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   210篇
  免费   10篇
  2023年   3篇
  2022年   6篇
  2021年   37篇
  2020年   11篇
  2019年   16篇
  2018年   19篇
  2017年   7篇
  2016年   11篇
  2015年   20篇
  2014年   15篇
  2013年   15篇
  2012年   20篇
  2011年   7篇
  2010年   4篇
  2009年   3篇
  2008年   2篇
  2007年   3篇
  2006年   1篇
  2005年   2篇
  2004年   2篇
  2003年   1篇
  2002年   2篇
  2001年   1篇
  1999年   4篇
  1998年   1篇
  1997年   1篇
  1996年   1篇
  1995年   1篇
  1994年   2篇
  1982年   1篇
  1971年   1篇
排序方式: 共有220条查询结果,搜索用时 15 毫秒
121.

Heavy metal (HM) contamination of the environment is a serious threat to sustainable crop production. Among the HMs, chromium (Cr) is one of the most toxic HMs that is known to negatively affect growth and metabolic activities of diverse crop plants. The present study was designed to investigate the ameliorative role of 5-aminolevulinic acid (ALA) under Cr stress in two maize (Zea mays L.) cultivars showing differential sensitivity to Cr tolerance. ALA is a biosynthesis precursor and it has a dominant regulatory effect related to physiological, respiratory, and photosynthesis processes in various plant species. Three concentrations of Cr (0, 5, and 10 mg kg−1) were tested under the graded levels of ALA application (0, 12.5, and 25 mg L−1). The results indicated that Cr stress differentially reduced plant growth attributes, gas exchange characteristics, photosynthetic pigments, and biomass in both the cultivars. Oxidative stress increased as evidenced in the form of electrolyte leakage, malondialdehyde, and hydrogen peroxide (H2O2) accumulation in plants. The anti-oxidative enzyme activities, that is, catalase (CAT), superoxide dismutase (SOD), and peroxidase (POD) both in the leaves and roots of maize cultivars decreased due to Cr stress. The concentration of Cr increased in roots and shoots of maize under Cr levels without ALA. Under Cr stress, ALA exogenous application markedly enhanced plant growth, photosynthetic pigments, gas exchange capacity, and biomass. Furthermore, ALA application decreased the Cr-induced oxidative stress in maize cultivars by improving the activities of CAT, POD, and SOD in plants. After ALA application, the Cr concentrations and total Cr uptake by plants differently decreased in both cultivars. The 6103 cultivar of maize was found to be a tolerant cultivar against Cr stress due to its strong defensive system with a higher rate of antioxidant enzyme activities. On the other hand, the other maize cultivar (9108) was found to be a sensitive cultivar against Cr stress due to its weak defense system with higher contents of reactive oxygen species. These findings suggest that ALA can play a regulatory role in maintaining optimum plant growth and efficient photosynthetic processes under Cr-challenged habitats in maize. Thus, ALA application may be used as a sustainable remedial strategy to alleviate Cr-induced stress in maize cultivars.

