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   3665篇
  免费   307篇
  国内免费   32篇
耳鼻咽喉   17篇
儿科学   110篇
妇产科学   77篇
基础医学   412篇
口腔科学   33篇
临床医学   299篇
内科学   932篇
皮肤病学   252篇
神经病学   234篇
特种医学   216篇
外国民族医学   2篇
外科学   390篇
综合类   32篇
预防医学   399篇
眼科学   16篇
药学   194篇
肿瘤学   389篇
  2022年   15篇
  2021年   31篇
  2020年   23篇
  2019年   43篇
  2018年   81篇
  2017年   66篇
  2016年   82篇
  2015年   88篇
  2014年   101篇
  2013年   168篇
  2012年   196篇
  2011年   187篇
  2010年   129篇
  2009年   132篇
  2008年   165篇
  2007年   200篇
  2006年   189篇
  2005年   174篇
  2004年   129篇
  2003年   115篇
  2002年   75篇
  2001年   87篇
  2000年   89篇
  1999年   92篇
  1998年   90篇
  1997年   70篇
  1996年   74篇
  1995年   76篇
  1994年   72篇
  1993年   54篇
  1992年   100篇
  1991年   43篇
  1990年   77篇
  1989年   76篇
  1988年   86篇
  1987年   57篇
  1986年   41篇
  1985年   24篇
  1984年   53篇
  1983年   20篇
  1982年   25篇
  1981年   23篇
  1980年   21篇
  1978年   16篇
  1977年   18篇
  1976年   20篇
  1975年   16篇
  1973年   15篇
  1971年   13篇
  1964年   15篇
排序方式: 共有4004条查询结果,搜索用时 140 毫秒
101.
BACKGROUND/AIMS: Biliary strictures are a serious cause of morbidity after liver transplantation. We have studied the role of altered bile composition as a mechanism of bile duct injury after human liver transplantation. METHODS: In 28 liver transplant recipients, bile samples were collected daily posttransplantation for determination of bile composition. Hepatic expression of bile transporters was studied before and after transplantation. Histopathological criteria as well as biliary concentrations of alkaline phosphatase (ALP) and gamma-glutamyltransferase (gamma-GT) were used to quantify bile duct injury. RESULTS: Early after transplantation, bile salt secretion increased more rapidly than phospholipid secretion, resulting in high biliary bile salt/phospholipid ratio (BA/PL). In parallel with this, mRNA levels of the bile salt transporters NTCP and BSEP increased significantly after transplantation, whereas phospholipid translocator MDR3 mRNA levels remained unchanged. Bile duct injury correlated significantly with bile salt secretion and was associated with a high biliary BA/PL ratio. CONCLUSIONS: Bile salt secretion after human liver transplantation recovers more rapidly than phospholipid secretion. This results in cytotoxic bile formation and correlates with bile duct injury. These findings suggest that endogenous bile salts have a role in the pathogenesis of bile duct injury after liver transplantation.  相似文献   
102.
The catabolic state of critical illness has been linked to the suppressed somatotropic GH-IGF-binding protein (IGFBP) axis. In critically ill patients it has been demonstrated that, compared with the conventional approach, which only recommended insulin therapy when blood glucose levels exceeded 12 mmol/liter, strict maintenance of blood glucose levels below 6.1 mmol/liter with intensive insulin therapy almost halved intensive care mortality, acute renal failure, critical illness polyneuropathy, and bloodstream infections. Poor blood glucose control in diabetes mellitus has also been associated with low serum IGF-I levels, which can be increased by insulin therapy. We hypothesized that intensive insulin therapy would improve the IGF-I axis, possibly contributing to the clinical correlates of anabolism. Therefore, this study of 363 patients, requiring intensive care for more than 7 d and randomly assigned to either conventional or intensive insulin therapy, examines the effects of intensive insulin therapy on the somatotropic axis. Contrary to expectation, intensive insulin therapy suppressed serum IGF-I, IGFBP-3, and acid-labile subunit concentrations. This effect was independent of survival of the critically ill patient. Concomitantly, serum GH levels were increased by intensive insulin therapy. The suppression of IGF-I in association with the increased GH levels suggests GH resistance induced by intensive insulin therapy, which was reflected by the decreased serum GH-binding protein levels. Intensive insulin therapy did not affect IGFBP-3 proteolysis, which was markedly higher in protracted critically ill patients compared with healthy controls. Also, intensive insulin therapy did not suppress the urea/creatinine ratio, a clinical correlate of catabolism. In conclusion, our data suggest that intensive insulin therapy surprisingly suppressed the somatotropic axis despite its beneficial effects on patient outcome. GH resistance accompanied this suppression of the IGF-I axis. To what extent and through which mechanisms the changes in the GH-IGF-IGFBP axis contributed to the survival benefit under intensive insulin therapy remain elusive.  相似文献   
103.
