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   2033篇
  免费   172篇
  国内免费   51篇
医药卫生   2256篇
  2024年   2篇
  2023年   19篇
  2022年   53篇
  2021年   120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   20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
  1972年   1篇
排序方式: 共有2256条查询结果,搜索用时 15 毫秒
51.
李敏  张淑蓉  张建文 《中国药师》2015,(10):1788-1790
摘 要 目的: 用火焰原子吸收分光光度计和原子双道荧光光度计分别对不同产地冻干地黄中的Pb、Cd、Cu、As和Hg 5种重金属和有害元素进行检测。方法: 采用硝酸-高氯酸对样品进行消化后,采用原子吸收分光光度法测定Pb、Cd和Cu含量,采用原子荧光光度法测定As和Hg的含量。 结果: 各元素线性关系良好,相关系数均大于0.997 4,平均回收率为97.88%~100.90%,RSD为0.019%~4.20%(n=6),同时发现10批样品中的4批样品部分重金属和有害元素超过《中国药典》限量标准。 结论:该方法准确度高,操作简便,快捷,适用于冻干地黄中重金属和有害元素的测定。  相似文献   
52.
AimAutism is a developmental disability characterized by severe deficits in social interaction and communication. The definite cause of autism is still unknown. The aim of this study is to find out the relation between exposure to Lead and/or mercury as heavy metals and autistic symptoms, dealing with the heavy metals with chelating agents can improve the autististic symptoms.MethodBlood and hair samples were obtained from 45 children from Upper Egypt with autism between the ages of 2 and 10 years and 45 children served as controls in the same age range, after taken an informed consent and fill a questionnaire to assess the risk factors. The samples were analyzed blindly for lead and mercury by using atomic absorption and ICP-MS. Data from the two groups were compared, then follow up of the autistic children after treatment with chelating agents were done.ResultsThe results obtained showed significant difference among the two groups, there was high level of mercury and lead among those kids with autism. Significant decline in the blood level of lead and mercury with the use of DMSA as a chelating agent. In addition, there was decline in the autistic symptoms with the decrease in the lead and mercury level in blood.ConclusionLead and mercury considered as one of the main causes of autism. Environmental exposure as well as defect in heavy metal metabolism is responsible for the high level of heavy metals. Detoxification by chelating agents had great role in improvement of those kids.  相似文献   
53.
Increase of distribution of environmental contaminants such as heavy metals have been caused the knowledge of the safety and hygiene of food is very important, especially eggs, because of its role in the daily diet. There are very few studies about the investigation of the heavy metal contents in egg-white. In this study, six heavy metals include Aluminium (Al), Arsenic (As), Lead (Pb), Cadmium (Cd), Mercury (Hg), Antimony (Sb) in egg-white from 32 industrial poultry farms were investigated, by ICP-OES. All the samples were collected in all area of Markazi Province, Iran in autumn 2013. The mean concentrations of heavy metals in egg-white as follows: 0.119 for Al, 0.785 for As, 0.750 for Pb, 0.249 for Cd, 0.270 for Hg and 0.186?mg/kg for Sb. Also, the concentration of the some heavy metals were higher than maximum allowable concentration that probably it is associated to use pesticides and activities of industrial factories around the poultry farms.  相似文献   
54.
目的:了解丰台区学龄儿童体内重金属分布现状及其与儿童智力发育和神经行为的相关性.方法:采用整群随机抽样的方法,抽取丰台区3所小学校的9 ~12岁的学龄儿童256名作为研究对象,进行瑞文智力测验和神经行为测验,检测血样和尿样中铬、镍、砷、硒、镉、汞、铊、铅含量.结果:256名儿童血铅、血硒、尿砷检出率为100%,铊检出率为0,其他金属的检出率在10.3% ~71.1%之间,儿童血铬、血硒、血铅,尿硒含量与IQ呈正相关(P<0.05);血汞、尿汞与IQ呈负相关(P<0.05);儿童血砷、尿砷、尿铬、尿铅、尿硒与神经行为呈负相关(P<0.05).结论:研究区域儿童体内各种金属均有检出应引起重视;汞对儿童的智商发育有不良的影响;硒对儿童智商有保护作用;金属砷、铬、硒、铊、铅对儿童神经行为发育有不良影响.  相似文献   
55.
The food chain is one of the major sources of human exposure to non-essential trace elements (TEs) present in soils. Human exposure to contaminated food is a worldwide health concern and a food safety issue that threatens agricultural trade. To assess the quality of Brazilian food products with respect to non-essential TEs, we evaluated arsenic (As), cadmium (Cd), and lead (Pb) contents in five major crops grown in Brazil: rice, wheat, corn, soybeans, and potatoes. The samples were collected from field trials with a record of long-term use of phosphate fertilizers in the states of Mato Grosso and Minas Gerais, Brazil. The TE concentrations in soils were all bellow the maximum allowable concentrations for agricultural soils. The mean concentrations of As, Cd, and Pb (μg kg−1 dry weight) were as follows: below the detection limit <15, 29, and <40 for rice; 19, 23, and 64 for wheat; 47, 40, and 95 for corn; 65, 23, and 106 for soybeans; and 59, 22, and <40 for potatoes, respectively. Significant differences were found in the As and Cd contents of the different wheat cultivars. The levels of As, Cd, and Pb found in the studied crops are well below the values reported in the literature and are in accordance with the Codex Alimentarius and the European Union and Brazilian guidelines, indicating that the concentrations of these elements in the crops do not pose a risk to human health.  相似文献   
56.
