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   3169篇
  免费   301篇
  国内免费   32篇
耳鼻咽喉   7篇
儿科学   121篇
妇产科学   52篇
基础医学   390篇
口腔科学   72篇
临床医学   364篇
内科学   573篇
皮肤病学   16篇
神经病学   191篇
特种医学   336篇
外科学   357篇
综合类   167篇
预防医学   301篇
眼科学   77篇
药学   358篇
  1篇
中国医学   1篇
肿瘤学   118篇
  2021年   37篇
  2018年   44篇
  2017年   32篇
  2016年   39篇
  2015年   40篇
  2014年   48篇
  2013年   107篇
  2012年   122篇
  2011年   120篇
  2010年   69篇
  2009年   73篇
  2008年   112篇
  2007年   121篇
  2006年   106篇
  2005年   108篇
  2004年   93篇
  2003年   98篇
  2002年   88篇
  2001年   82篇
  2000年   88篇
  1999年   93篇
  1998年   43篇
  1997年   39篇
  1996年   44篇
  1995年   50篇
  1994年   41篇
  1993年   56篇
  1992年   85篇
  1991年   74篇
  1990年   73篇
  1989年   85篇
  1988年   82篇
  1987年   108篇
  1986年   88篇
  1985年   100篇
  1984年   66篇
  1983年   52篇
  1982年   35篇
  1981年   42篇
  1980年   36篇
  1979年   44篇
  1978年   47篇
  1977年   39篇
  1976年   31篇
  1975年   31篇
  1974年   40篇
  1973年   40篇
  1972年   30篇
  1971年   40篇
  1970年   34篇
排序方式: 共有3502条查询结果,搜索用时 15 毫秒
71.
Atrial fibrillation (AF) and heart failure (HF) commonly coexist, and their co-presence is associated with adverse outcomes relating to thromboembolic events, HF progression, hospitalisation and death. Diastolic dysfunction (DD) is also frequently present in patients with HF and is an independent predictor of hospitalisation and mortality. The presence of DD is a strong predictor of incident AF in patients with HF. In this review, we provide mechanistic insight into pathophysiological processes that frequently promote the occurrence of AF, HF and DD and outline the yin-yang relationship between AF, DD and HF. More recently, invasive studies have also shown that asymptomatic paroxysmal atrial fibrillation (PAF) is a common phenomenon in HF patients. We examine complex inter-relationships between PAF, HF and DD and speculate upon the possible clinical influence of undiagnosed PAF in HF patients.  相似文献   
72.

In spite of increased efforts to integrate nutrition and agriculture there are relatively few methods developed to effectively do so in the design and analysis of agricultural interventions. In order to develop and test a method to link agricultural production and nutritional benefits, fall gardens were planted by researchers and low‐income households in five locations in the New River Valley, Virginia. Edible portion yield per square meter was calculated as a basic nutrition/agricultural yield measure. In order to use a more discriminating measure, crop nutrient yield equivalents (CNYE) for limiting nutrients (vitamins A and C, iron, and calcium) were calculated. The CNYE indicates the number of days that 100% of the USRDA would be supplied. Summing the CNYE scores across nutrients provided a ranking of the overall nutritional completeness (ONC) of the crops. The ONC ranking thus supplies a measure of yield and nutritional efficiency that can be adapted for different nutrition requirements and gardening conditions.  相似文献   
73.
74.
75.
Percutaneous drainage of chest abscesses in children   总被引:1,自引:0,他引:1  
Ball  WS  Jr; Bisset  GS  d; Towbin  RB 《Radiology》1989,171(2):431-576
Seven patients ranging in age from 3 to 18 years underwent percutaneous drainage of eight intrathoracic abscesses. Five of the abscesses were mediastinal or paramediastinal and resulted from esophageal perforation or esophageal anastomotic leakage. The abscesses resolved in each case, with a mean catheter drainage time of 28 days and no need for surgical intervention. Three of the abscesses were intrapulmonary, and each lay adjacent to a pleural surface. All three lung abscesses resolved within 19-24 days, without thoracotomy or wedge resection.  相似文献   
76.

