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   505篇
  免费   18篇
  2023年   6篇
  2022年   5篇
  2021年   18篇
  2020年   9篇
  2019年   15篇
  2018年   16篇
  2017年   15篇
  2016年   16篇
  2015年   31篇
  2014年   27篇
  2013年   44篇
  2012年   47篇
  2011年   43篇
  2010年   24篇
  2009年   30篇
  2008年   32篇
  2007年   33篇
  2006年   31篇
  2005年   19篇
  2004年   13篇
  2003年   7篇
  2002年   12篇
  2001年   2篇
  2000年   2篇
  1999年   3篇
  1998年   1篇
  1997年   1篇
  1996年   2篇
  1995年   3篇
  1994年   2篇
  1993年   7篇
  1992年   1篇
  1991年   1篇
  1988年   1篇
  1987年   1篇
  1986年   1篇
  1982年   1篇
  1979年   1篇
排序方式: 共有523条查询结果,搜索用时 578 毫秒
91.
Bioprospecting of marine natural products has recently produced a substantial number of drug candidates. Ulva fasciata Delile, belonging to the family Ulvaceae, is a green marine macro alga that grows profusely on the coastal seashore of South India. In the present study, we investigated the in vitro cytotoxic potential of a methanolic extract of U.fasciata Delile (MEUF) using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay against human colon carcinoma (HT-29), human hepatocyte carcinoma (Hep-G2), and human breast carcinoma (MCF-7) cell lines. Response surface methodology (RSM) was applied using central-composite experimental design (CCD) to obtain optimum combined effect of concentration and cancer cells with highest cytotoxicity. The effect of concentration, cancer cell lines as independent variables on absorbance (OD), percent cell survival and percent cell inhibition as dependent variables was investigated. Maximum cytotoxic activity of MEUF was established for Hep-G2 with lowest OD or percent cell survival; highest percent cell inhibition with significant difference (p > 0.05) was compared to HT-29 and MCF-7.  相似文献   
92.
93.
In agro-ecosystem, plant pathogens hamper food quality, crop yield, and global food security. Manipulation of naturally occurring defense mechanisms in host plants is an effective and sustainable approach for plant disease management. Various natural compounds, ranging from cell wall components to metabolic enzymes have been reported to protect plants from infection by pathogens and hence provide specific resistance to hosts against pathogens, termed as induced resistance. It involves various biochemical components, that play an important role in molecular and cellular signaling events occurring either before (elicitation) or after pathogen infection. The induction of reactive oxygen species, activation of defensive machinery of plants comprising of enzymatic and non-enzymatic antioxidative components, secondary metabolites, pathogenesis-related protein expression (e.g. chitinases and glucanases), phytoalexin production, modification in cell wall composition, melatonin production, carotenoids accumulation, and altered activity of polyamines are major induced changes in host plants during pathogen infection. Hence, the altered concentration of biochemical components in host plants restricts disease development. Such biochemical or metabolic markers can be harnessed for the development of “pathogen-proof” plants. Effective utilization of the key metabolites-based metabolic markers can pave the path for candidate gene identification. This present review discusses the valuable information for understanding the biochemical response mechanism of plants to cope with pathogens and genomics-metabolomics-based sustainable development of pathogen proof cultivars along with knowledge gaps and future perspectives to enhance sustainable agricultural production.  相似文献   
94.
