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   67414篇
  免费   3930篇
  国内免费   160篇
耳鼻咽喉   872篇
儿科学   1521篇
妇产科学   1354篇
基础医学   8952篇
口腔科学   2605篇
临床医学   5182篇
内科学   16921篇
皮肤病学   1660篇
神经病学   5953篇
特种医学   1661篇
外科学   9102篇
综合类   328篇
一般理论   26篇
预防医学   5788篇
眼科学   1258篇
药学   4435篇
中国医学   249篇
肿瘤学   3637篇
  2024年   38篇
  2023年   450篇
  2022年   205篇
  2021年   1109篇
  2020年   654篇
  2019年   1179篇
  2018年   2078篇
  2017年   1241篇
  2016年   1321篇
  2015年   2027篇
  2014年   2065篇
  2013年   3004篇
  2012年   5889篇
  2011年   5747篇
  2010年   2628篇
  2009年   1950篇
  2008年   4881篇
  2007年   5062篇
  2006年   5258篇
  2005年   4956篇
  2004年   4458篇
  2003年   4010篇
  2002年   3882篇
  2001年   1564篇
  2000年   2083篇
  1999年   1005篇
  1998年   232篇
  1997年   187篇
  1996年   200篇
  1995年   165篇
  1994年   134篇
  1993年   131篇
  1992年   127篇
  1991年   115篇
  1990年   80篇
  1989年   94篇
  1988年   75篇
  1987年   69篇
  1986年   88篇
  1985年   80篇
  1984年   98篇
  1983年   65篇
  1982年   87篇
  1981年   73篇
  1980年   81篇
  1979年   45篇
  1978年   46篇
  1977年   43篇
  1976年   45篇
  1974年   33篇
排序方式: 共有10000条查询结果,搜索用时 546 毫秒
51.
Introduction and objectiveWhen sleep apnea-hypopnea syndrome (SAHS) and cardiovascular disease occur concurrently, prognosis is affected. Echocardiography can detect structural cardiac abnormalities but using this technique in all patients would place a heavy burden on resources. The objective of this study was to investigate whether the N-terminal fraction of brain natriuretic peptide (NT-proBNP) can be used as a marker for silent heart disease.Patients and methodsNT-proBNP concentration was measured in the 114 consecutive patients with SAHS who underwent echocardiography before starting treatment. Left and right ventricular systolic and diastolic function, as well as structural abnormalities, were studied. Correlations between NT-proBNP concentration and the abnormalities detected were investigated. A receiver operating characteristics (ROC) curve was plotted for NT-proBNP concentration and cardiac abnormalities.ResultsData for 98 patients were finally analyzed. NT-proBNP concentration was significantly correlated with ventricular septal thickness (r=0.63), posterior wall thickness (r=0.45), and left ventricular enddiastolic diameter (r=0.51) (P<.0001 for all correlations). The area under the ROC curve was significant (0.870; 95% confidence interval, 0.801-0.939; P<.0001). Assuming that specificity would be more useful for clinical practice, we calculated that NT-proBNP concentrations below 100 and 200 pg/mL could rule out structural abnormalities with a reliability of 90% and 100%, respectively.ConclusionsNT-proBNP concentration was strongly correlated with echocardiographic abnormalities and so could be a useful tool for identifying patients who should be referred to the cardiologist.  相似文献   
52.
IntroductionTo analyse the effectiveness and safety of the indwelling pleural catheter in the management of recurrent malignant pleural effusion.Patients and methodsA prospective multicentre study was performed in 63 consecutive outpatients from four Spanish hospitals. A total of 43 men and 20 women were included, with a median age of 67 years. In seven of the cases treatment with pleurodesis had failed; in five other cases their lung was trapped; in another five cases after repeat therapeutic thoracocentesis, and the rest of them as a preference choice to pleurodesis. All patients had an indwelling pleural catheter inserted (PleurX®, Denver Biomedical).ResultsMost of patients (94.5%) reported an improvement in their respiratory symptoms (cough and dyspnoea) and their ability to function independently. Average length of the catheterisation was 45 days (6-222). Average amount of drained pleural effusion was 75 ml, with a frequency of drainage of between 3 and 4 times per week and once fortnightly. Spontaneous pleurodesis was achieved following 34.9% of procedures. No complications occurred during the insertion of the catheter. The post-catheterisation complications were empyema (3 cases), chest pain (2 cases), and tumour metastasis (3 cases).ConclusionsThe use of an indwelling pleural catheter is an effective palliative treatment in the outpatient management for patients suffering malignant pleural effusion. It is also a simple treatment that can be easily applied, does not require hospitalisation and can be easily managed by the patient at home, with a low rate of complications.  相似文献   
53.
54.
55.
