全文获取类型
收费全文 | 520篇 |
免费 | 24篇 |
国内免费 | 48篇 |
专业分类
化学 | 495篇 |
晶体学 | 1篇 |
力学 | 9篇 |
综合类 | 4篇 |
数学 | 1篇 |
物理学 | 82篇 |
出版年
2023年 | 9篇 |
2022年 | 8篇 |
2021年 | 12篇 |
2020年 | 17篇 |
2019年 | 10篇 |
2018年 | 6篇 |
2017年 | 15篇 |
2016年 | 13篇 |
2015年 | 19篇 |
2014年 | 16篇 |
2013年 | 39篇 |
2012年 | 33篇 |
2011年 | 27篇 |
2010年 | 25篇 |
2009年 | 39篇 |
2008年 | 22篇 |
2007年 | 31篇 |
2006年 | 29篇 |
2005年 | 25篇 |
2004年 | 23篇 |
2003年 | 19篇 |
2002年 | 15篇 |
2001年 | 15篇 |
2000年 | 18篇 |
1999年 | 14篇 |
1998年 | 11篇 |
1997年 | 11篇 |
1996年 | 11篇 |
1995年 | 12篇 |
1994年 | 9篇 |
1993年 | 7篇 |
1992年 | 5篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1988年 | 5篇 |
1987年 | 6篇 |
1986年 | 3篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1972年 | 1篇 |
排序方式: 共有592条查询结果,搜索用时 15 毫秒
1.
PENG Zi-cheng LI Ping ZHOU Tai-xi LI Xue-ming Wept. of Earth Space Science Univ. of Science Tech. of China Hefei )HU Zhi-sheng 《高等学校化学研究》1992,(3)
When was the earliest glass produced in China? This has still been a question so far. Some archaeologists have thought that Yu Guo beads are real glass, the earliest glass(1100-771 B. C. ) in China. However, more details of scientific investigations in this paper show that Yu Guo beads are mainly made of clastic quartz (>95%) with a small amount of clay and sintered under the low temperature(500-600℃). It is not a glassy body, but a kind of polycrystal ornaments. 相似文献
2.
3.
4.
5.
The monodisperse, porous poly(chloromethylstyrene-co-divinylbenzene) beads of 7.9 microm were prepared by a single-step swelling and polymerization method. The seed particles prepared by dispersion polymerization exhibited good absorption of the monomer phase. Based on this media, a weak cation-exchange (WCX) stationary phase for HPLC was synthesized by a new chemically modified method. The prepared resin has advantages of biopolymer separation, high column efficiency, low column backpressure, high protein mass recovery, and good resolution for proteins. The dynamic protein-loading capacity of the synthesized WCX packings was 18.2 mg/g. Five proteins were separated in 3.0 min using the synthesized WCX stationary phase. The experimental results show that the obtained WCX resin has very weak hydrophobicity. The WCX resin was also used for the rapid separation and purification of lysozyme from egg white in 5.0 min with only one step. The purity and specific bioactivity of the purified lysozyme were found to be more than 93% and 70 245 U/mg, respectively. 相似文献
6.
树脂对茶多酚与咖啡因的吸附分离 总被引:7,自引:1,他引:7
从低档绿茶末的水提取液中,利用离子交换,吸附树脂成功地分离出茶多酚与咖啡因,并详细考察了其交换与吸附性能。与其它方法相比,该树脂法具有产品收率高,成本低廉等特点。 相似文献
7.
O157∶H7大肠埃希菌是一种致病力非常强的微生物.近年来,陆续有其引起食物中毒事件的报道.1996年日本发生O157∶H7大肠埃希菌食物中毒的爆发流行,感染病例逾万人,死亡9例.2001年我国江苏及安徽等地也发生了肠出血性O157∶H7大肠埃希菌所引发的感染性腹泻事件.目前O157∶H7大肠埃希菌实验室常规检测方法为分离培养计数法,此法费时费力,需要几天的时间才能得到检测结果[1,2],缺乏应对突发事件的能力,因此亟需开发快速检测技术.近年来,多种微生物快速检测技术如ELISA法[3]、热解质谱测定法[4]、多聚酶链反应[5]、荧光成像技术[6]、生物发… 相似文献
8.
