全文获取类型
收费全文 | 1352篇 |
免费 | 49篇 |
国内免费 | 21篇 |
专业分类
化学 | 1009篇 |
晶体学 | 20篇 |
力学 | 40篇 |
数学 | 52篇 |
物理学 | 301篇 |
出版年
2024年 | 6篇 |
2023年 | 12篇 |
2022年 | 109篇 |
2021年 | 115篇 |
2020年 | 54篇 |
2019年 | 58篇 |
2018年 | 66篇 |
2017年 | 39篇 |
2016年 | 85篇 |
2015年 | 58篇 |
2014年 | 72篇 |
2013年 | 83篇 |
2012年 | 124篇 |
2011年 | 115篇 |
2010年 | 70篇 |
2009年 | 46篇 |
2008年 | 44篇 |
2007年 | 40篇 |
2006年 | 30篇 |
2005年 | 24篇 |
2004年 | 11篇 |
2003年 | 17篇 |
2002年 | 12篇 |
2001年 | 11篇 |
2000年 | 8篇 |
1999年 | 2篇 |
1997年 | 6篇 |
1996年 | 2篇 |
1995年 | 3篇 |
1994年 | 9篇 |
1993年 | 6篇 |
1992年 | 5篇 |
1991年 | 8篇 |
1990年 | 3篇 |
1989年 | 3篇 |
1988年 | 5篇 |
1987年 | 5篇 |
1986年 | 4篇 |
1985年 | 6篇 |
1984年 | 7篇 |
1983年 | 3篇 |
1982年 | 6篇 |
1981年 | 5篇 |
1980年 | 5篇 |
1978年 | 3篇 |
1977年 | 4篇 |
1975年 | 5篇 |
1973年 | 2篇 |
1935年 | 1篇 |
1933年 | 1篇 |
排序方式: 共有1422条查询结果,搜索用时 15 毫秒
101.
Nur Atiqah Mohd Nasuha 《Natural product research》2016,30(13):1532-1536
Marsdenia tinctoria is an indigo producing plant commonly found in Borneo, Malaysia. In this present study, one new flavone kapitone (1) and three known compounds, that is 3,2’-dihydroxyflavone (2), 1-methylcyclobutene (3) and dimethyl isatoate (4) were isolated from the Malaysia Borneo M. tinctoria R. Br. (Apocynaceae). These compounds were isolated and characterised using extensive chromatographic and spectroscopic methods. 相似文献
102.
Ashok Zakkula Sreekanth Dittakavi Malika Muskan Maniyar Naveem Syed Suresh P. Sulochana Mohd Zainuddin Ramesh Mullangi 《Biomedical chromatography : BMC》2019,33(11)
Isocitrate dehydrogenase (IDH) inhibitors comprise a novel class of anticancer drugs, which are approved to treat acute myeloid leukemia patients having mutations on IDH1/2. We report the development and validation of a high‐performance liquid chromatography (HPLC) method for the simultaneous quantitation of IDH inhibitors, namely enasidenib (EDB), ivosidenib (IDB) and vorasidenib (VDB), in mouse plasma as per the US Food and Drug Administration regulatory guidelines. The method involves extraction of EDB, IDB and VDB along with internal standard (IS; phenacetin) from mouse plasma (100 μl) using a simple protein precipitation process. The chromatographic analysis was performed on an HPLC system using a gradient mobile phase (comprising 10 mm ammonium acetate and acetonitrile in a flow‐gradient) and an X‐Terra Phenyl column. The UV detection wave length was set at λmax 265 nm. EDB, IDB, VDB and the IS eluted at 7.36, 8.60, 9.50 and 5.12 min, respectively, with a total run time of 10 min. The calibration curve was linear over a concentration range of 0.20–12.5 μg/ml for EDB and 0.50–12.5 μg/ml for IDB and VDB (r2 = ≥0.998 for all of the analytes). Validation results met the acceptance criteria. The validated HPLC method was successfully applied to a pharmacokinetic study in mice. 相似文献
103.
Z.M. Babar Wan Mohd Azizi Solachuddin JA Ichwan Qamar Uddin Ahmed Abul Kalam Azad Imranul Mawa 《Natural product research》2019,33(15):2266-2270
The current study provides a way of extraction for both active NSO and WSE from Nigella sativa seeds using 98% methanol. About 1?kg of ground seeds was macerated by 1:2.5 w/v (g/mL) for 72?hours. After rotary evaporation and 7 days of continuous drying and chilling at 50 and 4?°C, NSO and WSE were obtained at the same instant. Solubility tests of 24 solvents and 11 thin layer chromatographic analyses while 2, 2-diphenyl-1-picrylhydrazyl free radical scavenging assay of NSO (73.66) , WSE (33.32) and NSO?+?WSE (78.22) against ascorbic acid (IC50?=?4.28?mg/mL) was performed. WSE was found to be highly soluble in water and 5% NaOH exhibiting the same Rf value of 0.95 for EtOH:DMSO (9:1) against the honey. WSE has revealed more than twofold higher anti-oxidant activity than others. Formulation of WSE with Tualang honey may provide better targeted hydrophilic drug delivery systems. 相似文献
104.
