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   7009篇
  免费   478篇
  国内免费   26篇
医药卫生   7513篇
  2024年   5篇
  2023年   95篇
  2022年   79篇
  2021年   309篇
  2020年   200篇
  2019年   262篇
  2018年   292篇
  2017年   200篇
  2016年   174篇
  2015年   247篇
  2014年   289篇
  2013年   400篇
  2012年   622篇
  2011年   611篇
  2010年   369篇
  2009年   289篇
  2008年   463篇
  2007年   443篇
  2006年   404篇
  2005年   386篇
  2004年   362篇
  2003年   296篇
  2002年   269篇
  2001年   50篇
  2000年   41篇
  1999年   55篇
  1998年   29篇
  1997年   14篇
  1996年   20篇
  1995年   27篇
  1994年   15篇
  1993年   15篇
  1992年   16篇
  1991年   26篇
  1990年   11篇
  1989年   12篇
  1988年   14篇
  1987年   7篇
  1986年   11篇
  1985年   10篇
  1984年   5篇
  1980年   7篇
  1979年   5篇
  1976年   5篇
  1975年   7篇
  1974年   10篇
  1973年   5篇
  1971年   4篇
  1969年   4篇
  1966年   4篇
排序方式: 共有7513条查询结果,搜索用时 250 毫秒
1.
2.
3.
4.

Objective

To examine the association of placental levels of arsenic (As), cadmium (Cd), mercury (Hg), lead (Pb), manganese (Mn), and chromium (Cr) with birth outcomes (birth weight, length, and head circumference, low birth weight [LBW], gestational age, preterm delivery, and small for gestational age [SGA]) in mother-child pairs from the Environment and Childhood (INMA) Project in Spain.

Methods

Metal concentrations were measured in placenta tissue samples randomly selected from five INMA cohorts. Data on birth outcomes were obtained from medical records. Associations were assessed in a sub-sample of 327 mother-infant pairs by regression models adjusted for confounding factors and for all metals simultaneously. Effect modification by sex was also evaluated.

Results

Elevated placental Cd levels (>5.79 vs. <3.30?ng/g) were associated with reduced birth weight (?111.8?g, 95%CI?=??215.6; ?8.06, p-trend?=?0.01) and length (?0.62?cm, 95%CI?=??1.20; ?0.04, p-trend?=?0.02), while a 10% increase in Cd was associated with 1.21-fold increased odds (95%CI?=?1.01; 1.43) of LBW in the global sample but with 14% lower odds (95%CI?=?0.78; 0.96) of preterm delivery in males (Pinteraction?=?0.10). Detected (vs. undetected) Hg was associated with reduced head circumference (?0.49?cm, 95%CI?=??1.00; 0.03) in females (Pinteraction?=?0.03). A 10% increase in placental Mn was associated with slight increases in gestational age (0.04 weeks, 95%CI?=?0.01; 0.07) in the global sample and in head circumference (0.05?cm, 95%CI?=??0.01; 0.10) in females (Pinteraction?=?0.03). Elevated Cr levels (>99.6 vs. <56.1?ng/g) were associated with reduced birth length (?0.68?cm, 95%CI?=??1.33; ?0.04, p-trend?=?0.02) and slightly increased gestational age (0.35 weeks, 95%CI?=??0.07; 0.77, p-trend?=?0.08) in the global sample. As and Pb were detected in few placentas (27% and 13%, respectively) and were not associated with any studied birth outcome.

Conclusions

Data suggest that in utero exposure to Cd, Hg, and Cr could adversely affect fetal growth, whereas Mn and Cr appear to have a positive effect on gestational age. Given the relatively small number of subjects, sex-specific associations should be interpreted with caution.  相似文献   
5.
6.
7.
Background and aimsThe metabolic syndrome (MetS) is a cluster of coexisting cardiovascular risk factors. The role of specific dietary fats was reemphasized by dietary recommendations. This systematic review aims to assess evidence for the effect of dietary fat intake on MetS occurrence and reversion in adults.Methods and ResultsThe MEDLINE database was used to search the existing literature. We included observational studies that analyzed dietary fat intake in adults with MetS and clinical trials that compared the effects of different dietary fat diets on MetS and/or its components. Thirty articles were selected (14 observational and 16 clinical trials), and we included information of dietary fat and fatty acids as well as MetS, body mass index, cholesterol, hypertension, and diabetes in adults. SFA intake was found to be positively associated with MetS components. Most of the observational reviewed studies found beneficial associations between MUFA and PUFA (including n-3 and n-6 subtypes) intake and MetS components. Clinical trials also supported the benefits of MUFA- or PUFA-enriched diets (including low-fat diets) in reducing MetS.ConclusionsThe effects of dietary SFAs on MetS will be influenced by other specific nutrients. Replacement of SFA by MUFA and PUFA has been associated with a decrease in MetS. Dietary recommendations should emphasize on different qualities of fat intake, not only to reduce total fat intake, to obtain health benefits in adults.  相似文献   
8.
9.
Porcine epidemic diarrhoea virus (PEDV) infects pigs of all ages causing vomiting and diarrhoea. PEDV is transmitted via the oral–faecal route, and a very low dose is enough to infect susceptible pigs, resulting in significant production losses. This short communication aims to describe the introduction of PEDV into a 10,000-sow farrow-to-wean farm located in northwest Mexico. Following the onset of clinical signs, an outbreak investigation was conducted to determine the most probable route of introduction. Based on data collected from interviews, construction of a timeline of events, and the detection of PEDV RNA in feed samples and samples collected from various surfaces of feed transport vehicles, it was concluded that the most probable route for PEDV incursion into this breeding herd was contaminated feed or a contaminated feed transport vehicle. This paper describes how feed or feed transport could serve as potential routes of PEDV infection to a farm and highlights the importance of establishing biosecurity programs to mitigate these risks.  相似文献   
10.
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