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   3714篇
  免费   418篇
  国内免费   17篇
耳鼻咽喉   32篇
儿科学   98篇
妇产科学   68篇
基础医学   458篇
口腔科学   86篇
临床医学   461篇
内科学   647篇
皮肤病学   81篇
神经病学   390篇
特种医学   186篇
外科学   511篇
综合类   128篇
一般理论   1篇
预防医学   371篇
眼科学   102篇
药学   302篇
中国医学   2篇
肿瘤学   225篇
  2022年   28篇
  2021年   45篇
  2020年   38篇
  2019年   54篇
  2018年   73篇
  2017年   48篇
  2016年   58篇
  2015年   68篇
  2014年   80篇
  2013年   104篇
  2012年   211篇
  2011年   214篇
  2010年   125篇
  2009年   101篇
  2008年   145篇
  2007年   173篇
  2006年   153篇
  2005年   143篇
  2004年   155篇
  2003年   133篇
  2002年   132篇
  2001年   141篇
  2000年   136篇
  1999年   134篇
  1998年   67篇
  1997年   74篇
  1996年   63篇
  1995年   46篇
  1994年   48篇
  1993年   49篇
  1992年   65篇
  1991年   72篇
  1990年   48篇
  1989年   65篇
  1988年   65篇
  1987年   81篇
  1986年   70篇
  1985年   67篇
  1984年   45篇
  1983年   45篇
  1982年   28篇
  1981年   36篇
  1980年   28篇
  1979年   30篇
  1978年   30篇
  1977年   22篇
  1976年   32篇
  1974年   23篇
  1973年   25篇
  1971年   31篇
排序方式: 共有4149条查询结果,搜索用时 15 毫秒
81.
BACKGROUND: Although it is widely recognized that there are familial elements in the pathogenesis of hypertension, remarkably little is known about the influence of family history on response to specific antihypertensive agents. METHODS: This study was designed to address that issue by comparing the depressor response to lisinopril in a dose range of 10 to 40 mg in 74 patients enrolled as sibling pairs. Because all patients were treated with lisinopril, ambulatory blood pressure monitoring (ABPM), an objective measure not influenced by the investigators, was used to assess the primary blood pressure (BP) outcome variable. RESULTS: Diastolic BP was highly correlated between sibling pairs at baseline (r = 0.476; P < .03) and on treatment (r = 0.524; P = .0021). Ethnicity/race had a striking influence on lisinopril dose and response rate. Among African American patients, 23 of 28 reached the top dose of 40 mg/day, whereas only 14 of 36 Caucasian patients reached that dose level. Among Caucasians, 92% responded, and only 48% of African Americans. Responders were characterized by being younger and heavier, having significantly lower microalbuminuria at baseline, higher baseline renal plasma flow (RPF), and higher urinary kallikrein. CONCLUSION: Among Caucasians, the presence of a hypertensive sibling predicts a striking therapeutic response to angiotensin converting enzyme inhibition.  相似文献   
82.
83.
Evidence of anaerobic infection was sought in 83 patients with pulmonary disease with anaerobic culture and gas liquid chromatography (GLC) of mucopurulent sputum, or pleural fluid where appropriate. Saliva samples from nine healthy controls and 14 patients with cystic fibrosis were examined by the same methods to assess anaerobic content. Clinically significant anaerobic pleuropulmonary infection was not found in our patients with bronchitis, bronchiectasis and cystic fibrosis and occurred in only some of our patients with empyema and lung abscess. GLC of pleural fluid (empyema) or sputum (lung abscess) was helpful in identifying these cases, when a strongly positive reading was obtained. The gas liquid chromatogram was negative or only weakly positive in those patients where the presence of anaerobes was clinically insignificant, most probably resulting from contamination of the sputum samples by saliva. Results were rapidly available and the need for transtracheal aspiration to obtain specimens of bronchial secretion uncontaminated by mouth flora was avoided. The semiquantitative GLC would therefore appear to be a useful method for investigating specimens from patients with suspected anaerobic pleuropulmonary infection.  相似文献   
84.
85.
OBJECTIVE: To determine whether the relationship between smoking and disease severity in women with rheumatoid arthritis (RA) is associated with polymorphism at the glutathione S-transferase (GST) M1 locus. METHODS: Genotyping for GSTM1 was carried out using polymerase chain reaction methodology on 164 women with established RA. Smoking history was obtained on each patient. Radiographic damage was measured by the Larsen score, and functional outcome was assessed by the Health Assessment Questionnaire (HAQ). Data were analyzed by multiple regression analyses, with correction for age and disease duration. RESULTS: Ever having smoked was associated with a worse radiographic and functional outcome than was never having smoked. Both past and current smoking were associated with increased disease severity. Stratification by GSTM1 status revealed that polymorphism at this locus affected the relationship between smoking and disease outcome measures. Patients who lacked the GSTM1 gene and had ever smoked had significantly higher Larsen and HAQ scores than did those who lacked the gene and had never smoked. Radiographic outcome in these patients was worse than that in patients who had the GSTM1 gene and who had smoked. The associations were not affected by correction for socioeconomic status. Rheumatoid factor (RF) production was found to be associated with smoking in only the GSTM1-null patients. CONCLUSION: Our data suggest that disease outcome in female RA patients with a history of smoking is significantly worse than in those who have never smoked. Smoking was associated with the most severe disease in patients who carried the GSTM1-null polymorphism. This association may be due in part to a relationship between the GSTM1 polymorphism and RF production in smokers.  相似文献   
86.
The fate of the donor graft in allogeneic bone marrow transplantation, the presence of chimaerism and early relapse can be monitored by identification of the donor or recipient origin of haemopoietic cells in peripheral blood and bone marrow. We have done this by the use of highly informative locus-specific hypervariable DNA probes in two sex and blood group matched transplants. In four sex mismatched transplants the Y chromosome was identified by in situ hybridization using a biotinylated Y probe. Early engraftment by day 13 was detected in five of the six patients. Transient chimaerism occurred in half of the cases and was accompanied by the temporary appearance of the Philadelphia chromosome in one patient with chronic myeloid leukaemia without subsequent relapse. Persistence of the graft in the face of falling peripheral counts was documented in four of the six patients studied. The morphology as well as origin of the haemopoietic cells could be characterized by the Y probe analysis. In one patient, recipient lymphocytes were shown to co-exist with myeloid series of donor origin. We conclude that both techniques are highly specific, sensitive and can provide information within 24-48 h. Thus they are of value in guiding early therapeutic intervention in allogeneic transplantation.  相似文献   
87.
Influence of acoustic stress by noise on gastrointestinal motility in dogs   总被引:4,自引:0,他引:4  
The effects of acoustic stress (AS) on gastrointestinal motility and their prevention by previous treatment with naloxone, phentolamine, propranolol, muscimol, and diazepam were investigated in intact and vagotomized fasted dogs fitted with chronically implanted strain gauges on the antrum at 10 cm from pylorus and on the jejunum at 70 and 140 cm from the pylorus. These effects were compared to those produced by intracerebroventricular administration of ovine corticotropin releasing factor (oCRF). Beginning 40–50 min after the occurrence of a gastric migrating motor complex (MMC), a 1-hr hearing of prerecorded intense music through earpieces (<100 dB) delayed the occurrence of the next gastric MMC observed after 2.8±1.2 hr, while jejunal MMC were still present at a normal frequency. During AS, heart rate and plasma cortisol were significantly increased by 32.7 and 215%, respectively, 10–15 min after the beginning of hearing. The AS-induced lengthening of the gastric MMC cycle as well as cortisol increase were abolished after previous administration of diazepam (0.5 mg/kg intramuscular) or muscimol (10 g/kg intravenous), while they were still present after naloxone (0.1 mg/kg intravenous), phentolamine (0.2 mg/kg intravenous), or propranolol (0.1 mg/kg intravenous). CRF administered intracerebroventricularly (100 ng/kg) also delayed the occurrence of gastric MMC without affecting jejunal motility, and this effect was not antagonized by previous treatment with diazepam or muscimol. Both the effects of AS and CRF were abolished after bilateral thoracic vagotomy. These results suggest that the selective inhibition of gastric motility induced by noise in dog is due to the CNS release of CRF which affects, in turn, the vagal output to the stomach. The suppressive action of diazepam or GABA agonist on noise-induced gastric hypomotility may be related to blockade of the AS-induced CRF release.  相似文献   
88.
89.

