首页 | 官方网站   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   2020篇
  免费   172篇
  国内免费   51篇
医药卫生   2243篇
  2023年   19篇
  2022年   45篇
  2021年   119篇
  2020年   79篇
  2019年   47篇
  2018年   59篇
  2017年   77篇
  2016年   87篇
  2015年   95篇
  2014年   113篇
  2013年   149篇
  2012年   102篇
  2011年   159篇
  2010年   123篇
  2009年   95篇
  2008年   129篇
  2007年   115篇
  2006年   79篇
  2005年   62篇
  2004年   59篇
  2003年   46篇
  2002年   46篇
  2001年   28篇
  2000年   27篇
  1999年   20篇
  1998年   25篇
  1997年   20篇
  1996年   18篇
  1995年   22篇
  1994年   15篇
  1993年   14篇
  1992年   13篇
  1991年   13篇
  1990年   7篇
  1989年   10篇
  1988年   9篇
  1987年   7篇
  1986年   7篇
  1985年   13篇
  1984年   14篇
  1983年   12篇
  1982年   11篇
  1981年   4篇
  1980年   7篇
  1979年   3篇
  1978年   6篇
  1977年   5篇
  1976年   5篇
  1973年   1篇
  1972年   1篇
排序方式: 共有2243条查询结果,搜索用时 656 毫秒
1.
Oxidative stress and inflammation are two possible mechanisms related to nephrotoxicity caused by environmental pollutants. Ellagic acid, a powerful antioxidant phytochemical, may have great relevance in mitigating pollutant-induced nephrotoxicity and preventing the progression of kidney disease. This review discusses the latest findings on the protective effects of ellagic acid, its metabolic derivatives, the urolithins, against kidney toxicity caused by heavy metals, pesticides, mycotoxins, and organic air pollutants. We describe the chelating, antioxidant, anti-inflammatory, antifibrotic, antiautophagic, and antiapoptotic properties of ellagic acid to attenuate nephrotoxicity. Furthermore, we present the molecular targets and signaling pathways that are regulated by these antioxidants, and suggest some others that should be explored. Nevertheless, the number of reports is still limited to establish the efficacy of ellagic acid against kidney damage induced by environmental pollutants. Therefore, additional preclinical studies on this topic are required, as well as the development of well-designed clinical trials.  相似文献   
2.
In this study, the carbonic anhydrase (CA) enzyme was purified from Black Sea trout (Salmo trutta Labrax Coruhensis) kidney with a specific activity of 603.77 EU/mg and a yield of 35.5% using Sepharose-4B-l-tyrosine- sulphanilamide affinity column chromatography. For determining the enzyme purity and subunit molecular mass, sodiumdodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) was performed and single band was observed. The molecular mass of subunit was found approximately 29.71 kDa. The optimum temperature, activation energy (Ea), activation enthalpy (ΔH) and Q10 values were obtained from Arrhenius plot. Km and Vmax values for p-nitrophenyl acetate of the purified enzyme were calculated from Lineweaver-Burk graphs. In addition, the inhibitory effects of different heavy metal ions (Fe2+, Pb2+, Co2+, Ag+ and Cu2+) on Black Sea trout kidney tissue CA enzyme activities were investigated by using esterase method under in vitro conditions. The heavy metal concentrations inhibiting 50% of enzyme activity (IC50) were obtained. Finally Ki values and inhibition types were calculated from Lineweaver-Burk graphs.  相似文献   
3.
Exposure to trace metals may impact reproductive health outcomes through perturbations in maternal immune signaling molecules. We conducted a cross-sectional study of 390 pregnant women from the LIFECODES birth cohort and investigated the associations between 17 urinary metals and five immune biomarkers measured in the 3rd trimester (median 26 weeks gestation). We used linear regression to estimate pair-wise associations and applied elastic net and Bayesian kernel machine regression to identify important contributing exposures analytes as well as non-linear effects. Maternal urinary manganese, nickel, and barium were positively associated with maternal plasma interleukin-1β (IL-1β). Elastic net and Bayesian kernel machine regression identified manganese as the dominant trace metal in association with IL-1β. An interquartile range difference in manganese (0.6 μg/L) was associated with a 29 % increase in IL-1β (95 % CI: 12.4–48.2). In conclusion, trace metal exposures were associated with biomarkers of immune perturbations, and this warrants further investigation.  相似文献   
4.
