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   228篇
  免费   12篇
  2024年   2篇
  2023年   5篇
  2022年   15篇
  2021年   12篇
  2020年   10篇
  2019年   38篇
  2018年   18篇
  2017年   14篇
  2016年   13篇
  2015年   9篇
  2014年   14篇
  2013年   16篇
  2012年   15篇
  2011年   20篇
  2010年   7篇
  2009年   5篇
  2008年   3篇
  2007年   3篇
  2006年   1篇
  2005年   4篇
  2003年   3篇
  2001年   1篇
  1998年   2篇
  1992年   2篇
  1988年   1篇
  1986年   1篇
  1985年   2篇
  1983年   2篇
  1979年   1篇
  1953年   1篇
排序方式: 共有240条查询结果,搜索用时 31 毫秒
41.
Salicylic acid (SA) may reduce the negative impact of water deficit on growth and metabolite yield of Thymus daenensis Celak subsp. daenensis Celak. The effect of foliar application of SA and reduced irrigation on growth, oil yield, chemical components, and antibacterial and antioxidant activities of T. daenensis in field condition were investigated. Treatments comprised 0.0, 1.5 and 3.0 M SA applied to plants under normal irrigation and stressed conditions. Results indicated that irrigation regime had a significant effect on growing degree days (GDD) required to reach early and full flowering. Foliar application of SA influenced GDD from early growing stage to 50 % and full flowering, minimum radius and canopy diameter. The highest values of oil content (3.2 % v/w) and yield (14.9 g m?2) were obtained from application of 3.0 M SA. Percentage of some chemical constituents in the essential oil extracted from the plants under stress was higher than non-stressed plants. Thymol content was significantly reduced under stressed conditions. Foliar application of SA significantly improved carvacrol, α-thujene, α-pinene and p-cymene contents in the oils, but reduced thymol and, β-caryophyllene amounts. Our results showed that foliar application of SA reduced the negative effect of water deficit on thymol content in the essential oil of T. daenensis. The essential oils of T. daenensis exhibited antioxidant and antibacterial activities when plants were sprayed with 1.5 and 3.0 M SA, respectively.  相似文献   
42.
Leishmaniasis is a geographically widespread severe disease which includes visceral leishmaniasis, cutaneous leishmaniasis (CL). There are 350 million people at risk in over 80 countries. In the Old World, CL is usually caused by Leishmania major, Leishmania tropica, and Leishmania aethiopica complex which 90 % of cases occurring in Afghanistan, Algeria, Iran, Iraq, Saudi Arabia, Syria, Brazil, and Peru. Recently, some reports showed that some strains of L. major have internal transcribed space (ITS-1) with differential size exhibiting homology with the related gene in a divergent genus of kinetoplastida, the Crithidia. This prompted us to analyze the mentioned gene in 100 isolates obtained from patients with suspected CL. After obtaining samples from 100 patients, DNA extraction was performed and ITS-1 was analyzed using PCR–RFLP. These samples were sequenced for verifying their homology. Then, RPOIILS gene was analyzed in the samples that their ITS-1 gene exhibiting homology with the related gene in Crithidia. Results showed that 10 % of the isolates have ITS-1 exhibiting different size with the routine ones. Sequencing of them showed their similarity to the one from Crithidia fasciculata. RPOIILS gene encoding RNA polymerase II largest subunit analysis showed genetic diversity. This study might also help in solving the problems concerning Leishmaniasis outbreak currently facing in Iran and some other endemic regions of the world.  相似文献   
43.
44.
Background: COVID-19 is associated with higher mortality rates in patients with cancer. In this study, we aimed to evaluate the clinical outcomes, and laboratory and imaging data of patients with solid tumor infected with COVID-19 infection. Methods: This is a cross-sectional retrospective study performed in 2020-2022 on 85 patients with a previous diagnosis of solid tumors infected with COVID-19. We included all patients with tumors of solid organs that were diagnosed with COVID-19 infection and required hospitalization those patients previously hospitalized for treatments and were infected with COVID-19 during hospitalization. Demographic data of patients were collected using a checklist. We collected data regarding clinical outcome (discharge, hospitalization or death), duration of hospitalization, requiring ICU admission, duration of hospitalization divided by received drugs and type of tumor and mean survival time. Furthermore, we collected laboratory data from all patients. The radiologic characteristics of patients were also extracted from their data. Results: Breast cancer was the most common solid tumor (34.9%), followed by lung cancer (19.3%). The mortality rate was 24.1% (20 patients). The highest mortality rate in this study was for metastatic intestinal cancer to the lung (100%, one patient), followed by metastatic prostatic cancer to lung (50%, three patients). The highest hospitalization duration was for patients with glioblastoma multiform (GBM) (30 days). The mean survival time among patients with mortality was 19.15±1.80 days. The mean CT severity score of all patients was 27.53±22.90. Patient’s most common radiologic sign was air space consolidation (89.1%). The highest CT severity score was found in patients with stomach cancer (46.67±5.77). Conclusion: The mortality rate in this study was 24.1%. Based on the results of our study and previous research, special care should be provided to patients with solid tumors during the COVID-19 pandemic and in infected cases.  相似文献   
45.
