全文获取类型
收费全文 | 300篇 |
免费 | 10篇 |
专业分类
化学 | 226篇 |
晶体学 | 4篇 |
力学 | 4篇 |
数学 | 14篇 |
物理学 | 62篇 |
出版年
2024年 | 8篇 |
2023年 | 3篇 |
2022年 | 9篇 |
2021年 | 20篇 |
2020年 | 8篇 |
2019年 | 11篇 |
2018年 | 13篇 |
2017年 | 9篇 |
2016年 | 15篇 |
2015年 | 11篇 |
2014年 | 8篇 |
2013年 | 18篇 |
2012年 | 21篇 |
2011年 | 22篇 |
2010年 | 21篇 |
2009年 | 15篇 |
2008年 | 8篇 |
2007年 | 11篇 |
2006年 | 11篇 |
2005年 | 11篇 |
2004年 | 8篇 |
2003年 | 14篇 |
2002年 | 9篇 |
2001年 | 1篇 |
2000年 | 3篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1994年 | 3篇 |
1993年 | 1篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有310条查询结果,搜索用时 10 毫秒
101.
Min Xu Wenjing Qi Ling Zhang Jianping Lai Aziz-ur-Rehman Saadat Majeed Guobao Xu 《Mikrochimica acta》2014,181(7-8):737-742
The reaction of hydrogen tetracholoroaurate, sodium borohydride and the diazonium compound prepared from 4-aminobenzoic acid results in the formation of gold nanocorals (Au-NCs) for the first time. Scanning electron microscopy images and transmission electron microscopy images show that the Au-NCs are composed of nanowires with a diameter of 5.3 nm. A glassy carbon electrode modified with Au-NCs is found to trigger intense electrochemiluminescence of the luminol/H2O2 system at a potential of ?0.13 V. The effect was exploited to determine H2O2 in the 0.1 to 100 μM concentration range with a 30 nM detection limit. Figure
Gold nanocoral has been synthesized using diazonium salt chemistry for the first time. The Gold nanocoral-modified electrode show intense electrochemiluminescence at a low potential of ?0.13 V. 相似文献
102.
Structural Chemistry - Zika and dengue virus are flaviviruses which with the passage of time have become a serious challenge affecting millions of people around the world. To lessen the impact of... 相似文献
103.
Md Lutfor Rahman Gurumuthy Hegde Shaheen M. Sarkar Mashitah Mohd Yusoff 《中国化学快报》2014,25(12):1611-1614
The fluorine-substituted benzoate ester rod-shaped liquid crystals containing an azobenzene side chain linked with terminal double bonds were synthesized and characterized.The mesophase and photoswitching properties were determined by polarizing optical microscopy(POM),differential scanning calorimetry(DSC) and UV-visible spectrometry.The rod-shaped compound 4a having an odd number of carbon atoms in the alkyl chains exhibits nematic phase and SmA type phase whereas compound 4b having an even number of carbon atoms showed only nematic phase.Both fluorinecontaining compounds 4c and 4d showed only SmA type phases.The photoswitching properties of these compounds showed a rate of trans to cis isomerization ranging 19-20 s,whereas reverse process took around 230 min in solution.These materials may be ideal in the field of optically rewritable applications where both on and off rates should be crucial. 相似文献
104.
KhalidMohammed Khan GhulamMurtaza Maharvi Ahmed Abbaskhan Safdar Hayat MahmudTareqHassan Khan Talat Makhmoor M.Iqbal Choudhary Farzana Shaheen Atta‐ur‐Rahman 《Helvetica chimica acta》2003,86(2):457-464
Phytochemical investigation on the whole plant of Salsola foetida resulted in the isolation of three new phenolic compounds 1, 2 , and 3 , which exhibit tyrosinase inhibition with moderate antioxidant activity. Compounds 1 – 3 inhibited tyrosinase with IC50 2.61, 1.85, and 0.40 μM , while exhibiting DPPH radical scavenging activity with IC50 383, 427 and 378 μM , respectively. The structures of 1, 2 , and 3 were determined by modern spectroscopic techniques. 相似文献
105.