  相似文献   
122.
Intracerebral hemorrhage (ICH) is a severe form of brain injury, which is a major cause of mortality in humans. Hydrocephalus and cerebral hematoma lead to severe neurological deficits. A single autologous blood (ALB) injection in rats' brains induces hemorrhage and other conditions that regularly interfere with the standard treatment of several cellular and molecular pathways. Several studies have found that IGF-1/GLP-1 decreases the production of inflammatory markers in peripheral tissues, while some have found that they also have pro-inflammatory functions. Since these receptors are down-regulated in hemorrhagic situations, we looked into the potential neuroprotective effect of 4-hydroxyisoleucine (4-HI); 50 mg/kg and 100 mg/kg, an active compound Trigonellafoenum-graecum, on post-hemorrhagic deficits in rats. Long-term oral administration of 4-HI for 35 days has improved behavioral and neurochemical deficits and severe pathological changes and improved cellular and molecular markers, apoptotic markers in the ALB-induced ICH experimental model.Furthermore, the findings revealed that 4-HI also improved the levels of other neurotransmitters (Ach, DOPA, GABA, glutamate); inflammatory cytokines (TNF-alpha, IL-1β, IL-17), and oxidative stress markers (MDA, nitrite, LDH, AchE, SOD, CAT, GPx, GSH) in the brain when evaluated after Day 35. There is no proven treatment available for the prevention of post-brain hemorrhage and neurochemical malfunction; available therapy is only for symptomatic relief of the patient. Thus, 4-HI could be a potential clinical approach for treating post-brain haemorrhage and neurochemical changes caused by neurological damage. Furthermore, 4-HI may be linked to other standard therapeutic therapies utilized in ICH as a potential pharmacological intervention.  相似文献   
123.
Epidemiological evidence indicates infants immunised against diphtheria, pertussis and tetanus (DPT) are at decreased risk of sudden infant death syndrome (SIDS). Asymptomatic whooping cough and pyrogenic toxins of Staphylococcus aureus have been implicated in the aetiology of SIDS. The objectives of the present study were: (1) to determine if the DPT vaccine induced antibodies cross-reactive with the staphylococcal toxins; (2) to determine if antibodies to the pertussis toxin (PT) and the staphylococcal toxins were present in the sera of women during late pregnancy; (3) to examine the effects of infant immunisation on levels of antibodies to PT and the staphylococcal toxins; (4) to assess the effects of changes in immunisation schedules in the UK on the incidence and age distribution of SIDS. Enzyme-linked immunosorbent assays (ELISA) were used to measure binding of rabbit or human IgG to the DPT vaccine, PT, toxic shock syndrome toxin-1 (TSST-1) and staphylococcal enterotoxins A (SEA), B (SEB) and C (SEC). Neutralisation activity of anti-DPT serum was assessed by a bioassay for induction of nitric oxide from human monocytes by the staphylococcal toxins. Anti-DPT serum bound to the DPT vaccine, PT and each of the staphylococcal toxins. It also reduced the ability of the four toxins to induce nitric oxide from monocytes. In pregnant women, levels of IgG to PT, SEC and TSST-1 decreased significantly in relation to increasing weeks of gestation while antibodies to SEA and SEB increased. In infants' sera there were significant correlations between levels of IgG bound to DPT and IgG bound to PT, TSST-1 and SEC but not SEA or SEB. Antibody levels to the toxins in infants declined with age; sera from infants < or = 2 months of age had higher levels of IgG bound to the toxins than those older than 2 months. This pattern was observed for infants whose immunisation schedules began at 2 months of age or 3 months of age. The decrease in IgG bound to the toxins was, however, less for those immunised at 2 months. The decrease in SIDS deaths after the change in immunisation schedules was greatest in the 4-6-month age range. While DPT immunisation might prevent some unexplained infant deaths due to asymptomatic whooping cough, these data indicate that immunisation with DPT also induces antibodies cross-reactive with pyrogenic staphylococcal toxins implicated in many cases of SIDS. Passive immunisation of infants who have low levels of these antibodies might reduce further the numbers of these infant deaths.  相似文献   
124.
The technology available for cancer diagnosis and prognosis is not yet satisfactory at the molecular level, and requires further improvements. Micro RNAs (miRNAs) have been recently reported as useful biomarkers in diseases including cancer. We performed a miRNA expression profiling study using peripheral blood from breast cancer patients to detect and identify characteristic patterns. A total of 100 breast cancer patients and 89 healthy patients were recruited for miRNA genotyping and expression profiling. We found that hs-miR-196a2 in premenopausal patients, and hs-miR-499, hs-miR-146a and hs-miR-196a2 in postmenopausal patients, may discriminate breast cancer patients from healthy individuals. In addition, we found a significant association between two microRNA polymorphisms (hs-miR-196a2 and hs-miR-499) and breast cancer risk. However, no significant association between the hs-miR-146a gene and breast cancer risk was found. In summary, the study demonstrates that peripheral blood miRNAs and their expression and genotypic profiles can be developed as biomarkers for early diagnosis and prognosis of breast cancer.  相似文献   
125.
Apolipoprotein E (apoE) genotypes were determined in 165 Saudis. The prevalence of genotype, E3/E3, E3/E4 and E4/E4 was found to be 71, 27 and 2% respectively. The E3/E3 was the most prevalent genotype among the Saudis followed by E3/E4. However, other genotypes E2/E2, E2/E3 and E2/E4 were absent showing the absence of E2 allele in the test population. The high frequencies of the E3 allele (0.845) and E3/E3 genotype (0.71) and absence of E2 allele in Saudis under study are similar to those reported earlier for Native Americans, Mexican-Americans, Mayans, Cayapa, Mazatecan Indians and Mexican Mestizos populations.  相似文献   
126.
