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   4137篇
  免费   210篇
  国内免费   41篇
化学   2705篇
晶体学   41篇
力学   134篇
数学   443篇
物理学   1065篇
  2024年   15篇
  2023年   39篇
  2022年   126篇
  2021年   219篇
  2020年   171篇
  2019年   169篇
  2018年   169篇
  2017年   134篇
  2016年   202篇
  2015年   145篇
  2014年   211篇
  2013年   376篇
  2012年   305篇
  2011年   301篇
  2010年   238篇
  2009年   190篇
  2008年   210篇
  2007年   179篇
  2006年   137篇
  2005年   74篇
  2004年   99篇
  2003年   55篇
  2002年   56篇
  2001年   32篇
  2000年   28篇
  1999年   32篇
  1998年   20篇
  1997年   29篇
  1996年   26篇
  1995年   12篇
  1994年   26篇
  1993年   20篇
  1992年   19篇
  1991年   11篇
  1990年   19篇
  1989年   13篇
  1988年   15篇
  1987年   16篇
  1985年   23篇
  1984年   23篇
  1983年   15篇
  1982年   20篇
  1981年   13篇
  1980年   38篇
  1979年   11篇
  1977年   15篇
  1976年   10篇
  1973年   11篇
  1969年   9篇
  1968年   8篇
排序方式: 共有4388条查询结果,搜索用时 421 毫秒
131.
132.
This paper reviews the use of solid polymeric electrolyte (SPE) and gel polymeric electrolyte (GPE) in photoelectrochemical cell (PEC) and dye-sensitized solar cell (DSSC). The structure of PEC and its working principle are presented. The various types of polymer electrolytes utilized in PEC and DSSC have been highlighted in this review. It also highlights the comparison of performance of PEC and DSSC utilizing those polymer electrolytes. This review is completed with the list of other SPEs that potentially be tested in DSSC.  相似文献   
133.
Composites of polyaniline with yttrium oxide (Y2O3) nanoparticles have been prepared by chemical polymerizations method by increasing the weight percentage of yttrium oxide. X-Ray diffraction (XRD) and Fourier Transform Infrared Spectra (FTIR) were used to characterize the composites. XRD and FTIR pattern indicate that Polyaniline (PANI) is intercalated into the layers of Y2O3 nanoparticles successfully by in situ polymerization and therefore the degree of crystallinity increases due to crystalline of yttrium oxide nanoparticles. The scanning electron micrographs (SEM) also confirm the formation of dual phase of platelet as well as of flaky structure in PANI-Y2O3. Temperature dependant DC conductivity showed three dimensional variable ranges hopping (3D VRH) model. Activation energy, density of states and hopping length are calculated and found to be influenced by intercalating PANI into the layers of Y2O3 clay.  相似文献   
134.
135.
136.
Russian Journal of Electrochemistry - Zinc selenide has applications in the fabrication of low-cost solar cells and optoelectronic devices. Due to its optical properties and large direct bandgap,...  相似文献   
137.
Two series of new Cu(II) complexes derived from the reaction of copper acetate with the non-linear 1,2,3-triazole-based Schiff bases have successfully been synthesised. The structures of the ligands and its complexes were elucidated by elemental analysis, FT-IR, 1H-NMR and UV–visible spectroscopic techniques. The differential scanning calorimetry and polarizing optical microscopy supported the anisotropic properties of uncoordinated ligands in which the focal conic fan-shaped texture and/or broken fan-shaped texture characteristics of respective SmA and SmC phases were recorded. However, not all of their corresponding Cu(II) complexes are mesogenic. Although the iodo-substituted ligands with even parity C10H29 to C14H33 are non-stable and exhibit SmA phase which is not reproducible, the ultimate Cu(II) complexes show exclusively stable SmA phase. This observation can be ascribed to the enhanced colinearity and molecular anisotropic by the presence of Cu-N and Cu-O coordination modes. On the other hand, the comparison studies show that different positions of ortho-hydroxyl group affect the mesomorphic and thermal behaviour of ligands and Cu(II) complexes.  相似文献   
138.
Abstract

A series of new pyrimidine and quinazoline derivatives was synthesized by a Biginelli-like reaction of urea/thiourea, aldehyde, and ketone in the presence of hydrochloric acid as a catalyst. In a similar way, some novel diazatricyclo derivatives were obtained via a Biginelli-like reaction followed by an intramolecular Michael-type addition. The yields of products were reasonable after recrystallization from ethanol. All newly synthesized compounds were characterized using IR and NMR (1H and 13C) spectroscopy and elemental analysis. The antibacterial activity of these compounds was investigated against Staphylococcus aureus (RTCC, 1885), and Escherichia Coli (ATCC, 35922).

Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.  相似文献   
139.
Hexamethylenetetramine-bromine supported onto[3pc] silica gel rapidly converts trimethylsilyl ethers to their corresponding carbonyl compounds under microwave irradiation in solventless system.  相似文献   
140.
Research on Chemical Intermediates - ZnAl2O4/ZnO nanocomposites with different ZnO (20, 30, and 40 mol%) concentrations and coated samples on supports were successfully prepared through...  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