全文获取类型
收费全文 | 293702篇 |
免费 | 12796篇 |
国内免费 | 2749篇 |
专业分类
化学 | 186623篇 |
晶体学 | 3680篇 |
力学 | 10148篇 |
综合类 | 61篇 |
数学 | 33325篇 |
物理学 | 75410篇 |
出版年
2021年 | 2254篇 |
2020年 | 3599篇 |
2019年 | 5029篇 |
2018年 | 4313篇 |
2017年 | 3972篇 |
2016年 | 8264篇 |
2015年 | 6765篇 |
2014年 | 7888篇 |
2013年 | 15154篇 |
2012年 | 13093篇 |
2011年 | 14297篇 |
2010年 | 11000篇 |
2009年 | 10548篇 |
2008年 | 13489篇 |
2007年 | 12921篇 |
2006年 | 11905篇 |
2005年 | 11142篇 |
2004年 | 9807篇 |
2003年 | 8585篇 |
2002年 | 8972篇 |
2001年 | 8792篇 |
2000年 | 6967篇 |
1999年 | 4558篇 |
1998年 | 3504篇 |
1997年 | 3380篇 |
1996年 | 3494篇 |
1995年 | 2977篇 |
1994年 | 3086篇 |
1993年 | 2965篇 |
1992年 | 3212篇 |
1991年 | 3172篇 |
1990年 | 2976篇 |
1989年 | 2842篇 |
1988年 | 2771篇 |
1987年 | 2716篇 |
1986年 | 2720篇 |
1985年 | 3598篇 |
1984年 | 3633篇 |
1983年 | 3005篇 |
1982年 | 3241篇 |
1981年 | 3015篇 |
1980年 | 2786篇 |
1979年 | 2926篇 |
1978年 | 3128篇 |
1977年 | 3152篇 |
1976年 | 3181篇 |
1975年 | 2917篇 |
1974年 | 2989篇 |
1973年 | 3061篇 |
1972年 | 2367篇 |
排序方式: 共有10000条查询结果,搜索用时 109 毫秒
61.
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
62.
63.
64.
Functional Carbazole Liquid‐Crystal Block Codendrimers with Optical and Electronic Properties
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
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
65.
66.
67.
68.
The Effect of the Spacer of Bis(biurea) Ligands on the Structure of A2L3‐type (A=anion) Phosphate Complexes
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Prof. Biao Wu Dr. Shaoguang Li Prof. Yibo Lei Prof. Huaiming Hu Dr. Nader de Sousa Amadeu Prof. Dr. Christoph Janiak Dr. Jennifer S. Mathieson Dr. De‐Liang Long Prof. Leroy Cronin Prof. Xiao‐Juan Yang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(6):2588-2593
By tuning the length and rigidity of the spacer of bis(biurea) ligands L, three structural motifs of the A2L3 complexes (A represents anion, here orthophosphate PO43?), namely helicate, mesocate, and mono‐bridged motif, have been assembled by coordination of the ligand to phosphate anion. Crystal structure analysis indicated that in the three complexes, each of the phosphate ions is coordinated by twelve hydrogen bonds from six surrounding urea groups. The anion coordination properties in solution have also been studied. The results further demonstrate the coordination behavior of phosphate ion, which shows strong tendency for coordination saturation and geometrical preference, thus allowing for the assembly of novel anion coordination‐based structures as in transition‐metal complexes. 相似文献
69.
Single Crystal to Single Crystal (SC‐to‐SC) Transformation from a Nonporous to Porous Metal–Organic Framework and Its Application Potential in Gas Adsorption and Suzuki Coupling Reaction through Postmodification
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Dr. Rupam Sen Debraj Saha Dr. Subratanath Koner Dr. Paula Brandão Dr. Zhi Lin 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(15):5962-5971
A new amino‐functionalized strontium–carboxylate‐based metal–organic framework (MOF) has been synthesized that undergoes single crystal to single crystal (SC‐to‐SC) transformation upon desolvation. Both structures have been characterized by single‐crystal X‐ray analysis. The desolvated structure shows an interesting 3D porous structure with pendent ?NH2 groups inside the pore wall, whereas the solvated compound possesses a nonporous structure with DMF molecules on the metal centers. The amino group was postmodified through Schiff base condensation by pyridine‐2‐carboxaldehyde and palladium was anchored on that site. The modified framework has been utilized for the Suzuki cross‐coupling reaction. The compound shows high activity towards the C?C cross‐coupling reaction with good yields and turnover frequencies. Gas adsorption studies showed that the desolvated compound had permanent porosity and was microporous in nature with a BET surface area of 2052 m2 g?1. The material also possesses good CO2 (8 wt %) and H2 (1.87 wt %) adsorption capabilities. 相似文献
70.
Russian Journal of Organic Chemistry - A green protocol has been developed for the preparation of 2,2′-(arylmethylene)bis(3-hydroxy-5,5-dimethylcyclohex-2-en-1-ones) following the... 相似文献