I. M. Chung Mohd Ali A. Ahmad C. Y. Yu K. H. Ma J. G. Gwag Y. J. Park 《Chemistry of Natural Compounds》2005,41(6):650-653
One new compound 3,7,11,15,19-pentamethyl-9α,10α,11α,17α,18α-pentahydroxy-n-tetracosan-1-oxy-p-hydroxycaffeoate (oryzaterpenyl
caffeoate) (1), together with three known fatty acids linoleic acid, stearic acid and myristic acid were isolated and identified from the
rice grain of Oryza sativa. The structure of the new compound was elucidated by 1D and 2D NMR spectroscopic techniques (1H-1HCOSY, 1H-13C HETCOR) aided by EI-MS, and IR spectra.
__________
Published in Khimiya Prirodnykh Soedinenii, No. 6, pp. 535–537, November–December, 2005. 相似文献
105.
106.
Revathy Deivasigamani Nur Shahira Abdul Nasir Mohd Ambri Mohamed Muhamad Ramdzan Buyong 《Electrophoresis》2022,43(4):609-620
This article describes a dielectrophoresis (DEP)-based simulation and experimental study of human epidermal keratinocyte (HEK) cells for wounded skin cell migration toward rapid epithelialization. MyDEP is a standalone software designed specifically to study dielectric particles and cell response to an alternating current (AC) electric field. This method demonstrated that negative dielectrophoresis (NDEP) occurs in HEK cells at a wide frequency range in highly conductive medium. The finite element method was used to characterize particle trajectory based on DEP and drag force. The performance of the system was assessed using HEK cells in a highly conductive EpiLife suspending medium. The DEP experiment was performed by applying sinusoidal wave AC potential at the peak-to-peak voltage of 10 V in a tapered aluminum microelectrode array from 100 kHz to 1 MHz. We experimentally observed the occurrence of NDEP, which attracted HEK cells toward the local electric field minima in the region of interest. The DIPP-MotionV software was used to track cell migration in the prerecorded video via an automatic marker and estimate the average speed and acceleration of the cells. The results showed that HEK cell migration was accomplished approximately at 6.43 μm/s at 100 kHz with 10 V, and FDEP caused the cells to migrate and align at the target position, which resulted in faster wound closures because of the application of an electric field frequency to HEK cells in random locations. 相似文献
107.
Md. Khalid Anwer Essam A. Ali Muzaffar Iqbal Mohammed Muqtader Ahmed Mohammed F. Aldawsari Ahmed Al Saqr Mohd Nazam Ansari M. Ali Aboudzadeh 《Molecules (Basel, Switzerland)》2022,27(1)
Baricitinib (BTB) is an orally administered Janus kinase inhibitor, therapeutically used for the treatment of rheumatoid arthritis. Recently it has also been approved for the treatment of COVID-19 infection. In this study, four different BTB-loaded lipids (stearin)-polymer (Poly(d,l-lactide-co-glycolide)) hybrid nanoparticles (B-PLN1 to B-PLN4) were prepared by the single-step nanoprecipitation method. Next, they were characterised in terms of physicochemical properties such as particle size, zeta potential (ζP), polydispersity index (PDI), entrapment efficiency (EE) and drug loading (DL). Based on preliminary evaluation, the B-PLN4 was regarded as the optimised formulation with particle size (272 ± 7.6 nm), PDI (0.225), ζP (−36.5 ± 3.1 mV), %EE (71.6 ± 1.5%) and %DL (2.87 ± 0.42%). This formulation (B-PLN4) was further assessed concerning morphology, in vitro release, and in vivo pharmacokinetic studies in rats. The in vitro release profile exhibited a sustained release pattern well-fitted by the Korsmeyer–Peppas kinetic model (R2 = 0.879). The in vivo pharmacokinetic data showed an enhancement (2.92 times more) in bioavailability in comparison to the normal suspension of pure BTB. These data concluded that the formulated lipid-polymer hybrid nanoparticles could be a promising drug delivery option to enhance the bioavailability of BTB. Overall, this study provides a scientific basis for future studies on the entrapment efficiency of lipid-polymer hybrid systems as promising carriers for overcoming pharmacokinetic limitations. 相似文献
108.
