全文获取类型
收费全文 | 1217篇 |
免费 | 59篇 |
国内免费 | 139篇 |
专业分类
化学 | 317篇 |
晶体学 | 8篇 |
力学 | 19篇 |
综合类 | 12篇 |
数学 | 904篇 |
物理学 | 155篇 |
出版年
2024年 | 3篇 |
2023年 | 10篇 |
2022年 | 19篇 |
2021年 | 28篇 |
2020年 | 43篇 |
2019年 | 57篇 |
2018年 | 43篇 |
2017年 | 55篇 |
2016年 | 33篇 |
2015年 | 25篇 |
2014年 | 34篇 |
2013年 | 318篇 |
2012年 | 31篇 |
2011年 | 44篇 |
2010年 | 28篇 |
2009年 | 54篇 |
2008年 | 50篇 |
2007年 | 69篇 |
2006年 | 62篇 |
2005年 | 46篇 |
2004年 | 43篇 |
2003年 | 45篇 |
2002年 | 38篇 |
2001年 | 37篇 |
2000年 | 30篇 |
1999年 | 30篇 |
1998年 | 26篇 |
1997年 | 21篇 |
1996年 | 25篇 |
1995年 | 20篇 |
1994年 | 12篇 |
1993年 | 9篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1987年 | 4篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1983年 | 1篇 |
1982年 | 3篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1978年 | 2篇 |
1973年 | 1篇 |
1970年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有1415条查询结果,搜索用时 31 毫秒
31.
The purpose of this article is to study an existence of p-bases and mainly to give some regularity criteria for semilocal rings essentially of finite type over fields. 相似文献
32.
In the present paper we describe surjective Lie and Jordan maps onto left ideals of prime noncommutative rings. Further, we describe bijective linear maps of left ideals of centrally closed prime algebras preserving commutativity. 相似文献
33.
Attempted reaction of indolenines (which represent rather sterically hindered cyclic imines) with a series of dicarboxylic acid anhydrides yielded no expected product, the Castagnoli-Cushman lactam. Instead, products presumably formed via N-acyliminium species trapping by a carboxylate anion. Among them, hydrolytically labile 2:2 adducts of an indolenine and a cyclic anhydride, containing a 16-membered cyclic core, are particularly intriguing. This result contradicts the recently reported successful Castagnoli-Cushman reaction of indolenines with homophthalic anhydride suggesting a mechanistic switch in the course of the reaction. 相似文献
34.
This communication describes a convenient synthesis of fused bicyclic pyrazolones in a one-pot reaction procedure. Modified protocols are also developed to access 5,5-bicyclic and bulky pyrazolones in good yields. The method reported herein represents a practical approach to structurally diversified bicyclic pyrazolones. 相似文献
35.
36.
Giancarlo De Santis Luigi Fabbrizzi Maurizio Licchelli Piersandro Pallavicini Angelo Perotti Antonio Poggi 《Supramolecular chemistry》2013,25(2):115-125
Abstract The new ferrocene-containing water-soluble ligands 1 and 2 were synthesized and their protonation and complexation properties toward NiII and CuII studied as a function of pH, by means of potentiometric titration experiments. Electrochemical measurements were performed in aqueous solution on pure 1 and 2 and in the presence of NiII and CuII cations, in the pH range 2–12, allowing us to determine the redox potential values relative to the ferrocene oxidation in the free ligands and in their NiII and CuII complexes. 1 and 2 behave as redox switchable ligands, the former enhancing, the latter decreasing its binding ability upon oxidation of the appended ferrocene function. Besides, the CuII complex of ligand 1 and the NiII complex of ligand 2 behave as two-centre two-electron redox systems, the complexed metal cation being subject to further oxidation to MIII. 相似文献
37.
38.
通过利用半单环的结构定理、环的单位群的性质、环的阶及环的单位群的阶的关系等,确定了当n为素数,m=2~(t+1),t为正整数时,群环z_nD_m的代数结构和性质. 相似文献
39.
40.
Shibo Xu Kazutaka Takamatsu Prof. Dr. Koji Hirano Prof. Dr. Masahiro Miura 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(40):9400-9404
A NiCl2(PEt3)2-catalyzed regioselective C−H coupling of 8-aminoquinoline-derived benzamides with oxetanes has been developed. The reaction proceeds with concomitant removal of the 8-aminoquinoline auxiliary to directly form the corresponding seven-membered benzolactones, which frequently occur in natural products and bioactive molecules. Additionally, no stereochemical erosion is observed during the course of the reaction, and the use of enantioenriched and substituted oxetane thus provides a new avenue to the optically active benzolactone. 相似文献