全文获取类型
收费全文 | 744910篇 |
免费 | 10589篇 |
国内免费 | 4263篇 |
专业分类
化学 | 398888篇 |
晶体学 | 10655篇 |
力学 | 33303篇 |
综合类 | 85篇 |
数学 | 95940篇 |
物理学 | 220891篇 |
出版年
2021年 | 5692篇 |
2020年 | 6455篇 |
2019年 | 6970篇 |
2018年 | 8943篇 |
2017年 | 8902篇 |
2016年 | 13655篇 |
2015年 | 9197篇 |
2014年 | 13404篇 |
2013年 | 34643篇 |
2012年 | 27492篇 |
2011年 | 32972篇 |
2010年 | 22794篇 |
2009年 | 22376篇 |
2008年 | 29797篇 |
2007年 | 30043篇 |
2006年 | 28147篇 |
2005年 | 25332篇 |
2004年 | 23424篇 |
2003年 | 20494篇 |
2002年 | 20170篇 |
2001年 | 21378篇 |
2000年 | 16384篇 |
1999年 | 13007篇 |
1998年 | 10793篇 |
1997年 | 10479篇 |
1996年 | 10436篇 |
1995年 | 9141篇 |
1994年 | 9001篇 |
1993年 | 8717篇 |
1992年 | 9586篇 |
1991年 | 9626篇 |
1990年 | 9115篇 |
1989年 | 8905篇 |
1988年 | 8821篇 |
1987年 | 8647篇 |
1986年 | 8328篇 |
1985年 | 11329篇 |
1984年 | 11526篇 |
1983年 | 9479篇 |
1982年 | 10090篇 |
1981年 | 9722篇 |
1980年 | 9356篇 |
1979年 | 9795篇 |
1978年 | 10033篇 |
1977年 | 9944篇 |
1976年 | 10006篇 |
1975年 | 9481篇 |
1974年 | 9375篇 |
1973年 | 9614篇 |
1972年 | 6566篇 |
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
141.
Controlling effective interactions and spatial dispersion of nanoparticles in multiblock copolymer melts
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)
Debapriya Banerjee Kenneth S. Schweizer 《Journal of Polymer Science.Polymer Physics》2015,53(16):1098-1111
The microscopic Polymer Reference Interaction Site Model theory is employed to study, for the first time, the effective interactions, spatial organization, and miscibility of dilute spherical nanoparticles in non‐microphase separating, chemically heterogeneous, compositionally symmetric AB multiblock copolymer melts of varying monomer sequence or architecture. The dependence of nanoparticle wettability on copolymer sequence and chemistry results in interparticle potentials‐of‐mean force that are qualitatively different from homopolymers. An important prediction is the ability to improve nanoparticle dispersion via judicious choice of block length and monomer adsorption‐strengths which control both local surface segregation and chain connectivity induced packing constraints and frustration. The degree of dispersion also depends strongly on nanoparticle diameter relative to the block contour length. Small particles in copolymers with longer block lengths experience a more homopolymer‐like environment which renders them relatively insensitive to copolymer chemical heterogeneity and hinders dispersion. Larger particles (sufficiently larger than the monomer diameter) in copolymers of relatively short block lengths provide better dispersion than either a homopolymer or random copolymer. The theory also predicts a novel widening of the miscibility window for large particles upon increasing the overall molecular weight of copolymers composed of relatively long blocks. The influence of a positive chi‐parameter in the pure copolymer melt is briefly studied. Quantitative application to fullerenes in specific copolymers of experimental interest is performed, and miscibility predictions are made. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1098–1111 相似文献
142.
Development of biocompatible porous supports is a promising strategy in the field of tissue engineering for the repair and regeneration of bone tissues with severe damage. Graphene oxide aerogels (GOAs) are excellent candidates for the manufacture of these systems due to their porosity, ability to imitate bone structure, and mechanical resistance, and according to their surface chemical reactivity, they can facilitate osseointegration, osteogenesis, osteoinduction and osteoconduction. In this review, synthesis of GOAs from the most primary source is described, and recent studies on the use of these functionalized carbonaceous foams as scaffolding for bone tissue regeneration are presented. 相似文献
143.
Journal of Thermal Analysis and Calorimetry - In the present work, pyrolysis kinetic mechanism was studied for regenerated cellulosic fiber (RCF) and composite RCF containing silicon/nitrogen flame... 相似文献
144.
Yuyang Ji Rebekka S. Klausen 《Journal of polymer science. Part A, Polymer chemistry》2021,59(21):2521-2529
The synthesis of vinyl alcohol copolymers is limited due to the poor radical reactivity of vinyl acetate (VAc), the traditional precursor to polyvinyl alcohol (PVA). Main group monomers such as BN 2-vinylnaphthalene (BN2VN) have attracted attention as alternatives to VAc to form side chain hydroxyls via oxidation, but outstanding questions of molecular weight control remain. Herein we report systematic investigation of solvent, temperature, and initiator concentration as factors influencing BN2VN degree of polymerization. We find increased chain transfer to toluene, hypothesized to arise from differences in radical stabilization and reactivity by aromatic and BN aromatic rings. As a result of these combined efforts, high molecular weight (Mw ~ 105 g mol−1) BN2VN homopolymers and BN2VN-styrene copolymers were obtained. 相似文献
145.
Farsi R. Mohammadi M. K. Saghanezhad S. J. 《Russian Journal of Organic Chemistry》2021,57(12):2002-2009
Russian Journal of Organic Chemistry - Herein, we report the sulfonamide-functionalized covalent organic framework (COF-SO3H), prepared by condensation of melamine and terephthalaldehyde and... 相似文献
146.
147.
148.
Timm Bergholz Dr. Benjamin Oelkers Dr. Benedikt Huber Prof. Bernhard Roling Prof. Dr. Jörg Sundermeyer 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(6):2613-2620
New salts based on imidazolium, pyrrolidinium, phosphonium, guanidinium, and ammonium cations together with the 5‐cyanotetrazolide anion [C2N5]? are reported. Depending on the nature of cation–anion interactions, characterized by XRD, the ionic liquids (ILs) have a low viscosity and are liquid at room temperature or have higher melting temperatures. Thermogravimetric analysis, cyclic voltammetry, viscosimetry, and impedance spectroscopy display a thermal stability up to 230 °C, an electrochemical window of 4.5 V, a viscosity of 25 mPa s at 20 °C, and an ionic conductivity of 5.4 mS cm?1 at 20 °C for the IL 1‐butyl‐1‐methylpyrrolidinium 5‐cyanotetrazolide [BMPyr][C2N5]. On the basis of these results, the synthesized compounds are promising electrolytes for lithium‐ion batteries. 相似文献
149.
150.