BackgroundHeavy metal contamination has become a serious issue in this century especially detected in fish organs. Due to the presence of radioactive compounds in agricultural and sewage effluent, which destroys aquatic ecosystems, threatening human livelihoods. Health hazards associated with low and high consumption consumers assessed in five commercial fish species collected from Hurghada City, Egypt, during winter and summer, 2020. Atomic absorption spectrophotometer technique used for determination heavy meals in different organs and expressed as μg/g wet weight.ResultsHeavy metal concentrations in muscle ranged between:(0.054–0.109), (0.260–1.043), (0.264–0.897), (5.895–11.898), (0.381–0.970), (13.582–29.133) and (0.332–0.589) µg/g for Cd, Pb, Mn, Zn, Cu, Fe and Ni respectively, which were lower than those of gills and liver. These concentrations were within WHO, FAO/WHO, and EU standards. Consumption of edible species was lower than the (TDIs) established by the (JECFA) and Egyptian Standards. Even though THQ and TTHQ values were < 1 while, in children with highly consumer were> 1.ConclusionThis study concluded that intake of Red Sea fish is safe for human health. It is critical for consumers to be aware of the consequences of excessive fish consumption, particularly children with highly consumer, which represent possible health risks.  相似文献   
5.
The use of multifunctional materials for water remediation is a modern approach where adsorption phenomena and heterogeneous photocatalysis can be applied for the removal of pollutants. Since the ideal remediation system should be able to remove both organic and inorganic pollutants, a crucial aspect to consider is the knowledge of operational parameters affecting the removal process, especially when heavy metal ions are present in concoction as in real systems. Given the proven efficiency of multifunctional TiO2/Alg/FeNPs magnetic beads for the removal of model organic pollutants, this study investigated the possibility to exploit such system also for the removal of mixed heavy metals (MHM), specifically Cr(III), Cu(II), and Pb(II) ions, under ultraviolet irradiation at a wavelength of 254 nm. After a preliminary screening on the optimal catalyst loading, operating parameters such as the initial concentration of metal ions, contact and irradiation time, and pH were investigated to optimize the removal of metal ions using response surface methodology (RSM) via Box–Behnken design. Starting from a MHM solution containing 44 ppm of each metal ion, the removal of Pb(II), Cr(III), and Cu(II) ions in the aqueous solution was nearly completed (>98.4%) for all three ions within 72 min of irradiation at almost neutral pH (pH = 6.8). The stability of TiO2/Alg/FeNPs was confirmed by retrieving and reusing the beads in three consecutive cycles of heavy metals removal without observing significant changes in catalyst efficiency.  相似文献   
6.
Immune modulation by heavy metals may cause serious adverse health effects in humans, although the mechanisms involved are not well understood. Both cadmium and lead are important environmental and occupational toxins. Therefore, in the current study, the costimulatory/adjuvant effects and the T-cell-activating potential of these metals (i.e., CdCl2 and PbCl2), are examined. These immune-modulating properties are critical in the development of conditions such as allergy, hypersensitivity, and autoimmunity. Using the direct popliteal lymph node assay (PLNA) and reporter antigen-popliteal lymph node assay (RA-PLNA) both metals were examined individually for immunotoxicity. Mercury (i.e., HgCl2) was included for comparative purposes as its effects in the RA-PLNA are well documented. Seven days following a single footpad injection containing metal and/or RA (trinitrophenyl-ovalbumin [TNP-OVA] or TNP-Ficoll), BALB/c mice were sacrificed and the popliteal lymph nodes (PLNs) removed. PLN cellularity, TNP-specific antibody-secreting cells (ASCs), and lymphocyte subsets were assessed. All three metals strongly stimulated T- and B-cell proliferation and ASC production following coinjection with the RA TNP-OVA. In each case, ASC production was skewed towards the IgG1 isotype. In addition, all three metals induced IgG production to TNP-Ficoll (although relatively weakly in the case of Cd). These results show that each of these metals can provide adjuvant signals to promote lymphocyte proliferation and enhance adaptive immune responses to unrelated antigens. Skewing of immune responses towards T helper type 2 responses suggests that each of these metals can enhance allergic and hypersensitivity reactions to environmental antigens. Furthermore, the induction of IgG responses to TNP-Ficoll, a T-cell-independent antigen, indicates that each of these metals can activate neoantigen-specific T cells. T-cell activation by metals can lead to metal hypersensitivity and has been implicated in the development of autoimmunity. This is the first report of immune modulation by CdCl2 and PbCl2 in the RA-PLNA.  相似文献   
7.