Tomato (Lycopersicon esculentum) is one of the widely grown vegetables worldwide. Fusarium oxysporum f. sp. lycopersici (FOL) is the significant contributory pathogen of tomato vascular wilt. The initial symptoms of the disease appear in the lower leaves gradually, trail by wilting of the plants. It has been reported that FOL penetrates the tomato plant, colonizing and leaving the vascular tissue dark brown, and this discoloration extends to the apex, leading to the plants wilting, collapsing and dying. Therefore, it has been widely accepted that wilting caused by this fungus is the result of a combination of various physiological activities, including the accumulation of fungal mycelia in and around xylem, mycotoxin production, inactivation of host defense, and the production of tyloses; however, wilting symptoms are variable. Therefore, the selection of molecular markers may be a more effective means of screening tomato races. Several studies on the detection of FOL have been carried out and have suggested the potency of the technique for diagnosing FOL. This review focuses on biology and variability of FOL, understanding and presenting a holistic picture of the vascular wilt disease of tomato in relation to disease model, biology, virulence. We conclude that genomic and proteomic approachesare greater tools for identification of informative candidates involved in pathogenicity, which can be considered as one of the approaches in managing the disease.  相似文献   
127.
Microbial associations with corals are common and are most likely symbiotic, although their diversity and relationships with environmental factors and host species remain unclear. In this study, we adopted a 16S rRNA gene tag-pyrosequencing technique to investigate the bacterial communities associated with three stony Scleractinea and two soft Octocorallia corals from three locations in the Red Sea. Our results revealed highly diverse bacterial communities in the Red Sea corals, with more than 600 ribotypes detected and up to 1,000 species estimated from a single coral species. Altogether, 21 bacterial phyla were recovered from the corals, of which Gammaproteobacteria was the most dominant group, and Chloroflexi, Chlamydiae, and the candidate phylum WS3 were reported in corals for the first time. The associated bacterial communities varied greatly with location, where environmental conditions differed significantly. Corals from disturbed areas appeared to share more similar bacterial communities, but larger variations in community structures were observed between different coral species from pristine waters. Ordination methods identified salinity and depth as the most influential parameters affecting the abundance of Vibrio, Pseudoalteromonas, Serratia, Stenotrophomonas, Pseudomonas, and Achromobacter in the corals. On the other hand, bacteria such as Chloracidobacterium and Endozoicomonas were more sensitive to the coral species, suggesting that the host species type may be influential in the associated bacterial community, as well. The combined influences of the coral host and environmental factors on the associated microbial communities are discussed. This study represents the first comparative study using tag-pyrosequencing technology to investigate the bacterial communities in Red Sea corals.  相似文献   
128.
This study aimed to determine if sleep quality and psychological factors were associated with time to meet the discharge criteria to return to sport (RTS) following anterior cruciate ligament reconstruction (ACL-R) among athletes. A cohort-study design included 89 athletes following ACL-R. Each participant completed a battery of questionnaires at 6 different time points: within 3 days of injury occurrence and at post-surgery (1.5 m, 3 m, 4.5 m, 6 m and when discharge criteria were met). Assessment included sleep quality and quantity, symptoms of depression, anxiety, stress, psychological readiness to RTS and fear of re-injury. The primary outcome was the time needed to meet all discharge criteria to RTS. Sleep parameters and psychological factors were not associated with time to meet the discharge criteria to RTS. However, athletes that had lower scores of anxiety (OR 1.2 (95% CI 1.0, 1.3) and insomnia (OR 1.2 (95% CI 1.0, 1.3) at baseline were more likely to meet the RTS discharge criteria. Athletes with better sleep quality at 3m, 4.5m and 6m were more likely to meet the RTS discharge criteria OR 1.3 (95% CI 1.1, 1.7), 2.0 (95% CI 1.1–3.4) and 1.4 (95% CI 1.0, 1.9) respectively. Sleep quality and psychological factors were not associated with time to meet the discharge criteria to RTS but impacted whether athletes adhered and completed their rehabilitation program or not. Monitoring sleep quality and psychological factors of athletes before and following ACL-R surgery is important to identify athletes who could have difficulties in adhering to and completing their rehabilitation program to RTS.  相似文献   
129.
In soccer (football), dominant limb kicking produces higher ball velocity and is used with greater frequency than the non-dominant limb. It is unclear whether limb dominance has an effect on injury incidence. The purpose of this systematic review with meta-analysis is to examine the relationship between limb dominance and soccer injuries. Studies were identified from four online databases according to PRISMA guidelines to identify studies of soccer players that reported lower extremity injuries by limb dominance. Relevant studies were assessed for inclusion and retained. Data from retained studies underwent meta-analyses to determine relative risk of dominant versus non-dominant limb injuries using random-effects models. Seventy-four studies were included, with 36 of them eligible for meta-analysis. For prospective lower extremity injury studies, soccer players demonstrated a 1.6 times greater risk of injury to the dominant limb (95% CI [1.3–1.8]). Grouped by injury location, hamstring (RR 1.3 [95% CI 1.1–1.4]) and hip/groin (RR 1.9 [95% CI 1.3–2.7]) injuries were more likely to occur to the dominant limb. Greater risk of injury was present in the dominant limb across playing levels (amateurs RR 2.6 [95% CI 2.1–3.2]; youths RR 1.5 [95% CI 1.26–1.67]; professionals RR 1.3 [95% CI 1.14–1.46]). Both males (RR 1.5 [95% CI 1.33–1.68)] and females (RR 1.5 [95% CI 1.14–1.89]) were more likely to sustain injuries to the dominant limb. Future studies investigating soccer injury should adjust for this confounding factor by using consistent methods for assigning limb dominance and tracking use of the dominant versus non-dominant limb.  相似文献   
130.

