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   1854篇
  免费   138篇
  国内免费   4篇
耳鼻咽喉   11篇
儿科学   25篇
妇产科学   34篇
基础医学   315篇
口腔科学   55篇
临床医学   259篇
内科学   351篇
皮肤病学   15篇
神经病学   155篇
特种医学   39篇
外科学   239篇
综合类   7篇
预防医学   149篇
眼科学   22篇
药学   152篇
肿瘤学   168篇
  2023年   21篇
  2022年   17篇
  2021年   60篇
  2020年   44篇
  2019年   56篇
  2018年   73篇
  2017年   46篇
  2016年   51篇
  2015年   53篇
  2014年   71篇
  2013年   73篇
  2012年   163篇
  2011年   142篇
  2010年   92篇
  2009年   58篇
  2008年   126篇
  2007年   130篇
  2006年   124篇
  2005年   112篇
  2004年   90篇
  2003年   99篇
  2002年   84篇
  2001年   21篇
  2000年   20篇
  1999年   21篇
  1998年   6篇
  1997年   6篇
  1996年   9篇
  1995年   5篇
  1994年   7篇
  1993年   4篇
  1992年   9篇
  1991年   9篇
  1990年   6篇
  1989年   3篇
  1988年   7篇
  1987年   8篇
  1986年   7篇
  1985年   9篇
  1984年   5篇
  1983年   7篇
  1982年   4篇
  1981年   4篇
  1979年   2篇
  1978年   4篇
  1977年   3篇
  1975年   2篇
  1973年   3篇
  1972年   8篇
  1971年   5篇
排序方式: 共有1996条查询结果,搜索用时 140 毫秒
1.
The activity of LCAT (the controlling enzyme for cholesterol esterification in plasma) is known to be reduced in alcoholic cirrhosis, while little is known about early stage (liver steatosis) alcoholics. In this study, LCAT activity was assayed by Stokke and Norum's method, before and after a 15-day sobriety period, in liver steatosis and in cirrhosis alcoholics. Before alcohol withdrawal, LCAT activity was depressed in both groups. After the sobriety period, LCAT activity was significantly raised in liver steatosis patients, but was still lower than in controls; in cirrhosis patients, it was increased, but not significantly. According to our results, LCAT activity impairment in alcoholic liver disease is sustained by both the hypothesized mechanisms, alcohol-related metabolic disorders and lowered LCAT-enzyme production, but to different degrees, depending on the stage of the disease. In liver steatosis, metabolic disorders play a major role, as a liver-impairment-induced decrease in LCAT production seems rather unlikely, and increased LCAT activity is more likely to be sustained by metabolic normalisation than by any recovery of the damaged liver. However, the lack of improvement in about 20% of patients, and the fairly wide scattering of individual data, suggest a minor LCAT production impairment in liver steatosis too. In cirrhosis, the major role seems to be played by a permanent decrease in LCAT production, as no significant rise in LCAT activity was observed after alcohol withdrawal. However the restored LCAT activity observed in some patients could be related to improvement in the metabolic disorder, thus confirming the effectiveness of this mechnism in cirrhosis too.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
2.
3.
Background Oxidative stress and increased inflammation have been reported to be increased in subjects with diabetes and to be involved in the pathogenesis of cardiovascular complications after myocardial infarction (MI). It is well recognized that red wine has antioxidant and anti‐inflammatory activities. We examined the effects of moderate red wine intake on echocardiographic parameters of functional cardiac outcome in addition to inflammatory cytokines and nitrotyrosine (oxidative stress marker), in subjects with diabetes after a first uncomplicated MI. Methods One hundred and fifteen subjects with diabetes who had sustained a first non‐fatal MI were randomized to receive a moderate daily amount of red wine (intervention group) or not (control group). Echocardiographic parameters of ventricular dys‐synchrony, circulating levels of nitrotyrosine, tumour necrosis factor‐α (TNF‐α), interleukin‐6 (IL‐6), interleukin‐18 (IL‐18) and C‐reactive protein (CRP) were investigated at baseline and 12 months after randomization. Results After 1 year of diet intervention, concentrations of nitrotyrosine (P < 0.01), CRP (P < 0.01), TNF‐α (P < 0.01), IL‐6 (P < 0.01) and IL‐18 (P < 0.01) were increased in the control group compared with the intervention group. In addition, myocardial performance index (P < 0.02) was higher, and transmitral Doppler flow (P < 0.05), pulmonary venous flow analysis (P < 0.02) and ejection fraction (P < 0.05) were lower in the control group, indicating ventricular dys‐synchrony. The concentrations of nitrotyrosine, CRP, TNF‐α and IL‐6 were related to echocardiographic parameters of ventricular dys‐synchrony. Conclusions In subjects with diabetes, red wine consumption, taken with meals, significantly reduces oxidative stress and pro‐inflammatory cytokines as well as improving cardiac function after MI. Moderate red wine intake with meals may have a beneficial effect in the prevention of cardiovascular complications after MI in subjects with diabetes.  相似文献   
4.
