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   24747篇
  免费   1246篇
  国内免费   126篇
耳鼻咽喉   246篇
儿科学   545篇
妇产科学   545篇
基础医学   3088篇
口腔科学   1095篇
临床医学   1845篇
内科学   6544篇
皮肤病学   713篇
神经病学   1946篇
特种医学   587篇
外科学   3529篇
综合类   126篇
一般理论   4篇
预防医学   2149篇
眼科学   470篇
药学   1426篇
中国医学   106篇
肿瘤学   1155篇
  2023年   178篇
  2022年   395篇
  2021年   855篇
  2020年   467篇
  2019年   737篇
  2018年   954篇
  2017年   559篇
  2016年   523篇
  2015年   727篇
  2014年   1018篇
  2013年   1249篇
  2012年   1916篇
  2011年   2071篇
  2010年   1076篇
  2009年   1022篇
  2008年   1580篇
  2007年   1695篇
  2006年   1587篇
  2005年   1464篇
  2004年   1341篇
  2003年   1132篇
  2002年   1123篇
  2001年   223篇
  2000年   201篇
  1999年   203篇
  1998年   178篇
  1997年   167篇
  1996年   125篇
  1995年   105篇
  1994年   91篇
  1993年   92篇
  1992年   104篇
  1991年   97篇
  1990年   74篇
  1989年   69篇
  1988年   54篇
  1987年   66篇
  1986年   54篇
  1985年   52篇
  1984年   46篇
  1983年   38篇
  1982年   44篇
  1981年   47篇
  1980年   24篇
  1979年   34篇
  1978年   23篇
  1974年   26篇
  1973年   20篇
  1972年   19篇
  1971年   19篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Although firefighters have been shown in some studies to suffer chronic respiratory morbidity from their occupational exposures, an increased risk for dying from non-malignant respiratory diseases has not been documented in any previous retrospective cohort mortality study. In order to assess the possibility that an unusually strong "healthy worker effect" among firefighters might mask this increased risk, a mortality analysis of firefighters was carried out in three cities in relation to the United States population and also to a comparison cohort of police officers. The firefighters were employed between 1945 and 1980 and experienced 886 deaths by 1 January 1984; compared with the United States population they had a significantly reduced risk of dying from all causes (SMR = 82, 95% confidence interval, 77-87), and from non-malignant circulatory diseases (SMR = 81, 95% confidence interval 73-89), but no significant difference in risk of non-malignant respiratory diseases (SMR = 88, 95% confidence interval 66-117). Compared with police, the firefighters experienced a trend toward improved mortality outcomes for all causes investigated (SMR = 82), but they had an excess of deaths from non-malignant respiratory diseases (SMR = 141). The results indicate that firefighters are probably at increased risk for dying from non-malignant respiratory diseases; this increased risk may have been missed in previous studies because of the limitations of using a general reference population.  相似文献   
102.
Increased sweat concentrations (92, 76 and 80 mEq/l) were observed in a 7-year-old boy with pitressin-resistant diabetes insipidus. All previous observations of elevated sweat electrolytes in diabetes insipidus have been in infants less than 10 months of age. The sweat test is an exceptionally reliable, sensitive and specific test for the diagnosis of Cystic Fibrosis. Pitressin-resistant diabetes insipidus is one of the diseases associated with elevated sweat test results.  相似文献   
103.
Coalescence of the cerebral ventricles with formation of a single forebrain ventricle is described in an unusual case of agenesis of the corpus callosum with dehiscent fornices and severe hydrocephalus. The cerebral hemispheres were fully cleaved. The detached fornices were widely separated from the thalami. The membrana tectoria was retroverted over the midbrain and cerebellum, where it joined the fornices and merged with a curved membranous ependymal dome which, at a great distance, circumvented the thalami as it extended toward the anterior commissure. Other anomalies included arhinencephaly, multiple subependymal heterotopias, and Dandy-Walker malformation. Similar malformations have been described as interhemispheric cysts, as (holo)prosencephaly, or as midline telencephalic dysgenesis. The basic features of prosencephaly and agenesis of the corpus callosum are reviewed and compared to the present case.  相似文献   
104.
Nitric oxide (NO) has been reported to mediate several effects in response to muscarinic cholinergic stimulation in cardiovascular tissues. Recently, an attenuation of guinea pig cardiac myocyte contraction by NO has been described. The aim of the present study was to determine whether the indirect negative inotropic effect of M-cholinoceptor stimulation in human myocardium is in part due to an effect of endogenous NO. Therefore, the effect of carbachol was studied under control conditions and during inhibition of NO-synthase by pretreatment with NG-monomethyl-l-arginine (NMMA). Functional experiments were performed in isolated, electrically driven (1 Hz, 37°C) left ventricular papillary muscle strips of human myocardium. Since cytokines have been reported to be increased in the serum of patients with heart failure and could induce NO-synthase activity in failing myocardium, we compared samples from nonfailing and terminally failing (classified as NYHA IV) hearts. The indirect negative inotropic effect of carbachol (10 mol/l) was studied in the presence of the \-adrenoceptor agonist isoprenaline (0.03 mol/l).After stimulation with isoprenaline, carbachol significantly (P < 0.05) reduced force of contraction. This effect was diminished in failing myocardium compared to nonfailing, probably due to the diminished inotropic response most likely due to the lower cAMP levels in response to \-adrenoceptor stimulation in the former condition. Pretreatment with NMMA (100 mol/l) altered the antiadrenergic effect of carbachol neither in nonfailing nor in failing preparations. Furthermore, inhibition of guanylyl cyclase, the target enzyme of NO, by preincubation with methylene blue (10 mol/l) for 30 min had no effect on the carbachol-induced decrease in force of contraction. Basal force of contraction, as well as the positive inotropic effect of isoprenaline remained unaffected by NMMA or methylene blue.The present study provides evidence that the indirect negative inotropic effect of M-cholinoceptor agonists is not due to an effect of NO in the human myocardium. Furthermore, the well known enhancement of cGMP in response to M-cholinoceptor stimulation appears not to be involved in this antiadrenergic effect.  相似文献   
105.
