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   1351篇
  免费   64篇
  国内免费   5篇
耳鼻咽喉   7篇
儿科学   33篇
妇产科学   50篇
基础医学   155篇
口腔科学   37篇
临床医学   90篇
内科学   340篇
皮肤病学   60篇
神经病学   125篇
特种医学   51篇
外科学   98篇
综合类   4篇
预防医学   107篇
眼科学   46篇
药学   93篇
中国医学   6篇
肿瘤学   118篇
  2023年   4篇
  2022年   20篇
  2021年   41篇
  2020年   24篇
  2019年   40篇
  2018年   42篇
  2017年   27篇
  2016年   29篇
  2015年   39篇
  2014年   43篇
  2013年   73篇
  2012年   110篇
  2011年   118篇
  2010年   75篇
  2009年   50篇
  2008年   83篇
  2007年   72篇
  2006年   77篇
  2005年   85篇
  2004年   78篇
  2003年   67篇
  2002年   66篇
  2001年   8篇
  2000年   6篇
  1999年   8篇
  1998年   12篇
  1997年   12篇
  1996年   13篇
  1995年   15篇
  1994年   5篇
  1993年   7篇
  1992年   6篇
  1991年   7篇
  1990年   2篇
  1989年   7篇
  1988年   8篇
  1987年   8篇
  1986年   8篇
  1985年   13篇
  1984年   8篇
  1980年   2篇
  1979年   2篇
排序方式: 共有1420条查询结果,搜索用时 15 毫秒
41.
Administration of psychostimulants can elicit a sensitized response to the stimulating and reinforcing properties of the drugs, although there is scarce information regarding their effects at immune level. We previously demonstrated that an acute exposure to amphetamine (5 mg/kg, i.p.) induced an inhibitory effect on the splenic T-cell proliferative response, along with an increase in met-enkephalin at limbic and immune levels, 4 days following drug administration. In this study, we evaluated the amphetamine-induced effects at weeks one and three after the same single dose treatment (5 mg/kg, i.p.) on the lymphoproliferative response and on the met-enkephalin in the nucleus accumbens (NAc), prefrontal cortex (PfC), spleen and thymus. It was demonstrated that these effects disappeared completely after three weeks, although re-exposure to an amphetamine challenge induced the expression of sensitization to the effects of amphetamine on the lymphoproliferative response and on the met-enkephalin from NAc, spleen and thymus, but not in the PfC. Pre-treatment with MK-801 (0.1 mg/kg, i.p.), an N-methyl-d-aspartate (NMDA) glutamatergic receptor antagonist, blocked the effects of a single amphetamine exposure on the lymphoproliferative response and on met-enkephalin in the NAc and spleen. Furthermore, the NMDA receptor antagonist administered prior to amphetamine challenge also blocked the expression of sensitization in both parameters evaluated. These findings show a long-lasting amphetamine-induced sensitization phenomenon at the immune level in a parallel way to that occurring in the limbic and immune enkephalineric system. A glutamate mechanism is implied in the long-term amphetamine-induced effects at immune level and in the met-enkephalin from NAc and spleen.  相似文献   
42.
The main source of vitamin D is synthesis in the skin during exposure to ultraviolet radiation. The existence of photoaggravated diseases and the increasing incidence of skin cancer have prompted recommendations to avoid the sun. Here, we study the status of vitamin D in a healthy population and its relation to their habits of sun exposure. To do so, we designed a cross-sectional study that included 177 healthy people. We analyzed parameters about demographic data, sun exposure, and protection habits and estimated vitamin D dietary intake. We performed blood tests to measure serum 25-hydroxyvitamin D [25(OH)D], calcium, phosphorus, and intact parathyroid hormone. Mean levels (± standard deviation) of 25(OH)D were 24.0 (± 8.5) ng/ml. Seventy-six percent of the population did not reach recommended levels of vitamin D (30 ng/ml), including 4.5% who were vitamin D deficient (< 10 ng/ml). Levels were higher in young people (P = 0.04) and those with more sun exposure (P = 0.04). Smoking was associated with an increased risk of hypovitaminosis D (odds ratio, 1.8; 95% confidence interval, 1.00-3.35). On the basis of our findings, we should consider the risk of hypovitaminosis when we recommend sun avoidance, especially in some risk groups, because the sun is the most important source of this vitamin.  相似文献   
43.

