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   778篇
  免费   18篇
化学   592篇
晶体学   15篇
力学   18篇
数学   35篇
物理学   136篇
  2022年   4篇
  2021年   6篇
  2020年   8篇
  2019年   8篇
  2018年   5篇
  2017年   6篇
  2016年   7篇
  2015年   8篇
  2014年   17篇
  2013年   35篇
  2012年   44篇
  2011年   40篇
  2010年   27篇
  2009年   20篇
  2008年   36篇
  2007年   39篇
  2006年   35篇
  2005年   58篇
  2004年   38篇
  2003年   29篇
  2002年   46篇
  2001年   21篇
  2000年   25篇
  1999年   27篇
  1998年   3篇
  1997年   6篇
  1996年   7篇
  1995年   4篇
  1994年   7篇
  1993年   10篇
  1992年   9篇
  1991年   16篇
  1990年   11篇
  1989年   6篇
  1988年   8篇
  1987年   9篇
  1986年   11篇
  1985年   8篇
  1984年   17篇
  1983年   11篇
  1982年   3篇
  1981年   7篇
  1980年   10篇
  1979年   3篇
  1978年   11篇
  1977年   4篇
  1976年   5篇
  1973年   3篇
  1972年   4篇
  1958年   5篇
排序方式: 共有796条查询结果,搜索用时 562 毫秒
1.
Aqueous self-assembly of short peptides has attracted growing attention for the construction of supramolecular materials for various bioapplications. Herein, we describe how the thermolysin-assisted biocatalytic construction of a dipeptide hydrazide from an N-protected amino acid and an amino acid hydrazide leads to the formation of thermally stable supramolecular hydrogels. In addition, we demonstrate the post-assembly modification of the supramolecular architectures constructed in situ tethering hydrazide groups as a chemical handle by means of fluorescence imaging.  相似文献   
2.
Tsuyoshi Kitamura 《Tetrahedron》2004,60(43):9649-9657
Synthesis of (+)-anthramycin was examined. A pyrrolobenzodiazepine skeleton could be synthesized by reductive cyclization of pyrrolidine derivative, which was obtained by enyne metathesis. The conjugated enamide ester part of (+)-anthramycin derivative was constructed by cross-metathesis.  相似文献   
3.
The factors affecting pattern‐forming properties in reaction development patterning were examined with polyarylates with various bisphenol moieties. The developability of the photosensitive polyarylates was dependent on the properties of the subtituent (R) in the bisphenol moieties. The development time decreased in the following order: R?C(CH3)2 > fluorenyl unit ? phenolphthalein unit > C(CF3)2 > SO2. This order agreed with that of the reactivity between the polyarylates and ethanolamine, and these orders can be explained by pKa of the bisphenol used to prepare the polyarylates. The development with NH2? R′? OH resulted in successful positive‐tone pattern formation. However, pattern formation with the developers containing NH2? R′? OCH3 was unsuccessful. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2694–2706, 2006  相似文献   
4.
5.
6.
Quantum yields, lifetimes and shapes of fluorescence from polymers containing the trans-1,2-dicarbazolylcyclobutane (DCZB) or carbazolyl structures were studied in N,N-dimethylformamide. No sandwich-type excimer formation was observed for DCZB polymers. The so-called second excimer observed in poly(9-vinylcarbazole) might also be produced in poly(9-ethyl-3-vinylcarbazole).  相似文献   
7.
Intravascular clot formation is an important factor in a number of cardiovascular diseases. Therefore, the prevention of blood coagulation has become a major target for new therapeutic agents. One attractive approach is the inhibition of factor Xa (FXa), which is a key enzyme in coagulation cascade responsible for the generation of thrombin by limited proteolysis of its zymogen, prothrombin. We have investigated 1-arylsulfonyl-3-piperazinone derivatives, containing a 4-(piperidino)pyridine group in place of guanidino and/or amidino groups, and discovered compound M55113 (30a: 4-[(6-Chloro-2-naphthalenyl)sulfonyl]-1-[[1-(4-pyridinyl)-4-piperidinyl]methyl]piperazinone), as a potent inhibitor of FXa (IC50=0.06 microM) with high selectivity for FXa over trypsin and thrombin.  相似文献   
8.
9.
The functionalized pyranosyl hetero-olefins 4a, 13 and 15 received a remarkable diastereoselective addition of methyllithium to form threo adducts, one of which was introduced into a possible synthetic intermediate as 3 for maytansine (1) along Scheme I.  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