OBJECTIVES: The goal of this work was to assess whether high dietary glycemic load and glycemic index are associated with an increased risk of cardiovascular disease (CVD). BACKGROUND: The associations of dietary glycemic index and glycemic load with risk of CVD are not well established, particularly in populations consuming modest glycemic load diets. Moreover, risk may differ between lean and overweight subjects. METHODS: Associations of glycemic index and glycemic load with incident CVD were examined in a prospective cohort of 15,714 Dutch women age 49 to 70 years without diabetes or CVD. Dietary glycemic index and glycemic load were calculated using the glycemic index, carbohydrate content, and frequency of intake of individual foods. RESULTS: During 9 +/- 2 years of follow-up, 556 cases of coronary heart disease (CHD) and 243 cases of cerebrovascular accident (CVA) occurred. Dietary glycemic load (mean = 100; SD = 17) was associated with increased risk of CVD, adjusted for CVD risk factors and dietary variables, with a hazard ratio (HR) for the highest against lowest quartile of 1.47 (95% confidence interval [CI] 1.04 to 2.09; p(trend) = 0.03). Similar results were observed for dietary glycemic index with a corresponding HR of 1.33 (95% CI 1.07 to 1.67; p(trend) = 0.02). Glycemic load tended to be associated with both CHD (HR 1.44; 95% CI 0.95 to 2.19; p(trend) = 0.14) and CVA (HR 1.55; 95% CI 0.81 to 2.97; p(trend) = 0.10), but glycemic index only with CHD (HR 1.44; 95% CI 1.10 to 1.89; p(trend) = 0.01). Among overweight women (body mass index >25 kg/m2), glycemic load was associated with CVD (1.78; 95% CI 1.11 to 2.85; p(trend) = 0.04), but not among normal weight women (p(interaction) = 0.19). Body mass index did not modify the association of glycemic index with CVD. CONCLUSIONS: Among women consuming modest glycemic load diets, high dietary glycemic load and glycemic index increase the risk of CVD, particularly for overweight women.  相似文献   
104.
Wolf  DL; Lin  PH; Hollenbach  S; Wong  A; Phillips  DR; Sinha  U 《Blood》1995,86(11):4153-4157
The plasma clotting factors used to treat hemophiliacs who have developed inhibitory antibodies have a shared history of limited clinical safety and utility. To improve on existing bypass factors, we have developed a reversibly acylated form of human plasma factor Xa capable of providing a time-dependent release of procoagulant activity. Factor Xa was treated with p-amidinophenyl p'-anisate to generate anisoyl Xa. The chemical modification of the protein involves acylation of the active site serine residue of factor Xa. Anisoyl Xa deacylated in a time, pH, and temperature-dependent manner. Active factor Xa generated on deacylation of anisoyl Xa exhibited amidolytic and prothrombinase complex activities in in vitro assays, the level being comparable to those of untreated factor Xa. When Anisoyl Xa was infused into rabbits, active factor Xa was generated on deacylation of the acylated enzyme, which shortened the activated partial thromboplastin time (APTT) in a dose-dependent manner. The duration of effect on rabbit APTT could be directly correlated to the level of human plasma factor Xa. Because anisoyl Xa bypasses the "tenase" complex that is compromised in hemophilia A and B and is unaffected by inhibitory antibodies, it has the potential to be used as an effective bypass therapy.  相似文献   
105.
OBJECTIVE: To describe the incidence, cause, and course of anaemia in rheumatoid arthritis (RA). METHODS: Medical records of 225 patients who received a diagnosis of RA between 1990 and 1992 were reviewed longitudinally for mention of anaemia. Anaemia was classified as anaemia of chronic disease if ferritin concentrations reflected adequate body iron stores. Among iron depleted anaemic patients, iron deficiency anaemia was identified using the response to iron supplementation. RESULTS: Anaemia developed in 64% of the patients, mostly within 18 months of follow up, but disappeared again in 54% of those patients. The prevalence of anaemia varied from 39% to 53% throughout follow up. Iron depletion was found in 38% of anaemic patients; 40% of them did not recover from their anaemia after iron supplementation and were classified as having anaemia of chronic disease. Anaemia of chronic disease thus caused 77% and iron deficiency anaemia 23% of observed anaemia. Recovery from anaemia occurred in 42% of the patients with anaemia of chronic disease and in 72% of iron depleted patients after iron supplementation. Anaemic patients, particularly those with anaemia of chronic disease, had a significantly greater number of the American College of Rheumatism criteria for RA, significantly more erosive joint damage, and significantly increased concentrations of serum rheumatoid factor than patients without anaemia. CONCLUSION: Anaemia appeared as a frequent and dynamic manifestation. Recovery and recurrence of anaemia was observed throughout follow up, leading to a longstanding and relatively high prevalence of the condition. Iron deficiency was diagnosed frequently and follow up revealed a considerable overlap with anaemia of chronic disease, making this the most important cause of anaemia in RA. Recovery from anaemia occurred more frequently in iron depleted anaemic patients than in those with anaemia of chronic disease. Anaemic patients, particularly those with anaemia of chronic disease, seemed to have a more serious course of their RA compared with non-anaemic patients.  相似文献   
106.
