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   2393060篇
  免费   174561篇
  国内免费   4038篇
耳鼻咽喉   35140篇
儿科学   81285篇
妇产科学   67583篇
基础医学   343682篇
口腔科学   69404篇
临床医学   206612篇
内科学   471092篇
皮肤病学   51896篇
神经病学   187332篇
特种医学   93413篇
外国民族医学   992篇
外科学   364623篇
综合类   50085篇
现状与发展   2篇
一般理论   673篇
预防医学   184058篇
眼科学   54211篇
药学   178240篇
  3篇
中国医学   4914篇
肿瘤学   126419篇
  2018年   25847篇
  2017年   19481篇
  2016年   21292篇
  2015年   24335篇
  2014年   33890篇
  2013年   50673篇
  2012年   70228篇
  2011年   74927篇
  2010年   43994篇
  2009年   41314篇
  2008年   70276篇
  2007年   75827篇
  2006年   75877篇
  2005年   74517篇
  2004年   72285篇
  2003年   69480篇
  2002年   66902篇
  2001年   108155篇
  2000年   111484篇
  1999年   95046篇
  1998年   27089篇
  1997年   24244篇
  1996年   24597篇
  1995年   23279篇
  1994年   22070篇
  1993年   20459篇
  1992年   75657篇
  1991年   74396篇
  1990年   72848篇
  1989年   70072篇
  1988年   65062篇
  1987年   63892篇
  1986年   60201篇
  1985年   57702篇
  1984年   43337篇
  1983年   36914篇
  1982年   21872篇
  1981年   19652篇
  1979年   39845篇
  1978年   27853篇
  1977年   23896篇
  1976年   22488篇
  1975年   24579篇
  1974年   28824篇
  1973年   27757篇
  1972年   26049篇
  1971年   23985篇
  1970年   22553篇
  1969年   21134篇
  1968年   19675篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
Coronary magnetic resonance angiography (CMRA) is a technique in clinical evolution. Current clinical applications include assessment for coronary anomalies, aneurysms, bypass graft patency, and, in experienced centers, the exclusion of proximal and multivessel coronary artery disease (CAD). As local expertise increases and more extensive multicenter data become available, additional applications will be established. CMRA promises to supplement and in some cases obviate the need for X-ray contrast angiography, and to expand our understanding of the pathophysiology of CAD. Zusammenfassung Die Magnetresonanzangiographie der Koronargefäße (CMRA) ist eine sich ständig weiterentwickelnde Technik. Etablierte Anwendungen sind zurzeit die Beurteilung von koronaren Anomalien, Aneurysmen und der Durchgängigkeit von Bypasses. Auch der Ausschluss proximaler Koronarstenosen und einer koronaren Mehrgefäßerkrankung ist in einigen spezialisierten Zentren möglich. Mit zunehmender Erfahrung der jeweiligen Anwender und der Verfügbarkeit von Ergebnissen großer multizentrischer Studien können zukünftig weitere klinische Anwendungen etabliert werden. In der Zukunft könnte die CMRA ergänzende Informationen zur Indikationsstellung einer konventionellen Röntgenangiographie bringen und in einigen Fällen diese Untersuchung sogar ersetzen. Die CMRA wird unseren Einblick in die Pathophysiologie der koronaren Herzerkrankung sicher erweitern.  相似文献   
23.
There is a great deal of interest in developing less invasive markers for monitoring airway inflammation and the effect of possible novel anti-inflammatory therapies that may take time to impact on disease pathology. Exhaled nitric oxide (eNO) has been shown to be a reproducible, noninvasive indicator of the inflammatory status of the airway in the clinic. The aim of the present study was to determine the usefulness of measuring eNO as a marker of the anti-inflammatory impact of glucocorticoid and an inhibitor of kappaB kinase-2 (IKK-2) inhibitor 2-[(aminocarbonyl)amino]-5-(4-fluorophenyl)-3-thiophenecarboxamide (TPCA-1), in a pre-clinical model of airway inflammation. Rats were given vehicle, budesonide or TPCA-1 prior to exposure to lipopolysaccharide, previously shown to induce an increase in eNO and airway neutrophilia/eosinophilia. Comparison of the effect of the two compounds on inflammatory components demonstrated a significant correlation between the impact on eNO and inflammatory cell burden in the airway. The current study demonstrates the usefulness of profiling potential disease-modifying therapies on exhaled nitric oxide levels and the way in which an effect on this noninvasive biomarker relates to effects on pathological parameters such as lung cellularity. Information from studies such as the current one would suggest that the measurement of exhaled nitric oxide has potential for monitoring inflammatory status in lung tissue.  相似文献   
24.
BACKGROUND: Radioiodine therapy (RIT) combined with glucocorticoids is an effective therapy for Graves' disease, but it is debatable whether glucocorticoids should be applied in patients without Graves' ophthalmopathy (GO). METHODS: The effect of 0.4 - 0.5 mg prednisone every second day over a period of 5 weeks after RIT was monitored over a follow-up period of at least 12 months after RIT. A questionnaire was sent to 186 consecutive patients without GO concerning eye symptoms after RIT. 148 patients (80 %) answered. If eye symptoms had occurred after RIT, additional clinical examination was carried out at our outpatient clinic. The primary endpoint was the absence or onset of GO within the first year after RIT. RESULTS: Within 12 months after RIT the examination confirmed GO in 5 out of 148 patients (3.4 %). In all cases the symptoms were transient. No adverse reaction to the use of prednisone after RIT was noted. CONCLUSIONS: The risk of new GO in the first year after RIT was low and the clinical course of GO was mild when RIT was combined with a low-dose glucocorticoid regimen. Preventive administration of glucocorticoids can therefore be recommended in patients with Graves' disease even without evident GO.  相似文献   
25.
