首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   478篇
  免费   21篇
  国内免费   13篇
化学   459篇
晶体学   1篇
力学   3篇
综合类   13篇
数学   1篇
物理学   35篇
  2023年   10篇
  2022年   22篇
  2021年   69篇
  2020年   36篇
  2019年   23篇
  2018年   23篇
  2017年   13篇
  2016年   18篇
  2015年   20篇
  2014年   18篇
  2013年   17篇
  2012年   23篇
  2011年   21篇
  2010年   15篇
  2009年   19篇
  2008年   20篇
  2007年   26篇
  2006年   11篇
  2005年   13篇
  2004年   21篇
  2003年   16篇
  2002年   4篇
  2001年   9篇
  2000年   5篇
  1999年   2篇
  1998年   3篇
  1997年   4篇
  1996年   2篇
  1995年   2篇
  1994年   5篇
  1993年   1篇
  1992年   2篇
  1991年   3篇
  1990年   4篇
  1988年   2篇
  1987年   1篇
  1986年   2篇
  1985年   3篇
  1981年   2篇
  1979年   2篇
排序方式: 共有512条查询结果,搜索用时 15 毫秒
121.
Abstract

The aim of the study was to evaluate the effect of leaf extracts of four plants against some isolated fungal species from deteriorated books. Aqueous, methanol and chloroform extracts of selected plant species were screened in vitro for their antifungal activity against some book deteriorating fungal species. Fifteen species belonging to 09 genera were isolated and identified from infested books in library. Aqueous and solvent extracts of leaves of Azadiracta indica, Callistemon citrinus, Eucalyptus lanceolatus and Pongamia pinnata were tested against some dominant fungal species viz. Chaetomium spiralis, Alternaria alternata, Aspergillus flavus, Aspergillus niger, Aspergillus fumigatus and Rhizopus stolonifer. Solvent extracts exhibited potent inhibitory activity than aqueous extracts. However, these plant extracts exhibited moderate activity against A. flavus, C. spiralis, R. stolonifer and A. alternata.  相似文献   
122.
A facile and eco‐friendly biosynthetic route for preparing Pd truncated octahedrons (PdTOs) using firmiana simplex leaf extract was reported without any chemical reducing agents. The information of reducing components, reduction process and time were obtained by ATR‐FTIR imaging, FTIR and UV–Vis spectroscopy, respectively. TEM image revealed that more than 75% of PdNPs were composed of PdTOs with an average diameter of 9.2 nm. HR‐TEM analysis demonstrated that a single PdTO consisted of the mix of {100} and {111} crystal planes. SAED and XRD pattern confirmed the well crystalline nature of fcc structured PdTOs. The model reactions of electro‐oxidation of methanol and reduction of p‐nitrophenol (p‐NP) were adopted to explore the effects of structure and size of PdNPs on the catalytic properties. In the electro‐oxidation of methanol, the forward‐scan peak current density (If) of PdTOs was 10.05 mA cm‐2, 6.3 times and 1.9 times of PdNPs‐0 and PdNPs‐4:1, illustrating its superior electro‐catalytic property to that of spherical PdNPs. In the p‐NP reduction reaction, the apparent rate constant (Ka) over PdTOs was 0.358 min‐1, higher than spherical PdNPs‐0 (0.08 min‐1) with the similar particle size and lower than the same spherical PdNPs‐4:1 (0.562 min‐1) and commercial Pd/C (0.415 min‐1), which all about half the size of PdTOs. It has been demonstrated that electro‐chemical oxidation of methanol was a structure‐sensitive reaction, while the reduction of p‐NP was mainly dependent on the particle size of PdNPs.  相似文献   
123.
The presence of ultrasound-induced cavitation in sonodynamic therapy (SDT) treatments has previously enhanced the activity and delivery of certain sonosensitisers in biological systems. The purpose of this work was to investigate the potential for two novel anti-cancer agents from natural derivatives, sanguinarine and ginger root extract (GRE), as sonosensitisers in an SDT treatment with in vitro PANC-1 cells. Both anti-cancer compounds had a dose-dependent cytotoxicity in the presence of PANC-1 cells. A range of six discreet ultrasound power-frequency configurations were tested and it was found that the cell death caused directly by ultrasound was likely due to the sonomechanical effects of cavitation. Combined treatment used dosages of 100 μM sanguinarine or 1 mM of GRE with 15 s sonication at 500 kHz and 10 W. The sanguinarine-SDT and GRE-SDT treatments showed a 6% and 17% synergistic increase in observed cell death, respectively. Therefore both sanguinarine and GRE were found to be effective sonosensitisers and warrant further development for SDT, with a view to maximising the magnitude of synergistic increase in toxicity.  相似文献   
124.
The effect of a vegetable extract during the synthesis of an acrylovinylic copolymer on its pressure sensitive adhesive properties is examined. It is concluded that the vegetable extract presence induces improvement of the adhesion/cohesion balance. At the same time, introduction of this compound into the copolymer composition leads to a diminution of the macromolecular product conversion. Evidence is obtained by the determination of the peel strength of the copolymer film–support complex on glass supports.  相似文献   
125.
Nano materials find wide applications due to their behavior at nano scale. TiO2 nanoparticles (TiO2 NPs) was synthesized using Neem leaf extract. This is simple, rapid, eco‐friendly, cheaper and green tools for TiO2 NPs synthesis using agricultural waste at lower applied temperature. Characterization of the extracted TiO2 NPs was confirmed by XRD, SEM, EDAX, TEM, HR‐TEM, SAED, and FT‐IR, respectively. The catalytic activity of TiO2 NPs was investigated in synthesis of 1,2‐dihydroquinoline derivatives with excellent yields and low cost. Purification of the synthesized 1,2‐dihydroquinoline derivatives carried out by easy work‐up of non‐chromatographic methods.  相似文献   
126.
