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   1938篇
  免费   103篇
  国内免费   11篇
耳鼻咽喉   7篇
儿科学   47篇
妇产科学   25篇
基础医学   197篇
口腔科学   24篇
临床医学   124篇
内科学   595篇
皮肤病学   73篇
神经病学   133篇
特种医学   50篇
外科学   328篇
综合类   20篇
一般理论   1篇
预防医学   78篇
眼科学   42篇
药学   154篇
中国医学   3篇
肿瘤学   151篇
  2023年   18篇
  2022年   25篇
  2021年   68篇
  2020年   40篇
  2019年   73篇
  2018年   44篇
  2017年   50篇
  2016年   50篇
  2015年   54篇
  2014年   101篇
  2013年   130篇
  2012年   192篇
  2011年   222篇
  2010年   88篇
  2009年   89篇
  2008年   148篇
  2007年   105篇
  2006年   134篇
  2005年   105篇
  2004年   87篇
  2003年   55篇
  2002年   50篇
  2001年   19篇
  2000年   10篇
  1999年   9篇
  1998年   7篇
  1997年   7篇
  1996年   3篇
  1995年   9篇
  1994年   2篇
  1993年   4篇
  1992年   3篇
  1991年   8篇
  1990年   6篇
  1989年   2篇
  1988年   4篇
  1986年   5篇
  1985年   4篇
  1984年   2篇
  1982年   2篇
  1981年   3篇
  1980年   2篇
  1979年   2篇
  1976年   1篇
  1969年   1篇
  1968年   1篇
  1964年   2篇
  1958年   1篇
  1945年   1篇
  1929年   1篇
排序方式: 共有2052条查询结果,搜索用时 15 毫秒
81.
82.

Background

The intracerebral hemorrhage (ICH) score is a simple grading scale that can be used to stratify risk of 30 day mortality in ICH patients. A similar risk stratification scale for subarachnoid hemorrhage (SAH) is lacking. We sought to develop a risk stratification mortality score for SAH.

Methods

With approval from the Institutional Review Board, we retrospectively reviewed 400 consecutive SAH patients admitted to our institution from August 1, 2006 to March 1, 2011. The SAH score was developed from a multivariable logistic regression model which was validated with bootstrap method. A separate cohort of 302 SAH patients was used for evaluation of the score.

Results

Among 400 patients with SAH, the mean age was 56.9 ± 13.9 years (range, 21.5–96.2). Among the 366 patients with known causes of SAH, 292 (79.8 %) of patients had aneurysmal SAH, 65 (17.8 %) were angiogram negative, and 9 (2 %) were other vascular causes. The overall in-hospital mortality rate was 20 %. In multivariable analysis, the variables independently associated with the in-hospital mortality were Hunt and Hess score (HH) (p < 0.0001), age (p < 0.0001), intraventricular hemorrhage (IVH) (p = 0.049), and re-bleed (p = 0.01). The SAH score (0–8) was made by adding the following points: HH (HH1-3 = 0, HH4 = 1, HH5 = 4), age (<60 = 0, 60–80 = 1, ≥80 = 2), IVH (no = 0, yes = 1), and re-bleed within 24 h (no = 0, yes = 1). Using our model, the in-hospital mortality rates for patients with score of 0, 1, 2, 3, 4, 5, 6, and 7 were 0.9, 4.5, 9.1, 34.5, 52.9, 60, 82.1, and 83.3 % respectively. Validation analysis indicates good predictive performance of this model.

Conclusion

The SAH score allows a practical method of risk stratification of the in-hospital mortality. The in-hospital mortality increases with increasing SAH mortality score. Further investigation is warranted to validate these findings.  相似文献   
83.

Background

In Nepal, an estimated 2–4% of the population has chronic hepatitis B virus (HBV) infection. To combat this problem, from 2002 to 2004, a national three dose hepatitis B vaccination program was implemented to decrease infection rates among children. The program does not currently include a birth dose to prevent perinatal HBV transmission. In 2012, to assess the impact of the program, we conducted a serosurvey among children born before and after vaccine introduction.

