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   296篇
  免费   10篇
  国内免费   1篇
化学   202篇
晶体学   4篇
力学   6篇
数学   28篇
物理学   67篇
  2022年   11篇
  2021年   5篇
  2020年   6篇
  2019年   6篇
  2018年   3篇
  2017年   6篇
  2016年   6篇
  2015年   8篇
  2014年   7篇
  2013年   16篇
  2012年   34篇
  2011年   21篇
  2010年   10篇
  2009年   16篇
  2008年   12篇
  2007年   22篇
  2006年   20篇
  2005年   16篇
  2004年   6篇
  2003年   14篇
  2002年   3篇
  2001年   6篇
  2000年   4篇
  1999年   4篇
  1998年   3篇
  1997年   2篇
  1996年   1篇
  1995年   2篇
  1994年   2篇
  1993年   1篇
  1992年   3篇
  1991年   1篇
  1990年   2篇
  1989年   2篇
  1986年   6篇
  1985年   1篇
  1984年   2篇
  1983年   3篇
  1982年   1篇
  1981年   1篇
  1980年   1篇
  1979年   1篇
  1978年   1篇
  1977年   1篇
  1975年   3篇
  1970年   1篇
  1930年   2篇
  1907年   2篇
排序方式: 共有307条查询结果,搜索用时 15 毫秒
41.
Fixing a hole : Hydrothermal chemistry has been exploited in the preparation of a 3D framework material exhibiting 48 % accessible void volume and 1.5 % hydrogen uptake by weight at 120 kPa (see picture). The title compound also exhibits single‐chain magnetic behavior and reversible changes in magnetic properties upon solvation and desolvation.

  相似文献   

42.
Four compounds derived from 2‐aminothiazole and 2‐amino‐2‐thiazoline were prepared by coupling the respective bases with the acid chlorides of either 3‐ or 4‐(N,N‐dimethylamino)benzoic acid. Products were identified using infrared spectroscopy, 1H NMR spectroscopy and electrospray mass spectroscopy and in two cases by single‐crystal X‐ray diffraction. Of the four, N‐(thiazol‐2‐yl)‐3‐(N,N‐dimethylamino)‐benzamide (1), N‐(thiazolin‐2‐yl)‐4‐(N,N‐dimethylamino)benzamide (2), N‐(thiazolin‐2‐yl)‐3‐(N,N‐dimethylamino) benzamide (3) and N‐(thiazolin‐2‐yl)‐4‐(N,N‐dimethylamino)benzamide (4), the hydrochloride salts of compounds 3 and 4 showed anti‐inflammatory activity across a concentration range of 10?2?5 × 10?4 M while 3 (at a concentration of 10?5 M) was found to have no adverse effect on myocardial function. The X‐ray crystal structure of 2 and the 1:1 adduct structure of 3 with 3‐(N,N‐dimethylamino)benzoic acid are reported.  相似文献   
43.
44.
Core–shell bimetallic Au@Ni nanoparticles, with gold cores and thin nickel shells with overall size less than 10 nm, are synthesized and stabilized in pure cubic (fcc) and hexagonal (hcp) phase. Due to their unique crystal, electronic, and geometric structure, they show interesting magnetic and chemical properties. The Au@Nifcc is magnetic, whereas Au@Nihcp is non‐magnetic. Both the bimetallic nanostructures are stable to surface oxidation until 150 °C and show excellent catalytic activity for p‐nitrophenol reduction reaction.  相似文献   
45.
46.
Molecular Diversity - We herein report the facile synthesis of a series of 3,5-substituted-1,2,4-oxadiazole derivatives in good to excellent yields. The anti-inflammatory potential of the newly...  相似文献   
47.
So emulsional: Two hexavanadate-organic hybrids were synthesized and their amphiphilic properties were confirmed by forming emulsions in mixtures of water and nonpolar organic solvents, and were utilized as "emulsion catalysts" in deep desulfurization reactions (see figure). Their catalytic activities show a pH-dependent behavior, which can be explained by the size-change of emulsions and the appearance of reverse emulsions.  相似文献   
48.
The palladium-catalyzed C-H fluorination of 8-methylquinoline derivatives with nucleophilic fluoride is reported. This transformation involves the use of AgF as the fluoride source in combination with a hypervalent iodine oxidant. Both the scope and mechanism of the reaction are discussed.  相似文献   
49.
Ribonuclease?A (RNase A) serves as a convenient model enzyme in the identification and development of inhibitors of proteins that are members of the ribonuclease superfamily. This is principally because the biological activity of these proteins, such as angiogenin, is linked to their catalytic ribonucleolytic activity. In an attempt to inhibit the biological activity of angiogenin, which involves new blood vessel formation, we employed different dinucleosides with varied non-natural backbones. These compounds were synthesized by coupling aminonucleosides with dicarboxylic acids and amino- and carboxynucleosides with an amino acid. These molecules show competitive inhibition with inhibition constant (K(i)) values of (59±3) and (155±5) μM for RNase A. The compounds were also found to inhibit angiogenin in a competitive fashion with corresponding K(i) values in the micromolar range. The presence of an additional polar group attached to the backbone of dinucleosides was found to be responsible for the tight binding with both proteins. The specificity of different ribonucleolytic subsites were found to be altered because of the incorporation of a non-natural backbone in between the two nucleosidic moieties. In spite of the replacement of the phosphate group by non-natural linkers, these molecules were found to selectively interact with the ribonucleolytic site residues of angiogenin, whereas the cell binding site and nuclear translocation site residues remain unperturbed. Docked conformations of the synthesized compounds with RNase A and angiogenin suggest a binding preference for the thymine-adenine pair over the thymine-thymine pair.  相似文献   
50.
Pd(IV) -fluoride complexes, some of which are remarkably insensitive to water, have been synthesized and used in the title reaction, which proceeds with high selectivity to give the product of the C(sp(3) )?F coupling (see scheme, TfO=trifluoromethanesulfonate). Preliminary mechanistic studies implicate a pathway involving dissociation of pyridine followed by direct C?F coupling at the Pd center.  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