops are intrinsic to exchange-biased systems and the competition between anisotropies determines the asymmetric behavior of the magnetization reversal.  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