全文获取类型
收费全文 | 123713篇 |
免费 | 8906篇 |
国内免费 | 8386篇 |
专业分类
化学 | 59234篇 |
晶体学 | 1574篇 |
力学 | 9471篇 |
综合类 | 532篇 |
数学 | 36698篇 |
物理学 | 33496篇 |
出版年
2024年 | 157篇 |
2023年 | 911篇 |
2022年 | 1796篇 |
2021年 | 1931篇 |
2020年 | 2009篇 |
2019年 | 2119篇 |
2018年 | 11893篇 |
2017年 | 11785篇 |
2016年 | 8244篇 |
2015年 | 3381篇 |
2014年 | 3387篇 |
2013年 | 4183篇 |
2012年 | 8144篇 |
2011年 | 14753篇 |
2010年 | 8915篇 |
2009年 | 9288篇 |
2008年 | 10093篇 |
2007年 | 11647篇 |
2006年 | 3066篇 |
2005年 | 3663篇 |
2004年 | 3348篇 |
2003年 | 3482篇 |
2002年 | 2582篇 |
2001年 | 1580篇 |
2000年 | 1315篇 |
1999年 | 983篇 |
1998年 | 779篇 |
1997年 | 635篇 |
1996年 | 662篇 |
1995年 | 478篇 |
1994年 | 451篇 |
1993年 | 402篇 |
1992年 | 284篇 |
1991年 | 270篇 |
1990年 | 226篇 |
1989年 | 177篇 |
1988年 | 160篇 |
1987年 | 136篇 |
1986年 | 148篇 |
1985年 | 109篇 |
1984年 | 73篇 |
1983年 | 74篇 |
1982年 | 55篇 |
1981年 | 53篇 |
1980年 | 57篇 |
1979年 | 63篇 |
1978年 | 41篇 |
1914年 | 46篇 |
1912年 | 41篇 |
1909年 | 42篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
Simultaneous determination of cinnamaldehyde and its metabolite in rat tissues by gas chromatography–mass spectrometry 下载免费PDF全文
Hang Zhao Qian Yang Yanhua Xie Jiyuan Sun Honghai Tu Wei Cao Siwang Wang 《Biomedical chromatography : BMC》2015,29(2):182-187
Cinnamaldehyde (CA), an active ingredient isolated from the traditional Chinese medicine Cortex Cinnamomi, has a wide range of bioactivities. To clarify the distribution characteristics of CA, a selective and sensitive method utilizing gas chromatography–mass spetrometry was initially developed for simultaneously determining the concentration of CA and its metabolite cinnamyl alcohol in rat tissues. Selected ion masses of m/z 131, 105 and 92 were chosen, and separation of the analytes was performed on a DB‐5 ms (30 m × 0.25 mm, 0.25 µm, thickness) capillary column by gas chromatography–mass spectrometry. The calibration curves demonstrated good linearity and reproducibility over the range of 20–2000 and 20–4000 ng/mL for various tissue samples. Recoveries ranged from 86.8 to 107.5%, while intra‐ and interday relative standard deviations were all <11.3%. The analysis method was successfully applied in tissue distribution studies for CA and cinnamyl alcohol. As CA and cinnamyl alcohol may inter‐convert to one another, simultaneous determination of both analytes provides a comparative and accurate data for tissue study. The concentrations of CA and cinnamyl alcohol remaining in spleen were the highest among the main organs, including heart, liver, spleen, lung, kidney and brain. In addition, there was no long‐term accumulation of CA in rat tissues. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
2.
Jing Zhihong Ling Baoping Yu Yang Qi Wei Zhang Shufang 《Journal of Sol-Gel Science and Technology》2015,73(1):112-117
Journal of Sol-Gel Science and Technology - A novel gas sensing material, La–Y co-doped TiO2 nanoparticles, was synthesized by sol–gel method and applied to detect organic pollutants... 相似文献
3.
4.
5.
Synthesis of Small‐Sized,Porous, and Low‐Toxic Magnetite Nanoparticles by Thin POSS Silica Coating 下载免费PDF全文
Dr. Swee Kuan Yen D. Prathyusha Varma Wei Mei Guo Dr. Vincent H. B. Ho Dr. Vimalan Vijayaragavan Dr. Parasuraman Padmanabhan Prof. Kishore Bhakoo Prof. Subramanian Tamil Selvan 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(10):3914-3918
In this communication, we report the synthesis of small‐sized (<10 nm), water‐soluble, magnetic nanoparticles (MNPs) coated with polyhedral oligomeric silsesquioxanes (POSS), which contain either polyethylene glycol (PEG) or octa(tetramethylammonium) (OctaTMA) as functional groups. The POSS‐coated MNPs exhibit superparamagnetic behavior with saturation magnetic moments (51–53 emu g?1) comparable to silica‐coated MNPs. They also provide good colloidal stability at different pH and salt concentrations, and low cytotoxicity to MCF‐7 human breast epithelial cells. The relaxivity data and magnetic resonance (MR) phantom images demonstrate the potential application of these MNPs in bioimaging. 相似文献
6.
7.
8.
在中国科学技术大学夏季学期的研究型实验课程"化学科研基础训练"中开设"壳聚糖的制备与表征"综合实验,以龙虾壳为原料,通过除蛋白、脱盐、脱色、脱乙酰等一系列反应,制备得到目标产物壳聚糖。运用红外光谱、核磁共振仪、黏度法、滴定等对产品的结构及性能进行表征。 相似文献
9.
10.