Background

The study was carried out to determine the cytotoxic, antioxidant and gastro-protective effect of ethyl-4-[(3,5-di-tert-butyl-2-hydroxybenzylid ene)amino] benzoate (ETHAB) in rats.

Methodology/Principal Findings

The cytotoxic effect of ETHAB was assessed using a MTT cleavage assay on a WRL68 cell line, while its antioxidant activity was evaluated in vitro. In the anti-ulcer study, rats were divided into six groups. Group 1 and group 2 received 10% Tween 20 (vehicle). Group 3 received 20 mg/kg Omeprazole. Groups 4, 5 and 6 received ETHAB at doses of 5, 10, and 20 mg/kg, respectively. After an hour, group 1 received the vehicle. Groups 2–6 received absolute ethanol to induce gastric mucosal lesions. In the WRL68 cell line, an IC50 of more than 100 µg/mL was observed. ETHAB results showed antioxidant activity in the DPPH, FRAP, nitric oxide and metal chelating assays. There was no acute toxicity even at the highest dosage (1000 mg/kg). Microscopy showed that rats pretreated with ETHAB revealed protection of gastric mucosa as ascertained by significant increases in superoxide dismutase (SOD), pH level, mucus secretion, reduced gastric lesions, malondialdehyde (MDA) level and remarkable flattened gastric mucosa. Histologically, pretreatment with ETHAB resulted in comparatively better gastric protection, due to reduction of submucosal edema with leucocyte infiltration. PAS staining showed increased intensity in uptake of Alcian blue. In terms of immunohistochemistry, ETHAB showed down-expression of Bax proteins and over-expression of Hsp70 proteins.

Conclusion/Significance

The gastroprotective effect of ETHAB may be attributed to antioxidant activity, increased gastric wall mucus, pH level of gastric contents, SOD activity, decrease in MDA level, ulcer area, flattening of gastric mucosa, reduction of edema and leucocyte infiltration of the submucosal layer, increased PAS staining, up-regulation of Hsp70 protein and suppressed expression of Bax. Key words: ethyl 4-(3, 5-di-ter-butyl-2-hydroxybenzylamino) benzoate; toxicity; antioxidant; gastric-ulcer; anti-ulcer; histology; immunohistochemistry.  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