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   16064篇
  免费   1324篇
  国内免费   286篇
医药卫生   17674篇
  2023年   288篇
  2022年   331篇
  2021年   716篇
  2020年   550篇
  2019年   652篇
  2018年   579篇
  2017年   617篇
  2016年   583篇
  2015年   575篇
  2014年   1038篇
  2013年   1377篇
  2012年   889篇
  2011年   994篇
  2010年   788篇
  2009年   747篇
  2008年   835篇
  2007年   770篇
  2006年   624篇
  2005年   586篇
  2004年   486篇
  2003年   442篇
  2002年   348篇
  2001年   297篇
  2000年   247篇
  1999年   194篇
  1998年   184篇
  1997年   143篇
  1996年   118篇
  1995年   120篇
  1994年   121篇
  1993年   103篇
  1992年   96篇
  1991年   87篇
  1990年   83篇
  1989年   63篇
  1988年   67篇
  1987年   57篇
  1986年   68篇
  1985年   120篇
  1984年   108篇
  1983年   88篇
  1982年   70篇
  1981年   69篇
  1980年   65篇
  1979年   60篇
  1978年   51篇
  1977年   29篇
  1976年   37篇
  1975年   21篇
  1973年   22篇
排序方式: 共有10000条查询结果,搜索用时 479 毫秒
1.
Child benefits are typically paid from birth. This paper asks whether starting universal child benefits in pregnancy leads to improvements in infant health. Leveraging administrative birth registry and hospital microdata from England and Wales, I study the effects of the Health in Pregnancy Grant, a universal conditional cash transfer equivalent to three months of child benefit (190 GBP) as a lump sum to pregnant mothers from 2009 to 2011. I exploit quasi-experimental variation in eligibility with a regression discontinuity design in the date of birth of the baby. I find that the policy increased birth weight by 8–12 grams on average, reduced low birth weight (<2500 g) by 3-6 percent and decreased prematurity by 9–11 percent. Younger mothers, particularly those living in deprived areas, benefit the most. I present evidence that the mechanisms are unlikely to be antenatal care, nutrition or smoking, with reductions in stress remaining a possible explanation.  相似文献   
2.
目的探讨中国9个城市(简称九市)4~7岁儿童乳恒牙替换及其与体格生长的关系,分析恒牙发育长期变化趋势。方法采用分层整群抽样的方法,以4~7岁儿童为调查对象,于2015年6—10月在北京、哈尔滨、西安(北片),上海、南京、武汉(中片),广州、福州、昆明(南片)九市进行横断面调查,共37973名儿童,其中男19035名,女18938名。6岁以下每6个月为1组,6~<7岁1岁为1组。现场检查乳牙脱落、恒牙萌出情况,测量身高、体重等,并依据2009年中国儿童生长标准计算体格指标Z分值。采用Probit概率单位回归方法计算换牙年龄。不同性别、地区、年龄分组组间比较采用χ2检验或t检验。并利用1995年中国九市儿童体格发育调查中乳恒牙替换相关数据,分析恒牙发育的长期变化趋势。结果九市37973名儿童随着年龄增长换牙率逐渐增加,从4.0~<4.5岁的0.6%(42/7568)增长至5.5~<6.0岁的30.3%(2295/7583),6.0~<7.0岁达到74.5%(5680/7627)。除4.0~4.5岁组外,无论城郊男童换牙率均低于女童(P均<0.05);城区换牙率(男5.5~<6.0岁、女4.5~<5.0岁组之后)略高于郊区,如6.0~<7.0岁组男童城郊分别为74.2%(1427/1924)、69.2%(1305/1885)(χ2=11.446,P<0.01)。九市儿童换牙年龄为6.00(95%CI:5.98~6.01)岁。换牙年龄的第3~97百分位变化范围为4.88~7.11岁。女童中位换牙年龄(5.94岁)早于男童(6.06岁);城区(5.94岁)早于郊区(6.05岁);北片(5.97岁)、中片地区(5.97岁)略早于南片地区(6.05岁)。已换牙儿童体重、身高、体质指数Z分值均高于未换牙儿童(0.35±1.17比0.03±1.13、0.32±1.00比0.03±1.02、0.23±1.16比0.04±1.13,t=20.81、21.67、12.09,P均<0.05)。与1995年相比,2015年5.0岁以后儿童换牙率明显提高,如城区男童6.0~<7.0岁组1995年为63.8%(1146/1796),2015年提高至74.2%(1427/1924)(χ2=46.748,P<0.01);中位换牙年龄2015年较1995年提前0.24岁。结论九市4~7岁儿童换牙年龄女童早于男童,城区早于郊区,北、中片早于南片地区。换牙早晚与体格生长水平有关。近20年换牙年龄存在小幅提前趋势。  相似文献   
3.
