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   1746篇
  免费   320篇
  国内免费   8篇
耳鼻咽喉   2篇
儿科学   58篇
妇产科学   281篇
基础医学   82篇
口腔科学   27篇
临床医学   847篇
内科学   167篇
皮肤病学   51篇
神经病学   14篇
特种医学   238篇
外科学   49篇
综合类   56篇
预防医学   88篇
眼科学   5篇
药学   54篇
肿瘤学   55篇
  2024年   4篇
  2023年   43篇
  2022年   2篇
  2021年   7篇
  2020年   34篇
  2019年   18篇
  2018年   57篇
  2017年   90篇
  2016年   77篇
  2015年   98篇
  2014年   100篇
  2013年   98篇
  2012年   37篇
  2011年   58篇
  2010年   100篇
  2009年   99篇
  2008年   40篇
  2007年   48篇
  2006年   38篇
  2005年   26篇
  2004年   18篇
  2003年   29篇
  2002年   20篇
  2001年   34篇
  2000年   10篇
  1999年   46篇
  1998年   93篇
  1997年   110篇
  1996年   105篇
  1995年   93篇
  1994年   63篇
  1993年   48篇
  1992年   21篇
  1991年   24篇
  1990年   10篇
  1989年   32篇
  1988年   31篇
  1987年   19篇
  1986年   28篇
  1985年   30篇
  1984年   14篇
  1983年   13篇
  1982年   18篇
  1981年   12篇
  1980年   15篇
  1979年   4篇
  1978年   16篇
  1977年   15篇
  1976年   13篇
  1975年   13篇
排序方式: 共有2074条查询结果,搜索用时 0 毫秒
71.
Abstract: Background: Both peer and professional support have been identified as important to the success of breastfeeding. The aim of this metasynthesis was to examine women’s perceptions and experiences of breastfeeding support, either professional or peer, to illuminate the components of support that they deemed “supportive.” Methods: The metasynthesis included studies of both formal or “created” peer and professional support for breastfeeding women but excluded studies of family or informal support. Qualitative studies were included as well as large‐scale surveys if they reported the analysis of qualitative data gathered through open‐ended responses. Primiparas and multiparas who initiated breastfeeding were included. Studies published in English, in peer‐reviewed journals, and undertaken between January 1990 and December 2007 were included. After assessment for relevance and quality, 31 studies were included. Meta‐ethnographic methods were used to identify categories and themes. Results: The metasynthesis resulted in four categories comprising 20 themes. The synthesis indicated that support for breastfeeding occurred along a continuum from authentic presence at one end, perceived as effective support, to disconnected encounters at the other, perceived as ineffective or even discouraging and counterproductive. A facilitative approach versus a reductionist approach was identified as contrasting styles of support that women experienced as helpful or unhelpful. Conclusions: The findings emphasize the importance of person‐centered communication skills and of relationships in supporting a woman to breastfeed. Organizational systems and services that facilitate continuity of caregiver, for example continuity of midwifery care or peer support models, are more likely to facilitate an authentic presence, involving supportive care and a trusting relationship with professionals. (BIRTH 38:1 March 2011)  相似文献   
72.
Abstract: Background: The World Health Organization (WHO) developed the Baby‐Friendly Hospital Initiative to improve hospital maternity care practices that support breastfeeding. In Hong Kong, although no hospitals have yet received the Baby‐Friendly status, efforts have been made to improve breastfeeding support. The aim of this study was to examine the impact of Baby‐Friendly hospital practices on breastfeeding duration. Methods: A sample of 1,242 breastfeeding mother‐infant pairs was recruited from four public hospitals in Hong Kong and followed up prospectively for up to 12 months. The primary outcome variable was defined as breastfeeding for 8 weeks or less. Predictor variables included six Baby‐Friendly practices: breastfeeding initiation within 1 hour of birth, exclusive breastfeeding while in hospital, rooming‐in, breastfeeding on demand, no pacifiers or artificial nipples, and information on breastfeeding support groups provided on discharge. Results: Only 46.6 percent of women breastfed for more than 8 weeks, and only 4.8 percent of mothers experienced all six Baby‐Friendly practices. After controlling for all other Baby‐Friendly practices and possible confounding variables, exclusive breastfeeding while in hospital was protective against early breastfeeding cessation (OR: 0.61; 95% CI: 0.42–0.88). Compared with mothers who experienced all six Baby‐Friendly practices, those who experienced one or fewer Baby‐Friendly practices were almost three times more likely to discontinue breastfeeding (OR: 3.13; 95% CI: 1.41–6.95). Conclusions: Greater exposure to Baby‐Friendly practices would substantially increase new mothers’ chances of breastfeeding beyond 8 weeks postpartum. To further improve maternity care practices in hospitals, institutional and administrative support are required to ensure all mothers receive adequate breastfeeding support in accordance with WHO guidelines. (BIRTH 38:3 September 2011)  相似文献   
73.
Abstract: Background: Breastfeeding is the optimal feeding method for human infants. In the United Kingdom some women do not initiate breastfeeding, and many commence formula milk feeding after a brief period of breastfeeding. Infant feeding perceptions may develop early in life, and this research aimed to explore infant feeding awareness among primary school children as a first step toward informing appropriate health education interventions. Method: Fifty‐six children aged 5/6, 7/8, and 10/11 years were recruited from three schools in southern England. Children were shown a series of drawings, and were read a story about a hungry newborn baby. A creative method, “draw, write and tell,” was developed for this research. Children were asked to finish the story, showing how they thought the baby might be fed. They were given the opportunity to verbally interpret their work. A constant comparison method was used to analyze the data. Results: Children were aware of formula milk, breastfeeding, and solid foods. Formula milk feeding was referred to more frequently than breastfeeding. Some children combined feeding methods. Children appeared to have gained their awareness in various settings. Conclusions: Children have a range of perceptions around infant feeding. They appear receptive to new ideas on the subject while of primary school age. An opportunity for education in primary schools arises to present breastfeeding to children as a normal way to feed a baby, but it is vital that education is evidence based and any interventions are evaluated. (BIRTH 38:4 December 2011)  相似文献   
74.

