全文获取类型
收费全文 | 627篇 |
免费 | 61篇 |
国内免费 | 138篇 |
专业分类
化学 | 387篇 |
晶体学 | 19篇 |
力学 | 32篇 |
综合类 | 23篇 |
数学 | 76篇 |
物理学 | 289篇 |
出版年
2023年 | 4篇 |
2022年 | 17篇 |
2021年 | 12篇 |
2020年 | 18篇 |
2019年 | 17篇 |
2018年 | 13篇 |
2017年 | 26篇 |
2016年 | 12篇 |
2015年 | 27篇 |
2014年 | 29篇 |
2013年 | 27篇 |
2012年 | 29篇 |
2011年 | 40篇 |
2010年 | 41篇 |
2009年 | 32篇 |
2008年 | 52篇 |
2007年 | 46篇 |
2006年 | 55篇 |
2005年 | 43篇 |
2004年 | 28篇 |
2003年 | 27篇 |
2002年 | 23篇 |
2001年 | 24篇 |
2000年 | 21篇 |
1999年 | 10篇 |
1998年 | 7篇 |
1997年 | 4篇 |
1996年 | 8篇 |
1994年 | 6篇 |
1993年 | 8篇 |
1992年 | 10篇 |
1991年 | 4篇 |
1990年 | 4篇 |
1989年 | 5篇 |
1988年 | 12篇 |
1987年 | 5篇 |
1986年 | 7篇 |
1985年 | 4篇 |
1984年 | 8篇 |
1983年 | 7篇 |
1982年 | 4篇 |
1981年 | 4篇 |
1980年 | 5篇 |
1979年 | 4篇 |
1974年 | 4篇 |
1971年 | 3篇 |
1970年 | 5篇 |
1968年 | 4篇 |
1967年 | 3篇 |
1965年 | 4篇 |
排序方式: 共有826条查询结果,搜索用时 15 毫秒
1.
Finite groups acting on rings by automorphisms, and group-graded rings are instances of Hopf algebras H acting on H-module algebras A. We study such actions. Let AH = {a ε A¦h · A = (h) a, all h ε H}, the ring of H-invariants, and form the smash product A # H. We study the ring extensions AH A A # H. We prove a Maschke-type theorem for A # H-modules. We form an associated Morita context [AH, A, A, A # H] and use these to get connections between the various rings. 相似文献
2.
The solid-liquid interface motion of NaBi(WO4)2 (NBWO) melt crystal growth is observed in an in situ system, in which the whole processes of interface transition from fiat interface and cellular to dendrite are visualized. The spacing of the dendrite under smaller temperature gradient turns out to be larger than that under larger temperature gradient, which is found to be sensitive to the temperature distribution. The mechanism of dendrite growth of NBWO is studied based on the model of the growth units of anion coordination polyhedra. The { 001} face has two apex links, so it shows higher stability and has high growth rate and forms the arm of dendrite, whereas the {010} face has only one apex link, and thus shows relative slower growth rate and firstly forms the branches. 相似文献
3.
4.
In Situ Observation of Skeletal Shape Transition during BaB2O4 Crystal Growth in High-Temperature Solution 下载免费PDF全文
The transition from a fiat solid-liquid interface to a skeletal shape during BaB2O4 (BBO) single crystal growth in Li2B4O7 flux is observed in real time by an optical high-temperature in-situ observation system. The movement of crystal step is also investigated. The observation results demonstrate that the steps propagate along and parallel to the fiat interface when the crystal size is small. Nevertheless, they will ‘bend' close to the face centre if the crystal size becomes greater. Atomic force microscopy reveals that more deposition places near the face centre give rise to the bending of advancing steps and thus the formation of a vicinal interface structure. Measurements of step velocity show that the velocity keeps nearly constant at different moments for one specific step, whereas the step on a newly formed layer advanced faster than that on a previously formed one when the crystal size is larger than 210μm or so. Thus interracial morphological instability occurs and a skeletal interface is obtained. 相似文献
5.
6.
EucalyPtusgl0bulusLabill.(Myrtaceae)isakindofmedicinalplantwidelydistributedintheYunnanpr0vinceofChina.ItSleaves,rootSandffoitShavebeenusedastraditionalremediesforthetreatmentofinfluenza,dysentery,enteritis,rheumatalgiaandbleeding.BesidesvolatileterpenoidconstituentSintheessential0iloftheleavesandfruits,theoccurrenceofanumber0fphloroglucinol-sesquiterpene-or-m0n0terpene-c0upledcomPoundsnamedmacrocarpals'andeugl0bals'intheleavesandbudshasbeenrepofted.Inordertostudythechendcalandbioactivecon… 相似文献
7.
8.
9.
10.
Controlled drug delivery remains a research focus for public health to enhance patient compliance, drug efficiency and reduce
the side effects of drugs. Pectin, an edible plant polysaccharide, has been shown to be useful for the construction of drug
delivery systems for specific drug delivery. Several pectin derived formulations have been developed in our laboratory and
tested in vitro, ex vivo, and in vivo for the ability to deliver bioactive substances for therapeutic purposes in the context of interactions with living tissues.
Pectin derivatives carrying primary amine groups were more mucoadhesive and have shown potential in nasal drug delivery and
other mucosal drug delivery. Pectin derivatives with highly esterified galacturonic acid residues are more hydrophobic and
able to sustain the release of incorporated fragrances for a prolonged duration. Less esterified pectin derivatives are able
to penetrate deeper into the skin and may be useful in aromatherapy formulations. Pectin, in combination with zein, a corn
protein, forms hydrogel beads. The bound zein restricts bead swelling and retains the porosity of the beads; the pectin networks
shield the zein from protease attack. The complex beads are ideal vehicles for colon-specific drug delivery. Studies presented
in this paper indicate the flexibility and possibility to tailor pectin macromolecules into a variety of drug delivery systems
to meet different clinical requirements.
Mention of trade names or commercial products in this article is solely for the purpose of providing specific information
and does not imply recommendation or endorsement by the US Department of Agriculture. 相似文献