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   1981篇
  免费   121篇
  国内免费   12篇
耳鼻咽喉   9篇
儿科学   64篇
妇产科学   54篇
基础医学   249篇
口腔科学   42篇
临床医学   168篇
内科学   412篇
皮肤病学   31篇
神经病学   119篇
特种医学   71篇
外科学   344篇
综合类   40篇
预防医学   141篇
眼科学   70篇
药学   166篇
中国医学   3篇
肿瘤学   131篇
  2023年   11篇
  2022年   52篇
  2021年   72篇
  2020年   36篇
  2019年   59篇
  2018年   64篇
  2017年   42篇
  2016年   65篇
  2015年   40篇
  2014年   74篇
  2013年   99篇
  2012年   143篇
  2011年   141篇
  2010年   100篇
  2009年   95篇
  2008年   107篇
  2007年   102篇
  2006年   89篇
  2005年   82篇
  2004年   80篇
  2003年   70篇
  2002年   66篇
  2001年   27篇
  2000年   20篇
  1999年   12篇
  1998年   14篇
  1997年   11篇
  1996年   13篇
  1995年   15篇
  1994年   11篇
  1993年   12篇
  1992年   11篇
  1991年   15篇
  1990年   18篇
  1989年   19篇
  1988年   16篇
  1987年   15篇
  1986年   14篇
  1985年   15篇
  1984年   8篇
  1983年   15篇
  1981年   9篇
  1980年   12篇
  1979年   15篇
  1978年   13篇
  1974年   11篇
  1973年   12篇
  1972年   10篇
  1971年   8篇
  1970年   9篇
排序方式: 共有2114条查询结果,搜索用时 18 毫秒
41.
ObjectivesThe purpose of this work was to evaluate the prevalence of malocclusions and orthodontic treatment need among schoolchildren in Casablanca, Morocco.Materials and methodsA sample of 1000 children aged between 8 and 12 years, with no history of orthodontic treatment, was chosen at random in state schools in different administrative areas of the city of Casablanca. Data was registered using the method of Bjork et al. (1964). Orthodontic treatment need was assessed with the index used by the Swedish National Board of Health (SweNBH).ResultsWe found Angle Class I malocclusions in 61.4%, Class II in 24%, Class III in 10% and an indeterminate molar class with one or more missing molars in 4.6% of the children. Overjet was 1–4 mm in 63.8%, 4–6 mm in 17.2% and >6 mm in 10%. Bite was normal in 65.4%, 23.6% presented an overbite greater than 4 mm, 1.7% an anterior open bite ≤3 mm, 1.2% an anterior open bite >3 mm and 0.2% a bilateral open bite. Half of the sample presented anterior crowding, while only 2.5% presented posterior crowding. In all, 84.2% of the subjects needed some orthodontic treatment, and 15.8% needed no treatment. No statistically significant difference was found between sex or age and orthodontic treatment need (P>0.05).ConclusionsThis study found a strong need for orthodontic treatment, confirming the utility of implementing a programme of bucco-dental prevention and screening for malocclusion.  相似文献   
42.
43.
44.
45.
A novel poly(epsilon-caprolactone) (PCL) supramolecular network exhibiting shape-memory behavior was successfully constructed with pendant UPy units that are highly able to dimerize. The dynamic network was obtained by a simple and versatile strategy consisting of chain-extension reaction between α,ω-dihydroxyoligoPCL and hydroxylated UPy units in the presence of hexamethylene diisocyanate as a coupling agent and further intermolecular dimerization of the UPy along the polyurethane backbone. 1H NMR analyses confirmed the dynamic features of the system, and DMTA in tensile mode was investigated to assess the SMP properties. Recyclability was also assessed by taking advantage of these supramolecular networks. Further addition of cellulose nanocrystals into the polymer network enabled adjustment of the extent of the net-points and therefore the SMP features. As confirmed by dispersion tests in solution and SEM observations, these bio-based nanofillers were homogeneously distributed in the network via supramolecular interaction between the hydroxyl groups present on their surface and UPy moieties along the polyurethane backbone. Thus, the here developed nanomaterials might reveal applicability in areas where a combination of SMP and biocompatibility is needed.

Novel melt-recyclable poly(ε-caprolactone)/cellulose nanocrystals supramolecular nanocomposite networks with shape-memory behavior have been successfully constructed by playing with UPy chemistry.  相似文献   
46.
47.
Heart Failure Reviews - Previous primary studies have explored the association between blood pressure (BP) and mortality in ambulatory heart failure (HF) patients reporting varying and contrasting...  相似文献   
48.
BACKGROUND: In the general population, obesity is associated with increased risk of adverse outcomes. However, studies of patients with chronic disease suggest that overweight and obese patients may paradoxically have better outcomes than lean patients. We sought to examine the association of body mass index (BMI) and outcomes in stable outpatients with heart failure (HF). METHODS: We analyzed data from 7767 patients with stable HF enrolled in the Digitalis Investigation Group trial. Patients were categorized using baseline BMI (calculated as weight in kilograms divided by the square of height in meters) as underweight (BMI <18.5), healthy weight (BMI, 18.5-24.9, overweight (BMI, 25.0-29.9), and obese (BMI > or =30.0). Risks associated with BMI groups were evaluated using multivariable Cox proportional hazards models over a mean follow-up of 37 months. RESULTS: Crude all-cause mortality rates decreased in a near linear fashion across successively higher BMI groups, from 45.0% in the underweight group to 28.4% in the obese group (P for trend <.001). After multivariable adjustment, overweight and obese patients were at lower risk for death (hazard ratio [HR], 0.88; 95% confidence interval [CI], 0.80-0.96, and HR, 0.81; 95% CI, 0.72-0.92, respectively), compared with patients at a healthy weight (referent). In contrast, underweight patients with stable HF were at increased risk for death (HR 1.21; 95% CI, 0.95-1.53). CONCLUSIONS: In a cohort of outpatients with established HF, higher BMIs were associated with lower mortality risks; overweight and obese patients had lower risk of death compared with those at a healthy weight. Understanding the mechanisms and impact of the "obesity paradox" in patients with HF is necessary before recommendations are made concerning weight and weight control in this population.  相似文献   
49.
50.
Eighteen consecutive patients aged 5·5–24 years with Fanconi anaemia and diagnoses of aplastic anaemia ( n  = 8), myelodysplastic syndrome ( n  = 4), acute myeloid leukaemia ( n  = 6), received allogeneic haematopoietic stem cell transplants from alternative donors. All patients had been transfused, 13 had previously been treated with androgens and 14 had a history of infection. Donors were related human leucocyte antigen (HLA) mismatched for eight patients, unrelated HLA mismatched for seven patients and unrelated HLA matched for three patients. Cytoreduction included single dose total body irradiation (450 cGy), fludarabine (150 mg/m2) and cyclophosphamide (40 mg/kg). Immunosuppression included antithymocyte globulin and tacrolimus. Grafts were granulocyte colony-stimulating factor-mobilized, CD34+ T-cell-depleted peripheral blood stem cells in 15 patients and T-cell-depleted marrows in three. All 18 patients engrafted with 100% donor chimaerism; only one patient developed graft-versus-host disease (GVHD). With a median follow-up of 4·2 years, 13/18 patients were alive, 12 of these were disease-free. Five-year overall survival and disease-free survival were 72·2% and 66·6% respectively. Immune reconstitution was achieved at approximately 6 months post-transplant for most patients. These are encouraging results of T-cell-depleted transplants from alternative donors using fludarabine-based cytoreduction in 18 high-risk patients with Fanconi anaemia, with no evidence of rejection and minimal GVHD.  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