全文获取类型
收费全文 | 206篇 |
免费 | 9篇 |
专业分类
化学 | 140篇 |
晶体学 | 3篇 |
力学 | 12篇 |
数学 | 18篇 |
物理学 | 42篇 |
出版年
2024年 | 2篇 |
2023年 | 3篇 |
2022年 | 21篇 |
2021年 | 11篇 |
2020年 | 10篇 |
2019年 | 4篇 |
2018年 | 8篇 |
2017年 | 6篇 |
2016年 | 10篇 |
2015年 | 8篇 |
2014年 | 5篇 |
2013年 | 24篇 |
2012年 | 18篇 |
2011年 | 10篇 |
2010年 | 13篇 |
2009年 | 9篇 |
2008年 | 10篇 |
2007年 | 11篇 |
2006年 | 4篇 |
2005年 | 7篇 |
2004年 | 4篇 |
2003年 | 4篇 |
2002年 | 4篇 |
2000年 | 2篇 |
1999年 | 1篇 |
1997年 | 1篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1987年 | 1篇 |
1980年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有215条查询结果,搜索用时 15 毫秒
31.
M. Abid Ali P. J. Hickman A. T. Clementson 《The Journal of the Operational Research Society》1975,26(2):243-252
Automatic Interaction Detection (AID) is a multivariate statistical technique. This paper describes the algorithm and illustrates its application to a particular case study in the British fishing industry. 相似文献
32.
33.
Siddiqui Abuzar Abid Chamkha Ali J. 《Journal of Thermal Analysis and Calorimetry》2020,142(3):1345-1360
Journal of Thermal Analysis and Calorimetry - The steady flow of a nanofluid (mixture of titanium dioxide and water) in a rectangular channel under the influence of an inclined magnetic field is... 相似文献
34.
Abid Nazir Gill Areeba Iftikhar Ayoub Rashid Muhammad Amin Rana Rashad Mahmood Khan Hafiz M. Rafique Seemal Jelani Ahmad Adnan 《Journal of the Iranian Chemical Society》2018,15(9):1939-1945
The present study reports the green synthesis of starch–maleate (SM) at ambient temperature in solvent-free system using Rhizopus arrhizus lipase as a biocatalyst and maleic acid (MA) as an esterification agent. The synthetic scheme was found to be efficient, economical, and ecofriendly. The newly synthesized SM samples were characterized using Fourier transform infrared (FTIR) and proton nuclear magnetic resonance (1H NMR) spectroscopic techniques. The degree of substitution (DS) was found in the range of 0.53–0.62. Moreover, DS was found to be temperature and time-dependent. X-ray diffraction (XRD) exhibited that maleation did not change the crystalline nature of native starch. Scanning electron microscopy (SEM) revealed that size of SM granules was in the range of 4–18 µm. The activation energy (Ea) of SM formation was calculated to be 42.94 kcal mol?1 which clearly indicated the effective and rapid interaction of functional groups. Hence, the solvent-free solid-state synthetic methodology proved to be excellent for the synthesis of novel biomaterials with appreciable high DS for drug delivery and sorption of heavy metal ions from water. 相似文献
35.
Saeed Ullah Khattak Zafar Iqbal Irshad Ur Rehman Jamshaid Ahmad Abid Ali Khan 《Natural product research》2018,32(10):1212-1215
In the quest for bioactive natural products of fungal origin, Aspergillus flavus was isolated from rhizosphere of Mentha piperita using Potato Dextrose Agar (PDA) and Czapec Yeast Broth (CYB) nutrient media for metabolites production. In total, three different metabolites were purified using HPLC/LCMS and the structures were established using 500 Varian NMR experiments. Further the isolated metabolites in different concentrations (10, 100, 1000 μg/mL) were tested for herbicidal activity using Completely Randomized design (CRD) against the seeds of Silybum marianum and Avena fatua which are major threats to wheat crop in Pakistan. Among the isolated metabolites, one compound was found active against the test weed species whose activity is reported in the present work. The chemical name of the compound is 2-(1, 4-dihydroxybutan-2-yl)-1, 3-dihydroxy-6, 8-dimethoxyanthracene-9, 10(4aH, 9aH)-dione with mass of 388. Results showed that all seeds germinated in control treatment; however, with the metabolite treated, the growth was retarded to different levels in all parts of the weeds. At a dose of 1000 μg/mL of the pure compound, 100% seeds of S. marianum and 60% seeds of A. fatua were inhibited. Interestingly, the pure compound exhibited less inhibition of 10% towards the seeds of common wheat (Triticum aestivum). 相似文献
36.