Shaheen Siddiqui B Zhymabekovna Karzhaubekova Z Shahmanovna Burasheva G Adaibaevna Sultanova N 《Chemical & pharmaceutical bulletin》2007,55(9):1356-1360
Studies on the chemical constituents of the aerial parts of Kalidium foliatum have led to the isolation of three new and one known compounds. The structures of new constituents have been elucidated through spectral studies including 2D-NMR experiments (HMQC, HMBC, COSY, NOESY and J-resolved) and MS/MS fragmentation using Q-TOF mass spectrometer equipped with an ESI source as kalidiumoside C (=3beta-hydroxy-29-methylmalonoxy-olean-12-en-23,28-dioic acid-23-methyl-28-beta-D-glucopyranosyl ester; 1), kalidiunin (=3beta,23,29-trihydroxy-olean-12-en-28-methyl-oate; 2) and kalidiumoside D (=3beta,23,29-trihydroxyolean-12-en-28-oic acid-beta-D-glucopyranosyl ester; 3). The known compound was identified as 3beta,23,29-trihydroxy-olean-12-en-28-oic acid 4) through comparison of its spectral data with those reported in literature. Acid hydrolysis of both 2 and 3 yielded the known compound 4 providing a conclusive evidence of the proposed structures. 相似文献
106.
Farkhanda Shaheen Michal Dusek Dick de Vos 《Journal of organometallic chemistry》2007,692(14):3019-3026
Six palladium(II) dithiocarbamates of general formula Pd(AmDTC)2, where HAmDTC = aminedithiocarbamic acid, [Pd(II) piperidinedithiocarbamate (1), Pd(II) 4-methylpiperidinedithiocarbamate (2), Pd(II) N-methylbenzyldithiocarbamate (3), Pd(II) dibenzyldithiocarbamate (4), Pd(II) dicyclohexyldithiocarbamate (5), Pd(II) N-cyclohexyl-N-methyldithiocarbamate (6)] have been synthesized and characterized by elemental analyses, FT-IR, 1H and 13C NMR. The X-ray structure of Pd(II), compounds 3 and 4, showed that the ligands are chelated by both sulfur atoms with bond angles S1-Pd-S4 = 179.24(2)° and S2-Pd-S3 = 179.09(5)°, with a distorted square planar geometry around Pd. All these complexes were screened for cytotoxic and antibacterial effects and showed significant antibacterial activity and no substantial in vitro cytotoxicity indicating specificity of the compounds. 相似文献
107.
Muhammad Mohsin Iqbal Muhammad Imran Tousif Hussain Muhammad Asif Naeem Abdullah A. Al-Kahtani Ghulam Mustafa Shah Sajjad Ahmad Amjad Farooq Muhammad Rizwan Abdul Majeed Abdul Rehman Khan Shafaqat Ali 《Journal of Saudi Chemical Society》2021,25(2):101176
Widespread application of dyes and disposal of their untreated effluents into water bodies adversely affect the ecosystem due to their complex aromatic structures and persistent nature. The present study aims to utilize the cotton stalks biochar (CSB) and its composite with zinc oxide nanoparticles (CSB/ZnONPs) to evaluate for the decontamination their batch scale potential of Congo red dye from wastewater. The characterization of CSB and CSB/ZnONPs was performed with Fourier-transform infra-red (FTIR) spectroscopy, scanning electron microscopy, energy-dispersive X-ray (EDX) and point of zero charge (PZC) to get insight of their potential for the decontamination of CR. The effects of initial CR concentration (25–500 mg/L), dosage of CSB and CSB/ZnONPs (0.5–2 g/L), solution pH (2–10) and contact time (0–180 min) were evaluated on CR removal at temperature (25 ± 1.5 °C). The results disclosed that CSB/ZnONPs showed excellent adsorption potential (556.6 mg/g) in comparison with CSB (250 mg/g) and most of the other adsorbents previously studies in the literature. The equilibrium experimental data were equally explained with Freundlich and Langmuir isotherm models (R2 > 0.98) while kinetic data demonstrated the best fit with pseudo second order model. The CSB/ZnONPs composite exhibited excellent reusability (89.65%) after five adsorption/desorption cycles for the sequestration of CR from contaminated systems. The present study demonstrated that metallic nanocomposite of CSB (CSB/ZnONPs) is an excellent candidate for the cost effective and environment friendly decontamination of CR from industrial wastewater and is suggested to be considered for the decontamination of other pollutants from the wastewater. 相似文献
108.
