全文获取类型
收费全文 | 2775篇 |
免费 | 147篇 |
国内免费 | 10篇 |
专业分类
化学 | 2331篇 |
晶体学 | 12篇 |
力学 | 25篇 |
数学 | 289篇 |
物理学 | 275篇 |
出版年
2023年 | 21篇 |
2022年 | 36篇 |
2021年 | 35篇 |
2020年 | 51篇 |
2019年 | 39篇 |
2018年 | 28篇 |
2017年 | 22篇 |
2016年 | 101篇 |
2015年 | 103篇 |
2014年 | 90篇 |
2013年 | 141篇 |
2012年 | 207篇 |
2011年 | 235篇 |
2010年 | 140篇 |
2009年 | 86篇 |
2008年 | 185篇 |
2007年 | 173篇 |
2006年 | 158篇 |
2005年 | 166篇 |
2004年 | 166篇 |
2003年 | 127篇 |
2002年 | 115篇 |
2001年 | 69篇 |
2000年 | 37篇 |
1999年 | 35篇 |
1998年 | 27篇 |
1997年 | 32篇 |
1996年 | 29篇 |
1995年 | 27篇 |
1994年 | 17篇 |
1993年 | 18篇 |
1992年 | 21篇 |
1991年 | 13篇 |
1990年 | 14篇 |
1989年 | 12篇 |
1988年 | 25篇 |
1987年 | 18篇 |
1986年 | 7篇 |
1985年 | 14篇 |
1984年 | 18篇 |
1983年 | 5篇 |
1982年 | 6篇 |
1981年 | 13篇 |
1980年 | 4篇 |
1979年 | 5篇 |
1978年 | 14篇 |
1977年 | 4篇 |
1976年 | 4篇 |
1975年 | 3篇 |
1969年 | 5篇 |
排序方式: 共有2932条查询结果,搜索用时 15 毫秒
81.
Dupont-Gillain CC Jacquemart I Rouxhet PG 《Colloids and surfaces. B, Biointerfaces》2005,43(3-4):179-186
In the last years, adsorbed collagen was shown to form layers with a supramolecular organization depending on the substrate surface properties and on the preparation procedure. If the concentration of collagen and the duration of adsorption are sufficient, fibrillar collagen structures are formed, corresponding to assemblies of a few molecules. This occurs more readily on hydrophobic compared to hydrophilic surfaces. This study aims at understanding the origin of such fibrillar structures and in particular at determining whether they result from the deposition of fibrils formed in solution or from the building of assemblies at the interface. Therefore, type I collagen solutions with an increasing degree of aggregation were prepared, using the “neutral-start” approach, by ageing pH 5.8 solutions at 37 °C for 15 min, 2 or 7 days. The obtained solutions were used to investigate the influence of collagen aggregation in solution on the supramolecular organization of adsorbed collagen layers, which was characterized by X-ray photoelectron spectroscopy and atomic force microscopy. Polystyrene and plasma-oxidized polystyrene were chosen as substrates for the adsorption. The size and the density of collagen fibrils at the interface decreased upon increasing the degree of aggregation of collagen in solution. This is explained by a competitive adsorption process between monomers and aggregates of the solution, turning at the advantage of the monomers. More aggregated solutions, which are thus depleted in free monomers, behave like less concentrated solutions, i.e. lead to a lower adsorbed amount and less fibril formation at the interface. This study shows that the supramolecular fibrils observed in adsorbed collagen layers, especially on hydrophobic substrates, are not formed in the solution, prior to adsorption, but are built at the interface, through the assembly of free segments of adsorbed molecules. 相似文献
82.
Nemeshwaree Behary Sandy Eap Aurlie Cayla Feng Chai Nadia Benkirane-Jessel Christine Campagne 《Molecules (Basel, Switzerland)》2022,27(12)
Textile scaffolds that are either 2D or 3D with tunable shapes and pore sizes can be made through textile processing (weaving, knitting, braiding, nonwovens) using microfilaments. However, these filaments lack nano-topographical features to improve bone cell adhesion and proliferation. Moreover, the diameter of such filaments should be higher than that used for classical textiles (10–30 µm) to enable adhesion and the efficient spreading of the osteoblast cell (>30 µm diameter). We report, for the first time, the fabrication of biodegradable nanostructured cylindrical PLLA (poly-L-Lactic acid) microfilaments of diameters 100 µm and 230 µm, using a single step melt-spinning process for straightforward integration of nano-scale ridge-like structures oriented in the fiber length direction. Appropriate drawing speed and temperature used during the filament spinning allowed for the creation of instabilities giving rise to nanofibrillar ridges, as observed by AFM (Atomic Force Microscopy). These micro-filaments were hydrophobic, and had reduced crystallinity and mechanical strength, but could still be processed into 2D/3D textile scaffolds of various shapes. Biological tests carried out on the woven scaffolds made from these nano-structured micro filaments showed excellent human bone cell MG 63 adhesion and proliferation, better than on smooth 30 µm- diameter fibers. Elongated filopodia of the osteoblast, intimately anchored to the nano-structured filaments, was observed. The filaments also induced in vitro osteogenic expression, as shown by the expression of osteocalcin and bone sialoprotein after 21 days of culture. This work deals with the fabrication of a new generation of nano-structured micro-filament for use as scaffolds of different shapes suited for bone cell engineering. 相似文献
83.
84.
85.
86.
Abstract Organic-inorganic composites (OICs) were prepared via the in-situ polymerization of an organically (phenyl) substituted trialkoxysilane, phenyltriethoxysilane (PhTEOS), in the presence of poly(vinyl acetate) (PVAc). The mechanical reinforcement above T g previously observed in OICs of unfunctionalized organic polymers such as PVAc with acid catalyzed in-situ polymerized tetraalkoxysilane was not observed when the tetraalkoxysilane was replaced with PhTEOS. Although both systems are optically transparent and both exhibit a high degree of hydrogen bonding between the carbonyl of PVAc and the residual hydroxyls of the silicate, the polymerization of the alkoxide is different. The tetra-functional alkoxide polymerizes to form a load-supporting silicate network, leading to a high plateau in the tensile modulus above T g, whereas the trifunctional alkoxide reacts to form primarily low molecular weight oligomers. These increase the T g of the PVAc but do not provide mechanical reinforcement. 相似文献
87.
88.
89.
90.
Thomas Courant Valrie Gaëlle Roullin Cyril Cadiou Maït Callewaert Marie Christine Andry Christophe Portefaix Christine Hoeffel Marie Christine deGoltstein Marc Port Sophie Laurent Luce Vander Elst Robert Muller Michaël Molinari Franoise Chuburu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2012,124(36):9253-9256