Trial design

This was a multicenter cluster-randomized controlled trial.

Participants

A total of 227 patients ≥ 18 years old with a new onset of depressive symptoms who screened positive on the first two items of the Patient Health Questionnaire-9 (PHQ-9) were recruited by primary care physicians (PCPs) of eight health districts of three Italian regions from September 2009 to June 2011.

Intervention

PCPs of the intervention group received a specific collaborative care program including 2 days of intensive training, implementation of a stepped care protocol, depression management toolkit and scheduled meetings with a dedicated consultant psychiatrist.

Objective

The objective was to determine whether a collaborative care program for depression management in primary care leads to higher remission rate than usual PCP care.

Outcomes

Outcome was clinical remission as expressed on PHQ-9 < 5 at 3 months.

Randomization

An independent researcher used computer-generated randomization to assign involved primary care groups to the two alternative arms.

Blinding

PCPs and research personnel were not blinded.

Results

The 223 PCPs enrolled recruited 227 patients (128 in collaborative care arm, 99 in the usual care arm). At 3 months (n= 210), the proportion of patients who achieved remission was higher, though the difference was not statistically significant, in the collaborative care group. The effect size was of 0.11. When considering only patients with minor/major depression, collaborative care appeared to be more effective than usual care (P= .015).

Conclusions

The present intervention for managing depression in primary care, designed to be applicable to the Italian context, appears to be effective and feasible.  相似文献   
44.

Introduction

An evaluation was made of the accuracy of the Root ZX apex locator (J. Morita Corp, Tokyo, Japan) in widened foramina, considering the existing controversy over this issue in the literature.

Methods

Ten single-root teeth were embedded in an alginate mold. The foramina were widened from 0.6 mm to 1.0 mm. The measurements were taken with all possible file sizes ≥#10. The statistical accuracy of the Root ZX was calculated for the different diameters and for the influence of file size.

Results

The accuracy of the Root ZX apex locator with a range of error of ±0.5 mm was 87% in an apical foramen size of 0.6 mm and 84% using files size 45 or larger in an apical foramen size of 0.7 mm. With a tolerance of ±1 mm, the accuracy was 99% in an apical foramen size of 0.6 mm, 98% using files size 45 or larger in an apical foramen size of 0.7 mm, and 95% using files size 70 or larger in an apical foramen size of 0.8 mm. In the rest, accuracy was not certain. The measurements taken with smaller files were shorter. There were no cases of overestimation of the working length.