OBJECTIVE: To evaluate antiviral activity, tolerability, and safety of the protease inhibitor (PI) TMC114 boosted with low-dose ritonavir (RTV). DESIGN: A randomized, open-label, controlled, phase IIA clinical trial in 15 sites in Europe with 50 HIV-1-infected patients who had taken multiple PIs. METHODS: At entry, PIs in non-suppressive regimens were replaced with TMC114/RTV (300/100 or 600/100 mg twice daily, or 900/100 mg once daily) or left unchanged for 14 days. The time-averaged difference (DAVG) in HIV-1 RNA from baseline, change in HIV-1 RNA from baseline, proportions achieving plasma HIV-1 RNA < 400 copies/ml and > or = 0.5 and > or = 1.0 log10 copies/ml reductions in HIV-1 RNA, and safety were assessed. RESULTS: DAVG responses in all TMC114/RTV groups (range, -0.56 to -0.81 log10 copies/ml) were significantly greater (P < 0.001) than in the controls (-0.03 log10 copies/ml). Median change at day 14 was -1.38 and +0.02 log10 copies/ml for all TMC114/RTV groups and the control group, respectively. A reduction of > or = 0.5 and > or = 1.0 log10 copies/ml was attained by 97% and 76% of patients, respectively, in all TMC114/RTV groups and by 25% and 17%, respectively, in the control group. HIV-1 RNA < 400 copies/ml at any time during treatment was achieved by 40% in the TMC114/RTV groups and 8% in the control group. Most common reported adverse events were gastrointestinal and central nervous system disorders (mild to moderate severity). No dose relationship was observed. Biochemical, haematological and electrocardiographic parameters showed no significant changes. CONCLUSIONS: TMC114/RTV demonstrated a potent antiretroviral effect over 14 days in multiple-PI-experienced patients and was generally well tolerated.  相似文献   
107.
BACKGROUND & AIMS: In the absence of pathognomonic markers for Crohn's disease (CD) and ulcerative colitis (UC), the diagnosis of inflammatory bowel disease depends on a compendium of clinical, radiographic, endoscopic, and histologic criteria that bears imperfect specificity to the individual disorders. In 10% of cases of colitis, no differentiation can be made between CD and UC; these patients are diagnosed with indeterminate colitis (IC). We evaluated the value of anti-Saccharomyces cerevisiae antibodies (ASCA) and perinuclear antineutrophil cytoplasmic antibodies (pANCA) to increase diagnostic accuracy in categorizing IC. METHODS: Since 1996, 97 patients with IC from 3 centers (Leuven, Lille, and Vienna) were enrolled, analyzed for pANCA and ASCA, and followed up prospectively. RESULTS: A definitive diagnosis has been reached for 31 of 97 patients (32%). In these patients, ASCA+/pANCA- correlated with CD in 8 of 10 patients, whereas ASCA-/pANCA+ correlated with UC in 7 of 11 patients. The remaining 4 cases became CD, clinically behaving as UC-like CD. Almost half of the patients (47 of 97 [48.5%]) were negative for ASCA and pANCA, and 40 remain diagnosed with IC to date. Only 7 seronegative cases (14.9%) became CD or UC compared with 48% (24 of 50) of seropositive patients (P < 0.001). CONCLUSIONS: Results so far show that ASCA+/pANCA- predicts CD in 80% of patients with IC and ASCA-/pANCA+ predicts UC in 63.6%. Interestingly, 48.5% of patients do not show antibodies against ASCA or pANCA. Most of these patients remain diagnosed with IC during their further clinical course, perhaps reflecting a distinct clinicoserological entity.  相似文献   
108.
109.
110.
Membrane Potential of Coronary Endothelial and Smooth Muscle Cells. In the mammalian heart the supply of oxygen and energy-rich substrates through the coronary arterioles is continuously adapted to the variations of cardiac work. The coronary resistance arteries and the surrounding myocardium form a functional unit with multiple interactions between coronary endothelial cells, smooth muscle cells, perivascular nerves, and cardiac muscle cells. We describe the mechanisms underlying the electrical and chemical communication between the different cell types, the ionic channels contributing to the resting potential of endothelial and smooth muscle cells, and the mechanisms responsible for modulation of the resting potential. The main conclusion of our analysis is that the membrane potential of coronary endothelial and smooth muscle cells is one of the major determinants of coronary blood flow, and that modulation of the membrane potential provides a way to dilate or constrict coronary resistance arteries. It is proposed that the membrane potential of the myo-endothelial regulatory unit, i.e., of the endothelial cells and the underlying smooth muscle cells in the terminal arterioles, may function as an integrator of the numerous local and global vasodilator and constrictor signals that provide for the adaptation of coronary blood flow to the metabolic demands of the heart.  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