There is evidence that caesarean section delivery can impact on neonatal weight loss and weight gain patterns in the first 5 days of life. We conducted an integrative systematic review to examine the association of mode of delivery on early neonatal weight loss. Pubmed, Cumulative Index to Nursing and Allied Health Literature, Web of Science, Excerpta Medica dataBASE, and Medical Literature Analysis and Retrieval System Online were searched for relevant papers published before June 2019. Reference lists from the relevant papers were then backwards and forwards searched. As neonatal weight loss was reported in different formats, a meta‐analysis could not be carried out. Most studies did not distinguish between elective and emergency caesarean sections or instrumental and nonassisted vaginal deliveries. Seven papers were included. All papers except one found that caesarean section was associated with higher weight loss in the early days of life. Two papers presented data from studies on babies followed up to 1 month. One study found that on day 25, babies born by caesarean section had significantly higher weight gain than those born vaginally, while another found that by day 28, babies born vaginally gained more weight per day (11.9 g/kg/day) than those born by caesarean section (10.9 g/kg/day; p = .02). Overall, infants born by caesarean section lost more weight than those born vaginally, but due to the small number of studies included, more are needed to look at this difference and why it may occur. This discrepancy in weight between the two groups may be corrected over time, but future studies will need larger sample sizes and longer follow‐up periods to examine this.  相似文献   
4.
目的:对应用低分子肝素钙与奥扎格雷联合对患有脑血栓疾病的患者实施治疗的临床效果进行研究。方法整群选择在该院2012年12月—2014年12月就诊的患有脑血栓疾病的患者86例,随机分为对照组和治疗组,每组43例。采用奥扎格雷对对照组患者实施治疗;采用低分子肝素钙与奥扎格雷联合对治疗组患者实施治疗。对比神经功能缺损评分在药物治疗前后的变化幅度、脑神经功能恢复正常时间和脑血栓药物治疗计划实施总时间、脑血栓疾病药物治疗效果、用药期间的不良反应人数。结果治疗组患者神经功能缺损评分在药物治疗前后的变化幅度明显大于对照组;脑神经功能恢复正常时间(9.66±2.41)d和脑血栓药物治疗计划实施总时间(13.28±2.14)d明显短于对照组(13.62±3.47)、(17.39±3.20)d;脑血栓疾病药物治疗效果(总有效率90.6%)明显优于对照组(总有效率69.8%);用药期间的不良反应人数(1例)明显少于对照组(8例)。结论应用低分子肝素钙与奥扎格雷联合对患有脑血栓疾病的患者实施治疗的临床效果非常明显。  相似文献   
5.
Responsive feeding (RF) has been recognized as necessary to prevent all forms of malnutrition including stunting and childhood obesity. Specific RF guidelines have been developed, but it is unclear how RF behaviours can be monitored systematically. Therefore, developing valid and reliable abbreviated and pragmatic RF scales is an important global priority. This is challenging, as RF is a construct with multiple dimensions including recognizing and responding to hunger and satiety cues, providing a nurturing environment during feeding episodes, and understanding how feeding needs evolve as a function of the developmental stage of the young child. Further, RF is embedded within the responsive parenting framework that in addition to RF includes sleep, soothing and play routines and the interconnections between them. A recent pioneer study conducted in a rural area of Cambodia validated an 8‐item RF scale through direct feeding observations of 6‐ to 23‐month‐old infants at home, as part of two cross‐sectional surveys conducted before and after a complementary feeding intervention. It is important for similar research to be conducted elsewhere to find out if it is possible or not to develop a core RF scale that is valid and reliable and that has adequate specificity and sensitivity for application in community studies and population surveys globally. As highlighted in this article, different definitions of RF have been used in the field; thus, it is important to reach consensus on a single definition to help move this research area forward.  相似文献   
6.