Conclusions

The Root ZX apex locator was accurate for an apical size of 0.6 mm, independently of the file size; between 0.7 to 0.8 mm, we should adjust the files to the foramen, whereas above size 0.9 mm the locator is not accurate. The results show that the accuracy of this electronic apex locator is gradually lost as the foramen widens. Considering the stable conditions of in vitro studies, our findings advise caution in clinical application of the locator.  相似文献   
45.
BackgroundHyperinsulinemia and inflammation are inter-related pathways that link diet with the risk of several chronic diseases. Evidence suggests that these pathways may also increase prostate cancer risk.ObjectiveTo determine whether hyperinsulinemic diet and inflammatory diet are associated with prostate cancer incidence and mortality.Design, setting, and participantsWe prospectively followed 41 209 men in the Health Professionals Follow-up Study (1986–2014). Scores for two validated dietary patterns were calculated from food frequency questionnaires at baseline and updated every 4 yr.Outcome measurements and statistical analysisTotal, advanced, and lethal prostate cancer outcomes were assessed. Multivariable-adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) were determined for associations between two empirical hypothesis-oriented dietary patterns—empirical dietary index for hyperinsulinemia and empirical dietary inflammatory pattern—and prostate cancer risk estimated using Cox proportional hazard regression.Results and limitationsDuring 28 yr of follow-up, 5929 incident cases of total prostate cancer, including 1019 advanced and 667 fatal, were documented. In multivariable-adjusted models, there was a 7% higher risk of advanced prostate cancer (HR: 1.07; 95% CI: 1.01–1.15) and a 9% higher risk of fatal prostate cancer (HR: 1.09; 95% CI: 1.00–1.18) per standard deviation (SD) increase in the hyperinsulinemic diet. When stratified by age, the hyperinsulinemic diet was associated with only earlier-onset aggressive prostate cancer (men under 65 yr), with per SD HRs of 1.20 (95% CI: 1.06–1.35) for advanced, 1.22 (1.04–1.42) for fatal, and 1.20 (1.04–1.38) for lethal. The inflammatory diet was not associated with prostate cancer risk in the overall study population, but was associated with earlier-onset lethal prostate cancer (per SD increase HR: 1.16; 95% CI: 1.00–1.35).ConclusionsHyperinsulinemia and inflammation may be potential mechanisms linking dietary patterns with the risk of aggressive prostate cancer, particularly earlier-onset disease.Patient summaryAvoiding inflammatory and hyperinsulinemic dietary patterns may be beneficial for the prevention of clinically relevant prostate cancer, especially among younger men.  相似文献   
46.
Mechanical occlusion of the right coronary artery during aortic valve surgery is an infrequent but serious complication. Early recognition and expeditious management are important to reduce mortality. We developed a safe, quick, and easy technique to assess right coronary artery flow after aortic valve surgery. Direct intraoperative right coronary artery flow was measured by placing a transit-time flowmeter probe around the right coronary artery. We were able to promptly detect severe right coronary artery insufficiency in patients with acute unexpected right ventricular failure after aortic valve replacement.  相似文献   
47.
Treatment of retinitis by cytomegalovirus (CMV) in AIDS patients requires frequent repetitive injections of intravitreal ganciclovir (GCV). This study was undertaken to establish experimentally whether the intravitreal application of liposomally-entrapped GCV could prolong intraocular therapeutic levels when compared with the intravitreal injection of free GCV, and the clinical effectiveness of this approach in AIDS patients. Intraocular concentration of GCV was determined by means of an ELISA test in rabbit vitreous 2, 3, 7, and 14 days after a single intravitreal injection of either different doses of the free drug (0.2–20 mg) or 1 mg of liposomally-entrapped GCV. After 72 h, only the vitreous of rabbits injected with doses of free GCV greater than or equal to 5 mg showed therapeutic levels of the drug; no GCV was detected after 72 h with any of the doses applied. Moreover, the microscopic study revealed GCV-induced damage in retinal structures in the animals injected with a free GCV dose greater than or equal to 15 mg. Intravitreal injection to rabbits of 1 mg of liposomally-encapsulated GCV showed no retinal toxicity at any of the time points studied, and therapeutic levels were detected up to 14 days after injection (4.67 ± 0.39 g/ml). Five AIDS patients suffering CMV retinitis were injected with 0.5 mg of liposomally-entrapped GCV (2 mg of lecithin). Complete remission of the CMV retinitis was observed already at the third injection of 0.5 mg GCV (one per week) and relapse did not occur during the 2–4 month follow-up of the patients. In view of the results presented, it can be concluded that intravitreal injection of liposomally-encapsulated GCV increases the time period required for reinjections in the treatemnt of CMV retinitis.Abbreviations AIDS acquired immunodeficiency syndrome - AZT zidovudine - CMV cytomegalovirus - GCV ganciclovir  相似文献   
