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   21104篇
  免费   737篇
  国内免费   356篇
化学   13123篇
晶体学   126篇
力学   646篇
综合类   30篇
数学   3266篇
物理学   5006篇
  2023年   135篇
  2022年   230篇
  2021年   402篇
  2020年   354篇
  2019年   362篇
  2018年   325篇
  2017年   271篇
  2016年   616篇
  2015年   569篇
  2014年   635篇
  2013年   1158篇
  2012年   1111篇
  2011年   1247篇
  2010年   836篇
  2009年   761篇
  2008年   1069篇
  2007年   1069篇
  2006年   915篇
  2005年   903篇
  2004年   836篇
  2003年   791篇
  2002年   817篇
  2001年   517篇
  2000年   457篇
  1999年   374篇
  1998年   280篇
  1997年   266篇
  1996年   276篇
  1995年   289篇
  1994年   275篇
  1993年   215篇
  1992年   198篇
  1991年   207篇
  1990年   213篇
  1989年   173篇
  1988年   160篇
  1987年   160篇
  1986年   144篇
  1985年   243篇
  1984年   256篇
  1983年   175篇
  1982年   202篇
  1981年   161篇
  1980年   167篇
  1979年   155篇
  1978年   130篇
  1977年   171篇
  1976年   151篇
  1975年   121篇
  1973年   118篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Journal of Dynamics and Differential Equations - In this paper we focus on a class of symmetric vector fields in the context of singularly perturbed fast-slow dynamical systems. Our main question...  相似文献   
2.
Pentafluorosulfanyl (SF5)-containing compounds and corresponding analogs are a highly valuable class of fluorine-containing building blocks owing to their unique properties. The reason for that is the set of peculiar and tremendously beneficial characteristics they can impart on molecules once introduced onto them. Despite this, their application in distinct scientific fields remains modest, given the extremely harsh reaction conditions needed to access such compounds. The recent synthetic approaches via S−F, and C−SF5 bond formation as well as the use of SF5-containing building blocks embody a “stairway-to-heaven” loophole in the synthesis of otherwise-inaccessible chemical scaffolds only a few years ago. Herein, we report and evaluate the properties of the SF5 group and analogs, by summarizing synthetic methodologies available to access them as well as following applications in material science and medicinal chemistry since 2015.  相似文献   
3.
4.
5.
By tuning the length and rigidity of the spacer of bis(biurea) ligands L, three structural motifs of the A2L3 complexes (A represents anion, here orthophosphate PO43?), namely helicate, mesocate, and mono‐bridged motif, have been assembled by coordination of the ligand to phosphate anion. Crystal structure analysis indicated that in the three complexes, each of the phosphate ions is coordinated by twelve hydrogen bonds from six surrounding urea groups. The anion coordination properties in solution have also been studied. The results further demonstrate the coordination behavior of phosphate ion, which shows strong tendency for coordination saturation and geometrical preference, thus allowing for the assembly of novel anion coordination‐based structures as in transition‐metal complexes.  相似文献   
6.
In this study, the functional interaction of HPLW peptide with VEGFR2 (Vascular Endothelial Growth Factor Receptor 2) was determined by using fast 15N‐edited NMR spectroscopic experiments. To this aim, 15N uniformly labelled HPLW has been added to Porcine Aortic Endothelial Cells. The acquisition of isotope‐edited NMR spectroscopic experiments, including 15N relaxation measurements, allowed a precise characterization of the in‐cell HPLW epitope recognized by VEGFR2.  相似文献   
7.
8.
Journal of Solid State Electrochemistry - In this study, galvanostatic electrolysis, through the use of the platinum supported on Ti (Ti/Pt) and Ti/TiO2-nanotubes/PbO2 anodes, was conducted in an...  相似文献   
9.
10.
A fully quantitative theory of the relationship between protein conformation and optical spectroscopy would facilitate deeper insights into biophysical and simulation studies of protein dynamics and folding. In contrast to intense bands in the far-ultraviolet, near-UV bands are much weaker and have been challenging to compute theoretically. We report some advances in the accuracy of calculations in the near-UV, which were realised through the consideration of the vibrational structure of the electronic transitions of aromatic side chains.  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