Purpose

To assess short- and long-term mortality and rebleeding with endoscopic cyanoacrylate (EC) versus balloon-occluded retrograde transvenous obliteration (BRTO).

Materials and Methods

A retrospective cohort comparison was conducted of 90 EC patients and 71 BRTO patients from 1997 through 2015 with portal hypertension who presented due to endoscopically confirmed bleeding cardiofundal gastric varices. Patients underwent either endoscopic intra-varix injection of 4-carbon-n-butyl-2-cyanoacrylate or sclerosis with sodium tetradecyl sulfate with balloon occlusion for primary variceal treatment.

Results

Seventy-one BRTO patients and 90 EC patients, of whom 89% had cirrhosis and 35% were women, were included, with a respective average Model for End-Stage Liver Disease (MELD) score of 13.4 and 14.4, respectively. Mortality at 6 weeks was 14.4% for EC patients and 13.1% for BRTO patients (Kaplan-Meier/Wilcoxon, P = .85). No long-term mortality difference was observed (Cox hazard ratio [HR] = 0.89, P = .64). Also, 5.1% of EC patients and 3.5% of BRTO patients (Kaplan-Meier/Wilcoxon, P = .62) rebled at 6 weeks, but at 1 year, 22.0% of EC patients and 3.5% of BRTO patients had rebled (Kaplan-Meier/Wilcoxon, P < .01). Lower rates of long-term rebleeding were found with BRTO (Cox HR = 0.25, P = .03). No difference was seen in the rate of new portal hypertensive complications (Cox HR = 1.21, P = .464). However, 16/71 patients who underwent BRTO had simultaneous transjugular intrahepatic portosystemic shunt. Age, sex, MELD score, and presence of cirrhosis were the primary predictors of mortality. One death in the EC group and 5 deaths in the BRTO group were deemed to be procedurally related (chi-square, P = .088).