Objective

to assess the effects of transcutaneous electrical nerve stimulation (TENS) for pain relief in labour.

Search methods

studies were identified from a search of the Cochrane Pregnancy and Childbirth Group’s Trials Register (November 2008).

Selection criteria

randomised controlled trials comparing women receiving TENS for pain relief in labour vs routine care or placebo devices. All types of TENS machines were included.

Data collection and analysis

two review authors assessed all trials identified by the search strategy, carried out data extraction and assessed risk of bias.

Results

14 studies including 1256 women were included: 11 examined TENS applied to the back, two to acupuncture points and one to the cranium. Overall, there was little difference in satisfaction with pain relief or in pain ratings between TENS and control groups, although women receiving TENS to acupuncture points were less likely to report severe pain (risk ratio 0.41, 95% confidence interval 0.32–0.55). The majority of women using TENS would use it again in a future labour. There was no evidence that TENS had any impact on interventions and outcomes in labour. There was little information on outcomes for mothers and infants. No adverse events were reported.

Conclusions

there is only limited evidence that TENS reduces pain in labour and it does not seem to have any impact on other outcomes for mothers or infants. The use of TENS at home in early labour has not been evaluated. Although the guidelines of the National Institute for Health and Clinical Excellence recommend that TENS should not be offered to women in labour, women appear to be choosing it and midwives are supporting them in their choice. Given the absence of adverse effects and the limited evidence base, it seems unreasonable to deny women that choice. More robust studies of effectiveness are needed.  相似文献   
75.
Fibrinogen biosynthesis in isolated guinea pig megakaryocytes   总被引:5,自引:0,他引:5  
Leven  RM; Schick  PK; Budzynski  AZ 《Blood》1985,65(2):501-504
Fibrinogen synthesis was investigated in guinea pig megakaryocytes. Purified megakaryocytes were incubated with 35S-methionine in methionine-free incubation medium for 18 hours. Newly synthesized fibrinogen in megakaryocyte lysates enriched with purified carrier guinea pig fibrinogen was immunoprecipitated with a specific anti- guinea pig fibrinogen antiserum produced in rabbits. Proteins in the immunoprecipitates were analyzed with a 3.5% to 10.0% gradient polyacrylamide slab gel electrophoresis and auto-radiography. Radioactivity was detected in a protein band of 340,000 daltons. In order to verify fibrinogen synthesis, immunoprecipitate was analyzed by two-dimensional slab gel electrophoresis: (1) the first dimension separated unreduced fibrinogen using a 3.5% to 10.0% gradient gel; (2) following reduction by 2-beta-mercaptoethanol, fibrinogen chains were separated in the second dimension using a 10% gel. Alpha, beta, and gamma fibrinogen chains, which represented carrier guinea pig plasma fibrinogen, were visualized by Coomassie brilliant blue. Autoradiography identified the incorporation of radioactivity into the three fibrinogen chains. In control experiments, immunoprecipitates, produced by exposing megakaryocyte lysates to preimmune rabbit serum and goat anti-rabbit IgG, were also analyzed by the two-dimensional gel system. Radioactivity was not detected in sites corresponding to the migration of fibrinogen subunits. The study demonstrates that isolated guinea pig megakaryocytes can synthesize fibrinogen. The electrophoretic mobility of newly synthesized fibrinogen and subunits is similar to that of guinea pig plasma fibrinogen.  相似文献   
76.

