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   2369篇
  免费   138篇
  国内免费   40篇
  2547篇
  2023年   6篇
  2022年   31篇
  2021年   59篇
  2020年   11篇
  2018年   34篇
  2017年   24篇
  2016年   91篇
  2015年   213篇
  2014年   221篇
  2013年   243篇
  2012年   276篇
  2011年   201篇
  2010年   116篇
  2009年   90篇
  2008年   105篇
  2007年   72篇
  2006年   54篇
  2005年   89篇
  2004年   83篇
  2003年   61篇
  2002年   61篇
  2001年   46篇
  2000年   29篇
  1999年   13篇
  1998年   17篇
  1997年   10篇
  1996年   16篇
  1995年   6篇
  1994年   5篇
  1993年   14篇
  1992年   18篇
  1991年   10篇
  1990年   13篇
  1989年   12篇
  1988年   13篇
  1987年   5篇
  1986年   10篇
  1985年   6篇
  1983年   5篇
  1982年   5篇
  1978年   5篇
  1974年   6篇
  1973年   5篇
  1972年   5篇
  1968年   5篇
  1962年   5篇
  1957年   6篇
  1951年   5篇
  1947年   4篇
  1926年   4篇
排序方式: 共有2547条查询结果,搜索用时 11 毫秒
91.
92.

Background

Community based breastfeeding promotion programmes have been shown to be effective in increasing breastfeeding prevalence. However, there is limited data on the cost-effectiveness of these programmes in sub-Saharan Africa. This paper evaluates the cost-effectiveness of a breastfeeding promotion intervention targeting mothers and their 0 to 6 month old children.

Methods

Data were obtained from a community randomized trial conducted in Uganda between 2006–2008, and supplemented with evidence from several studies in sub-Saharan Africa. In the trial, peer counselling was offered to women in intervention clusters. In the control and intervention clusters, women could access standard health facility breastfeeding promotion services (HFP). Thus, two methods of breastfeeding promotion were compared: community based peer counselling (in addition to HFP) and standard HFP alone. A Markov model was used to calculate incremental cost-effectiveness ratios between the two strategies. The model estimated changes in breastfeeding prevalence and disability adjusted life years. Costs were estimated from a provider perspective. Uncertainty around the results was characterized using one-way sensitivity analyses and a probabilistic sensitivity analysis.

Findings

Peer counselling more than doubled the breastfeeding prevalence as reported by mothers, but there was no observable impact on diarrhoea prevalence. Estimated incremental cost-effectiveness ratios were US$68 per month of exclusive or predominant breastfeeding and U$11,353 per disability adjusted life year (DALY) averted. The findings were robust to parameter variations in the sensitivity analyses