Background

A suitable definition of primary care to capture the variety of prevailing international organisation and service-delivery models is lacking.

Aim

Evaluation of strength of primary care in Europe.

Design and setting

International comparative cross-sectional study performed in 2009–2010, involving 27 EU member states, plus Iceland, Norway, Switzerland, and Turkey.

Method

Outcome measures covered three dimensions of primary care structure: primary care governance, economic conditions of primary care, and primary care workforce development; and four dimensions of primary care service-delivery process: accessibility, comprehensiveness, continuity, and coordination of primary care. The primary care dimensions were operationalised by a total of 77 indicators for which data were collected in 31 countries. Data sources included national and international literature, governmental publications, statistical databases, and experts’ consultations.

Results

Countries with relatively strong primary care are Belgium, Denmark, Estonia, Finland, Lithuania, the Netherlands, Portugal, Slovenia, Spain, and the UK. Countries either have many primary care policies and regulations in place, combined with good financial coverage and resources, and adequate primary care workforce conditions, or have consistently only few of these primary care structures in place. There is no correlation between the access, continuity, coordination, and comprehensiveness of primary care of countries.

Conclusion

Variation is shown in the strength of primary care across Europe, indicating a discrepancy in the responsibility given to primary care in national and international policy initiatives and the needed investments in primary care to solve, for example, future shortages of workforce. Countries are consistent in their primary care focus on all important structure dimensions. Countries need to improve their primary care information infrastructure to facilitate primary care performance management.  相似文献   
90.
Musculoskeletal computer models allow us to quantitatively relate morphological features to biomechanical performance. In non-human apes, certain morphological features have long been linked to greater arm abduction potential and increased arm-raising performance, compared to humans. Here, we present the first musculoskeletal model of a western lowland gorilla shoulder to test some of these long-standing proposals. Estimates of moment arms and moments of the glenohumeral abductors (deltoid, supraspinatus and infraspinatus muscles) over arm abduction were conducted for the gorilla model and a previously published human shoulder model. Contrary to previous assumptions, we found that overall glenohumeral abduction potential is similar between Gorilla and Homo. However, gorillas differ by maintaining high abduction moment capacity with the arm raised above horizontal. This difference is linked to a disparity in soft tissue properties, indicating that scapular morphological features like a cranially oriented scapular spine and glenoid do not enhance the abductor function of the gorilla glenohumeral muscles. A functional enhancement due to differences in skeletal morphology was only demonstrated in the gorilla supraspinatus muscle. Contrary to earlier ideas linking a more obliquely oriented scapular spine to greater supraspinatus leverage, our results suggest that increased lateral projection of the greater tubercle of the humerus accounts for the greater biomechanical performance in Gorilla. This study enhances our understanding of the evolution of gorilla locomotion, as well as providing greater insight into the general interaction between anatomy, function and locomotor biomechanics.  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