Eldefrawi ME Azer NL Nath N Anis NA Bangalore MS O'Connell KP Schwartz RP Wright J 《Applied biochemistry and biotechnology》2000,87(1):25-35
An automated flow fluorometer designed for kinetic binding analysis was adapted to develop a solid-phase competitive fluoroimmunoassay
for urinalysis of opiates. The solid phase consisted of polymer beads coated with commercial monoclonal antibodies (MAbs)
raised against morphine. Fluorescein-conjugated morphine (FL-MOR) was used as the fluorescein-labeled hapten. The dissociation
equilibrium constant (K
D
) for the binding of FL-MOR to the anti-MOR MAb was 0.23 nM. The binding of FL-MOR to the anti-MOR MAb reached steady state within minutes and was displaced effectively by morphine
and other opiates. Morphine-3-glucuronide (M3G), the major urinary metabolite of heroin and morphine, competed effectively
with FL-MOR in a concentration-dependent manner for binding to the antimorphine MAb and was therefore used to construct the
calibration curve. The sensitivity of the assay was 0.2 ng/mL for M3G. The assay was effective at concentrations of M3G from
0.2 to 50 ng/mL, with an IC50 of 2 ng/mL. Other opiates and heroin metabolites that showed >50% crossreactivity when present at 1 μg/mL included codeine,
morphine-6-glucuronide, and oxycodone. Methadone showed very low crossreactivity (<5%), which is a benefit for testing in
patients being treated for opiate addictions. The high sensitivity of the assay and the relatively high cutoff value for positive
opiate tests allows very small sample volumes (e.g., in saliva or sweat) to be analyzed. A double-blind comparison using 205
clinical urine samples showed good agreement between this single-step competitive assay and a commercially performed enzyme
multiplied immunoassay technique for the detection of opiates and benzoylecgonine (a metabolite of cocaine). 相似文献
9.
GuoXiangCHENG GuangLingPEI LingGangZENG LiYongZHANG ChaoLIU 《中国化学快报》2004,15(2):242-245
In this paper, the surface imprinted cross-linked polystyrene beads were prepared via suspension polymerization with styrene (St), divinylbezene (DVB), polyvinyl alcohol (PVA1788),the mixture of Span 85 and xylene or the mixture of Span 85 and paraffin as monomer,cross-linking agent, dispersion stabilizer and templates, respectively. The results indicate that there are dense cavities on the surface of beads, and the diameter and density of cavity are related with the composition and amount of emulsion template. The forming mechanism of cavity from thermodynamics and dynamics was proposed. 相似文献
10.
Cestari AR Vieira EF Dos Santos AG Mota JA de Almeida VP 《Journal of colloid and interface science》2004,280(2):380-386
In this work, chitosan beads were synthesized in acidic medium and cross-linked in 1% glutaraldehyde solution. The characterization of the materials using TG/DTG, XRD, and BET surface areas showed that the beads did not modify their characteristics after the cross-linking reaction. The cross-linked beads were utilized as adsorbents for the removal of the yellow-, blue-, and red-anionic reactive dyes from aqueous solutions at pH 2.0. Adsorption of the yellow-dye increased from 25 to 50 degrees C. However, adsorption of the blue-dye decreased from 25 to 50 degrees C. Interestingly, the adsorption of the red-dye decreased from 25 to 35 degrees C and increased from 45 to 50 degrees C. The kinetic data were evaluated using an Avrami kinetic model, where the parameter n was related to the determination of changes in the adsorption mechanisms. Adsorption data of the dyes in relation to the contact time, the chemical structures of the dyes, and temperature were presented and were discussed. 相似文献