Abstract

The focus of this work is to extract a natural dye for colouring camel wool as a substitute for synthetic dyes used in the Sadu House of Kuwait. Their target is to keep the tradition of tent and rug production natural in all its manifestations. Therefore, our task was to find an abundant source that provides a colour preferably red to purple. Hibiscus rosa sinensis (HRS) is an abundantly available plant in Kuwait that was explored for extraction of the red dye to colour camel wool permanently. The powdered petals of red flowers of HRS was extracted with 5% acetic acid which yielded a deep red colour that showed a great potential for woollen fibre dyeing. The use of mordants like alum and some metal salts manifested a wide range of fixed colours which intensified at 85 °C. The colours produced had excellent fastness and was accepted by the Sadu House.  相似文献   
127.
There had been some reports demonstrating the green synthesis of silver nanoparticles using guava (Psidium guajava (L.) extract); however, detailed and in-depth interrogation of the vital synthesis parameters for rapid, facile, efficacious synthesis at room temperature, and robust characterization of the as-prepared nanoparticle is currently lacking. This study presents a comprehensive delineation of the sustainable phyto-fabrication of biogenic guava phenolic extract functionalized silver nanoparticles (GVE-SNP) based on guava phenolic extract as the sole reductant/stabilizer, as well as the synthesis optimization, thorough physicochemical characterization and potential biological applications of the as-prepared nanosilver. The results revealed that successful synthesis of GVE-SNP was instantaneous and maximum intensity of the plasmonic peak at 425 nm was achieved in less than 10 min. GVE-SNP was found to present stable, well-dispersed, round, uniform, and crystalline nanoparticles of about 5.88 nm. The FTIR and RAMAN spectra indicated that GVE-SNP surface was properly capped by bioactives from GVE. The nanoparticles displayed potent radical scavenging activity against ABTS+ and DPPH. Also, GVE-SNP exhibited a significant and dose–response inhibitory effect against tyrosinase. Furthermore, the nanoparticles displayed good cytotoxicity against L929 fibroblast and were found to possess strong antimicrobial properties, inhibiting the growth of S. aureus and S. epidermidis.  相似文献   
128.
The extract from Pelargonium zonale stalks exhibits activity against Candida albicans and exerts an effect on the HeLa cell line. The action against C. albicans cells was analysed using light, CLSM, SEM, and TEM microscopes. The observations indicate that the extract influenced fungal cell morphology and cell metabolic activity. The morphological changes include cell wall damage, deformations of cell surfaces, and abnormalities in fungal cell shape and size. Cells of C. albicans treated with the extract exhibited disturbances in the budding pattern and a tendency to form agglomerates and multicellular chains. The P. zonale extract caused a significant decrease in the metabolic activity of C. albicans cells. Cells died via both apoptosis and necrosis. The antitumor activity of the extract was analysed using the MTT assay. The P. zonale extract exhibited minor cytotoxicity against the HeLa cell line but a dose-dependent cytopathic effect was noticed. The P. zonale extract is a promising source for the isolation of antifungal and anticancer compounds.  相似文献   
129.
Three phytochemicals, curcumin 1, demethoxycurcumin 2 and β-sitosterol-3-O-β-d-glucopyranoside 3 have been isolated from the ethyl acetate extract of rhizomes of Curcuma aromatica. Chemical structures of all the three isolates were determined using spectroscopic and chemical analyses. β-Sitosterol-3-O-β-d-glucopyranoside has been isolated for the first time from this plant.  相似文献   
130.
In this study, Co0.5Ni0.5Nd0.02Fe1.98O4 nanoparticles CoNiNd (NPs) were synthesized by combustion method linked with biosynthesis with and without different plant extracts such as Lavender, Ginger, Flax-Seed, Lemon Juice, Tragacanth Gum, and Dates Fruit. Co0.5Ni0.5Nd0.02Fe1.98O4 nanoparticles (NPs) with plant extracts (CoNiNd plant extracts) were analyzed by XRD, TEM and SEM methods. The structure of Co-Ni spinel ferrite was confirmed by XRD and the shape and the size of nanoparticles were examined via SEM and TEM and the size was found between 17 and 25 nm. The anti-cancer activity of NPs on cancer cells such as human colorectal carcinoma (HCT-116) and human cervical cells (Hela) were investigated. The cytotoxicity of was examined by MTT assay and followed by measuring the inhibitory concentration (IC50) values after 48 h treatments. The cell viability assay confirmed a decrease in the cancer cell viability post NPs treatments and showed dose-dependent inhibitory action. The treatments of CoNiNd (NPs) and CoNiNd plant extracts via Lavender plant extract showed most profound inhibitory action on both cancer cells than extracts other plant extracts. The IC50 values were for HCT-116 cells were found to be in range of 15.75–42.55 µg/mL and 13.44 to 35.65 µg/mL for HeLa cells. In contrast, the treatment of CoNiNd (NPs) and CoNiNd plant extracts showed inhibitory action but the percentage of inhibition was higher in HEK-293 cells. Our results showed that CoNiNd (NPs) and CoNiNd plant extracts possess potential application in the colon and cervical cancer treatments and we recommend molecular analysis of NPs mediated cancer cell death for future applications.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号