Conclusions

Our strategy to promote community based peer counselling is unlikely to be cost-effective in reducing diarrhoea prevalence and mortality in Uganda, because its cost per DALY averted far exceeds the commonly assumed willingness-to-pay threshold of three times Uganda’s GDP per capita (US$1653). However, since the intervention significantly increases prevalence of exclusive or predominant breastfeeding, it could be adopted in Uganda if benefits other than reducing the occurrence of diarrhoea are believed to be important.  相似文献   
93.
研究报道的介形类化石系采自浙江省桐庐县瑶林镇沈村剖面早二叠世船山组,计14 属4 亚属22 种,包括4新种和4未定种。其中12属4亚属和19种产自船山组第三段,并被归为Hollinella(Praehollinella) ema ciata Basslerella ola 组合,代表早二叠世船山世隆林期。牙形刺化石主要产自船山组第一段,带化石Streptogna thodus elegantulus 及其共生的其它牙形刺化石,指明船山组第一段的时代为中、晚卡西莫夫期到早格泽里期。根据介形类动物群生态组合和岩石特征,推测船山组第三段是在温暖的近岸浅水且为低能的开阔海环境下沉积的。  相似文献   
94.
海洋生物制药现状及展望   总被引:4,自引:0,他引:4  
现代生物技术在制药产业中发挥了重要作用,海洋生物技术的出现和发展推动了海洋生 物药物的研究,是今后生物技术药物的发展方向。综述了生物技术在海洋药物开发中的应用,并 展望了新世纪海洋生物制药的前景。  相似文献   
95.
The aim of this study was to study the serotypes and clonal diversity of pneumococci causing invasive pneumococcal disease in Catalonia, Spain, in the era of 13-valent pneumococcal conjugate vaccine (PCV13). In our region, this vaccine is only available in the private market and it is estimated a PCV13 vaccine coverage around 55% in children. A total of 1551 pneumococcal invasive isolates received between 2010 and 2013 in the Molecular Microbiology Department at Hospital Sant Joan de Déu, Barcelona, were included. Fifty-two serotypes and 249 clonal types—defined by MLST—were identified. The most common serotypes were serotype 1 (n = 182; 11.7%), 3 (n = 145; 9.3%), 19A (n = 137; 8.8%) and 7F (n = 122; 7.9%). Serotype 14 was the third most frequent serotype in children < 2 years (15 of 159 isolates). PCV7 serotypes maintained their proportion along the period of study, 16.6% in 2010 to 13.4% in 2013, whereas there was a significant proportional decrease in PCV13 serotypes, 65.3% in 2010 to 48.9% in 2013 (p<0.01). This decrease was mainly attributable to serotypes 19A and 7F. Serotype 12F achieved the third position in 2013 (n = 22, 6.4%). The most frequent clonal types found were ST306 (n = 154, 9.9%), ST191 (n = 111, 7.2%), ST989 (n = 85, 5.5%) and ST180 (n = 80, 5.2%). Despite their decrease, PCV13 serotypes continue to be a major cause of disease in Spain. These results emphasize the need for complete PCV13 vaccination.  相似文献   
96.
贵州遵义松林中南村黑沙坡下寒武统牛蹄塘生物群下部层位产有大型三叶虫,计有2属3种,1未定种:Zhenbaspis subconica S. G Zhang in Lu et al. , 1974, Z. longa Zhou in Lee et al. , 1975 ; Zhenbaspis sp. , Runnania similis Lee in Yin et Lee, , 1978, 确认 Zhenbaspis (Zhenxiongaspis) Lin et Yin in Yin et Lee, 1978,为 Zhenbastn‘sChang et Chu in Lu et al. ,1974的同义名。探讨Zhenbaspis的古地理分布及演化趋势。论文还描述与Zhenbaspis,Runnania共生的Tsunyidiscus及Mianxiandiscus,其中Mianxiandiscus产于下生物群即牛蹄塘组近底部,再次证实牛蹄塘下生物群的时代早于澄江生物群。  相似文献   
97.
The metabolism of hepcidin is profoundly modified in chronic kidney disease (CKD). We investigated its relation to iron disorders, inflammation and hemoglobin (Hb) level in 199 non-dialyzed, non-transplanted patients with CKD stages 1–5. All had their glomerular filtration rate measured by 51Cr-EDTA renal clearance (mGFR), as well as measurements of iron markers including hepcidin and of erythropoietin (EPO). Hepcidin varied from 0.2 to 193 ng/mL. The median increased from 23.3 ng/mL [8.8–28.7] to 36.1 ng/mL [14.1–92.3] when mGFR decreased from ≥60 to <15 mL/min/1.73 m2 (p = 0.02). Patients with absolute iron deficiency (transferrin saturation (TSAT) <20% and ferritin <40 ng/mL) had the lowest hepcidin levels (5.0 ng/mL [0.7–11.7]), and those with a normal iron profile (TSAT ≥20% and ferritin ≥40), the highest (34.5 ng/mL [23.7–51.6]). In multivariate analysis, absolute iron deficiency was associated with lower hepcidin values, and inflammation combined with a normal or functional iron profile with higher values, independent of other determinants of hepcidin concentration, including EPO, mGFR, and albuminemia. The hepcidin level, although it rose overall when mGFR declined, collapsed in patients with absolute iron deficiency. There was a significant interaction with iron status in the association between Hb and hepcidin. Except in absolute iron deficiency, hepcidin’s negative association with Hb level indicates that it is not down-regulated in CKD anemia.  相似文献   
98.
Common DNA fragments of the α-globin gene were observed in five races of adult common carp: mirror, scaly-German, Yamato-Suwa, Yamato-Saku, and Yamato-hybrid carp. There were different hybridization patterns between the Japanese carp and the German carp. Three to four DNA fragments hybridized with α-globin and indicated polymorphysim in the globin gene of carp.