The present study compared four different sites and conditions for the measurement of maximal inspiratory pressure (MIP) and maximal expiratory pressure (MEP) in 38 spontaneous breathing tracheotomised patients. Of the patients, 28 had chronic obstructive pulmonary disease (COPD). The four different conditions were: 1) through a cuff inflated cannula (condition A); 2) through the mouth with a deflated cannula (condition B); 3) through the mouth with a phonetic uncuffed cannula (condition C); and 4) through the mouth after stoma closure (condition D). Five trials in each condition were performed using a standardised method. The measurement of both MIP and MEP differed significantly depending on the condition of measurement. MIP taken in condition A was significantly higher when compared with conditions B, C and D. MEP in condition A was significantly higher when compared with condition B and D. In condition A the highest frequency of the best measurement of MIP and MEP was observed at the fourth and fifth effort, respectively. The same results were obtained after the selection of only COPD patients. In conclusion, respiratory muscle assessment differs significantly depending on measurement condition. Measurement through inflated cannula tracheotomy yields higher values of both maximal inspiratory and maximal expiratory pressure.  相似文献   
26.
Chronic obstructive pulmonary disease (COPD) is characterised by a local pulmonary inflammatory response to respiratory pollutants and by systemic inflammation. Tumour necrosis factor (TNF)-alpha has been implicated in systemic effects of COPD and operates by binding the p55 (R1) and p75 (R2) TNF-alpha receptors. To investigate the contribution of each TNF-alpha receptor in the pathogenesis of COPD, the present study examined the effects of chronic air or cigarette smoke (CS) exposure in TNF-alpha R1 knockout (KO) mice, TNF-alpha R2 KO mice and wild type (WT) mice. CS was found to significantly increase the protein levels of soluble TNF-alpha R1 (by four-fold) and TNF-alpha R2 (by 10-fold) in the bronchoalveolar lavage of WT mice. After 3 months, CS induced a prominent pulmonary inflammatory cell influx in WT and TNF-alpha R1 KO mice. In TNF-alpha R2 KO mice, CS-induced pulmonary inflammation was clearly attenuated. After 6 months, no emphysema was observed in CS-exposed TNF-alpha R2 KO mice in contrast to WT and TNF-alpha R1 KO mice. CS-exposed WT and TNF-alpha R1 KO mice failed to gain weight, whereas the body mass of TNF-alpha R2 KO mice was not affected. These current findings suggest that both tumour necrosis factor-alpha receptors contribute to the pathogenesis of chronic obstructive pulmonary disease, but tumour necrosis factor-alpha receptor-2 is the most active receptor in the development of inflammation, emphysema and systemic weight loss in this murine model of chronic obstructive pulmonary disease.  相似文献   
27.
28.
BACKGROUND/AIMS: Spontaneous bacterial peritonitis (SBP) is an important complication in cirrhotic patients. The aim of the present study was to assess the incidence, predictive factors and prognosis for renal impairment (RI) after SBP in cirrhotic patients from southern Brazil. METHODS: Of the 1030 hospitalizations evaluated, 114 episodes of SBP were diagnosed in 94 patients (mean age 49 years; 76.59% men). SBP diagnosis was established when the ascitic fluid polymorphonuclear cell count was equal to or greater than 250 cells/mm3. Five cases were excluded. The variables assessed as possible predictors of steady or progressive RI were blood urea nitrogen and creatinine levels before the diagnosis of SBP; type of infection, antibiotic prophylaxis, first episode or recurrent SBP, presence of gastrointestinal bleeding and hepatic encephalopathy during hospitalization, SBP resolution, Child-Pugh classification, levels of blood pressure, ascitic fluid and blood polymorphonuclear cell count, bacteriological data (positive and negative ascitic fluid culture), albumin, bilirubin, sodium and prothrombin time at the moment of diagnosis. RESULTS: The incidence of SBP was 11.07%. In 61 (55.96%) episodes, SBP was associated with RI (transient in 57.37%; steady in 19.67%; and progressive in 22.95%). The mortality rate associated with progressive RI was 100%; 58.33% with steady RI; and 2.85% with transient RI. The mortality rate in patients with or without RI was 36.07% and 6.25%, respectively (P<0.001). The level of creatinine (greater than or equal to 1.3mg/dL) before the diagnosis of SBP and the rate of infection resolution were the only predictors of RI in the multivariate analysis. CONCLUSIONS: RI after SBP is a common complication, and indicates a poor prognosis for this infection. High levels of creatinine before infection and the rate of infection resolution are independent predictors of RI.  相似文献   
29.
Low molecular weight heparins are widely used in the prophylaxis and treatment of thrombotic disorders. The effect of low molecular weight heparins on coagulation was examined ultrastructurally in an animal model. A test and a control group was formed, each consisting of five rabbits. Nadroparine (225 Institute of Chaoy Unit/kg twice daily) was applied to the test group for 10 days. The control group received 1 ml saline solution subcutaneously. Blood and vascular tissue samples collected at the end of the 10th day were evaluated under a JEM 100 B electron microscope. Platelet degranulation and agglutination was observed in the control group. Fibrin materials were detected in the cytoplasms and surroundings of degranulated platelets. Erythrocyte accumulation was remarkable on the vascular endothelium with intact coagulation periods. In the test group, outer membranes of platelets, hyalomere, and granular structures in the granulomeres were detected to be nearly intact. There were rare erythrocytes in the large vascular lumens. The aggregation phase had occurred but no agglutination was detected. Nadroparine seems to preserve consistency of lipoprotein membranes of platelets and granular structures containing enzymes, which contribute to the coagulation mechanisms.  相似文献   
30.
Summary: A female patient with isovaleric acidaemia had a successful outcome from pregnancy.  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