Accumulating evidence suggests that antipsychotics (APs) that lead to sustained blockade of dopamine D(2) receptors are more likely to induce acute extrapyramidal side effects (EPS) compared to APs that only occupy D(2) receptors transiently. It is unclear, however, whether a similar relationship exists for long-term AP-induced motoric side effects like tardive dyskinesia (TD). The objective of this study was to ascertain whether transient (via daily subcutaneous (s.c.) injections) vs continuous (via osmotic minipump) AP-induced D(2) receptor occupancy differentially affects the development of haloperidol-induced vacuous chewing movements (VCMs), an animal model of TD. Six groups of 12 rats received 0.1, 0.25, or 1 mg/kg of haloperidol or vehicle (n=36) via osmotic minipump (to provide within-day sustained) or daily s.c. injection (within-day transient) for 8 weeks. VCMs were measured on a weekly basis and D(2) occupancy levels were measured in vivo using [(3)H]-raclopride at the end of the experiment. Minipump-treated rats developed HAL dose-dependent D(2) occupancies of 0.1 mg/kg/day (57%), 0.25 mg/kg/day (70%), and 1 mg/kg/day (88%). S.C.-treated rats also developed HAL dose-dependent D(2) occupancies of 0.1 mg/kg/day (83% peak, 3% trough), 0.25 mg/kg/day (89% peak, 0% trough), and 1 mg/kg/day (94% peak, 17% trough). A total of 43% of rats given 0.25 and 1 mg/kg/day of HAL via minipump developed high VCMs compared to only 8% of the rats given the same doses via daily s.c. injections. The 0.1 mg/kg dose did not give rise to VCMs beyond vehicle levels regardless of the route of administration. These findings support the contention that D(2) occupancy levels induced by chronic HAL must be high and sustained through the day before significant risk of VCMs, and perhaps also TD, emerges.  相似文献   
56.
57.
OBJECTIVE: The objective of this study was to radiographically quantify bone density and bone height preservation in tooth extraction alveolus filled with xenograft. STUDY DESIGN: The maxillary and mandibular fourth deciduous molars and fourth premolars of 6 minipigs were removed. Randomly, in 3 animals the right side was used as the test side and in the other 3 animals the left side was the test side. Intraoral radiographs were performed to compare the condition at the initial time and 3 months later. Measurements of bone height and bone density were performed using KS300 (Zeiss) software. RESULTS: After 3 months, there was a statistically significant smaller bone height loss for the test group. The test group presented a statistically greater bone density immediately after tooth extraction. However, after 3 months there was no statistically significant difference between the groups. CONCLUSIONS: The results suggest that treatment of postextraction alveolus with xenograft can preserve bone height initially but differences in bone density compared to when no xenograft is used are not sustained.  相似文献   
58.
Hip fracture results in excess mortality and functional disability. This study sought to identify predictors of mortality and limited functional ability 1 year after hip fracture. We conducted a 1-year follow-up of a prospective population-based inception cohort of 218 hip fracture patients who had been consecutively admitted and discharged from hospital during the previous year. Mortality was observed to be independently associated with poor mental status (relative risk [RR]=6.96; 95% confidence interval [95% CI], 1.73–28.00), prefracture limited functional ability (RR=4.35; 95% CI, 1.32–14.36), institutionalized disposition at discharge (RR=2.92; 95% CI, 1.02–8.38), and male gender (RR=2.44; 95% CI, 1.01–5.93). Independent predictors of limited functional ability were prefracture functional disability (RR=34.14; 95% CI, 3.13–372.33), poor mental status (RR=9.71; 95% CI, 1.57–59.82), age >80 years (RR=4.03; 95% CI, 1.48–11.00), and female gender (RR=3.57; 95% CI, 0.08–0.98). On discharge, special attention and care should thus be given to all patients displaying any of the above predictive factors.  相似文献   
59.
We propose a new self-organizing neural model that performs principal components analysis. It is also related to the adaptive subspace self-organizing map (ASSOM) network, but its training equations are simpler. Experimental results are reported, which show that the new model has better performance than the ASSOM network.  相似文献   
60.
Background and objectiveTo analyse frequency, characteristics and patient survival with lung cancer (LC) and Common Obstructive Pulmonary Disease (COPD), comparing them with patients that do not have COPD.Material and methodsA retrospective study, of patients diagnosed by means of cytohistology. Survival was estimated by the Kaplan-Meier method. Statistical analysis was carried out using SPSS 15.0.ResultsA total of 996 patients were diagnosed, 39.8% with COPD. Mean age70±9.19 years. GOLD stages: I 18.2%, II 53.6%, III 24%, IV 4.2%. The histological types: squamous cell carcinoma 48.2%, adenocarcinoma 22%, and small cell carcinoma 22.5%. Survival was longer in the COPD group.ConclusionsLC and COPD are combined in 39.8%. Squamous cell type is more frequent and survival was longer in the COPD group.  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