This study reports our experience in 6 cases of acute idiopathic scrotal oedema. Although children were the primary targets, this pathologic condition was also encountered in adults. Specific diagnosis of acute idiopathic scrotal oedema, opposed to other causes of scrotal swelling, is based on history, an objective examination, velocimetric Doppler exam and echography. Correct diagnosis is important in order to avoid unnecessary surgery. We are inclined to consider acute idiopathic scrotal oedema as an allergic disorder and recommend a follow-up within two days.  相似文献   
5.
Chain transfer constants (Ctr) for three phosphonated thiols in methyl methacrylate (MMA) polymerization at 60°C were determined from measurements of the degree of polymerization. These thiols were: diethyl 2-mercaptoethyl phosphate ( 1 ), diethyl 2-mercaptoethylamidophosphate ( 2 ), and tetraethyl mercaptomethylethylene bis(phosphate) ( 3 ). Transfer efficiencies of the thiols were found to be dependent upon their structures. The Ctr value of thiol 2 with MMA was the lowest in the present series, which can be attributed to a possible charged tautomeric form which eventually may reduce the electron density on the thiol, thus rendering the chain transfer reaction with the PMMA radical less feasible. Ctr values of thiol 1 were evaluated at 55, 60, 65, 70 and 75°C. This thiol behaves as an “azeotropic” transfer agent for MMA at 96°C.  相似文献   
6.
Risk factors for cardiovascular diseases and venous thromboembolism involve both acquired and hereditary conditions. Among the latter, mutations in genes coding for coagulation factors (factor V Leiden [Arg506Gly], G20210A in the 3'-untranslated region of factor II ) and variant C677T of the methylenetetrahydrofolate reductase (MTHFR ) are often involved and co-inherited. These three factors were genotyped simultaneously in the same 96-well plate, using a real-time polymerase chain reaction (PCR) Taqman assay and minor groove binding DNA oligonucleotides (MGB probes). While primers and MGB probes matched their corresponding single nucleotide polymorphism (SNP), the real-time MGB program was identical for each target gene. Homozygous wild-type (WT; -/-), heterozygous (+/-) or homozygous (+/+) variants (n = 362) were selected for factor V (n = 115, with -/-, 40; +/-, 40; +/+, 35), factor II (n = 122, with -/-, 60; +/-, 60; +/+, 2), and MTHFR (n = 120, with -/-, 40; +/-, 40; +/+, 40), according to the results of conventional PCR-restriction fragment length polymorphism (PCR-RFLP), but the allelic discrimination was performed blind. Results of the real-time MGB and PCR-RFLP assays were identical. This new assay was easy and fast with high throughput, without risk of molecular carryover, and cost-effective for laboratories utilizing the Taqman or related fluorescence reading methods. These advantages make it particularly suitable for large-scale combined genotyping of several polymorphisms in the routine setting.  相似文献   
7.
The risk of hemorrhage in infants with severe coagulopathies unresponsive to fresh frozen plasma (FFP) infusions may preclude therapeutic invasive interventional procedures. We describe the successful use of recombinant factor VIIa (rFVIIa) in two such infants, the first with cirrhosis requiring paracentesis and the second with necrotizing enterocolitis requiring laparotomy. This report reviews the current concepts on the mechanism of action of the drug rFVIIa and considers its expanded use in infants unresponsive to FFP replacement.  相似文献   
8.
