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   18772篇
  免费   1686篇
  国内免费   12147篇
化学   27789篇
晶体学   655篇
力学   386篇
综合类   498篇
数学   198篇
物理学   3079篇
  2024年   72篇
  2023年   325篇
  2022年   433篇
  2021年   510篇
  2020年   501篇
  2019年   525篇
  2018年   408篇
  2017年   505篇
  2016年   632篇
  2015年   680篇
  2014年   1397篇
  2013年   1311篇
  2012年   1171篇
  2011年   1345篇
  2010年   1337篇
  2009年   1564篇
  2008年   1634篇
  2007年   1533篇
  2006年   1667篇
  2005年   1725篇
  2004年   1675篇
  2003年   1562篇
  2002年   1447篇
  2001年   1267篇
  2000年   924篇
  1999年   821篇
  1998年   827篇
  1997年   596篇
  1996年   617篇
  1995年   682篇
  1994年   560篇
  1993年   402篇
  1992年   465篇
  1991年   487篇
  1990年   401篇
  1989年   348篇
  1988年   101篇
  1987年   43篇
  1986年   34篇
  1985年   27篇
  1984年   20篇
  1983年   17篇
  1982年   3篇
  1981年   1篇
  1980年   1篇
  1959年   1篇
  1951年   1篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
51.
A new cobalt(Ⅱ) complex with tridentate ligand 2, 6-bis (benzimidazol-2-yl)pyridine has been synthesized by microwave irradiation method and characterized by elemental analysis,electrochemical and spectral methods. The binding of the complex with calf thymus DNA has also been investigated by absorption and fluorescence spectra.  相似文献   
52.
A mild, regioselective 1, 3-dipolar cycloaddition protocol for the preparation ofphenylselenomethyl isoxazolines through substituted allyl phenyl selenides and nitrile oxides wasreported.  相似文献   
53.
2,5-Disubstituted oxazoles were prepared conveniently by treatment of aromatic α-methyl ketones and nitriles with poly[styrene(iodosodiacetate)] in one-pot process.  相似文献   
54.
As photosensitizer for solar cell, a new ruthenium (Ⅱ) complex with four ester groups had been synthesized, in which a phenol substituted by {[(2-hydroxy-5-tert-butylbenzyl)(pyridyl-2-methyl)amino]methyl} is covalently linked to ruthenium (Ⅱ) tris-bipyridine. The structures of the new compounds were confirmed by NMR and ESI-MS spectra. The electrochemical and photochemical properties were also studied.  相似文献   
55.
The first intramolecular charge transfer transition based on 2-ureido-4[1H]-pyrimidinone binding module was reported.  相似文献   
56.
A facile solid phase synthesis of 2-substituted 1,3-oxazin-6-ones using polymer-supported Meldrum‘s acid has been reported. Reaction of the resin-bound cyclic malonic acid ester with triethyl orthoformate and subsequent double substitution with amide, afforded the corresponding polymer-supported acylaminomethylene cyclic malonic acid ester, which upon thermal treatment led to 1, 3-oxazin-6-ones in good yields and with high purity.  相似文献   
57.
程志林  万惠霖刘赞 《中国化学》2004,22(12):1454-1455
Zeolite A rods by self-assembly of zeolite A microcrystal were successfully synthesized by microwave-assisted hydrotherrnal synthesis. The average size of zeolite crystals consisting of self-assembling materials was about 300 nm and the length of zeolite rods was in the range of 15--30μm.  相似文献   
58.
The relation of the isoelectric point (IEP) and the point of zero net charge (PZNC) of the hydrotalcite-like compounds was discussed. It was found that the IEP does not equal to the PZNC and the IEP is higher than the PZNC. The structural positive charges existing in the HTlc,which cause the difference between the IEP and the PZNC. The effects of the structural positive charges of the HTlc on its IEP and PZNC are the same as the specific adsorption of metal cations.  相似文献   
59.
Two novel polymerizable dyes with anthraquinone residue have been prepared, and their structures were characterized by FTIR, ^1HNMR and EA.  相似文献   
60.
A mono-funtionalised tetraphenylporphyrin (TPP) bearing valine moiety at the phenyl ring was synthesized for photocytotoxicity examination in four steps, starting from regiospecific mono-nitration of TPP at the phenyl ring. The in vitro photocytotoxicitic effect against SPC-Al adenocarcinona cell line was tested.  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