Conclusions

BRTO is associated with a lower rate of rebleeding but no change in mortality.  相似文献   
77.
BACKGROUND: Oxidative stress plays a role in the pathogenesis of nonalcoholic steatohepatitis (NASH). Yo jyo hen shi ko (YHK) is a complex compound purported to reduce reactive oxygen species (ROS) by blocking the propagation of radical-induced reactions. The aim of this study was to evaluate the role of the effect of YHK in experimental NASH. METHODS: NASH was induced in male ob/ob mice by a high-fat (HF) diet or methionine/choline-deficient (MCD) diet for 4 weeks. YHK-treated animals received YHK solution orally (20 mg/kg/day) in both experimental diets (n=6; each group) while control animals received only vehicle. RESULTS: The MCD and HF groups developed moderate diffuse macrosteatosis, hepatocellular ballooning, and a diffuse inflammatory infiltrate. With the addition of YHK, there was a marked reduction in macrosteatosis in both groups. This was associated with decreased lipoperoxide and reduced glutathione-GSH concentrations as well as reduced serum aminotransferases and improved histological markers of inflammation. These changes were also associated with weight loss in the MCD+YHK group and diminished weight gain in the HF+YHK group. CONCLUSION: YHK therapy blunts the development of macrosteatosis in these models of NASH and significantly reduces markers of oxidative stress. YHK also diminishes weight gain in this obesity prone model. Our findings warrant further study on the mechanisms involved with these effects.  相似文献   
78.
The purpose of this study was to develop an algorithm for identifying patients with chronic hepatitis B virus (HBV) using automated data sources from two US health systems and evaluate the algorithm's performance by quantifying the incidence of hepatocellular carcinoma (HCC) among chronic HBV patients. To allow comparisons with estimates from automated databases that may not contain all data elements used in this algorithm, we created three definitions of chronic HBV infection and used these definitions to create three overlapping cohorts. We compared the incidence of HCC in each cohort with the incidence of HCC in a matched general population comparison cohort with no evidence of HBV. Patients who met the most stringent criteria for chronic HBV infection (based on the standard definition of 6 months of infection using repeat laboratory tests and record review) were 146 times more likely to develop HCC than matched comparison patients (adjusted hazard ratio = 146.5, 95% CI: 74.0-289.8). Those not meeting the stringent criteria, but who met the criterion of at least one positive hepatitis B surface antigen test were 30 times more likely to develop HCC than comparison patients (adjusted hazard ratio = 29.8, 95% CI: 16.5-53.6). Finally, patients who met the criterion based on at least one HBV diagnosis were 38 times more likely to develop HCC than matched comparison patients (adjusted hazard ratio = 37.8, 95% CI: 25.9-55.1). The magnitude of the relative increase in HCC risk seen using different criteria used to define HBV infection indicate that these automated data algorithms can identify patients with chronic HBV infection.  相似文献   
79.
BACKGROUND & AIMS: Esophagogastroduodenoscopy (EGD) is the current standard for evaluating esophageal varices, yet there is no universally accepted system of grading varices endoscopically and several studies have shown interobserver variability of endoscopic grading. High-resolution endoluminal ultrasound 20 MHz (HRES) has been shown to detect varices accurately and can be performed without sedation. Our aim was to compare the detection of esophageal varices by transnasal HRES and EGD. METHODS: We prospectively studied 37 cirrhotic patients being evaluated for esophageal varices. HRES was used to measure the largest esophageal variceal diameter and then EGD was performed. Photographs were taken for both procedures. Three blinded investigators graded the EGD photographs at 2 periods. End points were as follows: (1) the correlation of HRES variceal diameter and EGD grading of varices, and (2) the assessment of interobserver and intraobserver variation in varix grading by EGD. RESULTS: The correlation between the transnasal HRES and EGD was .63, with a 95% confidence interval of .37-.80. The HRES detected early varices that were not seen by EGD. The interobserver correlation for EGD scoring was .87 or greater in all comparisons and the intraobserver correlation was .91 or greater. CONCLUSIONS: In conclusion, there is a significant correlation between transnasal HRES size measurement of esophageal varices and EGD. HRES is much more sensitive in detecting early esophageal varices and may not require sedation, suggesting that it may be more tolerable to patients and is worth further study.  相似文献   
80.
Adler  A; Albo  V; Blatt  J; Whiteside  TL; Herberman  RB 《Blood》1989,74(5):1690-1697
Activation and expansion in culture with rIL-2 of peripheral blood (PB) and/or bone marrow (BM) specimens derived from children with ALL and ANLL, with active disease (AP) and in remission were studied (RP). Baseline NK cytolytic activity from AP was found to be depressed, whereas RP-derived cells had normal NK activity, as assayed against K562 targets. Culture in rIL-2 significantly enhanced the NK activity of both AP- and RP-derived cells and generated LAK activity, as assayed by 4-hour 51Cr release, against NK-resistant Raji cell line and against fresh, allogeneic, and autologous tumor cells. Lytic activity against fresh, cryopreserved leukemia blasts was of lower than that found against cell lines. In three patients higher lytic activity against autologous than against allogeneic blasts was demonstrated. Expansion in culture with rIL-2 varied from twofold to 120-fold. rIL-2 activation and expansion was better in RP than in AP. The predominant phenotype of activated cells, as determined by flow cytometry, was [mean % (SD)]: CD3- = 54 (12), CD8+ = 55 (17), and NKH1+ = 26 (7). The consistently high level of CD8+ cells was accompanied by very low levels of CD4+ cells: mean = 11% (14). Double-marker analysis showed mean of 33% (10) for CD3+/NKH1+ cells and mean = 32 (11) for CD8+/NKH1+ cells, implying that these populations were overlapping. Kinetics of expression of cell surface markers during 2 to 3 weeks in culture showed that CD8+ and NKH1+ enrichment occurred during the first week and lasted for up to 4 weeks, whereas CD4+ expression decreased after the second week. A significant decrease in the expression of IL-2 receptors (CD25) was observed from the second week of culture. This study shows the feasibility of in vitro generation of killer cells from PB and BM of pediatric leukemia patients.  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