全文获取类型
收费全文 | 181篇 |
免费 | 6篇 |
国内免费 | 20篇 |
专业分类
化学 | 141篇 |
力学 | 8篇 |
综合类 | 2篇 |
数学 | 10篇 |
物理学 | 46篇 |
出版年
2023年 | 1篇 |
2022年 | 2篇 |
2021年 | 1篇 |
2019年 | 1篇 |
2018年 | 1篇 |
2017年 | 1篇 |
2016年 | 1篇 |
2015年 | 3篇 |
2013年 | 12篇 |
2012年 | 12篇 |
2011年 | 33篇 |
2010年 | 19篇 |
2009年 | 28篇 |
2008年 | 7篇 |
2007年 | 1篇 |
2005年 | 2篇 |
2004年 | 14篇 |
2003年 | 8篇 |
2002年 | 9篇 |
2001年 | 6篇 |
1999年 | 1篇 |
1998年 | 2篇 |
1996年 | 2篇 |
1994年 | 3篇 |
1993年 | 5篇 |
1992年 | 8篇 |
1991年 | 9篇 |
1990年 | 2篇 |
1989年 | 9篇 |
1988年 | 3篇 |
1982年 | 1篇 |
排序方式: 共有207条查询结果,搜索用时 15 毫秒
1.
A new PVC membrane potentiometric sensor that is highly selective to Fe(III) ions was prepared by using 2-[(2-hydroxy-1-propenyl-buta-1,3-dienylimino)-methyl]-4-p-tolylazo-phenol [HPDTP] as a suitable carrier. The electrode exhibits a linear response for iron(III) ions over a wide concentration range (3.5 × 10−6 to 4.0 × 10−2) with a super Nernstian slope of 28.5 (±0.5) per decade. The electrode can be used in the pH range from 4.5 to 6.5. The proposed sensor shows fairly a good discriminating ability towards Fe3+ ion in comparison to some hard and soft metals such as Fe2+, Cd2+, Cu2+, Al3+ and Ca2+. It has a response time of <15 s and can be used for at least 2 months without any measurable divergence in response characteristics. The electrode was used in the direct determination of Fe3+ in aqueous samples and as an indicator electrode in potentiometric titration of Fe(III) ions. 相似文献
2.
Mohammad Baghery Mahmoudian Ali Reza Nejad Ahmad Iran 《Russian Journal of Electrochemistry》2021,57(6):567-579
Russian Journal of Electrochemistry - Zinc selenide has applications in the fabrication of low-cost solar cells and optoelectronic devices. Due to its optical properties and large direct bandgap,... 相似文献
3.
Shahmirzaee Mozhgan Shafiee Afarani Mahdi Arabi Amir Masoud Iran Nejhad Ahmad 《Research on Chemical Intermediates》2017,43(1):321-340
Research on Chemical Intermediates - ZnAl2O4/ZnO nanocomposites with different ZnO (20, 30, and 40 mol%) concentrations and coated samples on supports were successfully prepared through... 相似文献
4.
Iran Sheikhshoaie Helen Stoeckli-Evans Alireza Akbari S. Ali Yasrebi S. Yousef Ebrahimipour 《Arabian Journal of Chemistry》2012,5(2):173-178
The crystal and molecular structure of methanol {E-N′-(2-hydroxybenzlidene)benzohydrazido}dioxidomolybdenum (VI) was determined by single crystal X-ray diffraction. B3LYP/DZP basis set theoretical calculations nicely reproduce the X-ray experimental geometry. The obtained results are discussed in connection with the electronic and structural properties of the compound. 相似文献
5.
Shokoofe Jahandari Mohammad Ali Taher Hamid Fazelirad Iran Sheikhshoai 《Mikrochimica acta》2013,180(5-6):347-354
We describe a silver(I)-selective carbon paste electrode modified with multi-walled carbon nanotubes and a silver-chelating Schiff base, and its electrochemical response to Ag(I). Effects of reduction potential and time, accumulation time, pH of the solution and the stripping medium were studied by differential pulse anodic stripping voltammetry and optimized. The findings resulted in a method for the determination of silver over a linear response range (from 0.5 to 235 ng?mL?1) and with a detection limit as low as 0.08 ng?mL?1. The sensor displays good repeatability (with the RSD of ±?2.75 % for 7 replicates) and was applied to the determination of Ag(I) in water samples and X-ray photographic films. Figure
Open circuit accumulation of Ag(I) onto a surface of EHPO-MCPE and determination by Differential pulse anodic stripping voltammetry 相似文献
6.