Striatal glutamatergic inputs are known to participate in the modulation of dopaminergic transmission. Accordingly, the non-competitive N-methyl-D-aspartate receptor antagonists memantine and amantadine increase striatal dopamine levels, the latter being widely used in Parkinson's disease therapy. Based on our previous work revealing increased function of dopamine receptors and dopamine transporter after amantadine treatment, we studied the effects of repeated memantine administration on dopaminergic neurotransmission. On rat striatal membranes, dopamine-stimulated [(35)S]GTPgammaS binding was significantly reduced (20%) after 2 days injection with memantine (20 mg/kg per day, i.p.) but not after longer treatments (4 or 7 days). Evaluation of [(3)H]SCH 23390 and [(3)H]spiperone specific bindings only revealed a significant increase in D1 receptor density after 4 or 7 days treatment. Finally, none of these treatments were found to change the activity of the neuronal dopamine transporter in striatal synaptosomes. This shows that amantadine and memantine differentially affect striatal dopaminergic transmission, which could indicate that these two related aminoadamantanes display distinct pharmacodynamic properties.  相似文献   
9.
The peptide angiotensin-(1–7) [Ang-(1–7)] is known to enhance water transport in rat inner medullary collecting duct (IMCD). The aim of this study was to determine the mechanism of the Ang-(1–7) effect on osmotic water permeability (P f). P f was measured in the normal rat IMCD perfused in vitro in presence of agonists [Ang-(1–7), arginine vasopressin (AVP) and Ang-(3–8)], and antagonists of the angiotensin and the vasopressin cascade. Ang-(1–7), but not Ang-(3–8), increased P f significantly. The effect of Ang-(1–7) on P f was abolished by its selective antagonist, A-779, added before or after Ang-(1–7). Prostaglandin E2 and the protein kinase A inhibitor H8 also blocked the Ang-(1–7) effect. Blockade of vasopressin V1 receptors by antagonists did not change the Ang-(1–7) effect, but pre-treatment with a V2 antagonist abolished the effect of Ang-(1–7) on P f. Similarly, pre-treatment with A-779 inhibited AVPs effect on P f. Forskolin-stimulated P f was blocked both by A-779 and by the V2 antagonist. Finally, Ang-(1–7) increased cAMP levels in fresh IMCD cell suspensions whilst the forskolin-stimulated cAMP synthesis was decreased by A-779 and the V2 antagonist. These data provide evidence that Ang-(1–7) interacts via its receptor with the AVP V2 system through a mechanism involving adenylate-cyclase activation.  相似文献   
10.
BACKGROUND: Epstein-Barr virus (EBV) may be causally associated with non-Hodgkin Lymphoma (NHL) in HIV-infected patients. OBJECTIVES: To compare EBV load in whole blood in AIDS-NHL patients, HIV non-AIDS patients and non-HIV-infected persons, and to prospectively measure EBV load in whole blood in AIDS-NHL patients. STUDY DESIGN: Longitudinal and prospective study. RESULTS: We observed no statistical difference in EBV load between AIDS-NHL (3.69log(10) copies/mL [interquartile range (IQR): 2.89-4.27]) and HIV non-AIDS patients (3.08log(10) copies/mL [IQR: 1.29-3.57]) but AIDS-NHL patients had significantly higher EBV loads than HIV-negative controls (1.19log(10) copies/mL [IQR: 0.00-3.29]). We noticed an inverse correlation between CD4+ lymphocytes count and EBV load in patients with AIDS-NHL (r(2)=0.41, P=0.01). In the longitudinal study, the mean EBV load three months after NHL diagnosis decreased significantly (mean difference=-1.69log(10) copies/mL [95% confidence interval: -0.32; -3.04]; P=0.03) under chemotherapy but was still elevated in patients with relapses or no response to chemotherapy. CONCLUSION: Although EBV load seems a suboptimal marker for the diagnosis of AIDS-NHL, we observed a significant decrease of EBV load in patients treated with chemotherapy and a strong association between NHL outcome and EBV load in whole blood.  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