Methods

In 2012, a cross-sectional nationally representative stratified cluster survey was conducted to estimate hepatitis B surface antigen (HBsAg) prevalence among children born from 2006 to 2007 (post-vaccine cohort) and among children born from 2000 to 2002 (pre-vaccine cohort). Demographic data, as well as written and oral vaccination history were collected. All children were tested for HBsAg; mothers of HBsAg positive children were also tested. Furthermore, we evaluated the field sensitivity and specificity of the SD Bioline HBsAg rapid diagnostic test by comparing results with an enzyme immunoassay.

Results

Among 2181 post-vaccination cohort children with vaccination data by either card or recall, 86% (95% confidence interval [CI] 77–95%) received ≥3 hepatitis B vaccine doses. Of 1200 children born in the pre-vaccination cohort, 0.28% (95% CI 0.09–0.85%) were positive for HBsAg; of 2187 children born in the post-vaccination cohort, 0.13% (95% CI 0.04–0.39%) were positive for HBsAg (p = 0.39). Of the six children who tested positive for HBsAg, two had mothers who were positive for HBsAg. Finally, we found the SD Bioline HBsAg rapid diagnostic test to have a sensitivity of 100% and a specificity of 100%.

Conclusions

This is the first nationally representative hepatitis B serosurvey conducted in Nepal. Overall, a low burden of chronic HBV infection was found in children born in both the pre and post-vaccination cohorts. Current vaccination strategies should be continued.  相似文献   
84.
The current sociopolitical context of schooling is positioning play as incongruous with children's academic learning. As a result, teacher educators must increasingly guide future early childhood professionals to develop the skills and knowledge necessary to become effective play advocates. This includes articulating the value of play across the lifespan to a variety of stakeholders. Yet, ironically, many adult women entering the early childhood profession report that a wide range of barriers prevent them from including play in their adult lives. Two case studies highlight how early childhood graduate students use their experiences with play across the lifespan as a foundation for becoming play advocates. Nel Noddings's care ethics and feminist poststructural critiques of the construct of care inform the analysis and discussion of the findings. Implications suggest the importance of guiding early childhood professionals to acknowledge self-care as a component of care and play as an essential expression of self-care.  相似文献   
85.
86.
ObjectiveAs a long-standing Clinical and Translational Science Awards (CTSA) Program hub, the University of Pittsburgh and the University of Pittsburgh Medical Center (UPMC) developed and implemented a modern research data warehouse (RDW) to efficiently provision electronic patient data for clinical and translational research.Materials and MethodsWe designed and implemented an RDW named Neptune to serve the specific needs of our CTSA. Neptune uses an atomic design where data are stored at a high level of granularity as represented in source systems. Neptune contains robust patient identity management tailored for research; integrates patient data from multiple sources, including electronic health records (EHRs), health plans, and research studies; and includes knowledge for mapping to standard terminologies.ResultsNeptune contains data for more than 5 million patients longitudinally organized as Health Insurance Portability and Accountability Act (HIPAA) Limited Data with dates and includes structured EHR data, clinical documents, health insurance claims, and research data. Neptune is used as a source for patient data for hundreds of institutional review board-approved research projects by local investigators and for national projects.DiscussionThe design of Neptune was heavily influenced by the large size of UPMC, the varied data sources, and the rich partnership between the University and the healthcare system. It includes several unique aspects, including the physical warehouse straddling the University and UPMC networks and management under an HIPAA Business Associates Agreement.ConclusionWe describe the design and implementation of an RDW at a large academic healthcare system that uses a distinctive atomic design where data are stored at a high level of granularity.  相似文献   
87.
DNA methylation is a reversible biological signal   总被引:17,自引:0,他引:17       下载免费PDF全文
The pattern of DNA methylation plays an important role in regulating different genome functions. To test the hypothesis that DNA methylation is a reversible biochemical process, we purified a DNA demethylase from human cells that catalyzes the cleavage of a methyl residue from 5-methyl cytosine and its release as methanol. We show that similar to DNA methyltransferase, DNA demethylase shows CpG dinucleotide specificity, can demethylate mdCpdG sites in different sequence contexts, and demethylates both fully methylated and hemimethylated DNA. Thus, contrary to the commonly accepted model, DNA methylation is a reversible signal, similar to other physiological biochemical modifications.  相似文献   
88.
BACKGROUND Patients with autoimmune hepatitis(AIH) require life-long immunosuppressive agents that may increase the risk of poor corona virus disease 2019(COVID-19)outcomes.There is a paucity of large data at the population level to assess whether patients with AIH have an increased risk of severe diseases.AIM To evaluate the impact of pre-existing AIH on the clinical outcomes of patients with COVID-19.METHODS We conducted a population-based,multicenter,propensity score-matched cohort study with...  相似文献   
89.
Sacco RL  Chong JY  Prabhakaran S  Elkind MS 《Lancet》2007,369(9558):331-341
Treatments for acute ischaemic stroke continue to evolve. Experimental approaches to restore cerebral perfusion include techniques to augment recanalising therapies, including combination of antiplatelet agents with intravenous thrombolysis, bridging therapy of combining intravenous with intra-arterial thrombolysis, and trials of new thrombolytic agents. Trials with MRI selection criteria are underway to expand the window of opportunity for thrombolysis. Sonothrombolysis and novel endovascular mechanical devices to retrieve or dissolve acute cerebral occlusions are being tested. Approaches to improve cerebral perfusion with other devices and induced hypertension are also being considered. Although numerous neuroprotective agents have not shown benefit, trials of hypothermia, magnesium, caffeinol, high doses of statins, and albumin are continuing. The findings of these randomised trials are anticipated to allow improved treatment of patients with acute stroke.  相似文献   
90.