目的探讨血浆置换(简称PE)床边治疗重型肝炎的临床疗效。方法60例病例采用常规内科治疗加PE治疗,比较PE治疗前后临床症状缓解时间及血生化变化。结果临床症状缓解迅速,黄疸减退,白蛋白、胆碱脂酶升高,PT恢复,补体上升,不影响肾功及电解质。结论PE为重型肝炎一种行之有效的治疗方法。  相似文献   
8.
目的通过对检测微量元素的分析,了解近阶段儿童微量元素分布状况,社会人群对补足常规微量元素的认知情况;通过对检测重金属铅和镉的分析,了解儿童受铅和镉的污染状况,干预后的改变情况。方法随机将2年门诊就诊的资料齐全的122例患儿进行静脉血检测常规微量元素、铅和镉;并对干预处理后的106例儿童进行复查。结果缺铁占22.13%,缺钙占7.37%,缺锌占4.1%,缺镁占1.64%,无铜和磷的缺乏。重金属铅大于100μg/L的49例,占40.16%;镉大于5μg/L的2例,占1.64%。对血铅大于40μg/L的106例患儿进行干预,对干预前后进行统计学比较及u检验,差异具有统计学意义。结论常规微量元素的缺乏有明显下降趋势,人群对补足常规微量元素有很高的认识,其危害明显的减少。重金属的污染对儿童健康的危害有上升的趋势,社会人群的知晓度很小;用合适的干预来降低血铅是很有效的,值得临床推广宣传。  相似文献   
9.
We hypothesized that increased ambient concentrations of metals, as a consequence of escalating urbanization and industrialization of the Gulf region will respond in increased contamination of edible fish species. In this study, we report concentrations of chromium, manganese, cobalt, copper, zinc, arsenic, cadmium, mercury and lead in meat and liver of wild Red-spot emperor (Lethrinus lentjan) from three sampling points at the UAE coast. Analysis was performed by the ICP-MS/microwave digestion. Our study has shown that meat and liver metal content was significantly higher in areas with higher industrial activity, although metal values did not exceed permitted levels of fish for human consumption.  相似文献   
10.
Lead poisoning in a precious metals refinery fire assayer and a routine OSHA inspection prompted an investigation of the index facility, a survey of the industry, and efforts to notify assayers of this previously unrecognized hazard. Air and blood samples were obtained at the index facility. Management personnel from all fire assay laboratories in Rhode Island and southern Massachusetts were interviewed. The industry's trade association, OSHA, NIOSH, trade unions, and the media were asked to assist in a nationwide notification effort. Assayers at the index facility had excessive exposures to lead due to an age-old, lead-based assaying method that remains the industry gold standard. Blood lead levels of the three assayers (mean 61.3 μ/dl, range 48–86 μg/dl) were considerably higher than those of 16 other refinery workers (mean 27.4 μg/dl, range 13–49 μg/dl). The industry survey revealed inadequate knowledge of both the lead hazard and the applicability of the OSHA lead standard. Notification efforts failed in large part due to economic obstacles. The notification of workers at high risk of lead exposure and the eradication of occupational lead poisoning will require greater attention to economic forces. © 1994 Wiley-Liss, Inc.  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-23

京公网安备 11010802026262号