Triflic acid-catalyzed highly stereoselective friedel-crafts aminoalkylation of indoles and pyrroles
A simple and efficient synthesis to both enantiomers of highly enantiomerically enriched alpha-trifluoromethyl-alpha-(heteroaryl)-glycine derivatives via highly stereoselective aminoalkylation of indoles and pyrroles is described. The triflic acid-catalyzed reaction of enantiomeric 3,3,3-trifluoro-pyruvate-alpha-methylbenzyl imines with indoles and pyrroles and the subsequent Pd-catalyzed hydrogenolysis of the methylbenzyl group provided the products in high yields and excellent enantioselectivities. 相似文献
37.
Khan A Silversides JD Madden L Greenman J Archibald SJ 《Chemical communications (Cambridge, England)》2007,(4):416-418
The copper(II) complex of a novel rhodamine-azamacrocycle conjugate binds to the CXCR4 chemokine receptor and competes effectively against anti-CXCR4 monoclonal antibodies. The copper macrocycle unit adopts a trans-II configuration in the solid state. 相似文献
38.
Resonance Absorption Spectroscopy (ARAS) has been used to measure O‐atom concentration behind reflected shock waves in the temperature range 2690–3360 K at total pressures of about 250 kPa and using mixtures of N2O and H2 highly diluted in Ar. For the chosen experimental conditions, only a few elementary reactions exerted an appreciable influence on the O‐atom profile so that the rate coefficient k2 for the reaction O + H2 → OH + H, directly responsible for the oxygen atom concentration decrease could be deduced by comparison between the experiment and computed simulation. In the actual temperature range we found: k2(cm3 mol−1 s−1) = 9.25 × 1014 exp(−9740/T(K)), with a percentage standard deviation of 8%. The influence of experimental uncertainties is discussed. This rate constant is compared with those reported previously in the literature. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 686–695, 2000 相似文献
39.
Hasan M. Khan Muhammad Ismail Muhammad Abid Zia Khalid Khan 《Isotopes in environmental and health studies》2013,49(2):295-301
The analysis of gamma-emitting radionuclides in nature, i.e. 226Ra, 232Th, 40K and 137Cs, has been carried out in soil samples collected from Peshawar University Campus and surrounding areas using a high purity germanium detector coupled with a computer-based high-resolution multichannel analyser. The activity concentrations in soil ranged from 30.20±0.65 to 61.90±0.95, 50.10±0.54 to 102.80±1.04, 373.60±4.56 to 1082±11.38 and 9.50±0.11 to 46.60±0.42 Bq kg?1 for 226Ra, 232Th, 40K and 137Cs, with a mean value of 45±7.70, 67±12.50, 878±180 and 19±9.20 Bq kg?1, respectively. The radium equivalent activity, internal and external hazard indices have mean values of 203.40±29.40 Bq kg?1, 0.56 and 0.68, respectively. The mean values of outdoor and indoor absorbed dose rates in air and the annual effective dose equivalents were found to be 106.50 and 128 nGy h?1 and 0.19 and 0.54 mSv y?1, respectively. In the present study, 40K was the major radionuclide present in soil samples. The presence of 137Cs indicates that this area also received some fallout from the nuclear accident of the Chernobyl power plant in 1986. The activity concentrations of radionuclides found in soil samples during the current investigation were nominal. Therefore, they are not associated with any potential source of health hazard to the public. 相似文献
40.