This study was conducted to characterize canine bone marrow-derived mesenchymal stem cells (BMSCs); in vivo tracking in mice, and therapeutic evaluation in canine clinical paraplegia cases. Canine BMSCs were isolated, cultured, and characterized in vitro as per International Society for Cellular Therapy criteria, and successfully differentiated to chondrogenic, osteogenic, and adipogenic lineages. To demonstrate the homing property, the pGL4.51 vector that contained luciferase reporter gene was used to transfect BMSCs. Successfully transfected cells were injected around the skin wound in mice and in vivo imaging was done at 6, 12 and 24 hr post MSCs delivery. In vivo imaging revealed that transfected BMSCs migrated and concentrated predominantly toward the center of the wound. BMSCs were further evaluated for allogenic therapeutic potential in 44 clinical cases of spinal cord injuries (SCI) and compared with conventional therapy (control). Therapeutic potential as evaluated by different body reflexes and recovery score depicted significantly better results in stem cell-treated group compared to control group. In conclusion, allogenic canine BMSCs can serve as potent therapeutic candidate in cell-based therapies, especially for diseases like SCI, where the conventional medication is not so promising.  相似文献   
95.
The present investigation was undertaken to fabricate modified transport fluconazole transdermal spray using ethyl cellulose and Eudragit® RS100 as film-forming polymers. Eudragit® RS100 (X 1) and ethyl cellulose (X 2) were selected as independent variables in 32 full factorial design, whereas drug transport in first hour (Y 1) and the time required for 50% drug transport (Y 2) were selected as dependent variables. Eutectic blend of camphor and menthol was used as permeation enhancer cum solvent for film-forming polymers. The pH, viscosity, volume of solution delivered upon each actuation, spray angle, ex–in vivo physical evaluation and in vitro drug transport of the formulated products were evaluated. The optimized batch B16 containing 5.25% w/w ethyl cellulose and 10.6% w/w Eudragit® RS100 was formulated by overlapping the contour plots of Y 1 and Y 2. The pH, viscosity, volume of solution sprayed upon each actuation and spray angle of the batch B16 was 6.3, 52.9 cPs, 0.24 ml and 82.6° respectively. The film of optimized batch was flexible and dermal-adhesive. The responses Y 1 and Y 2 of batch B16 were 7.91 μg/ml and 347 min respectively. The kinetics of drug transport was best explained by the Korsmeyer and Peppas model. The eutectic mixture consisting of equal parts of camphor and menthol showed improved drug permeation through shed snake skin. Short-term stability study demonstrated insignificant changes in performance characteristics.  相似文献   
96.
97.
Plant Molecular Biology Reporter - Doubled haploids offer a rapid method of producing homozygous lines for accelerated breeding of varieties and hybrids necessary to address the food demands of the...  相似文献   
98.
The transition metal elements like copper act as double-edged sword for living cells. Cu, a redox active metal, is essential for various biological processes, but at higher concentrations it leads to toxicity by inducing production of reactive oxygen species (ROS). Thus, the objective of the present study was to investigate the effects of exogenously applied castasterone on oxidative stress markers and redox homeostasis managers in Brassica juncea plants subject to copper stress for 30 days. Copper-exposed plants showed accumulation of free radicals (H2O2 and superoxide anion) and lipid peroxidation. However, the exogenous treatment of seeds via the seed soaking method with different concentrations of castasterone reduced H2O2 production, superoxide anion radical content, and lipid peroxidation, thus indicating improved detoxification of ROS. Enzyme activity was increased by 19.19% for guaiacol peroxidase, 16.20% for superoxide dismutase, 35.74% for glutathione peroxidase, 27.58% for dehydroascorbate reductase, and 42.75% for ascorbate peroxidase, with castasterone pre-soaking under copper stress. The levels of non-enzymatic antioxidants were also increased with castasterone pre-treatment under copper stress. It may be concluded that castasterone treatment enhanced redox homeostasis managers in addition to increased levels of osmoprotectants.  相似文献   
99.
Species endangerment, as determined by the national and international authorities, are crucial in conservation decisions at local and regional scales. While species are the priority unit of conservation, the subspecies of widespread species are often neglected in conservation planning and research, irrespective of their unique genetic identity. Peripheral populations of widespread species are often isolated and endangered while their status on the IUCN Red List is considered as ‘Least Concern’. We advocate for the evaluation of widespread polytypic species, and to recognize the importance of assessing intraspecific populations that are distinct from the distribution of widespread species.  相似文献   
100.
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