Relative acidities (Delta pK(a)) of phenols and oxidation potentials (Delta E(ox)) of the phenoxide anions have been calculated for nine para-substituted phenols using density functional theory. Solvent effects were incorporated using the conductor-like polarisable continuum method. Using the calculated Delta pK(a) and Delta E(ox) values in a thermodynamic cycle, the DeltaBDE (bond dissociation enthalpy) of the phenols were also determined with all values calculated to within 1.5 kcal mol(-1) of experiment. The Delta pK(a) and Delta E(ox) values were calculated for 6-hydroxy-2,2,5,7,8-pentamethylchroman (HPMC), a model for alpha-tocopherol for which there are no known experimental values. The acidity of this compound is raised by 2.4 pK(a) units and lowered by -0.79 V relative to phenol with a calculated Delta BDE of -14.9 kcal mol(-1). There is a negative correlation (r(2) = 0.86) between the Delta pK(a) and the Delta BDE values. A stronger and positive correlation is found between the Delta E(ox) (r(2) = 0.98) and the Delta BDE values. Using these correlations it is uncovered that hydrogen abstraction of phenols, as measured by the Delta BDE, is driven by electron transfer rather than by proton transfer. 相似文献
109.
Amir Zada Nauman Ali Muhammad Ateeq Ali M. Huerta-Flores Zahid Hussain Shabana Shaheen Mohib Ullah Sharafat Ali Imran Khan Wajid Ali Muhammad Ishaq Ali Shah Waliullah Khan 《中国化学会会志》2020,67(6):983-989
Energy crises and environmental pollution have sparked tremendous research work to handle their impacts. Herein, we fabricated Au/g-C3N4 nanocomposites to produce H2 and degrade 2,4-dichlorophenol (2,4-DCP) under visible light and at different wavelengths. Interestingly, the optimized photocatalyst generated 114 μmol H2 and degraded 25% 2,4-DCP in 1 hr as compared with 10 μmol H2 generation and 8% 2,4-DCP degradation by pure g-C3N4. This improvement is credited to the extended light absorption and improved charge induction from gold to g-C3N4 even at 590 nm as confirmed from photoluminescence, surface photovoltage, and photoelectrochemical study of the samples. Moreover, the surface catalytic property of g-C3N4 was much improved after loading a proper amount of gold nanoparticles. We hope that this technique to photosensitize semiconductors with noble metal nanoparticles may provide a feasible way to construct surface plasmon resonance-assisted photocatalysts to cope with energy crises and environmental pollution simultaneously. 相似文献
110.
A new aromatic glycoside, shamiminol was isolated from the stem bark of Bombax ceiba along with the known constituents stigmasta-3,5-diene, lupenone, (+/-)-lyoniresinol 2a-O-beta-D-glucopyranoside and opuntiol, obtained for the first time from this plant. The structure of shamiminol was elucidated on the basis of extensive 1D- and 2D-NMR spectroscopic and mass spectrometric studies as 3,4,5-trimethoxyphenol 1-O-beta-D-xylopyranosyl-(1 --> 2)-beta-D-glucopyranoside (1). 相似文献