Potatoes (Solanum tuberosum L.) from the high Tiber valley area (TVA; Tuscany, Italy), have been sampled and analyzed for selected mineral content (Na, Mg, K, Ca, and Mn, Fe, Cu and Zn) and vitamin C, the year 2012; some samples from 2011 and 2013 crops were also collected and analyzed. The varieties were Daytona (DAY), Kennebec (KEN), Sifra (SIF) and Volare (VOL). Control samples consisted of mixed commercial varieties from the local market, namely C1, C2 and C3. The low content of sodium, especially for KEN (46 ± 3 mg/kg FD (freeze dry), year 2012) and SIF (47 ± 3) (VOL (55 ± 3) and DAY (61 ± 3) have a little higher values) is worth of note and in agreement with the scarce concentration of Na in the soil (291 ± 12 mg/kg DM). Magnesium was abundant in KEN (1434 ± 75 mg/kg FD, year 2012) and VOL (1334 ± 70). The content of K for DAY and KEN (13,147 ± 900 and 13,185 ± 900 mg/kg FD) was higher than for VOL and SIF; whereas Ca was in the range 340 ± 16–490 ± 28 mg/kg FD. The contents of Cu and Zn were higher in KEN (8.1 ± 0.3 and 25 ± 1 mg/kg FD) when compared to the other varieties and controls. The content of vitamin C is high for KEN and SIF and decreased significantly upon cooking (50% for KEN).  相似文献   
57.
A valid method based on heat-assisted slurry sampling graphic furnace atomic absorption spectrometry (HASS-GFAAS) was developed for the accurate determination of trace Pb in food standard reference materials (SRMs). The HASS technique significantly improved Pb recovery and precision compared to conventional slurry sampling techniques. The optimized HASS procedure was performed as follows: first, the sample (particle size  150 μm) was diluted with 0.05% (v/v) Triton X-100 containing 2% HNO3 and 1% H2O2 followed by heating for 20 min at 120 °C on a heating block. Next, the obtained slurry was sonicated in an autosampler cup, and finally, the slurry was introduced into a graphite tube and analyzed by the GFAAS with a Pb electrodeless discharge lamp (EDL). Calibration with aqueous standard solutions was used for Pb determination in food samples. The characteristic mass and limit of detection for Pb based on the integrated absorbance for a 2% (m/v) sample were 12 ± 0.6 pg and 0.003 mg kg−1, respectively. The accuracy (95.1–102% recovery) and good precision (0.1–3.6%) of this procedure are illustrated by the results obtained for the 12 food reference materials. The proposed method is suitable for determination of trace Pb in solid food samples.  相似文献   
58.
The presence of cadmium (Cd), lead (Pb) and mercury (Hg) was investigated in fish and seafood products collected from the FAO Major Fishing Area 34, Eastern Central Atlantic. Samples were purchased from different retail outlets in Italy. Samples were selected so as to assess human exposure through diet. Metals were detected by Q-ICP-MS and Hg-AAS. All the metal concentrations detected were largely below the maximum levels (MLs) established by the European Union. The exposure assessment was undertaken by matching the concentration of Cd, Pb and total Hg in fish and other seafood products selected purposed according to Italian consumption data. The estimated weekly intakes (EWIs) for the evaluated elements related to the consumption of fish and other seafood products by the median of the Italian total population accounted for 14%, 2% and 14% of the standard tolerable weekly intake (TWI) for Cd and Hg as well as the provisional tolerable weekly intake (PTWI) for Pb, respectively.  相似文献   
59.
Heavy drinkers in Scotland may consume 1600 g ethanol per week. Due to its low price, cider may be preferred over other beverages. Anecdotal evidence has linked cider to specific health hazards beyond other alcoholic beverages. To examine this hypothesis, nine apple and pear cider samples were chemically analysed for constituents and contaminants. None of the products exceeded regulatory or toxicological thresholds, but the regular occurrence of acetaldehyde in cider was detected. To provide a quantitative risk assessment, two collectives of exclusive drinkers of cider and vodka were compared and the intake of acetaldehyde was estimated using probabilistic Monte–Carlo type analysis. The cider consumers were found to ingest more than 200-times the amount of acetaldehyde consumed by vodka consumers. The margins of exposure (MOE) of acetaldehyde were 224 for the cider and over 220,000 for vodka consumers. However, if the effects of ethanol were considered in a cumulative assessment of the combined MOE, the effect of acetaldehyde was minor and the combined MOE for both groups was 0.3. We suggest that alcohol policy priority should be given on reducing ethanol intake by measures such as minimum pricing, rather than to focus on acetaldehyde.  相似文献   
60.
Lead (Pb), a known environmental toxicant, adversely affects almost all organ systems. In this study, we investigated the effects of maternal lead exposure on fetal rat cerebellum. Female Sprague–Dawley rats were given lead nitrate in drinking water (0, 0.5, and 1%) for two weeks before conception, and during pregnancy. Fetuses were collected by caesarian section on gestational day 21 and observed for developmental abnormalities. The fetal cerebellar sections from control and 1% lead group were stained with cresyl violet. Immunohistochemical expressions of p53, Bax, Bcl-2, and caspase 3 were quantified by AnalySIS image analyzer (Life Science, Germany). Lead exposure induced developmental abnormalities of eyes, ear, limbs, neck and ventral abdominal wall; however, these abnormalities were commonly seen in the 1% lead-treated group. In addition, lead also caused fetal mortality and reduced body growth in both dose groups and reduced brain weight in the 1% lead-treated group. The fetal cerebella from the 1% lead-treated group showed unorganized cerebellar cortical layers, and degenerative changes in granule and Purkinje cells such as the formation of clumps of Nissl granules. An increase in Bax and caspase 3, and a decrease in Bcl-2 (p?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