全文获取类型
收费全文 | 4611篇 |
免费 | 1076篇 |
国内免费 | 699篇 |
专业分类
化学 | 5713篇 |
晶体学 | 11篇 |
力学 | 86篇 |
综合类 | 11篇 |
数学 | 166篇 |
物理学 | 399篇 |
出版年
2024年 | 4篇 |
2023年 | 54篇 |
2022年 | 98篇 |
2021年 | 131篇 |
2020年 | 268篇 |
2019年 | 123篇 |
2018年 | 184篇 |
2017年 | 131篇 |
2016年 | 271篇 |
2015年 | 352篇 |
2014年 | 335篇 |
2013年 | 437篇 |
2012年 | 382篇 |
2011年 | 358篇 |
2010年 | 335篇 |
2009年 | 342篇 |
2008年 | 405篇 |
2007年 | 331篇 |
2006年 | 315篇 |
2005年 | 287篇 |
2004年 | 259篇 |
2003年 | 319篇 |
2002年 | 87篇 |
2001年 | 86篇 |
2000年 | 82篇 |
1999年 | 53篇 |
1998年 | 39篇 |
1997年 | 73篇 |
1996年 | 69篇 |
1995年 | 59篇 |
1994年 | 22篇 |
1993年 | 25篇 |
1992年 | 24篇 |
1991年 | 8篇 |
1990年 | 11篇 |
1989年 | 7篇 |
1988年 | 4篇 |
1987年 | 4篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1983年 | 3篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 2篇 |
排序方式: 共有6386条查询结果,搜索用时 187 毫秒
31.
32.
33.
T. Katsuki 《Russian Chemical Bulletin》2004,53(9):1859-1870
The recent development of asymmetric Baeyer—Villiger oxidation of prochiral and racemic ketones is briefly summarized, focusing on the regio- and stereocontrol of the oxidation attained by regulating the stereoelectronic demand in the step of rearrangement of the Criegee intermediate.Based on the report presented at the International Conference Modern Trends in Organoelement and Polymer Chemistry dedicated to the 50th anniversary of the A. N. Nesmeyanov Institute of Organoelement Compounds of the Russian Academy of Sciences (Moscow, May 30–June 4, 2004).Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1784–1794, September, 2004. 相似文献
34.
35.
36.
37.
IntroductionIsodonenanderianus (Hand . Mazz .)H .W .Li(Labiatae) ,widelydistributedinthesouthernpartsofYunnanProvince ,hasbeenusedinChinesetraditionalfolkmedicineasanti inflammatoryanddetoxifiedagent.1Previousphytochemicalinvestigationhasshownthepres enceofaser… 相似文献
38.
光学活性化合物的工业合成 总被引:9,自引:0,他引:9
本文介绍了光学活性化合物研究现状及发展趋势。并从技术和经济角度论述了工业合成光学活性化合物的可能性 相似文献
39.
Two vanadyl salen complexes having peripheral styryl substituents have been reacted with 1-methyl-3-(3-mercaptopropyl)-imidazolium chloride using azoisobutyronitrile as radical initiator. The resulting compounds contain at the same time a vanadyl salen complex and one imidazolium cation. In agreement with the expectations in view of their structure, these compounds were insoluble in conventional organic solvents, but completely miscible in imidazolium ionic liquids. These vanadyl salen complexes bonded to an imidazolium cation are highly active and reusable catalysts for the cyanosilylation of aldehydes. Moderate enantiomeric excesses were obtained using the chiral version of this complex. 相似文献
40.
I. E. Karpeiskaya L. F. Godunova E. S. Levitina M. R. Lyubeznova E. I. Klabunovskii E. S. Shpiro G. N. Baeva E. D. Lubuzh L. B. Krentsel' A. D. Litmanovich N. A. Plate 《Russian Chemical Bulletin》1992,41(10):1858-1867
Pd complexes have been obtained from linear and cross-linked copolymers ofR,S-, R-, andS-1-(4-vinylphenyl)ethylamine (1) with styrene and divinylbenzene. Reduction of these compounds gave catalysts which were active in the reductive solvolysis of -acetaminocinnamic acid azlactone (2) and hydrogenation of the solvolysis products -acetamidocinnamic acid (ACA), its esters, and its 1-phenylethylamide. The catalysts showed no enantioselective properties in the reductive hydrolysis, but were more active than the catalyst obtained in the absence of the polymer (the monomeric analog). The use of polymeric catalysts has shown that, in reductive aminolysis, the chiral nucleophile plays the dominant part in determining the stereoselectivity of the reaction, rather than the chiral ligand of the catalytic complex. The polymer matrix stabilizes the low-valent state of the palladium in the complex. In the hydrogenation of ACA and its esters, the catalyst on the cross-linked polymer is much more active than its monomeric analog, but showed no enantioselectivity. Hydrogenation of acetamidocinnamic acidR-andS-1-phenylethylamides on a chiral Pd-polymer catalyst occurred with double asymmetric induction.Deceased.N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, 117913 Moscow. A. V. Topchiev Institute of Petrochemical Synthesis, Russian Academy of Sciences, 117912 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 10, pp. 2368–2380, October, 1992. 相似文献