Lubna Atta Ruqaiya Khalil Khalid Mohammed Khan Moatter Zehra Faiza Saleem Mohammad Nur-e-Alam Zaheer Ul-Haq 《Molecules (Basel, Switzerland)》2022,27(4)
Dental caries, a global oral health concern, is a biofilm-mediated disease. Streptococcus mutans, the most prevalent oral microbiota, produces extracellular enzymes, including glycosyltransferases responsible for sucrose polymerization. In bacterial communities, the biofilm matrix confers resistance to host immune responses and antibiotics. Thus, in cases of chronic dental caries, inhibiting bacterial biofilm assembly should prevent demineralization of tooth enamel, thereby preventing tooth decay. A high throughput screening was performed in the present study to identify small molecule inhibitors of S. mutans glycosyltransferases. Multiple pharmacophore models were developed, validated with multiple datasets, and used for virtual screening against large chemical databases. Over 3000 drug-like hits were obtained that were analyzed to explore their binding mode. Finally, six compounds that showed good binding affinities were further analyzed for ADME (absorption, distribution, metabolism, and excretion) properties. The obtained in silico hits were evaluated for in vitro biofilm formation. The compounds displayed excellent antibiofilm activities with minimum inhibitory concentration (MIC) values of 15.26–250 µg/mL. 相似文献
109.
Amir Mahgoub Awadelkareem Eyad Al-Shammari Abd Elmoneim O. Elkhalifa Mohd Adnan Arif Jamal Siddiqui Mejdi Snoussi Mohammad Idreesh Khan Z R Azaz Ahmad Azad Mitesh Patel Syed Amir Ashraf 《Molecules (Basel, Switzerland)》2022,27(4)
Eruca sativa Mill. (E. sativa) leaves recently grabbed the attention of scientific communities around the world due to its potent bioactivity. Therefore, the present study investigates the metabolite profiling of the ethanolic crude extract of E. sativa leaves using high resolution-liquid chromatography-mass spectrometry (HR-LC/MS), including antibacterial, antioxidant and anticancer potential against human colorectal carcinoma cell lines. In addition, computer-aided analysis was performed for determining the pharmacokinetic properties and toxicity prediction of the identified compounds. Our results show that E. sativa contains several bioactive compounds, such as vitamins, fatty acids, alkaloids, flavonoids, terpenoids and phenols. Furthermore, the antibacterial assay of E. sativa extract showed inhibitory effects of the tested pathogenic bacterial strains. Moreover, the antioxidant activity of 2,2-diphenyl-1-picrylhydrazyl (DPPH) and hydrogen peroxide (H2O2) were found to be IC50 = 66.16 μg/mL and 76.05 μg/mL, respectively. E. sativa also showed promising anticancer activity against both the colorectal cancer cells HCT-116 (IC50 = 64.91 μg/mL) and Caco-2 (IC50 = 83.98 μg/mL) in a dose/time dependent manner. The phytoconstituents identified showed promising pharmacokinetics properties, representing a valuable source for drug or nutraceutical development. These investigations will lead to the further exploration as well as development of E. sativa-based nutraceutical products. 相似文献
110.
Mandeep Kumar Arora Anish Ratra Syed Mohammed Basheeruddin Asdaq Ali A. Alshamrani Abdulkhaliq J. Alsalman Mehnaz Kamal Ritu Tomar Jagannath Sahoo Jangra Ashok Mohd Imran 《Molecules (Basel, Switzerland)》2022,27(6)
Plumbagin, a hydroxy-1,4-naphthoquinone, confers neuroprotection via antioxidant and anti-inflammatory properties. The present study aimed to assess the effect of plumbagin on behavioral and memory deficits induced by intrahippocampal administration of Quinolinic acid (QA) in male Wistar rats and reveal the associated mechanisms. QA (300 nM/4 μL in Normal saline) was administered i.c.v. in the hippocampus. QA administration caused depression-like behavior (forced swim test and tail suspension tests), anxiety-like behavior (open field test and elevated plus maze), and elevated anhedonia behavior (sucrose preference test). Furthermore, oxidative–nitrosative stress (increased nitrite content and lipid peroxidation with reduction of GSH), inflammation (increased IL-1β), cholinergic dysfunction, and mitochondrial complex (I, II, and IV) dysfunction were observed in the hippocampus region of QA-treated rats as compared to normal controls. Plumbagin (10 and 20 mg/kg; p.o.) treatment for 21 days significantly ameliorated behavioral and memory deficits in QA-administered rats. Moreover, plumbagin treatment restored the GSH level and reduced the MDA and nitrite level in the hippocampus. Furthermore, QA-induced cholinergic dysfunction and mitochondrial impairment were found to be ameliorated by plumbagin treatment. In conclusion, our results suggested that plumbagin offers a neuroprotective potential that could serve as a promising pharmacological approach to mitigate neurobehavioral changes associated with neurodegeneration. 相似文献