Zusammenfassung


DNA-Homologie des α-Globin-Genes bei fünf Karpfenrassen, Cyprinus carpio
Identische Fragmente des α-Globin-Genes wurden bei fünf Rassen des adulten gemeinen Karpfens (Spiegeikarpfen, deutscher Schuppenkarpfen, Yamato-Suwa-, Yamato-Saku-und Yamato-Hybrid-karpfen) gefunden. Es gab verschiedene Hybridisationsmuster zwischen dem japanischen und dem deutschen Karpfen. Drei bis vier DNA-Fragmente hybridisierten mit α-Globin und wiesen auf einen Polymorphismus des Globingenes des Karpfens hin.

Résumé


Homologie de DNA dans le gène d'α-globine chez cinq races de carpe, Cyprinus carpio
Des fragments communs de DNA dans des gènes d'α-globine ont été observés chez cinq races de carpe commune adulte: carpe miroir, allemande écailleuse, Yamato-Suwa, Yamato-Saku et Yamato-hybride. Il existait différentes combinaisons d'hybridation entre la carpe allemande et la carpe japonaise. Trois à quatre fragments de DNA hybridisaient avec l'α-globine et indiquaient un polymorphisme dans les gènes de globine de carpe.  相似文献   
99.
100.

Aim

To study the pattern and prevalence of dyslipidemia in a large representative sample of four selected regions in India.

Methods

Phase I of the Indian Council of Medical Research–India Diabetes (ICMR-INDIAB) study was conducted in a representative population of three states of India [Tamil Nadu, Maharashtra and Jharkhand] and one Union Territory [Chandigarh], and covered a population of 213 million people using stratified multistage sampling design to recruit individuals ≥20 years of age. All the study subjects (n = 16,607) underwent anthropometric measurements and oral glucose tolerance tests were done using capillary blood (except in self-reported diabetes). In addition, in every 5th subject (n = 2042), a fasting venous sample was collected and assayed for lipids. Dyslipidemia was diagnosed using National Cholesterol Education Programme (NCEP) guidelines.

Results

Of the subjects studied, 13.9% had hypercholesterolemia, 29.5% had hypertriglyceridemia, 72.3% had low HDL-C, 11.8% had high LDL-C levels and 79% had abnormalities in one of the lipid parameters. Regional disparity exists with the highest rates of hypercholesterolemia observed in Tamilnadu (18.3%), highest rates of hypertriglyceridemia in Chandigarh (38.6%), highest rates of low HDL-C in Jharkhand (76.8%) and highest rates of high LDL-C in Tamilnadu (15.8%). Except for low HDL-C and in the state of Maharashtra, in all other states, urban residents had the highest prevalence of lipid abnormalities compared to rural residents. Low HDL-C was the most common lipid abnormality (72.3%) in all the four regions studied; in 44.9% of subjects, it was present as an isolated abnormality. Common significant risk factors for dyslipidemia included obesity, diabetes, and dysglycemia.

Conclusion

The prevalence of dyslipidemia is very high in India, which calls for urgent lifestyle intervention strategies to prevent and manage this important cardiovascular risk factor.  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