全文获取类型
收费全文 | 437093篇 |
免费 | 5079篇 |
国内免费 | 1312篇 |
专业分类
化学 | 208627篇 |
晶体学 | 5372篇 |
力学 | 22521篇 |
综合类 | 8篇 |
数学 | 75918篇 |
物理学 | 131038篇 |
出版年
2021年 | 3509篇 |
2020年 | 3906篇 |
2019年 | 4287篇 |
2018年 | 15612篇 |
2017年 | 15601篇 |
2016年 | 14401篇 |
2015年 | 6098篇 |
2014年 | 8426篇 |
2013年 | 18739篇 |
2012年 | 18087篇 |
2011年 | 26511篇 |
2010年 | 17548篇 |
2009年 | 17657篇 |
2008年 | 21143篇 |
2007年 | 22917篇 |
2006年 | 13903篇 |
2005年 | 13320篇 |
2004年 | 12601篇 |
2003年 | 11628篇 |
2002年 | 10628篇 |
2001年 | 11344篇 |
2000年 | 8674篇 |
1999年 | 6638篇 |
1998年 | 5561篇 |
1997年 | 5280篇 |
1996年 | 5150篇 |
1995年 | 4325篇 |
1994年 | 4218篇 |
1993年 | 4072篇 |
1992年 | 4464篇 |
1991年 | 4619篇 |
1990年 | 4426篇 |
1989年 | 4269篇 |
1988年 | 4061篇 |
1987年 | 4184篇 |
1986年 | 3948篇 |
1985年 | 4971篇 |
1984年 | 5019篇 |
1983年 | 4139篇 |
1982年 | 4239篇 |
1981年 | 3968篇 |
1980年 | 3886篇 |
1979年 | 4163篇 |
1978年 | 4129篇 |
1977年 | 4123篇 |
1976年 | 4127篇 |
1975年 | 3868篇 |
1974年 | 3831篇 |
1973年 | 3888篇 |
1972年 | 2727篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
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
102.
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
103.
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
104.
Vereshchagin Anatoly N. Karpenko Kirill A. Elinson Michail N. Minaeva Alexandra P. Goloveshkin Alexander S. Hansford Karl A. Egorov Mikhail P. 《Molecular diversity》2020,24(4):1327-1342
Molecular Diversity - A novel five-component diastereoselective synthesis of polysubstituted 2-piperidinones is reported. The Knoevenagel condensation–Michael addition–Mannich cascade... 相似文献
105.
106.
Functional Carbazole Liquid‐Crystal Block Codendrimers with Optical and Electronic Properties 下载免费PDF全文
Ismael Gracia Beatriz Feringán Prof. José Luis Serrano Dr. Roberto Termine Dr. Attilio Golemme Dr. Ana Omenat Prof. Joaquín Barberá 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(3):1359-1369
The synthesis and characterisation of a family of block codendrimers consisting of highly versatile mesogenic and carbazole‐containing 2,2‐bis(hydroxymethyl)propionic acid (bis‐MPA) dendrons are reported. The liquid‐crystal behaviour was investigated by means of differential scanning calorimetry, polarised‐light optical microscopy and X‐ray diffraction. Depending on the chemical structure of the constituent dendrons, the codendrimers show lamellar or columnar mesophases. On the basis of the experimental results, models both at the molecular level and in the mesophase are proposed. The physical properties of the block codendrimers derived from the presence of the carbazole moiety in their structure were investigated: photoluminescence in solution and in the mesophase, electrochemical behaviour and hole transport. Electrodeposition of carbazole dendrons afforded a globular supramolecular conformation in which the mesogenic molecular side plays a key role. 相似文献
107.
108.
109.
110.