Aim of the study

To evaluate the antidiabetic and antioxidant effects of various fractions of Phyllanthus simplex on alloxan induced diabetes in rats.

Materials and methods

Hypoglycemic effect of Phyllanthus simplex fractions was evaluated in normal and diabetic rats. Diabetes was induced by intraperitoneal injection of alloxan monohydrate (120 mg/kg). Normal and diabetic rats were divided into different groups (six rats each group) and orally administered with petroleum ether (P.E.) (200 and 400 mg/kg), ethyl acetate (EtOAc) (100 and 200 mg/kg), methanol (125 and 250 mg/kg), water fraction (150 and 300 mg/kg) and glibenclamide (10 mg/kg) for 21 days. Blood samples were collected from overnight fasted normal rats on day 21, from overnight fasted diabetic rats at 7, 14 and 21 days of treatment and analyzed for blood glucose level. On day 22 blood samples were collected from diabetic rats to estimate biochemical parameters, rats were sacrificed by single stunning and tissues were excised to measure their antioxidant and glycogen status.

Results

In the normoglycemic rats, MeOH (125 and 250 mg/kg) and aqueous fractions (150 and 300 mg/kg) showed a significant (P < 0.05) hypoglycemic effect on day 21. In diabetic control rats, MeOH (125 and 250 mg/kg) and aqueous fractions (150 and 300 mg/kg) showed significant antihyperglycemic effect (P < 0.001). The active fractions (MeOH and aqueous) of Phyllanthus simplex also increased the body weight of diabetic rats significantly compared to the control group. The active fractions were able to normalize the marked alterations in antioxidant enzymes and antioxidant parameters levels in liver and kidney. Treatment with the active fractions also normalized the diabetic induced hyperlipidemia and liver glycogen.

Conclusions

These results demonstrate the antidiabetic and antioxidant potential of fractions of Phyllanthus simplex and suggests that the plant may have therapeutic value in diabetes and related complications.  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