全文获取类型
收费全文 | 78269篇 |
免费 | 11586篇 |
国内免费 | 8276篇 |
专业分类
化学 | 53876篇 |
晶体学 | 797篇 |
力学 | 5084篇 |
综合类 | 620篇 |
数学 | 9551篇 |
物理学 | 28203篇 |
出版年
2024年 | 238篇 |
2023年 | 1466篇 |
2022年 | 2501篇 |
2021年 | 2538篇 |
2020年 | 2727篇 |
2019年 | 2729篇 |
2018年 | 2416篇 |
2017年 | 2220篇 |
2016年 | 3305篇 |
2015年 | 3501篇 |
2014年 | 4165篇 |
2013年 | 5492篇 |
2012年 | 6669篇 |
2011年 | 6786篇 |
2010年 | 4663篇 |
2009年 | 4630篇 |
2008年 | 4893篇 |
2007年 | 4391篇 |
2006年 | 4126篇 |
2005年 | 3636篇 |
2004年 | 2956篇 |
2003年 | 2241篇 |
2002年 | 2095篇 |
2001年 | 1859篇 |
2000年 | 1672篇 |
1999年 | 1730篇 |
1998年 | 1470篇 |
1997年 | 1280篇 |
1996年 | 1314篇 |
1995年 | 1135篇 |
1994年 | 1078篇 |
1993年 | 916篇 |
1992年 | 814篇 |
1991年 | 703篇 |
1990年 | 599篇 |
1989年 | 505篇 |
1988年 | 393篇 |
1987年 | 364篇 |
1986年 | 309篇 |
1985年 | 312篇 |
1984年 | 206篇 |
1983年 | 183篇 |
1982年 | 149篇 |
1981年 | 115篇 |
1980年 | 84篇 |
1978年 | 57篇 |
1977年 | 55篇 |
1976年 | 50篇 |
1975年 | 58篇 |
1973年 | 57篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Nanocomposite hydrogel consisting of Na‐montmorillonite with enhanced mechanical properties
下载免费PDF全文
![点击此处可从《Journal of Polymer Science.Polymer Physics》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Ting Li Shuangfei Xiang Piming Ma Huiyu Bai Weifu Dong Mingqing Chen 《Journal of Polymer Science.Polymer Physics》2015,53(14):1020-1026
A new kind of nanocomposite (NC) hydrogel with Na‐montmorillonite (MMT) is presented in this article. The NC hydrogels were synthesized by free radical copolymerization of acrylamide and (3‐acrylamidopropyl) trimethylammonium chloride (ATC) in the presence of MMT and N,N′‐methylene‐bis‐acrylamide used as chemical cross‐linker. Due to the cation‐exchange reaction between MMT and ATC (cationic monomer) during the synthesis of NC hydrogels, MMT platelets were considered chemical “plane” cross‐linkers, different from “point” cross‐linkers. With increasing amount of MMT, the crosslinking degree enhanced, causing a decrease of the swelling degree at equilibrium. Investigations of mechanical properties indicated that NC hydrogels exhibited enhanced strength and toughness, which resulted from chemical interaction between exfoliated MMT platelets and polymer chains in hydrogels. Dynamic shear measurements showed that both storage modulus and loss modulus increased with increasing MMT content. The idea described here provided a new route to prepare hydrogels with high mechanical properties by using alternative natural Na‐MMT. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1020–1026 相似文献
32.
33.
34.
35.
Unsymmetrical Pyrene‐Fused Phthalocyanine Derivatives: Synthesis,Structure, and Properties
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Houhe Pan Chao Chen Kang Wang Prof. Dr. Wenjun Li Prof. Dr. Jianzhuang Jiang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(8):3168-3173
Novel pyrene‐fused unsymmetrical phthalocyanine derivatives 2,3,9,10,16,17‐hexakis(2,6‐dimethylphenoxy)‐22,25‐diaza(2,7‐di‐tert‐butylpyrene)[4,5]phthalocyaninato zinc complex Zn[Pc(Pz‐pyrene)(OC8H9)6] ( 1 ) and 2,3,9,10‐tra(2,6‐dimethylphenoxy)‐15,18,22,25‐traza(2,7‐di‐tert‐butylpyrene)[4,5]phthalocyaninato zinc compound Zn[Pc(Pz‐pyrene)2(OC8H9)4] ( 2 ) were isolated for the first time. These unsymmetrical pyrene‐fused phthalocyanine derivatives have been characterized by a wide range of spectroscopic and electrochemical methods. In particular, the pyrene‐fused phthalocyanine structure was unambiguously revealed on the basis of single crystal X‐ray diffraction analysis of 1 , representing the first structurally characterized phthalocyanine derivative fused with an aromatic moiety larger than benzene. 相似文献
36.
37.
Richiro Ushimaru Zhang Chen Houyuan Zhao Po-hsun Fan Prof. Dr. Hung-wen Liu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(9):3586-3590
Albomycin δ2 is a sulfur-containing sideromycin natural product that shows potent antibacterial activity against clinically important pathogens. The l -serine-thioheptose dipeptide partial structure, known as SB-217452, has been found to be the active seryl-tRNA synthetase inhibitor component of albomycin δ2. Herein, it is demonstrated that AbmF catalyzes condensation between the 6′-amino-4′-thionucleoside with the d -ribo configuration and seryl-adenylate supplied by the serine adenylation activity of AbmK. Formation of the dipeptide is followed by C3′-epimerization to produce SB-217452 with the d -xylo configuration, which is catalyzed by the radical S-adenosyl-l -methionine enzyme AbmJ. Gene deletion suggests that AbmC is involved in peptide assembly linking SB-217452 with the siderophore moiety. This study establishes how the albomycin biosynthetic machinery generates its antimicrobial component SB-217452. 相似文献
38.
39.
40.