Background

Gloriosa superba produces an array of alkaloids including colchicine, a compound of interest in the treatment of various diseases. The tuber of Gloriosa superba is a rich source of colchicine which has shown anti-gout, anti-inflammatory, and anti-tumor activity. However, this promising compound remains expensive and Gloriosa superba is such a good source in global scale. Increase in yield of naturally occurring colchicine is an important area of investigation.

Materials and Methods

The effects of inoculation by four arbuscular mycorrhizal (AM), fungi, Glomus mossae, Glomus fasciculatum, Gigaspora margarita and Gigaspora gilmorei either alone or supplemented with P-fertilizer, on colchicine concentration in Gloriosa superba were studied. The concentration of colchicine was determined by high-performance thin layer chromatography.

Results

The four fungi significantly increased concentration of colchicine in the herb. Although there was significant increase in concentration of colchicine in non-mycorrhizal P-fertilized plants as compared to control, the extent of the increase was less compared to mycorrhizal plants grown with or without P-fertilization. This suggests that the increase in colchicine concentration may not be entirely attributed to enhanced P-nutrition and improved growth. Among the four AM fungi Glomus mossae was found to be best. The total colchicine content of plant (mg / plant) was significantly high in plants inoculated with Glomus mossae and 25 mg kg−1phosphorus fertilizer (348.9 mg /plant) while the control contain least colchicine (177.87 mg / plant).

Conclusion

The study suggests a potential role of AM fungi in improving the concentration of colchicine in Gloriosa superba tuber.  相似文献   
77.

Objective

infants of women with diabetes in pregnancy are at increased risk of hypoglycaemia. If the infant's blood glucose is low and the mother is unable to breast feed/provide sufficient expressed breast milk, infants are often given formula. Some hospitals encourage women with diabetes to express breast milk before birth. However, there is limited evidence for this practice, including its impact on labour and birth, e.g. causing premature birth may be a concern. A pilot study was undertaken to establish the feasibility of conducting an adequately powered randomised controlled trial to evaluate this practice.

Design

consecutive eligible women with pre-existing or gestational diabetes (requiring insulin), planning to breast feed and attending the study hospital were offered participation. Inclusion criteria: 34-36 weeks of gestation; singleton pregnancy; cephalic presentation; and able to speak, read and write in English. Exclusion criteria: history of spontaneous preterm birth, antepartum haemorrhage, placenta praevia and suspected fetal compromise. Women were encouraged to express colostrum twice a day from 36 weeks of gestation, and advised how to store the colostrum, which was frozen for their infant's use after birth. They were asked to keep a diary documenting their expressing. Data: demographic questionnaire, telephone interview at six and 12 weeks postpartum and medical record data.

Setting

a public, tertiary, women's hospital in Melbourne, Australia.

Participants

43 women with diabetes in pregnancy (requiring insulin).

Findings

cardiotocographs were undertaken after the first expressing episode and none of the infants showed any sign of fetal compromise. Forty per cent of infants received formula in the 24 hours postpartum. The proportion of infants receiving any breast milk at six weeks was 90%, and this decreased to 75% at 12 weeks. No women showed evidence of hypoglycaemia post expressing. The intervention was positively received by most women; 95% said that they would express antenatally again if the practice proved to be beneficial. The amount of colostrum varied according to the number of expressions, the length of time in the study and the time spent expressing, with a median of 14 days expressing and 39.6 ml of colostrum obtained.

Key conclusions

the small number of women in this pilot was not an adequate number to examine safety or efficacy, but this study does provide evidence that it would be feasible and desirable to conduct a randomised controlled trial of antenatal milk expressing for women with diabetes requiring insulin in pregnancy.

Implications for practice

it is important that this widespread practice undergoes rigorous evaluation to assess both efficacy and safety. Until such evidence is available, the authors suggest that the routine encouragement of antenatal milk expressing in women with diabetes in pregnancy should cease.  相似文献   
78.
79.
80.
The sting of Giant Asian honeybee (Apis dorsata) or Bambara in Sinhala and Karunge Kulavi in Tamil is a common environmental hazard in Sri Lanka known to cause immediate allergic reactions, which could be fatal in sensitized individuals. We reported myocardial infarction, bowel gangrene and fatal anaphylaxis in a prospectively proven case series and the association of these uncommon complications with delayed removal of stingers from the patients' skin.  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