48.
Gaucher disease is an autosomal recessive disorder. It is characterized by the accumulation of glucosylceramide in lysosomes of mononuclear phagocyte system, attributable to acid β-glucosidase deficiency. The main consequences of this disease are hepatosplenomegaly, skeletal lesions and, sometimes, neurological manifestations. At sub-inhibitory concentrations, several competitive inhibitors act as chemical chaperones by inducing protein stabilization and increasing enzymatic activity. Here we tested two iminosugars (NB-DNJ and NN-DNJ) and four aminocyclitols with distinct degrees of lipophilicity as pharmacological chaperones for glucocerebrosidase (GBA). We report an increase in the activity of GBA using NN-DNJ, NB-DNJ and aminocyclitol 1 in stably transfected cell lines, and an increment with NN-DNJ and aminocyclitol 4 in patient fibroblasts. These results on specific mutations validate the use of chemical chaperones as a therapeutic approach for Gaucher disease. However, the development and analysis of new compounds is required in order to find more effective therapeutic agents that are active on a broader range of mutations.  相似文献   
49.
INTRODUCTION: Deep vein thrombosis (DVT) induces a systemic chronic inflammation and it has been associated with atherosclerosis. Increased levels of total sialic acid (TSA) have been shown to correlate with inflammation and atherosclerotic processes. The aim of this study was to investigate whether or not increased levels of TSA are associated with a history of DVT and with inflammation and coagulation markers, as well as with the lipid profile. MATERIALS AND METHODS: TSA, fibrinogen, C-reactive protein (CRP), fibrin D-dimer (D-dimer), prothrombin fragment 1+2 (F1+2), endogenous thrombin generation, cholesterol and triglycerides were measured in 68 patients who had suffered, in the previous 6-12 months, a first episode of idiopathic DVT, and in 68 age- and sex-matched healthy subjects. RESULTS: Levels of TSA, fibrinogen, CRP and D-dimer observed in patients were significantly higher than those detected in healthy subjects. TSA positively correlated with fibrinogen (R=0.47, p<0.01), cholesterol (R=0.46, p<0.01), triglycerides (R=0.38, p<0.01) and CRP (R=0.28, p<0.05). The logistic regression analysis confirmed that both high fibrinogen (> or =340 mg/dl) and cholesterol (> or =267 mg/dl) levels significantly and independently influence the TSA concentration. TSA levels above the 95th percentile of controls (>72 mg/dl) were detected in 33% of patients (OR=8.9; p<0.0001; 95% CI 2.4 to 31.7). CONCLUSIONS: Patients with a history of DVT had associated high levels of TSA. In these patients, TSA correlated to markers of inflammation activity and lipid profile. Thus, TSA appears to be a useful vascular inflammatory marker in idiopathic DVT.  相似文献   
50.
Increased erythrocyte aggregation (EA) has been observed in patients with ischaemic heart disease (IHD), although most of these studies have been performed in the acute phase when reactant proteins may account for this increase. Little is known about the role played by the erythrocyte itself in this aggregation process. To ascertain the contribution of both plasma and erythrocyte factors to EA in IHD, we investigated the following parameters in 78 survivors of acute myocardial infarction (AMI) and in a well-matched control group of 98 subjects: EA, glucose, total cholesterol (T-Chol), low-density lipoprotein-cholesterol (LDL-Chol), high-density lipoprotein-cholesterol (HDL-Chol), triglycerides, apolipoproteins A(1) and B, protein and functional fibrinogen, plasma sialic acid, membrane sialic acid, and the cholesterol and phospholipid content of the erythrocyte membrane. AMI survivors showed higher glucose (p<0.001), a borderline increase in triglycerides (p = 0.043), and a statistical decrease in Apo A(1) (p= 0.003) relative to controls. EA, functional fibrinogen, and plasma sialic acid were statistically higher in AMI survivors than in controls (p= 0.001; p<0.001; p= 0.011, respectively). Membrane sialic acid content was statistically lower in AMI patients than in controls (p= 0.026). No differences were observed in either membrane cholesterol or phospholipids. Multivariate logistic regression analysis, in which EA was dichotomized as higher or lower than 8.7, demonstrated that triglyceride levels higher than 175 mg/dL (OR= 7.7, p= 0.001) and functional fibrinogen levels higher than 320 mg/dL (OR= 3.7, p= 0.004) were independently associated with a greater risk of erythrocyte hyperaggregability. Our results suggest that plasma lipids, predominantly triglycerides, and fibrinogen may not only enhance the development of ischaemic events by their recognized atherogenic mechanisms, but also by increasing EA.  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