A 6-month protocol of oral pulse calcitriol was used in nine uraemic children (2–14 years old) on dialysis who presented with renal osteodystrophy. Calcitriol was administered twice a week, 4 g per dose for patients over 30 kg and 3g for patients less than 30 kg. Plasma levels of parathyroid hormone, calcium, phosphorus and alkaline phosphatase were carefully controlled during the study. Parathyroid hormone levels decreased by 68% and 56% by the 2nd and 6th months of treatment in seven patients, while they remained unchanged in two patients with focal segmental glomerulosclerosis and massive proteinuria. Eight hypercalcaemic episodes from 77 determinations were observed, all of them recovered after 1 week of vitamin D withdrawal. We conclude that oral calcitriol pulse therapy is a good alternative for renal osteodystrophy in uraemic children. Careful monitoring of plasma parathyroid hormone and calcium is needed during follow-up when using this approach in paediatric patients.  相似文献   
106.
The present study describes a clinical trial in which Spanish patients suffering from peripheral vascular disease (Fontaine stage II) were given specific lipid supplements. Designed as a longitudinal intervention study, patients were provided with olive oil for 3 months, followed by a 3 month wash-out period, then supplemented with a combination of fish oil and olive oil for the final 3 months. Changes in plasma and lipoprotein fatty acid composition and susceptibility of LDL to in vitro oxidation were examined. Furthermore, lipid-supplement-induced changes in LDL properties were measured as relative electrophoretic mobility and macrophage uptake. In addition, thirteen patients not provided with olive oil and fish oil were included as a control group and twenty healthy age-matched individuals were used as a reference group. A complete clinical study and a nutritional survey concerning food habits and lifestyle were performed every 3 months. Yao indices and claudicometry did not change significantly with dietary intervention although changes in plasma lipid composition suggested an improvement in the condition of the patients. The intake of the fish-oil supplement resulted in significantly increased plasma levels of eicosapentaenoic acid (20:5n-3) and docosahexaenoic acid (22:6n-3) in comparison with baseline concentrations, olive-oil and control groups. Fish-oil consumption significantly decreased plasma triacylglycerol levels compared with the olive-oil period, control and reference groups. The susceptibility of LDL to Cu-mediated oxidation was lower in the patients consuming olive oil and the fish-oil supplement than in the control group, and the uptake of LDL by macrophages was significantly lower in the group supplemented with fish oil. In conclusion, consumption of olive oil together with a dietary supplement of fish oil may be useful in the nutritional management of patients suffering from peripheral vascular disease in terms of increasing plasma n-3 long-chain polyunsaturated fatty acids and decreasing susceptibility of LDL to oxidation.  相似文献   
107.
Presentation of eight cases of urinary candidiasis in patients who underwent radical cystectomy and were managed using by-pass of the urinary tract, oral antifungal therapy and solutions in the way of intermittent instillation through nephrostomy catheters.  相似文献   
108.
Trigonocervicotomy is a barely invasive technique for the treatment of infravesical obstruction, first introduced in the 60's by Turner-Warkic and Orandi. To achieve good results with this procedure, the selection criteria must take into account a series of parameters such as age, sexual activity, PSA, prostate weight (below 30 grams) and others. In addition to its low morbidity, a larger percentage of patients preserve ejaculation than with the use of other techniques, also the neck sclerosis rate being lower as seen in all our series and expertise. The efficacy of this technique was studied on 100 patients.  相似文献   
109.
Inhaled bronchodilators are used in acute asthma for relief of airway obstruction. Continuous monotherapy with beta 2 adrenergic can increase hyperresponsiveness because these drugs do not control inflammation. Asthma mortality and morbidity have been related to an increased beta 2-agonists use. Epidemiologic data however do not show a cause/effect relationship. Until controversies are cleared on, beta 2-agonists should be used for relieving acute asthma attacks, for preventing exercise-induced bronchospasm and eventually on an as needed basis. Long acting beta 2-agonists can be effective in moderate/severe asthma. Daily short acting beta 2 use by inhalation, a partial clinical response and its overuse in acute asthma suggest the need for antiinflammatory treatment.  相似文献   
110.
Purpose: To investigate possible associations between genetic markers and Primary Open-Angle Glaucoma (POAG). Methods: A number of genetic markers were typed in 84 unrelated patients with POAG and compared with a random sample of healthy individuals. The markers were Transferrin, Group Specific Component, G1m (1), G1m (2) and G3m (5) Allotypes, Adenylate Kinase, Adenosin Deaminase, Glyoxalase I and Acid Phosphatase and PCR-based markers HLA-DQA1 and D1S80. Results: No significant differences were found except the strong association between the group of POAG patients and Acid Phosphatase ACP*C allele (2 = 32.86; p < 0.0001). Conclusions: Since Acid Phosphatase gene is localized to chromosome 2p23, this result could be a first comprehensive step in the localization of POAG genes.  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