ObjectivesTo explore the relationships among potentially modifiable factors related to childbirth and effective breastfeeding initiation at approximately 36 hours after birth and duration and exclusivity at hospital discharge, 2 weeks, 2 months, and 6 months after birth in primiparous women and to explore whether modifiable and nonmodifiable secondary factors and covariates influenced the relationships among factors related to childbirth and these breastfeeding outcomes.DesignA prospective, longitudinal, cohort study.SettingThe postpartum units of two general hospitals in eastern Canada.ParticipantsNinety-seven mother–infant dyads.MethodsWe recorded demographic, childbirth, obstetric history, and breastfeeding data through chart review. A breastfeeding observation was completed at approximately 36 hours after birth by unit nurses. Participants maintained breastfeeding logs in hospital and for 6 months after birth and completed three self-report questionnaires before discharge. We analyzed outcomes using backward stepwise linear and logistic regression.ResultsOne childbirth factor, labor induced with oxytocin, was negatively associated with effective initiation of breastfeeding, and none was related to breastfeeding duration and exclusivity at any time point. Maternal weight; professional support; and newborn’s gestational age at birth, 5-minute Apgar score, weight loss, LATCH score, and active feeds (newborn actively suckled at the breast) were significantly associated with breastfeeding outcomes.ConclusionInduction of labor with oxytocin should be used judiciously; when used, nurses must be hypervigilant to assess the mother–infant dyad for breastfeeding issues and to intervene to prevent or remediate them.  相似文献   
7.
目的分析早发型子痫前期应用低分子肝素期待治疗的临床效果。方法回顾分析2017-01—2018-12间在郑州大学第一附属医院产科终止妊娠的95例早发型子痫前期患者的临床资料。按终止妊娠前是否应用低分子肝素分为2组。对照组(47例)给予降压、解痉等治疗;观察组(48例)在对照组基础上加用低分子肝素。结果2组分娩孕周、妊娠延长时间、妊娠并发症发生率、新生儿出生体质量、新生儿窒息及胎儿宫内窘迫发生率、新生儿Apgar评分等,差异均无统计学意义(P>0.05)。结论对早发型子痫前期患者在常规治疗基础上短期应用低分子肝素,不能延长妊娠时间,不改善母婴结局。  相似文献   
8.
9.
The analysis of quality of life (QoL) data can be challenging due to the skewness of responses and the presence of missing data. In this paper, we propose a new weighted quantile regression method for estimating the conditional quantiles of QoL data with responses missing at random. The proposed method makes use of the correlation information within the same subject from an auxiliary mean regression model to enhance the estimation efficiency and takes into account of missing data mechanism. The asymptotic properties of the proposed estimator have been studied and simulations are also conducted to evaluate the performance of the proposed estimator. The proposed method has also been applied to the analysis of the QoL data from a clinical trial on early breast cancer, which motivated this study.  相似文献   
10.
Patients with active cancer are at an increased risk of arterial and venous thromboembolism (VTE) and bleeding events. Historically, in patients with cancer, low molecular weight heparins have been preferred for treatment of VTE, whereas warfarin has been the standard anticoagulant for stroke prevention in patients with atrial fibrillation (AF). More recently, direct oral anticoagulants (DOACs) have been demonstrated to reduce the risk of venous and arterial thromboembolism in large randomized clinical trials of patients with VTE and AF, respectively, thus providing an attractive oral dosing option that does not require routine laboratory monitoring. In this review, we summarize available clinical trial data and guideline recommendations, and outline a practical approach to anticoagulation management of VTE and AF in cancer.  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