Stability of an implant is defined by its ability to undergo physiological loading–unloading cycles without showing excessive tissue damage and micromotions at the interface. Distinction is usually made between the immediate primary stability and the long-term, secondary stability resulting from the biological healing process. The aim of this research is to numerically investigate the effect of initial implantation press-fit, bone yielding, densification and friction at the interface on the primary stability of a simple bone–implant system subjected to loading–unloading cycles. In order to achieve this goal, human trabecular bone was modeled as a continuous, elasto-plastic tissue with damage and densification, which material constants depend on bone volume fraction and fabric. Implantation press-fit related damage in the bone was simulated by expanding the drilled hole to the outer contour of the implant. The bone–implant interface was then modeled with unilateral contact with friction. The implant was modeled as a rigid body and was subjected to increasing off-axis loading cycles. This modeling approach is able to capture the experimentally observed primary stability in terms of initial stiffness, ultimate force and progression of damage. In addition, it is able to quantify the micromotions around the implant relevant for bone healing and osseointegration. In conclusion, the computationally efficient modeling approach used in this study provides a realistic structural response of the bone–implant interface and represents a powerful tool to explore implant design, implantation press-fit and the resulting risk of implant failure under physiological loading.  相似文献   
46.
47.
Sodium benzoate (SB) is a widely used preservative and antimicrobial substance in many foods and soft drinks. However, this compound is generally recognized as safe food additives, but evidence has suggested that a high intake of SB may link to attention deficit‐hyperactivity disorder in children. Present study investigate the effects of oral administration of different concentrations of SB (0.56, 1.125, and 2.25 mg/mL) for 4 weeks, on the learning and memory performance tests, and also the levels of malondialdehyde (MDA), reduced glutathione (GSH), and acetylcholinesterase activity (AChE) in the mouse brain. The results showed that SB significantly impaired memory and motor coordination. Moreover, SB decreased reduced GSH and increased the MDA level in the brain significantly (P < 0.001). However, nonsignificant alteration was observed in the AChE activity. These findings suggest that short‐term consumption of SB can impair memory performance and increased brain oxidative stress in mice.  相似文献   
48.
In this study Saccharomyces cerevisiae yeast cells was used as a novel vehicle for encapsulation of vitamin D3. The effects of initial cholecalciferol concentration (100,000 and 500,000 IU/g yeast), yeast cell pretreatment (plasmolysis with NaCl) and drying method (spray or freeze drying) on microcapsules properties were investigated. It was found that the vitamin concentration and drying method had significant influence on encapsulation efficiency (EE) and size of yeast microcapsules. Furthermore, EE values were more increased by the plasmolysis treatment. The highest EE was obtained for plasmolysed and spray dried yeast cells prepared using initial cholecalciferol concentration of 2.5 mg per gram of yeast cells (76.10?±?6.92%). The values of mean particle size were 3.43–7.91 μm. The presence of cholecalciferol in yeast microcapsules was confirmed by X-ray diffraction (XRD) and Fourier transform-infrared (FT-IR) analyses. The in vitro cholecalciferol release from yeast microcapsules in phosphate buffer saline solution (PBS) followed a controlled release manner consistent with a Fickian diffusion mechanism. In addition, the release studies in simulated gastrointestinal tract showed sustained release of cholecalciferol in the stomach condition and significant release in intestinal medium.  相似文献   
49.
This study was conducted to investigate biodenitrification efficiency with starch‐stabilized nano zero valent iron (S‐nZVI) as the additional electron donor in the presence of S2O3 in aqueous solutions, under anaerobic conditions. The main challenge for nZVI application is their tendency to agglomeration, thereby resulting in loss of reactivity that necessitates the use of stabilizers to improve their stability. In this study, S‐nZVI was synthesized by chemical reduction method with starch as a stabilizer. The synthesized nanoparticles were characterized by TEM, XRD, and FTIR. Transmission electron microscopy (TEM) image shows S‐nZVI has a size in the range of 5–27.5 nanometer. Temperature and S‐nZVI concentration were the important factors affecting nitrate removal. Biodenitrification increased at 35°C and 500 mg/L of S‐nZVI, in these conditions, biodenitrification efficiency increased from 40.45 to 78.84%. Experimental results suggested that biodenitrification increased by decreasing initial nitrate concentration. In the bioreactor biodenitrification rate was 94.07% in the presence of S‐nZVI. This study indicated that, Fe2+ could be used as the only electron donor or as the additional electron donor in the presence of S2O3 to increase denitrification efficiency.  相似文献   
50.
A new ascomycetous black yeast-like species was recovered from healthy plant (Avicennia marina) of Hara protected mangrove forests at Qeshm Island, Iran. Morphological, physiological analysis as well as a molecular analysis of the internal transcribed spacer (ITS) and partial large ribosomal subunit (D1/D2 domains) confirmed the placement of this strain in the genus Aureobasidium and based on considerable sequence divergence, distinguishable cardinal growth temperatures and salt tolerance a new species Aureobasidium mangrovei sp. nov. is proposed. However, the type strain micro-morphologically is not clearly distinguishable from other members of the genus. The type strain, Aureobasidium mangrovei was preserved in a metabolically inactive state at the Iranian Biological Resource Centre, Tehran, Iran as IBRC-M 30265T and the ex-type culture is deposited in the CBS yeast collection of the Westerdijk Fungal Biodiversity Institute, Utrecht, The Netherlands as CBS 142205T. The GenBank accession numbers for the nucleotide sequences of the large subunit ribosomal DNA and ITS region are KY089084 and KY089085, respectively. The MycoBank number of the new species is MB 823444.  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