Spectroscopy Investigation on Conformational Transition of Tea Glycoconjugate from Green Tea 总被引:5,自引:0,他引:5
The conformational transition of a new glycoconjugate, tea glycoconjugate (TGC), was investigated by spectroscopy techniques including circular dichroism (CD) and ultraviolet (UV) spectroscopy. The solution behaviors of TGC in the mediums of different temperature, pH value, and ions were compared. Results showed that the native conformation of TGC was partially ordered. The CD value and UV absorbance of TGC altered with the change of pH value, temperature, the addition of ions, and also accompanied order-disorder transition. Especially the conditions with temperature higher than the glass transition temperature (Tg=62℃), higher pH value or lower pH value will have the most impact on the conformation of TGC, which will destroy the hydrogen bonds between the TGC molecules. The results indicated that the outside factors play important roles on the stability of the conformation of TGC. 相似文献
7.
氮肥管理对夏玉米土壤CH4和N2O排放的影响 总被引:11,自引:0,他引:11
通过设置四个不同的氮肥管理措施, 即氮肥施用量300 kg N/ha (N300)和250 kg N/ha (N250)、改进的施肥模式(Optimized)以及施用缓释肥(SRU), 研究华北平原夏玉米生长季土壤与大气之间CH4和N2O的交换通量及相应措施的减排潜力. 结果表明, 在2008年整个夏玉米生长季, 土壤都是大气CH4的净吸收库和N2O的排放源. 夏玉米生长季土壤氧化吸收的CH4总量从大到小依次为Optimized > N250 > SRU > N300, 对应的吸收总量依次为624.16、590.07、487.89以及316.02 g CH4-C/ha, 各处理间氧化吸收的CH4总量无显著差异. 与N300和N250这两个处理相比, 依据夏玉米对氮肥的需肥规律以及玉米根层土壤速效氮的供给能力而确定氮肥施用量, 同时再平衡施用磷肥和钾肥的改进施肥模式能够显著降低夏玉米生长季N2O的排放. 施用聚乙烯包膜的尿素也能够显著降低夏玉米季N2O的排放. 夏玉米生长季土壤排放的N2O总量从大到小依次为N300 > N250 > Optimized > SRU, 对应的排放总量依次为3462.18、2340.07、1680.00以及911.91 g N2O-N/ha, 相应的N2O排放系数分别为1.15%、0.94%、0.91%以及0.30%. 相似文献
8.
采用了硝酸+高氨酸消化样品,AFS-2202原子荧光光谱仪测定中药田七中砷的含量,该方法的检出限可达0.09μg·L~(-1),回收率在91.0%~109.2%之间。 相似文献
9.
LI QiuYue & REN YanXia College of Science China Agricultural University Beijing China LMAM School of Mathematical Sciences Center for Statistical Science Peking University Beijing 《中国科学 数学(英文版)》2011,(7)
In this paper we establish a large deviation principle for the occupation times of critical branching α-stable processes for large dimensions d > 2α, by investigating two related nonlinear differential equations. Our result is an extension of Cox and Griffeath’s (in 1985) for branching Brownian motion for d > 4. 相似文献
10.
外源一氧化氮对镉胁迫下番茄幼苗叶绿体保护作用的光谱学分析 总被引:1,自引:0,他引:1
镉(Cd)是重要的重金属污染源,一氧化氮(NO)是近年来发现的一种普遍存在于生物界的信使分子,研究表明其参与了植物对Cd胁迫的应答反应调控。文章用硝普纳(SNP)作为NO供体,向番茄幼苗喷洒100mol·L^-1SNP1d后加入50mol·L^-1Cd处理7d,取完全展开叶片,提取叶绿体进行光谱学研究,分别测定了叶绿体室温吸收光谱、叶绿体低温荧光光谱和DCPIP电子传递效率等指标,研究外源NO缓解Cd对叶绿体毒性的影响。结果发现,CA对叶绿素a、叶绿素b和类胡萝b素含量都有不同程度的降低,NO处理缓解了CA的影响,使叶绿体室温吸收光谱的吸收率提高;CA导致686nm处峰(PSII)偏移4nrn,峰值降低33%,734nm处峰值降低23%,外源NO缓解了Cd对光合系统的影响,使得叶绿体低温荧光光谱在686和734nm的峰值分别仅下降17%和100o;以DCPIP为人工电子受体,Cd处理的叶绿体中DCPIP还原速率较慢,光合电子传递(H2O→DCPIP)速率降低1.5倍,外源NO处理显著缓解了Cd对电子传递链的抑制,使其光合电子传递速率恢复到对照的水平。该研究可为NO处理增强植物对Cd胁迫的抗性提供理论依据。 相似文献