全文获取类型
收费全文 | 273197篇 |
免费 | 3835篇 |
国内免费 | 1131篇 |
专业分类
化学 | 151523篇 |
晶体学 | 3945篇 |
力学 | 10524篇 |
综合类 | 3篇 |
数学 | 32694篇 |
物理学 | 79474篇 |
出版年
2021年 | 1919篇 |
2020年 | 2287篇 |
2019年 | 2573篇 |
2018年 | 2841篇 |
2017年 | 2750篇 |
2016年 | 4658篇 |
2015年 | 3322篇 |
2014年 | 4786篇 |
2013年 | 12657篇 |
2012年 | 9988篇 |
2011年 | 12101篇 |
2010年 | 7754篇 |
2009年 | 7520篇 |
2008年 | 10974篇 |
2007年 | 10965篇 |
2006年 | 10197篇 |
2005年 | 9556篇 |
2004年 | 8454篇 |
2003年 | 7391篇 |
2002年 | 7320篇 |
2001年 | 7627篇 |
2000年 | 5790篇 |
1999年 | 4595篇 |
1998年 | 3900篇 |
1997年 | 3950篇 |
1996年 | 3686篇 |
1995年 | 3419篇 |
1994年 | 3269篇 |
1993年 | 3307篇 |
1992年 | 3577篇 |
1991年 | 3576篇 |
1990年 | 3371篇 |
1989年 | 3289篇 |
1988年 | 3354篇 |
1987年 | 3228篇 |
1986年 | 3094篇 |
1985年 | 4319篇 |
1984年 | 4450篇 |
1983年 | 3648篇 |
1982年 | 4052篇 |
1981年 | 3887篇 |
1980年 | 3782篇 |
1979年 | 3776篇 |
1978年 | 3986篇 |
1977年 | 3806篇 |
1976年 | 4006篇 |
1975年 | 3558篇 |
1974年 | 3663篇 |
1973年 | 3929篇 |
1972年 | 2402篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
Amphiphilic thermoset elastomers from metal‐free,click crosslinking of PEG‐grafted silicone surfactants 下载免费PDF全文
Michael A. Brook Frances Lasowski Heather Sheardown 《Journal of polymer science. Part A, Polymer chemistry》2015,53(9):1082-1093
The hydrophobicity of silicone elastomers can compromise their utility in some biomaterials applications. Few effective processes exist to introduce hydrophilic groups onto a polysiloxane backbone and subsequently crosslink the material into elastomers. This problem can be overcome through the utilization of metal‐free click reactions between azidoalkylsilicones and alkynyl‐modified silicones and/or PEGs to both functionalize and crosslink silicone elastomers. Alkynyl‐functional PEG was clicked onto a fraction of the available azido groups of a functional polysiloxane, yielding azido reactive PDMS‐g‐PEG rake surfactants. The reactive polymers were then used to crosslink alkynyl‐terminated PDMS of different molecular weights. Using simple starting materials, this generic yet versatile method permits the preparation and characterization of a library of amphiphilic thermoset elastomers that vary in their composition, crosslink density, elasticity, hydrogel formation, and wettability. An appropriate balance of PEG length and crosslink density leads to a permanently highly wettable silicone elastomer that demonstrated very low levels of protein adsorption. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1082–1093 相似文献
43.
44.
L. Resse L.G.S. Oliveira C.I.L. de Araujo A.R. Pereira R.L. Silva 《Physics letters. A》2019,383(14):1655-1659
In this work, we have used the MuMax3 software to simulate devices consisting of a ferromagnetic thin film placed over a heavy metal thin film. The devices are two interconnected partial-disks where a Néel domain wall is formed in the disks junction. In our simulations we investigate devices with disk radius nm and different distance d between the disks centers (from nm to nm). By applying strong sinusoidal external magnetic fields, we find a mechanism able to create, annihilate and even manipulate a skyrmion in each side of the device. This mechanism is discussed in terms of interactions between skyrmion and domain wall. The Néel domain wall formed in the center of the device interacts with the Néel skyrmion, leading to a process of transporting a skyrmion from one disk to the other periodically. Our results have relevance for potential applications in spintronics such as logical devices. 相似文献
45.
Michael Dickson 《Foundations of Physics》2015,45(10):1330-1340
46.
47.
48.
49.
Vanessa R. Machado Louis P. Sandjo Giovanni L. Pinheiro Milene H. Moraes Mario Steindel Moacir G. Pizzolatti 《Natural product research》2018,32(3):275-281
The natural product lupeol 1 was isolated from aerial parts of Vernonia scorpioides with satisfactory yield, which made it viable to be used as starting material in semisynthetic approach. Ten lupeol derivatives 2–11 were prepared by classical procedures. Including, five new esters derivatives 7–11, which were obtained by structural modifications in the isopropylidene fragment. All semisynthetic compounds and lupeol 1–11 were confirmed by 1H NMR, 13C NMR and HRMS. Their antiprotozoal activity was evaluated in vitro against L. amazonensis and T. cruzi. Derivative 6 showed the best antitrypanosomal activity (IC50 = 12.48 μg/mL) and the lowest cytotoxic derivative (CC50 = 161.50 μg/mL). The mechanism of action of the most active derivatives (4, 6 and 11) is not dependent from the enzyme trypanothione reductase. 相似文献
50.