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   38782篇
  免费   1101篇
  国内免费   460篇
化学   25697篇
晶体学   222篇
力学   980篇
综合类   32篇
数学   6204篇
物理学   7208篇
  2022年   329篇
  2021年   441篇
  2020年   475篇
  2019年   491篇
  2018年   401篇
  2017年   332篇
  2016年   806篇
  2015年   749篇
  2014年   845篇
  2013年   2075篇
  2012年   1749篇
  2011年   2141篇
  2010年   1238篇
  2009年   1195篇
  2008年   1904篇
  2007年   1975篇
  2006年   1809篇
  2005年   1786篇
  2004年   1618篇
  2003年   1483篇
  2002年   1425篇
  2001年   786篇
  2000年   679篇
  1999年   553篇
  1998年   500篇
  1997年   507篇
  1996年   577篇
  1995年   474篇
  1994年   504篇
  1993年   434篇
  1992年   405篇
  1991年   417篇
  1990年   383篇
  1989年   384篇
  1988年   373篇
  1987年   336篇
  1986年   317篇
  1985年   506篇
  1984年   565篇
  1983年   377篇
  1982年   543篇
  1981年   479篇
  1980年   466篇
  1979年   454篇
  1978年   435篇
  1977年   452篇
  1976年   418篇
  1975年   365篇
  1974年   357篇
  1973年   348篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
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   
2.
3.
4.
Journal of Computer-Aided Molecular Design - Accurate predictions of acid dissociation constants are essential to rational molecular design in the pharmaceutical industry and elsewhere. There has...  相似文献   
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.
7.
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   
8.
9.
Following colonisation of South America by the Spanish, many new naturally occurring substances were sent to Europe. One of these was the silvery, unreactive metal, platinum, discovered in New Grenada in the mid-eighteenth century. It was often found in granular form, associated with gold, and the challenge to chemists was to refine it, produce it as wire or sheet, and determine its chemical properties. This interested the professor of chemistry at the University of Edinburgh, Joseph Black, who was able to obtain samples from London-based Spanish contacts, particularly Ignacio Luzuriaga. This paper examines how Black transmitted his knowledge of the metal to large numbers of students attending his annual course.  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